Experimental Models for Autism Spectrum Disorder ...

Rev J Autism Dev Disord DOI 10.1007/s40489-016-0088-7

REVIEW PAPER

Experimental Models for Autism Spectrum Disorder Follow-Up for the Validity Uma Devi 1 & Vikas Kumar 1 & Pushpraj S Gupta 1 & Suchita Dubey 2 & Manjari Singh 3 & Swetlana Gautam 3 & Jitendra K Rawat 3 & Subhadeep Roy 3 & Rajnish Kumar Yadav 3 & Mohd Nazam Ansari 4 & Abdulaziz S. Saeedan 4 & Gaurav Kaithwas 3

Received: 1 January 2016 / Accepted: 16 August 2016 # Springer Science+Business Media New York 2016

Abstract Autism spectrum disorders (ASDs) are often considered to be genetic. They are characterized by unificational behavioral abnormalities which are classified in two basic domains: social relations and social communication, and restricted and repetitive pattern of behaviors and activity. Clinical research has evidenced that genetic and environmental factors play a major role in the development of ASD, and it is contemplated to be a multifactorial as well. Augmentation in the field of molecular genetics and neuroscience allows the pharmacologist to explore more features of ASDs using genetic, humanoid, and nonhumanoid models. Hence, the present review was undertaken to elucidate the major concepts associated with the models of ASD, such as gene or chromosome incrimination; face, predict, and construct validities; behavioral assays; and advantages and disadvantages of preclinical models along with constrains in developing genetic models for ASD. Keywords ASD . Mouse models . Maternal toxicity . Genetic models * Gaurav Kaithwas [email protected] 1

Department of Pharmaceutical Sciences, Faculty of Health Science, Allahabad Agricultural Institute- Deemed to be University, Sam Higginbottom Institute of Agriculture, Technology and Sciences, Allahabad 211007, Uttar Pradesh, India

2

Department of Pharmaceutical Sciences, Amity University Campus, Lucknow 226028, Uttar Pradesh (U.P.), India

3

Department of Pharmaceutical Sciences, School of Bioscience and Biotechnology, Babasaheb Bhimrao Ambedkar University (A central University), Lucknow 200 265, Uttar Pradesh, India

4

Department of Pharmacology, College of Pharmacy, Prince Sattam Bin Abdulaziz University, Al-Kharj, Kingdom of Saudi Arabia

Introduction Autism spect rum disorders (ASDs) are complex neurodevelopmental disorders with uncertain pathogenesis defined by qualitative impairment in social interaction and social communication, and restricted and repetitive patterns of behavior, interests, or activity. ASD exhibits high prevalence rate of 1– 2 per 100 people. Consequently, ASD is the major serious problem worldwide. Moreover, it is reported that ASD is four times more frequently occurs in male than female and it is among the heritable disorders evident by family and twin studies with a concordance rate of 70–90 % for monozygotic twins (DiCiccoBloom et. al. 2006; Folstein and Rosen-Sheidley 2001; Bailey et al 1995). The etiology of ASD is not well known, and it is thought to be that brain development is affected which may be due numerous potential risk factors ranging from genetic to epigenetic, to environmental. A number of genetic modifications which can increase the risk of developing ASD include mutations, chromosomal deletions, or duplication (copy number variation (CNV)) (Sebat et. al. 2007). Although ASDs belong to human, since mice having similar kind of gene expression mouse models plays an important role in better understanding the etiology and the genetic aspect of ASD and thus help to develop more effective therapies. Most of the characteristics of ASD-like deficits in social interaction and communication, and repetitive and stereotyped motor behavior are modeled in mice (Crawley 2004, 2007a, b). Advances in the fields of experimental genetics and molecular biology have led to the development of various genetically modified mouse models targeting various genes associated with ASD, and other animal models induced by drug administration, surgical injury, or viral infection are developed with pathophysiological and genetic aberration characteristics of human clinical disorders. The models can be tremendously beneficial for enumerating disorder etiology, effects on organic and cellular function, and therapeutic efficacy of novel treatment strategies.

Rev J Autism Dev Disord

The present review describes the major mouse models and recently developed nonhuman primate models along with their important features that have been developed, and a brief description on behavioral assays was used to study ASD (Table 1). The review also explores the validity of these models, i.e., the face, predict, and construct validity, where face validity is used to assess behavioral phenotypic similarities of the model, construct validity determines the potential of the model to mimic the pathophysiology of the disorder, and predict validity takes about the pharmacological similarity of the model (Table 2).

Models of ASD ASD is a complex neurodevelopmental disorder with no singular pathology (heterogeneous in nature). Since mice have comparable similar kind of genetic expression to humans (98 % of human genes), this makes an excellent model to understand the various diseases. Various animal and genetically modified models are designed to modeling the core features associated with the ASD in order to understand the mechanism underlying the ASD. Rodents are widely used to screen the drugs, study the mechanisms, and study the underlying pathology for ASD. Both the regular/routine (e.g., Sprague-Dawley, albino Wistar, Norway rats, etc.) and null/ knockout (KO) (e.g., OT and AVP KO, FMR 1KO, etc.) rodents are used to study the various aspects of ASD. The null or KO rodents are the ones where a specific gene has been kept silence (null) or has been removed (KO). Such animals are preferably used to study the function and behavior of a particular gene and thereby hold a very significant space in the ASD research. However, it is difficult to generate animal model that displays all the features of ASD because of the multifactorial nature. In this section, we have covered the animal models induced by maternal risk factors, genetically modified mouse model, and humanoid and nonhumanoid models that display many of characteristic features of ASD to better understand this complex disorder.

Environmental Toxicant It has been suggested that prenatal exposure of environmental toxicant affects the developing brain which increases the risk of developing ASD. Indirect evidences are found with exposure of external environmental toxicants like lead, ethyl alcohol, methyl mercury, arsenic, organophosphate insecticides, DDT, and polychlorinated biphenyl while evidence-based studies are available with the exposure to thalidomide, valproic acid (VPA), misoprostol, infection with influenza virus, rubella virus, and cytomegalovirus. Rodent models developed for the risk factors include maternal respiratory infection with influenza virus, behavioral abnormalities induced by

VPA, and maternal immune activation (MIA) with polyinosine/cytosine, lipopolysaccharide (LPS)-induced neuropathology, terbutaline-induced hyperactivity along with 5methoxy tryptamine-induced ASD (Grabrucker 2013; Folstein and Rosen-Sheidley 2001). In this section, we have discussed rodent models of maternal risk factors. PolyI:C Induced Polyinosine/cytosine (PolyI:C) is synthetic, double-stranded RNA that evokes an antiviral-like immune reaction by maternal immune activation. The polyI:C MIA model has been extensively studied with regard to the behavior of the offspring, as well as their neuropathology, neurochemistry, structural MRI, and more recently, electrophysiology (Patterson 2009; Meyer et al. 2011; Hsiao et al. 2011). The offsprings exhibit deficits in ultrasonic vocalizations (USVs), USVs emitted by altricial rodent pups are whistle-like sounds with frequencies between 30 and 90 kHz (Branchi et al 2001). Measurement of USVs appears to be a promising strategy in order to determine the communication deficits of rodent, self-grooming, marble burying, and perseveration in the water maze reflecting the behavioral similarities to the core symptoms of ASD like increased repetitive/stereotyped motor behaviors along with deficits in social interaction and communication (Patterson 2009; Hsiao et al. 2011). The offspring also displays a number of other behaviors found in subsets of ASD subjects such as difficulty with changes, insistence on sameness, enhanced anxiety, and eye blink conditioning (Patterson 2009; Dammann and Meyer 2001). LPS-Induced Neuropathy Maternal LPS administration yields offspring which mimics the infection by gram-negative bacteria. The neuropathology in the LPS model ranges from severe to very mild, which depends upon the treatment protocol. The increased cell density and limited dendritic arbors in the hippocampus are major Pathophysiological associations with this model (Baharnoori et al. 2009). The behavioral patterns include fewer ultrasonic USVs (communication), less play behavior including pinning, sniffing the partner, crawls over/under the other animal, and partner mounting. The prenatal LPS exposure results in social deficits, communication abnormalities, and cognitive inflexibility, i.e., ASD-like effects (Pinheiro et al. 2012). VPA-Induced ASD Women taking VPA for mental illness or epilepsy during early pregnancy are at elevated risk for ASD, and the same has been exploited as a model for preclinical screening (Markram et al. 2007; Schneider et al. 2008; Hsiao et al. 2011). In pregnant rats, a single injection of VPA results in behavioral abnormalities

3

2

Environmental toxicant models Polyinosine/cytosine

1

A3.3

A3.2

A3.1

Genetic models Models for genes associated with autism Fragile-X mental retardation 1 (FMR 1): this gene provides information for making a protein FMRP. Methyl-CpG-binding protein (MECP2): this gene provides information for making protein MeCP2. Gamma-aminobutyric acid receptor subunit β3 (GABA β3)

Opioids

2.3

A

Oxytocin (OT)

2.2

Terbutaline

1.4

Neuropeptide models Vasopressin (AVP)

Valproic acid

1.3

2.1

LPS model (single prenatal exposure)

1.2

1.1

Models

Heterozygous

Homozygous

KO mouse

Homozygous

–

Heterozygous

Homozygous

Homozygous

Heterozygous

Heterozygous

Type of model

Mecp2-null mouse, Mecp2308/Y mouse

Fmr1-null mouse

Mu-opioid receptor KO mice

Brattleboro rats, V1aR KO mice V1bR KO mice, Oxytocin KO mice

Rat pups

Rat pups

Mouse

Mouse

Animal used

Screening models for autism spectrum disorders

S. no.

Table 1

Yes

Yes

–

–

15q11-13

Xq28

Xq27

–

Chromosome 20

No

Mixed

Mixed

Yes

Mixed

Mixed

Yes

–

Avpr1b gene

Yes

Face

Validity

–

Location of chromosome

Yes

Yes

Yes

Yes

Yes

Yes

Yes

–

Maybe

Maybe

Predict

Angleman syndrome

Rett syndrome

–

Yes

Fragile-X syndrome

Altered social interaction and communication problem

Altered social interaction and communication problem

Altered social interaction

Fewer ultrasonic vocalization (communication), less play behavior including pinning, sniffing the partner, crawls over/under the other animal, and partner mounting Increased stereotypic/repetitive behavior, decreased social interaction, altered sensitivity to sensory stimuli, impaired PPI, elevated anxiety, impaired reversal learning, altered eye blink conditioning, and enhanced fear memory processing Impaired school performance, cognitive dysfunction, and an increased incidence of psychiatric disorders

Ultrasonic vocalizations, self-grooming

–

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Construct

Associated characteristics

(Homanics et al. 1997; DeLorey et al. 1998)

(Chahrour and Zoghbi 2007)

(Moy et. al. 2006).

(Silverman et al.2010; Insel 2010; Ross and Young 2009) (Silverman et al. 2010; Insel 2010; Ross and Young 2009) (Frescka and Davis 1991; Sher 1997)

(Bergman et al. 1984)

(Patterson 2009; Schneider et al. 2008)

(Patterson 2009; Dammann and Meyer 2001; Hsiao et al. 2011) (Pinheiro et al.2012)

References


B

A3.5

A3.4

B3.1

A3.10

A3.9

A3.8

A3.7

vA3.6

S. no.

PRICKLE2 mutant mice (prickle planar cell polarity protein 2):PRICKLE2 gene encodes a homolog of drosophila prickle. Exact function of this gene is not known however mice studies suggested that it may involved in seizure prevention. PAX6 KO mouse Paired box 6 gene play a important role in the formation of organs and tissues during embryonic development. Models for genes associated with cell adhesion proteins Neurexin 1: this protein like other neurexin proteins, contains epidermal growth factor repeats and laminin G domains

Neurofibromatosis type 1 (NF1): this gene gives instruction for making a protein neurofibromin. 7-Dehydrocholesterol reductase (DHCR7): DHCR7 gene provides information for making the enzyme 7-dehydrocholesterol reductase. Tuberous sclerosis 1 (TSC1) and tuberous sclerosis 2 (TSC2): TSC1 gene provides information for making a protein hamartin, while TSC2 for producing tuberin. Phosphatase and tensin homolog (PTEN): PTEN gene provides information for making a PTEN enzyme. 22q11.2 deletion syndrome

Models

Table 1 (continued)

11p13

–

Mouse

Mouse

Mice

Homozygous

2p16

Chromosome 16 PRICKLE 1 and 2 gene

– –

10q23.3

–

Mouse

Mouse

9q34,16p13.3

Heterozygous

11q13.4

Heterozygous

Tsc1-null mouse

17q11.2

Heterozygous

Nf1-null, heterozygous, and NF123a−/− mouse Dhcr7-null and heterozygous mouse


Type of model

Animal used

Yes

–

–

–

Yes

Yes

Yes

Yes

Face

Validity

–

–

–

–

Yes

Yes

–

–

Yes

–

Yes

Yes

–

Yes

–

Construct

No

Predict

Normal anxiety related behaviors, locomotor activity, and spatial learning and memory

WAGR syndrome, decreased locomotor, ataxia

Social deficits and enhanced spatial memory

Velo-cardio syndrome

Rett syndrome

Tuberous sclerosis

RSH/Smith-Lemli-Opitz syndrome

Neurofibromatosis-1


(Szatmari et al 2007; Zahir et al. 2008)

(Szatmari et al. 2007)

(Hida et al. 2011)

(Gothelf et al. 2007)

(Napoli 2012)

(Folstein and Rosen-Sheidley 2001)

(Wassif et al. 2001)

(Costa et al. 2001)

References


E

D

C

E3.2

E3.1

D3.1

C3.2

C3.1

B3.5

B3.4

B3.3

B3.2

S. no.

Other genetic models SERT (SLC6A4) (serotonin transporter gene): this gene encodes an integral membrane protein that transports the neurotransmitter serotonin from synaptic spaces into presynaptic neurons.

Genetic models derived from human genetic studies Engrailed 2: homeobox-containing genes have a role in controlling development. Homeobox A1 and A2 (HOXA1 and HOXA2): in vertebrates, the genes encoding the class of transcription factors homeobox genes are found in clusters named A, B, C, and D on four separate chromosomes Genetic models based upon rodent strains BTBR mouse

Contactin-associated protein (CNTNAP2): this protein like other neurexin proteins, contains epidermal growth factor repeats and laminin G domains Cadherin protein: cadherin protein is a class of type 1 transmembrane proteins and have role in cell adhesion. Shank 2: SH3 and multiple ankyrin repeat domains protein 2 encoded by SHANK2 gene. Neuroligin 3: neuroligin 3 gene encodes a member of a family of neuronal cell surface proteins.

Models

Table 1 (continued)

SERT-null and heterozygous mouse

Mouse

En1 and En2 (engrailed) null mouse Hoxa1-null mouse

Mouse

Homozygous

Heterozygous

Yes

Yes

–

–

Yes

Yes

–

Yes

No

–

Yes

Yes

Yes

–

Yes

–

–

Yes

Yes

–

–

–

–

No

Yes

–

Yes

Yes

Construct

Predict

Face

Validity

17q11

–

7p15.3,7p15.2

Homozygous

Homozygous

7p15

Xq13.1

11q13

16q22

7q35


Homozygous

Homozygous

Heterozygous

Homozygous

Mouse

Mouse

Homozygous

Type of model

Mouse

Animal used

–

Decrease in ultrasonic vocalizations, decreased social interaction

Low sociability, communication impairment and stereotype or repetitive behaviors

Asperger syndrome

Rett syndrome

With less anxious, decrease juvenile play, deficits in sensory motor gating and increased preservation behavior

Ultrasonic vocalizations (USVs), social interaction, and display repetitive behavior Down’s syndrome, Fragile-X syndrome

Altered social interaction, restricted and repetitive behavior


(Schain and Freedman 1961; Mulder et al. 2004)

(Amaralet et al. 2008; Silverman et al. 2010)

(Borzychowski et al. 2006; Gupta and State 2007) (Studer et al.1998)

(Chih et al. 2004; Comoletti et al. 2004; Laumonnier et al. 2004)

(Won et al. 2012)

(Winslow et al. 2000; DeLorey et al. 2008)

(Winslow et al. 2000; DeLorey et al. 2008)

References


6.2

Nonhuman primate model Neonatal amylgdala lesion in Rhesus monkey Maternal autoantibody model in rhesus monkey

6.1

6

Neonatal infection model Borna virus model

Humanoid model

4.1

MAO-A-null mouse

Monoamine oxidase-A (MAO-A): MAO-A encode mitochondrial enzymes which catalyze the oxidative deamination of amines. RELN (Reelin gene) The RELN gene provides instruction for making a protein called reelin . it produce in brain before and after birth. FOX P2(−/−) mice FOX P2 gene encodes a member of the forkhead/winged-helix (FOX) family of transcription factors.

Rhesus monkey

Rhesus monkey

Mouse

Rat

Mice

Reeler mutant mice

Animal used

Models

5

4

E3.4

E3.3

S. no.

Table 1 (continued)

– –

–

15q11-13

–

7q31

7q22


–

Homozygous

Heterozygous

Type of model

Yes (high)

Yes

Yes

Possibly yes

–

–

–

Average

No

Predict

No

Face

Validity

Yes (high)

Yes

Yes

Average

Yes

Yes

Construct

Less overall activity, exploration of the test environment Whole body stereotype

Social play deficits, cognitive deficits, development and regional abnormalities Developmental abnormalities and anxiety

Difficulty in learning to produce the vocal movements needed for speech, as well as extensive other language deficits

–


(Bauman et al. 2010; Bachelevier 1994) (Adolphs 2010; Martin et al. 2008)

(Takumi 2010)

(Netsler and Hymen et al. 2010)

(Mac Dermot et al. 2005; Mulder, et al. 2004)

(Fatemi 2005; Liu et al. 2001)

(Schain and Freedman 1961; Mulder et al. 2004)

References


Rev J Autism Dev Disord Table 2

Behavioral assays for screening of autism spectrum disorders

S. no.

Behavioral assays

A

Inappropriate social interactions Social approach to a stranger mouse; reciprocal social interactions; conditioned place preference to conspecifics; preference for social novelty; social recognition Juvenile play; nesting patterns in the home cage; resident intruder interaction Partition test; social transmission of food preference B Impairments in social communication Behavioral responses to social olfactory cues from conspecifics; deposition of social olfactory pheromones; vocalizations emitted during social interactions; responses to vocalizations from conspecifics; parental retrieval of separated pups; ultrasonic vocalizations by separated pups C Repetitive and restrictive behaviors Motor stereotypes, including circling, jumping and back flips; preservative hole board exploration; extinction of a learned response in an operant chamber; reversal of a position habit in an appetitive T-maze task; reversal of a position habit in an appetitive Y maze task; reversal of a position habit in the Morris water maze; spontaneous responses to errors during reversal tasks; nose poke, hole board test Associated symptoms and behavioral tests for mice A

B C D

E

F

G

H

I

J

K

Seizures Sensitivity to audiogenic seizures; sensitivity to drug induced seizures; observer scoring; electroencephalography (EEG) recordings Motor clumsiness Balance beam foot slips; rotarod motor coordination and balance; footprint analysis Aggression Resident intruder attack; Isolation induced fighting; tube test for social dominance Sleep disturbances Circadian running wheels; videotaped observations of home cage sleep and activity patterns; EEG recordings Hypersensitivity and hyposensitivity to sensory stimuli Acoustic startle; tactile startle; hot plate; Von Frey hairs; attentional neglect tape test; unresponsiveness to sensory attentional cues (failure to disengage attention) Brain overgrowth Brain weight, volume, size of structures, and pathways; measurements at neonatal, juvenile, and adult time points Developmental progression Developmental milestones in neonates; repeated testing of all relevant behaviors at juvenile and adult ages Home cage observation; novel object test; behavior in an open field; marble burying test; self-grooming assay; exploratory locomotion in a novel open field; sniffing of novel objects

Anxiety Elevated plus maze; light ↔ dark exploration; Vogel conflict test; acoustic startle; ultrasonic vocalizations; marble burying; foot shock induced freezing Theory of mind deficits Location of buried food following observation of conspecifics; social transmission of food preference task; avoidance of aggressive encounters Intellectual disability Acquisition of Morris water maze tasks; acquisition of T maze tasks; contextual and cued fear conditioning; operant learning tasks; attentional measures on five choice serial reaction attentional task; hidden platform task; radial arm maze; active avoidance; passive avoidance

References (Silverman et al. 2010; Vogel 2002; Mathiasen and Dicamillo 2010)

(Silverman et al. 2010; Vogel 2002)

(Silverman et al. 2010; Vogel 2002; Rossi and Yin 2012; Bertholet and Cruscio 1991; Givens et al. 1992; Henderson 1972; Paylor et al. 1993; Wenk et al.1984; Brioni and McGaugh 1988)

(Silverman et al. 2010)

(Silverman et al. 2010) (Silverman et al. 2010) (Silverman et al. 2010; Vogel 2002)

(Vogel 2002)



(Hsiao et al. 1996; Mathis et al. 1991; Morris 1981; Morris et al. 1982; Gage et al. 1984; Vogel 2002; Bell et al. 2003; Wu and Melton 1993; Presti et al. 2003; Yan et al. 2004; DeLorey et al. 1998; Turner et al. 2001; Silverman et al. 2010; Mehta et al. 2011) (Walf and frye 2007; Vogel 2002; Heinrichs and Koob 2005) (Silverman et al. 2010)

(Vogel 2002; Bertholet and Cruscio 1991; Givens et al. 1992; Henderson 1972; Paylor et al. 1993; Wenk et al. 1984; Rossi and Yin 2012; Sago et al. 1998; Lalonde et al. 2004; Mineur et al. 2002; Yan et al. 2004; DeLorey et al. 1998)


such as increased stereotyped/repetitive behavior, decreased social interaction, altered sensitivity to sensory stimuli, elevated anxiety, impaired reversal learning, altered (enhanced) eyeblink conditioning (Stanton et al. 2007; Patterson 2011), and enhanced fear memory processing, all of which are consistent with ASD in humans (Schneider et al. 2008; Patterson 2009). It is interesting that maternal VPA exposure leads to reduced expression of neuroligin (an ASD candidate gene) in experimental subjects (Kolozsi et al. 2009). Electrophysiological studies indicate that VPA offspring exhibit abnormal microcircuit connectivity (Rinaldi et al. 2008), which may be related to MRI studies showing impaired long-range functional connectivity in individuals with ASD. There are also immune abnormalities such as decreased weight of the thymus, decreased splenocyte response to stimulation, and a lower IFNγ/IL-10 ratio. Most of these abnormalities are found only in male offspring, which is consistent with the male bias in ASD incidence (Schneider et al. 2008). Terbutaline-Induced ASD When terbutaline crosses placenta (Bergman et al. 1984) and by overstimulating β2-adrenoceptor (β2ARs) in the fetal brain, they can disrupt the replication and differentiation of developing neurons (Slotkin et al. 2001). The use of terbutaline by the women during pregnancy showed impaired school performance, cognitive dysfunction, and increased incidence of psychiatric disorders in the offsprings (Feenstra 1992; Pitzer et al. 2001). Animals treated with terbutaline on postnatal 2 to 5 showed consistent patterns of hyperreactivity to novelty and aversive stimuli when assessed in a novel open field, as well as in the acoustic startle response test. Overstimulation of the β2AR by terbutaline results in microglial activation associated with innate neuroinflammatory pathways and behavioral abnormalities. Postnatal β2AR stimulation by terbutaline can provide a useful animal model for ASD to facilitate understanding of neuropathology in this disorder and to develop potential future treatments (Connors et al. 2005). However, the same has not been exploited to its full and needs to be explored further.

Mutated Neuropeptide Models The pharmacological and genetic manipulations of oxytocin (OT) and vasopressin (AVP) have established the importance of these neuropeptides in the regulation of complex social behaviors. Moreover, functional alterations in these systems may contribute not only to social deficits of ASD but also to repetitive behaviors (Ross and Young 2009; Insel 2010). In addition to this, researchers reported that peptides having opioid activity may involve in pathogenesis of ASD. Panksepp firstly observed that there are few similarities between the features of ASD and long-term effects of morphine like reduced social

contact, declined pain sensitivity, insistence on sameness, and delayed developmental milestones (Panksepp 1979). OT and AVP KO Mice OT and AVP are two neuropeptides that play crucial roles in reproductive, social, and adaptive behaviors. Among their firmly established roles in mammals, there is the ability of OT and AVP to make individuals to remember previously met individuals, i.e., a form of social recognition that is essential to establish all complex relationships. The gene for AVP and OT are located on 20p11-12, and a single critical mutation could influence the expression of both (Ross and Young 2009; Silverman et al. 2010; Insel 2010). The OT and AVP KO mice reflect, impairment in social recognition has been observed confirming that the OT/AVP system is crucially involved in the processing of socially relevant cues. Thus, the OT/AVP system may represent a common end point at which several genetic alterations converge to produce the disturbance of social behavior, that is the hallmark of ASD (Ross and Young 2009; Insel 2010). Opioid The opioid excess theory says that children with ASD are symptomatic due to excess opioid-like substances, whose effects on the brain can produce the symptoms of autism. Opioids and opioid-like substances, especially when in excess, exert many effects upon hormones and hormonal regulation. A number of researchers have suggested that excessive brain opioid activity could explain the purported decreased pain sensitivity observed in ASD and contribute to or even determine the pathogenesis of ASD (Frescka and Davis 1991; Sher et al. 1997). The opiate addicted animals exhibit less sensitivity to pain, less emotional status with stereotyped behaviors, and social interaction impairments, the features of ASD. The animals have also demonstrated reversal of ASD symptoms following administration of naloxone (Wimersma Greidanus et al. 1988). However, the predict validity of these animal models remain to be ascertained, considering the inconsistent results of studies measuring opioid levels (Tordjman et al. 1997) and the absence of clear benefits of opiate antagonist therapies (naloxone or naltrexone) in individuals with ASD (Sandman et al. 1991; Sandman 1992; Willemsen-Swinkels et al. 1995). In fact, one study even found that naltrexone actually increased stereotyped in ASD (Willemsen-Swinkels et al. 1995).

Genetic Models The etiology of ASD is poorly understood; however, involvement of strong genetic component is evident from the 70 to


80 % concordance between identical twins. Various genes like FMR1, MECP2, tuberous sclerosis (TSC) 1, TSC2, HOXA-1, HOXA-2, RELN, MAO-A, WNT-2, NF1, 3β-hydroxysteroid Δ7-reductase (DHCR7), and SERT have been identified to be linked with ASD (Moy et al. 2006). The genetic linkage has been very well exploited by targeted disruption or mutation of a specific gene to develop various models for ASD. Due to large numbers of associated loci with ASD, the most common strategy for genetic modification is by generating a null allele or target disruption, which a portion of locus is disrupted and thereby form a nonfunctional protein. The other strategy is to design an allele, associated with disease in humans. The genetic mouse models discussed below are both targeted disruption based and disease associated allele based. FMR-1 KO Mouse The FMR1-KO mouse displays some core behavioral features of ASD and is considered to be one of the best animal models for ASD. Fragile-X syndrome is caused by mutations on the X chromosome of gene fragile X mental retardation 1 (FMR-1). The disorder shares a number of associated features in common with ASD, intellectual disability, attention deficit hyperactivity disorder, and epilepsy as associated behavior in ASD. The fragile X leads to sever reduction in FMR1 protein expression which plays a role in RNA binding and transition regulation. Fmr1 KO mice display some behavioral features of ASD including impaired social interaction and repetitive behavior along with cognitive and spatial learning deficits (Moy et. al. 2006). MeCP 2 Mutant Mice Rett syndrome (RT) is another genetic disorder that maps on X chromosome, like fragile X syndrome. The disorder is mostly prevalent in females and is marked by ASD-associated features, like severe intellectual disability, slowed growth rate, seizures, and hypoactivity and features characteristic of RT such as stereotyped hand movements, abnormal breathing, motor deficits, and scoliosis. The mutations in methyl-CpGbinding protein (MeCP2) accounting for majority of cases causing the disease are in the gene MeCP2. The allele found in the patient including either a missense mutation CP2 protein is associated with the two global methods of transcriptional repression, i.e., protein binding to methylated CpG islands in genomic DNA and histone deacetylation. In the female mouse model of MeCP2 disruption, the mice appear normal until about 16 weeks of age (a mouse typically is mature by 4 weeks and dies at 2–3 years). Behavioral deficits in these mice include enhanced anxiety in the open field, reduced nest building, and aberrant social interactions. Genetic background modifies learning and memory performance also (Chahrour and Zoghbi 2007). Mice overexpressing MeCP2

also develop a progressive neurological disorder with, surprisingly, an enhancement in synaptic plasticity, motor, and contextual learning skills between age 10 and 20 weeks, and, at an older age, hypoactivity, seizures, and abnormal forelimb clasping, all of which are reminiscent of human RT syndrome (Chahrour and Zoghbi 2007). GABRB3-Deficient Mice Impairment of GABAergic transmission contributes to the development of ASDs. GABA is the main inhibitory neurotransmitter in adulthood and is released by interneurons which contain the GABA-synthesizing enzymes glutamic acid decarboxylase (GAD) and GAD67 (IMGSAC 2001). Dysfunction of GABAergic signaling mediates ASD-like stereotyped in the majority of animal models and is obtained by experimentally manipulating candidate genes for ASD susceptibility or environmental risk factors. Mice lacking the GABA receptor subunit β3 (GABRB3) display high mortality rate and symptoms consistent to Angelman’s syndrome, including learning and memory deficits, poor motor skills, stereotyped behaviors, and seizure susceptibility (Homanics et al. 1997; DeLorey et al. 1998). More recently, GABRB3 gene deficient mice have been shown to exhibit impaired social and exploratory behaviors, deficits in nonselective attention, and hypoplasia of cerebellar vermal lobules, thus resembling a wide range of ASD phenotypes (DeLorey et al. 2008). NF1 KO NF1 KO mice are a model for neurofibromatosis (a genetic neurodevelopmental disorder that leads to nerve tumors, memory problems, and often, ASD) exhibits deficits in social interaction and social learning (Costa 2002). NF1-KO mice through several behavioral tests are observed to have the most dramatic difference with control mice in a test of Bsocial learning.^ Further, mice carrying a specific allele of Nf1 show deficient social transmission of food preference, impaired fear conditioning, spatial learning, and retarded acquisition of motor performance on a rotarod, but without the increased tumor incidence (Costa et al. 2001). DHCR7 Null Mouse DHCR7, the enzyme required for the terminal enzymatic step of cholesterol biosynthesis and the deficiency leads to SmithLemli-Opitz syndrome is an intellectual disability/ malformation syndrome with behavioral components of ASD. Dhcr7 gene modification (Dhcr7–/–) results in neonatal lethality and multiple organ system malformations (Wassif et al. 2001).


TSC Null Mouse

Neurexin 1α KO Mouse

TSC is a genetic disease caused by mutation in either one of the two genes, TSC1 and TSC2. Cerebellum has been identified as a key area where the link between TSC and ASD resides. Deleting TSC gene in animals produces signs of ASD symptoms including abnormal social interaction, repetitive behavior, and abnormal communication (Folstein and Rosen-Sheidley 2001).

Neurexin 1 is part of a three-member family of genes coding for proteins involved in communication between neurons. It is associated with glutamate, the neurotransmitter known to elevate neuronal activity and play a role in early wiring of the brain. The model contains a biallelic deletion of the neurexin 1 (Nrxn1) gene, and the same has been associated with ASD. The model is useful for understanding the role of neurexins in the development of ASD. The properties of neurexins suggested that they function as synaptic recognition molecules (Ushkaryov et al. 1992) and mediate transsynaptic interactions via binding to neuroligins (Ichtchenko et al. 1995). Copy number variations in the neurexin-1α gene (but not the neurexin-1β gene) were repeatedly observed in patients with ASDs (Szatmari et al. 2007; Zahir et al. 2008). The neurexin1α KO mice demonstrate normal anxiety-related behaviors, locomotor activity, spatial learning, and memory. Their motor learning abilities are significantly enhanced. The mice is also observed with large increase in repetitive grooming behaviors, indicating an abnormality with face validity, impaired sensory motor gating, and impairment in nest-building behaviors (Etherton et al. 2009).

PTEN Mutant Mice Phosphatase and tensin homolog on chromosome 10 (PTEN) is a protein encoded by PTEN gene which is a tumor suppressor gene. Defects in the PTEN gene have been sighted to be a potential cause of ASD. Hampered energy production in neurons has been reported when defective PTEN gene interacts with the protein of P53 gene. This leads to mitochondrial DNA damage and abnormal level of energy production in the cerebellum and hippocampus brain regions critical for social behavior and cognition (Napoli et al. 2012). Recently, a transgenic mouse line has been generated in which PTEN expression is cleverly deleted in restricted populations of neurons in the cerebral cortex (layers III–V) and dentate gyrus (granular layer and polymorphic layer) of the hippocampus (Kwon et al. 2006). These PTEN mutant mice display deficits in a wide range of social interaction and learning assays including social interaction/learning, nest building, social preference test, and caged social interaction (Kwon et al. 2006). These deficits in social interaction and social learning are reminiscent of those observed in subject of ASD, which suggest that these animals have good face validity as a model of symptoms in the ASD social domain. Interestingly, PTEN mutant mice also exhibit neuroanatomical abnormalities that are hallmarked by a phenotype of progressive macrocephaly (Kwon et al. 2001).

Tbx1 Heterogenous Mice Congenic Tbx1 heterozygous mice exhibit lower levels of active and passive affiliative social interaction. Congenic HT mice are impaired in affiliative social interaction at 2 months of age without confounding alterations in aggression, olfactory investigation, or motor behavior. Alternatively or additionally, Tbx1 deficiency has demonstrated to alter prenatal/postnatal/adult neurogenesis. When individuals with 22q11.2 hemizygosity reach adulthood, defective working memory is worse in those with schizophrenia than in those without it (Van Amelsvoort et al. 2004). Higher and increasing levels of anxiety are a risk factor for later developing schizophrenia in 22q11.2 cases (Gothelf et al. 2007).

CNTNAP2 KO Mouse The contactin-associated protein like 2 (CNTNAP2) is a member of the neuronal neurexin superfamily that is involved in cell-to-cell interaction and is associated with specific language improvement and ASD. It is likely to play an important role in brain development (Alarcon et al. 2008). It is intriguing that CNTNAP2 expression is elevated in circuits in the human cortex that are important for language development. In addition, CNTNAP2 polymorphisms are associated with language disorders, and the expression of this gene can be regulated by FOXP2, mutations in which can cause language and speech disorders (Panaitof et al. 2010). In light of these associations, a CNTNAP2 KO mouse model has been developed with strong association between ASD and allied neurodevelopmental disorders. CNTNAP2 KO mouse shows deficits in communication (USVs) and social interaction and display repetitive behavior. These mice also exhibit several other features of ASD like seizures, mild cortical laminar disorganization, and hyperactivity. The CNTNAP2 KO mouse model of ASD shows striking parallels with human disease and is a new tool for mechanistic and therapeutic research in ASD (Vernes et al. 2008). SHANK-2 Mutant Mouse Shank 2 (also known as ProSAP1) is a multidomain scaffolding protein and signaling adaptor enriched at excitatory neuronal synapses. Mutations in the human SHANK-2 gene have


recently been associated with ASD and intellectual disability (Patterson 2011). Shank 2-mutant (Shank2−/−) mice carrying a mutation identical to the ASD-associated microdeletion in the human SHANK-2 gene exhibit ASD-like behaviors including reduced social interaction, decreased social communication by ultrasonic vocalizations, and repetitive jumping. These mice show a marked decrease in N-methyl- D -aspartate (NMDA) glutamate receptor (NMDAR) function. Shank2−/− mice showed impaired spatial learning and memory in the Morris water maze test, impairments in social communication in USVs, and other ASD-like abnormalities like enhanced jumping mostly mixed with upright scrabbling, normal grooming, and decreased digging behaviors impaired nesting behavior, hyperactivity in assays including the open field test, anxiety-like behavior in an elevated plus maze, and increased grooming in a novel object recognition arena (Goddard et al. 1996). NLGN3 KO Mouse Neuroligin (NLGN) 3 gene is encoded by neuroligin 3 protein, a neuronal cell surface protein. Neuroligin is involved in the formation and remodeling of central nervous system synapse and are site-specific ligand for beta neurexin. Loss of function mutations in NLGN3 and NLGN4 have been found in affected siblings with ASD, and these genes have been proposed to cause rare monogenic forms of ASD (Chih et al. 2004; Comoletti et al. 2004; Laumonnier et al. 2004). Neurexins, the binding partners for neuroligins, have also recently been implicated as ASD susceptibility genes; a knockout mouse approach has been employed to study the role of neuroligins in synapse formation and function. NLGN3 KO rats exhibit complete loss of target protein (NLGN3) with less anxious, decrease juvenile play, deficits in sensory motor gating, and increased preservation behavior. It would be worthwhile to mention that neuroligin 2 overexpressing transgenic also displayed stereotyped jumping, enlarged synaptic contact, and reduced GABA clustering along with anxiety-like behavior (Etherton et al. 2009). En2 KO Mouse Engrailed 2 (En2) is one of the most strongly linked gene to ASD. En2 encodes the protein involved in the development of cerebellum. Mice with the poor expression of En2 exhibit abnormalities in cerebral circuits and cell membranes (Gupta and State 2007). En2 gene is located in a chromosomal region that is frequently abnormal in individuals affected with ASD. Consistent with this, En2 KO mice display cerebellar hypoplasia, a reduction in the number of Purkinje neurons in the cerebellum and foliation defects, all of which is a parallel features observed in ASD. En2 KO juvenile males display a reduction in play behavior, social interaction, and

allogrooming compared to wild types. The differences in social behavior are reduced in adults; however, adult KO males display increased levels of autogrooming (repetitive) behavior. Deficits in spatial learning and memory tasks were detected in En2 KO mice as well. Thus, the En2 KO mouse model displays both face (social behavior disruption) and construct (cerebellar defects, genetic risk factor) validities. However, the model does not presently suggest potential pharmacological interventions to reverse these deficits (Borzychowski et al. 2006).

HOXB1 Mutant Mice The HOXB1 gene, located on human chromosome 17q21.32, is a member of the HOX gene family of homeobox transcription factors and is critically involved in the development of the brain stem. HOXB1 gene expression is limited to rhombomere 4 and to neural crest cells migrating out of this region, resulting in a gross reduction or complete loss of the facial motor nucleus in HOXB1 mutant mice (Goddard et al. 1996; Studer et al. 1996). HOXB1 gene expression occurs very early in mouse development, at a time, interestingly, overlapping with the window of maximal prenatal sensitivity in rodent models of ASD (Courchesne 1997). HOXB1 gene expression is also strongly upregulated by HOXA1 (Studer et al. 1998) and the two genes indeed synergize in patterning hindbrain structures, cranial nerves, and pharyngeal arches, so that double-mutant mice display prominent malformations while single mutants suffer much milder abnormalities (Studer et al. 1998). A gene-to-gene interaction between HOXB1 and HOXA1 gene variants was initially proposed to contribute to ASD (Ingram et al. 2000).

BTBR Mouse The BTBR mouse strain shows phenotype relevant to the diagnostic symptoms of ASD, i.e., low sociability, communication impairment, and stereotypical or repetitive behaviors. BTBR pups emit more and longer ultrasonic vocalization. Their repertoire of vocalization is also narrower in comparison to pups from standard mouse strains. BTBR mice are associated with high blood levels of corticosterone accounting for the exaggerated response to stress (Benno et al. 2009). Such enhanced stress could cause or aggravate the behavioral phenotype of these mice. Anatomically, BTBR mice lacks of the corpus callosum and a reduced hippocampal commissure (Silverman et al. 2010). Overall, a number of BTBR mouse behaviors are consistent with autism, and the most striking anatomical feature in this strain is consistent with many, but not all, studies of the corpus callosum in ASD (Amaral et al. 2008).


5-HT Transporter (SERT) Ala56 Mice Hyperserotonemia or increased whole blood serotonin [i.e., 5hydroxy-tryptamine (5-HT)] is a well-replicated biomarker that is present in approximately 30 % of subjects with ASD (Schain and Freedman 1961; Mulder et al. 2004). The SERT gene (SLC-6A4) has been associated with whole blood 5-HT levels and ASD susceptibility. A genome-wide study of whole blood 5-HT as a quantitative trait found association with the SERT encoding gene SLC-6A 4, as well as with ITGB-3, which encodes the SERT-interacting protein integrinβ3. In both cases, the strongest evidence for association was found in males (Weiss et al. 2004, 2005; Carneiro 2008). Linkage studies in ASD also implicate the 17q 11.2 region containing SLC-6A 4, with stronger evidence in males (Sutcliffe et al. 2005). The potential parallels of ASD-associated deficits in the SERT Ala56 mice have been observed, such as decrease in ultrasonic vocalizations, decreased social interaction, and modest enhancement in the startle response during prepulse inhibition tests and rigid compulsive behavior. REELER Mouse The RELN locus encodes a large glycoprotein that acts as a serine protease of the extracellular matrix (Fatemi 2005). REELER is an autosomal recessive mutant mouse with impaired motor coordination, tremors and ataxia, cortical lamination, abnormal positioning of neurons, and aberrant orientation (Falconer 1951). Analysis of the central nervous system in the mutant mouse revealed multiple defects such as inverted cell bodies and fibers. The REELER mouse has been linked with ASD along with other neuropsychiatric disorders including schizophrenia, bipolar disorder, and depression (Fatemi 2001). Nevertheless, REELER mouse has been extensively used as a mouse model for ASD. In addition to the abovementioned motor defects, REELER mouse also demonstrated increase in anxiety, stereotyped behavior, social dominance, and learning deficits (Lalonde et al. 2004). Heterozygous REELER mice were also found to have decreased dendritic spine density (Liu et al. 2001) and reduced levels of oxytocin receptors in the brain (Liu et al. 2005). PRICKLE2 Mutant Mice The researchers found that mice lacking PRICKLE-2 have social deficits and enhanced spatial memory, which is involved in the development of synapses, the junctions between neurons (Hida et al. 2011). Around the same time, a team of collaborators found mutations in PRICKLE-2 and a related gene, PRICKLE-1, in people with myoclonus epilepsy, characterized by muscle twitching (Tao et al. 2011). PRICKLE-2 has been shown to be expressed all over the mouse brain, but especially in the hippocampus, a region important for learning

and memory (Tao et al. 2011). Using the Bthree-chamber^ social test, the researchers also showed that unlike controls, the PRICKLE2 mutants spend significantly less time inspecting a new mouse than a new object. PAX6 KO Mice PAX6 is a pivotal player in brain development and maintenance. It is expressed in embryonic and adult neural stem cells, in astrocytes in the entire central nervous system, and in neurons in the olfactory bulb, amygdala, thalamus, and cerebellum, functioning in highly context-dependent manners. Human PAX6 gene is originally identified in chromosomal region 11p13 as one related with WAGR (Wilm’s tumor, aniridia, genitourinary malformations, and intellectual disability) syndrome which is a rare genetic disorder caused by chromosomal deletion of the 11p12-p14 region. Recent studies have identified PAX6 mutations in individuals who manifest intellectual disability, aniridia, and ASD. Furthermore, chromosome 11p13, on which PAX6 is located, is implicated as a possible locus for ASD susceptibility by a linkage study (Szatmari et al. 2007). Pax6c KO mice demonstrated a decreased locomotor activity and ataxia due to defects in motor performance and prefrontal deficits. FOXP2 Mutant Mice No mutations in the gene coding region of FOXP2 have been directly linked to ASD, but the gene appears to regulate other genes, such as CNTNAP2 and MET, which have been associated with the disorder (Kurt and fisher 2012). Two genetically engineered strains of mice, each carrying a different FOXP2 mutation were developed recently. One strain carried the genetic glitch producing an error in a segment of the FOXP2 protein that binds to DNA. The strain has difficulty in learning to produce the vocal movements needed for speech, as well as extensive other language deficits. The mutation in the second strain was marked by a shortened version of the protein that disrupts its function altogether and was identified in another family with even more severe language deficits. Both mutant strains of mice have motor learning deficits, trouble in mastering the auditory-motor association, impairments in learning of motor skills, and loss of exploratory behavior, the features of ASD (Schain and Freedman 1961; Mulder et al. 2004; MacDermot et al. 2005).

Neonatal Infection Models: Borna Virus Rodent Models Borna disease virus (BDV) is an extremely neurotropic virus that causes persistent and nonlethal infection of neural cells. BDV is an enveloped, nonsegmented, negative-sense, single


standard RNA virus of family Bornaviridae with in Mononergavirales order. It causes wide spectrum of neurological disorders in wide range of vertebrates. Lewis rats infected with BDV at birth survive because they fail to develop classical antivirus cellular immune response to virus replication in the brain. The pathological outcomes of neonatal BDV infection include defects in the cerebellum and limbic system, hyperreactivity, circadian rhythm disturbance, social play deficits, cognitive deficits, chronic anxiety, and developmental and regional abnormalities in serotonin and norepinephrine concentrations (Briese et al. 1994; De la Torre et al. 1996; Rubin et al. 1998; Carbone et al. 1991; Bautista et al. 1994, 1995; Pletnikov et al. 1999a, b, 2000, 2001, 2002; Hornig et al. 1999).

Humanoid Model for Autism Evidence suggested that abnormalities in chromosomes contribute to the risk of ASD and the duplication of human chromosome 15q11-13 is most commonly involved in ASD. The humanoid model for ASD is generated by interstitial duplication in mouse chromosome 7c that is highly syntenic to human 15q11-13 by using a Cre-loxP-based chromosome engineering technique. It is the first chromosome engineered mouse model for human chromosome 15q11-13 duplication that fulfills not only the face validity of human ASD phenotypes but also construct validity based on human chromosome abnormality. This model will be a founder mouse model for forward genetics of ASD and an invaluable tool for its therapeutic development (Tatkumi et al. 2010).

Nonhumanoid Primate Models Nonhuman primates share many features of human physiology, anatomy, and behavior; thus, it forms an ideal species to study a variety of human disorders like ASD, Parkinson’s disease, and Alzheimer’s disease, although it is in very early stages of developing valid animal models of ASD have an important role in understanding the ASD emergent of treatment and prevention strategies. Nonhuman primates such as rhesus macaques (Macaca mulatta) share 90–93 % alignment of nucleotide sequences with humans. The advantage with this model lies in similarities with human physiology, anatomy, and complex social behavior (Bauman et al. 2010; Capitanio and Emborg 2008; Burns et al., 1983).

resulting in damage to amygdala and surrounding cortex (Bachevalier 1994). When placed in social pairs, the neonatal amygdala-lesioned infants showed less overall activity, exploration of testing environment and social behavior initiation as compared to age-matched controls (Bauman et al. 2010). However, the model does not demonstrate high face and construct validity (Adolphs 2010). Maternal Autoantibody Model Recent research has suggested that certain forms of ASD are associated with maternal autoantibodies directed against fetal brain tissue proteins. Amaral and colleagues have evaluated this model in Rhesus monkey (Martin et al. 2008). Behavioral observations of monkeys prenatally exposed to purified IgG from mothers of children with ASD showed more whole body stereotyped than untreated control monkeys and monkeys prenatally exposed to purified IgG from mother of typically developing children (Bauman et al. 2010). This model shows high construct validity, moderate face validity, and if proved successful, it could also demonstrate high predict validity as the same is under development.

Zebrafish Zebrafish model is widely used for understanding the field of developmental biology (Dawid 2004; Halpern et al. 1995; Hanneman et al. 1988; Vesterlund et al. 2011; Weis 1968), although it is not so popular model for understanding the ASD as mouse model while fast oogenesis and embryo development allows rapid experimental assays. Additionally, transparency of embryo and development of embryo outside the mother body allows for the study of growth and development of brain cell and tissues in the living embryo (Tropepe and Sive 2003). Zebrafish have similar kind of structural and functional region as in ASD patient, so it is an outstanding model used to disclose the genes involved in ASD, but the behavioral phenotypes associated with ASD are difficult to recapitulate (Dooley and zon 2000). Henceforth, other models are useful for study the behavioral phenotypes associated with ASD. Many ASD genes such as DISC1, CHD8, MET, AUTS2, FMR1, SYNGAP1, and SHANK3 are studied in zebrafish (Elsen 2009; De Rienzo et al. 2011; Bernier et al. 2014; Gauthier et al. 2010).

Songbirds Neonatal Amygdala Lesions The nonhuman primate models of ASD developed by Bachevalier was primarily based on study of six peer reared monkeys that received aspiration lesions of amygdala,

Communication problem (both verbal and nonverbal) is the core characteristic in children with ASD. Understanding the vocal learning by the songbirds appears as an excellent model to study the stereotype aspect of ASD. Songbird model can be


used both as a molecular and a behavioral model to understand the human speech and language development (Banerjee et al. 2014). Mutation in a FOXP2 gene is related to speech and language disorder, and the distribution of FOXP2 gene is remarkably similar as in the brain of both human and songbird, mainly in the subregions responsible for the learning and production of vocalization. CNTNAP2 gene is involved in human language-related circuits (Alarcon et al 2008) and plays important role in vocal communication in human as well as songbirds (Panaitof et al 2010). In the lack of models for vocal communication, this model might play very crucial role in

understanding the cellular and molecular mechanism behind the language development in the human.

Fig. 1 Overview of autism spectrum disorders. TS tuberous sclerosis, ReTT Rett syndrome, Avrp1 vasopressin receptor, Cadps2 calciumdependent secretion activator 2, Gabrb3 GABA A receptor beta3 subunit, Oxtr oxytocin receptor, Slc6a4 solute carrier family 6, member

4 (serotonin transporter), CNTNAP2 contactin-associated protein 2, EN 2 engrailed-2, Met tyrosine kinase/hepatocyte growth factor receptor, Foxp2 Forkhead box protein 2, PTEN phosphatase and tensin homolog, CAM complementary and alternative therapies

Behavioral Manifestations of ASD and Respective Screening Assay The Diagnostic and Statistical Manual for Mental Disorders (DSM) in May 2013 published DSM-V supersending DSMIV-TR. Within DSM-V, diagnoses classified as autism, Asperger syndrome, PDD-NOS, and childhood disintegrative


disorder are generalized as ASD. As per DSM-V, the symptomatic features of ASD are classified into two major domains a brief outline of the domains associated with ASD is enumerated in Fig. 1. The symptoms of domain I concerned with impairments in social relations and social communication .A battery of behavioral assays are available to screen the domain I, including reciprocal social interaction, social transmission of food preference, social approach to stronger mouse, vocalizations during social interaction, parental retrieval of separated pups, deposition of social olfactory pheromones, etc. (Table 2). The symptom domain II is concerned with restrictive interests and repetitive behaviors or activities. Individuals with ASD have preoccupations, which could be of abnormal intensity. The repetitive behaviors are also associated with self-injury-associated features like pocking own eye, skin picking, hand biting, hand banging, and head banging (Fig. 1). This domain includes behavioral assays as more stereotyped, including circling, jumping and back flips, preservative hole board exploration, etc. (Table 2). In addition to the two core symptom domains, there are a number of symptoms associated with ASD. In particular, anxiety, hyperactivity, short attention span, irritability, mood instability, aggression, self-injurious behavior, and poor impulse control and in addition, sensory sensitivities as to sound, sight, smell, taste, or touch certain stimuli is also associated with ASD. The associated symptoms for ASD are screened as per the subdomains. The symptoms like anxiety, mind deficits, and intellectual disability can be screened using elevated plus maze test, vogel conflict test, and many more. In fact, the screening is entirely dependent on the type of the subdomains to be explored. Some of the widely employed screening methods and their respective domain are listed in Table 2.

Discussion Mouse models are cardinal to advance understanding of the mechanistic basis of ASD, as well as to test potential therapies. There is a growing list of models with good construct validity meaning that they carry a mutation in a known risk gene, face validity, or bearing some physical or behavioral resemblance to the human disorder. There are number of difficulties in developing animal models with simultaneous face, construct, and predictive features of autism. One of the constrains associated with the development of a suitable model for ASD are lack of objective biomarkers and divergent pathogencity of the disorder. Another noteworthy constrain is deficiency in social interaction and communication which can only be approximated in rodent model. As already altercated, there is difficulty in concluding large behavioral diversities in single model and participation of numerous genes makes it more troublesome. No pathogenic feature of ASD can be assayed, and there are constrains in assessing social

communication in primates as well. Quantitative measurements of reward value of social interaction are yet to be modeled. However, the advantages associated with mouse models are cost-effectiveness, short gestation period, large number of litters, time effectiveness, and rapid results. At the same time, it is worthwhile to mention that mouse models show low face validity and poor construct validity due to chartless etiology. Alignment of nucleotide sequences in rodents is entirely different from humans; therefore, predict validity is low as well. Another major disadvantage with mouse model is prefrontal cortex (a major ASD affected area) is poorly developed in rodents. Acknowledgments All the authors are thankful to the University Grants Commission, India. Compliance with Ethical Standards Conflict of Interest The authors declare that they have no conflict of interest. Research Involving Human Participants and/or Animals This article does not contain any studies with human participants or animals performed by any of the authors. Informed Consent Informed consent is not required since the review article does not contain any studies with human participants or animals.

References Adolphs, R. (2010). What does the amygdale contribute to social cognition? Annals of the New York Academy of Science, 1191, 42–61. Alarcon, M., Abrahams, B. S., Stone, J. L., Duvall, J. A., Perederiy, J. V., Bomar, J. M., et al. (2008). Linkage, association, and geneexpression analyses identify CNTNAP2 as an autism-susceptibility gene. American Journal of Human Genetics. doi:10.1016/j. ajhg.2007.09.005A. Amaral, D. G., Schumann, C. M., & Nordahl, C. W. (2008). Neuroanatomy of autism. Trends in Neurosciences, 31, 137–145. Amelsvoort, V., Henry, J., Morris, R., Owen, M., Linszen, D., Murphy, K., & Murphy, D. (2004). Cognitive deficits associated with schizophrenia in velo-cardio-facial syndrome. Schizophrenia Research, 70, 223–232. Bachelevier, J. (1994). Medical temporal lobe structure and autism—a review of clinical and experimental findings. Neuropsychologia, 32, 627–648. Baharnoori, M., Brake, W. G., & Srivastava, L. K. (2009). Prenatal immune challenge induces developmental changes in the morphology of pyramidal neurons of the prefrontal cortex and hippocampus in rats. Schizoprenia Research, 107, 99. Bailey, A., Le Couteur, A., Gottesman, I., Bolton, P., Simonoff, E., Yuzda, E., et al. (1995). Autism as a strongly genetic disorder: evidence from a British twin study. Psychological Medicine, 25, 63–77. doi:10.1017/S0033291700028099. Banerjee, S., Riordan, M., & Bhat, M. A. (2014). Genetic aspects of autism spectrum disorders: insights from animal models. Frontiers in Cellular Neuroscience. doi:10.3389/fncel.2014.00058.

Rev J Autism Dev Disord Bauman, M. D., Crawley, J. N., & Berman, R. F. (2010). Autism: animal models. Encyclopedia of Life Sciences (ELS). Chichester: Willey. doi:10.1002/9780470015902.a0022368. Bautista, J. R., Schwartz, G. J., de la Torre, J. C., Moran, T. H., & Carbone, K. M. (1994). Early and persistent abnormalities in rats with neonatally acquired borna disease virus infection. Brain Research Bulletin, 34, 31–40. Bautista, J. R., Rubin, S. A., Moran, T. H., Schwartz, G. J., & Carbone, K. M. (1995). Developmental injury to the cerebellum following perinatal Borna disease virusinfection. Developmental Brain Research, 90, 45–53. Bell, K., Shokrian, D., Potenzieri, C., & Whitaker-Azmitia, P. M. (2003). Harm avoidance, anxiety, and response to novelty in the adolescent S-100B transgenic mouse: role of serotonin and relevance to Down syndrome. Neuropsychopharmacology, 28, 1810–1816. Benno, R., Smirnova, Y., Vera, S., Liggett, A., & Schanz, N. (2009). Exaggerated responses to stress in the BTBR T+tf/J mouse: an unusual behavioural phenotype. Behavioural Brain Research, 197, 462–465. Bergman, B., Bokstrom, H., Borga, O., Enk, L., Hedner, T., & Wangberg, B. (1984). Transfer of terbutaline across the human placenta in late pregnancy. European Journal of Respiratory Diseases. Supplement, 134, 81–86. Bernier, R., Golzio, C., Xiong, B., Stessman, H. A., Coe, B. P., Penn, O., Witherspoon, K., Gerdts, J., Baker, C., Vulto-van Silfhout, A. T., et al. (2014). Disruptive CHD8 mutations define a subtype of autism early in development. Cell, 158, 263–276. Bertholet, J. Y., & Crusio, W. E. (1991). Spatial and non-spatial spontaneous alternation and hippocampal mossy fibre distribution in nine inbred mouse strains. Behavioural Brain Research, 43, 197–202. Borzychowski, A. M., Sargent, I. L., & Redman, C. W. (2006). Inflammation and pre-eclampsia. Seminars in Fetal and Neonatal Medicine, 11, 309–316. Branchi, I., Santucci, D., & Alleva, E. (2001). Ultrasonic vocalisation emitted by infant rodents: a tool for assessment of neurobehavioural development. Behavioural Brain Research, 125, 49–56. Briese, T., Schneemann, A., Lewis, A. J., Park, Y. S., Kim, S., Ludwig, H., et al. (1994). Genomic organization of Borna disease virus. Proceedings of the National Academy of Sciences of the United States of America, 91, 4362–6. Brioni, J. D., & McGaugh, J. L. (1988). Post-training administration of GABAergic antagonists enhances retention of aversively motivated tasks. Psychopharmacology, 96, 505–510. Burns, R. S., Chiueh, C. C., Markey, S. P., Ebert, M. H., Jacobowitz, D. M., Kopin, I. J. (1983). A primate model of parkinsonism: selective destruction of dopaminergic neurons in the pars compacta of the substantia nigra by N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Proceedings of the National Academy of Sciences of the United States of America, 80(14), 4546–4550. Capitanio, J. P., Emborg, M. E. (2008). Contributions of non-human primates to neuroscience research. Lancet, 371(9618), 1126–35. Carbone, K. M., Park, S. W., Rubin, S. A., Waltrip, R. W., 2nd, & Vogelsan, G. B. (1991). Borna disease: association with a maturation defect in the cellular immune response. Journal of Virology, 65, 6154–6164. Carneiro, A. M., Cook, E. H., Murphy, D. L., & Blakely, R. D. (2008). Interactions between integrinalphaIIbbeta3 and the serotonin transporter regulate serotonin transport and platelet aggregation in mice and humans. The Journal of Clinical Investigation, 118, 1544–1552. Chahrour, M., & Zoghbi, H. Y. (2007). The story of Rett syndrome: from clinic to neurobiology. Neuron, 56, 422–437. Chih, B., Afridi, S. K., Clark, L., & Scheiffele, P. (2004). Disorderassociated mutations lead to functional inactivation of neuroligins. Human Molecular Genetics, 13, 1471–1477. Comoletti, D., De Jaco, A., Jennings, L. L., Flynn, R. E., Gaietta, G., Tsigelny, I., Ellisman, M. H., & Taylor, P. (2004). The Arg451Cys-

neuroligin-3 mutation associated with autism reveals a defect in protein processing. The Journal of Neuroscience, 24, 4889–4893. Connors, S. L., Crowell, D. E., Eberhart, C. G., Copeland, J., Newschaffer, C. J., Spence, S. J., & Zimmerman, A. W. (2005). beta2-Adrenergic receptor activation and genetic polymor-phisms in autism: data from dizygotic twins. Journal of Child Neurology, 20, 876–884. Costa, R. M. (2002). Mechanism for the learning deficits in a mouse model of neurofibromatosis type 1. Nature, 415, 526–530. Costa, R. M., Yang, T., Huynh, D. P., Pulst, S. M., Viskochil, D. H., Silva, A. J., & Brannan, C. I. (2001). Learning deficits, but normal development and tumor predisposition, in mice lacking exon 23a of Nf1. Nature Genetics, 27, 399–405. Courchesne, E. (1997). Brainstem, cerebellar and limbic neuroanatomical abnormalities in autism. Current Opinion of Neurobiology, 7, 269– 278.14. Crawley, J. N. (2004). Designing mouse behavioral tasks relevant to autistic-like behaviors. Mental Retardation and Developmental Disabilities Research Reviews, 10, 248–58. Crawley, J. N. (2007a). Mouse behavioral assays relevant to the symptoms of autism. Brain Pathology, 17, 448–59. Crawley, J. N. (2007b). Medicine. Testing hypotheses about autism. Science, 318, 56–7. Dammann, O., & Meyer, U. (2001). Schizophrenia and autism: both shared and disorder-specific pathogenesis via perinatal inflammation? Pediatric Research, 69, 26R–33R. Dawid, I. B. (2004). Developmental biology of zebrafish. Annals of the New York Academy of Sciences, 1038, 88–93. De la Torre, J. C., Bode, L., Dürrwald, R., Cubitt, B., & Ludwig, H. (1996). Sequence characterization of human Borna disease virus. Virus Research, 44(1), 33–44. De Rienzo, G., Bishop, J. A., Ma, Y., Pan, L., Ma, T. P., Moens, C. B., Tsai, L. H., & Sive, H. (2011). Disc1 regulates both beta-cateninmediated and noncanonical Wnt signaling during vertebrate embryogenesis. The FASEB Journal, 25, 4184–4197. DeLorey, T. M., Handforth, A., Anagnostaras, S. G., Homanics, G. E., Minassian, B. A., Asatourian, A., Fanselow, M. S., DelgadoEscueta, A., Ellison, G. D., & Olsen, R. W. (1998). Mice lacking the b3 subunit of the GABAA receptor have the epilepsy phenotype and many of the behavioural characteristics of Angelman syndrome. The Journal of Neuroscience, 18, 8505–8514. DeLorey, T. M., Sahbaie, P., Hashemi, E., Homanics, G. E., & Clark, J. D. (2008). Gabrb3 gene deficient mice exhibit impaired social and exploratory behaviors, deficits in non-selective attention and hypoplasia of cerebellar vermal lobules: a potential model of autism spectrum disorder. Behavioural Brain Research, 187, 207–220. DiCicco-Bloom, E., Lord, C., Zwaigenbaum, L., Courchesne, E., Dager, S. R., Schmitz, C., Schultz, R. T., Crawley, J., & Young, L. J. (2006). The developmental neurobiology of autism spectrum disorder. The Journal of Neuroscience, 26, 6897–6906. Dooley, K., & Zon, L. I. (2000). Zebrafish: a model system for the study of human disease. Current Opinion in Genetics & Development, 10, 252–256. Elsen, G. E., Choi, L. Y., Prince, V. E., & Ho, R. K. (2009). The autism susceptibility gene met regulates zebrafish cerebellar development and facial motor neuron migration. Developmental Biology, 335, 78–92. Etherton, M. R., Blaiss, C. A., & Powell, C. M. (2009). Mouse neurexin1α deletion causes correlated electrophysiological and behavioural changes consistent with cognitive impairments. Proceedings of the National Academy of Sciences of the United States of America, 106(42), 17998–18003. Falconer, D. S. (1951). Two new mutants. Btrembler^ and Breeler^, with neurological actions in the house mouse (Musmusculus L.). Journal of Genetics, 50, 192–201.

Rev J Autism Dev Disord Fatemi, S. H. (2001). Reelin mutations in mouse and man: from reeler mouse to schizophrenia, mood disorders, autism and lissencephaly. Molecular Psychiatry, 6, 129–133. Fatemi, S. H. (2005). Reelin glycoprotein: structure, biology and roles in health and disease. Molecular Psychiatry, 10, 251–257. Feenstra, M. G. (1992). Functional neuroteratology of drugs acting on adrenergic receptors. Neurotoxicology, 13, 55–63. Folstein, S. E., & Rosen-Sheidley, B. (2001). Genetics of autism: complex aetiology for a heterogeneous disorder. Nature Reviews. Genetics, 2, 943–955. Frescka, E., & Davis, K. L. (1991). The opioid model in psychiatric research. In C. B. Nemeroff (Ed.), Neuropeptides and psychiatric disorders (pp. 169–191). Washington, DC: American Psychiatric Press. Gage, F. H., Dunnett, S. B., & Bjorklund, A. (1984). Spatial learningand motor deficits in aged rats. Neurobiology of Aging, 5, 43–48. Gauthier, J., Champagne, N., Lafreniere, R. G., Xiong, L., Spiegelman, D., Brustein, E., Lapointe, M., Peng, H., Cote, M., Noreau, A., et al. (2010). De novo encoding the synaptic scaffolding protein SHANK3 in patients ascertained for schizophrenia. Proceedings of the National Academy of Sciences of the United States of America, 107, 7863–7868. Givens, B. S., Olton, D. S., & Crawley, J. N. (1992). Galanin in themedial septal area impairs working memory. Brain Research, 582, 71–77. Goddard, J. M., Rossel, M., Manley, N. R., & Capecchi, M. R. (1996). Mice with targeted disruption of Hoxb-1 fail to form the motor nucleus of the VIIth nerve. Development, 122, 3217–3228. Gothelf, D., Feinstein, C., Thompson, T., Eugene, Penniman, L., Stone, E. V., Kwon, H., & Eliez, S. (2007). Risk factors for the emergence of psychotic disorders in adolescents with 22q11.2 deletion syndrome. The American Journal of Psychiatry, 164, 663–669. Grabrucker, A. M. (2013). Environmental factors in autism. Frontiers in Psychology, 3, 118. Gupta, A. R., & State, M. W. (2007). Recent advances in the genetics of autism. Biological Psychiatry, 61, 429–37. Halpern, M. E., Thisse, C., Ho, R. K., Thisse, B., Riggleman, B., Trevarrow, B., Weinberg, E. S., Postlethwait, J. H., Kimmel, C. B. (1995). Cell-autonomous shift from axial to paraxial mesodermal development in zebrafish floating head mutants. Development. 4257–4264. Hanneman, E., Trevarrow, B., Metcalfe, W. K., Kimmel, C. B., & Westerfield, M. (1988). Segmental pattern of development of the hindbrain and spinal cord of the zebrafish embryo. Development, 103, 49–58. Heinrichs, S. C., & Koob, G. F. (2005). Application of experimental stressors in laboratory rodents. In J. Crawley, C. Gerfen, R. McKay, M. Rogawski, D. Sibley, & P. Skolnick (Eds.), Current protocols in neuroscience (pp. 8.4.1–8.4.17). Hoboken (NJ): Wiley. Henderson, N. D. (1972). Relative effects of early rearing environment and genotype on discrimination learning in house mice. Journal of Comparative and Physiological Psychology, 79, 243–253. Hida, Y., Fukaya, M., Hagiwara, A., Deguchi-Tawarada, M., Yoshioka, T., Kitajima, I., Inoue, E., Watanabe, M., & Ohtsuka, T. (2011). Prickle2 is localized in the postsynaptic density and interacts with PSD-95 and NMDA receptors in the brain. Journal of Biochemistry, 149, 693–700. Homanics, G. E., Delorey, T. M., Firestose, L. L., Quinalan, J. J., Handforth, A., Harrison, et al. (1997). Mice devoid of aaminobutyrate type A receptor b3 subunit have epilepsy, cleft palate, and hypersensitive behavior. Proceedings of the National Academy of Sciences of the United States of America, 94, 4143–4148. Hornig, M., Weissenbock, H., Horscroft, N., & Lipkin, W. I. (1999). An infection-based model of neurodevelopmental damage. Proceedings of the National Academy of Sciences of the United States of America, 96, 12102–12107.

Hsiao, K., Chapman, P., Nilsen, S., Eckman, C., Harigaya, Y., Younkin, S., Yang, F., & Cole, G. (1996). Correlative memory deficits, Ab elevation, and amyloid plaques in transgenic mice. Science, 274, 99–102. Hsiao, E. Y., Bregere, C., Malkova, N., Patterson, P. H. (2011). Modeling features of autism in rodents. In: D.G. Amaral, G. Dawson, D. H. Geschwind (Eds) Autism spectrum disorders (pp. 935-962) Ichtchenko, K., Hata, Y., Nguyen, T., Ullrich, B., Missler, M., Moomaw, C., & Sudhof, T. C. (1995). Neuroligin 1: a splice-site specific ligand for ß-neurexins. Cell, 81, 435–443. Ingram, J. L., Stodgell, C. J., Hyman, S. L., Figlewicz, D. A., Weitkamp, L. R., & Rodier, P. M. (2000). Discoverey of allelic variants of HOXA1 & HOXB1: genetic susceptibility to autistic spectrum disorder. Teratology, 62, 393–405. Insel, T. R. (2010). The challenge of translation in social neuroscience: a review of oxytocin, vasopressin and affiliative behavior. Neuron, 65, 768–779. International Molecular Genetic Study of Autism Consortium (IMGSAC). (2001). A genomewide screen for autism: strong evidence for linkage to chromosomes 2q, 7q, and 16p. American Journal of Human Genetics, 69, 570–581. Kolozsi, E., Mackenzie, R. N., Roullet, F. I., Decatanzaro, D., & Foster, J. A. (2009). Prenatal exposure to valproic acid leads to reduced expression of synaptic adhesion molecule neuroligin 3 in mice. Neuroscience, 163, 1201–1210. Kurt, S., & Fisher, S. E. (2012). Foxp2 mutations impair auditory-motor association learning. PloS One. doi:10.1371/journal.pone.0033130. Kwon, C. H., Zhu, X., Zhang, J., Knoop, L. L., Tharp, R., Smeyne, R. J., Eberhart, C. G., Burger, P. C., & Baker, S. J. (2001). Pten regulates neuronal soma size: a mouse model of Lhermitte-Duclos disease. Nature Genetics, 29, 404–411. Kwon, C. H., Luikart, B. W., Powell, C. M., Zhou, J., Matheny, S. A., Zhang, W., Li, Y., Baker, S. J., & Parada, L. F. (2006). Pten regulates neuronal arborization and social interaction in mice. Neuron, 50, 377–388. Lalonde, R., Hayzoun, K., Derer, M., Mariani, J., & Strazielle, C. (2004). Neurobehavioural evaluation of Relnrl-orl mutant mice and correlations with cytochrome oxidase activity. Neuroscience Research, 49, 297–305. Laumonnier, F., Bonnet-Brilhault, F., Gomot, M., Blanc, R., David, A., Moizard, M. P., Raynaud, M., Ronce, N., Lemonnier, E., Calvas, P., Laudier, B., Chelly, J., Fryns, J. P., Ropers, H. H., Hamel, B. C., Andres, C., Barthelemy, C., Moraine, C., & Briault, S. (2004). Xlinked mental retardation and autism are associated with a mutation in the NLGN4 gene, a member of the neuroligin family. American Journal of Human Genetics, 74, 552–557. Liu, W. S., Pesold, C., Rodriguez, M. A., Carboni, G., Auta, J., Lacor, P., Larson, J., Condie, B. G., Guidotti, A., & Costa, E. (2001). Downregulation of dendritic spine and glutamic acid decarboxylase 67 expressions in the reelin haploinsufficient heterozygous reeler mouse. Proceedings of the National Academy of Sciences, 98, 3477–3482. Liu, W., Pappas, G. D., & Carter, C. S. (2005). Oxytocin receptors in brain cortical regions are reduced in haploinsufficient (+/-) reeler mice. Neurological Research, 27(4), 339–345. MacDermot, K. D., Bonora, E., Sykes, N., Coupe, A. M., Lai, C. S. L., Vernes, S. C., Vargha-Khadem, F., Mekenzie, F., Smith, R. L., Monaco, A. P., & Fisher, S. E. (2005). Identification of FOXP2 truncation as a novel cause of developmental speech and language deficits. American Journal of Human Genetics, 76, 1074–1080. Markram, H., Rinaldi, T., & Markram, K. (2007). The intense world syndrome—an alternative hypothesis for autism. Frontiers in Neuroscience, 1, 77–96. Martin, L. A., Ashwood, P., Braunschweig, D., Cabanlit, M., Van de Water, J. V., & Amaral, D. G. (2008). Stereotypies & hyperactivity

Rev J Autism Dev Disord in rhesus monkey exposed to IgG from mothers of children with autism. Brain, Behavior, and Immunity, 22, 806–816. Mathiasen, J. R., & Dicamillo, A. (2010). Social recognition in assay in the rat. Behavioral Neuroscience, 8(51), 1–15. Mathis, C., De Barry, J., & Ungerer, A. (1991). Memory deficits induced by g-L-glutamyl-L-aspartate and D-2-amino-5phosphono-valerate in a Y-maze avoidance task: relationship to NMDA receptor antagonism. Psychopharmacology, 105, 546–552. Mehta, M. V., Gandal, M. J., & Siegel, S. J. (2011). mGluR5-antagonist mediated reversal of elevated stereotyped, repetitive behaviour in the VPA model of autism. PloS One. doi:10.1371/journal. pone.0026077. Meyer, U., Feldon, J., Dammann, O. (2011 ). Schizophrenia and autism: both shared and disorder-specific pathogenesis via perinatal inflammation? Pediatric Research, 5 Pt 2, 26R-33R. doi:10.1203/PDR.0 b013e318212c196. Mineur, Y. S. (2002). Behavioural and neuroanatomical characterization of the Fmr1 knockout mouse. Hippocampus, 12, 39–46. Morris, R. G. M. (1981). Spatial localisation does not depend on the presence of local cues. Learning and Motivation, 12, 239–260. Morris, R. G. M. P., Garrud, P., Rawlins, J. N. P., & O’Keefe, J. (1982). Place navigation impaired in rats with hippocampal lesions. Nature, 297, 681–683. Moy, S. S., Nadler, J. J., et al. (2006). Mouse models of autism spectrum disorder: the challenge for behavioural genetics. American Journal of Medical Genetics, 142C, 40–51. Mulder, E. J., Anderson, G. M., Kema, I. P., de Bildt, A., van Lang, N. D., den Boer, J. A., & Minderaa, R. B. (2004). Platelet serotonin levels in pervasive developmental disorders and mental retardation: Diagnostic group differences, within-group distribution, and behavioural correlates. Journal of the American Academy of Child and Adolescent Psychiatry, 43, 491–499. Napoli, E., Ross-Inta, C., Wong, S., Hung, C., Fujisawa, Y., Sakaguchi, D., Angelastro, J., Omanska-Klusek, A., Schoenfeld, R., & Giuliv, C. (2012). Mitochondrial dysfunction in Pten Haplo-insufficient mice with social deficits and repetitive behavior: interplay between Pten and p53. PloS One, 7(8), e42504. Nestler, E. J., & Hymen, S. E. (2010). Animal models of neuropsychiatric disorders. Nature Neuroscience, 13, 1161–1169. Panaitof, S. C., Abrahams, B. S., Dong, H., Geschwind, D. H., & White, S. A. (2010). Language-related Cntnap2 gene is differentially expressed in sexually dimorphic nuclei essential for vocal learning in songbirds. The Journal of Comparative Neurology, 518, 1995–2018. Panksepp, J. (1979). A neurochemical theory of autism. Trends in Neurosciences, 2, 174–177. Patterson, P. H. (2009). Immune involvement in schizophrenia and autism: etiology, pathology and animal models. Behavioural Brain Research, 204, 313–321. Patterson, P. H. (2011). Modeling autistic features in animals modeling autistic features in animals. Pediatric Research, 69, 34R–40R. Paylor, R., Baskall, L., & Wehner, J. M. (1993). Behavioural dissociations between C57BL/6 and DBA/2 mice on learning and memorytasks: a hippocampal-dysfunction hypothesis. Psychobiology, 21, 11–26. Pinheiro, M. L., Ribeiro, A., Ferraz-de-Paula, V., & Palermo-Neto, J. (2012). Alpha-7 nicotinic receptor stimulation modifies cytokine profile in OVA-sensitized mice. Brain, Behavior, and Immunity, 26, S1–S50. Pitzer, M., Schmidt, M. H., Esser, G., & Laucht, M. (2001). Child development after maternal tocolysis with beta-sympathomimetic drugs. Child Psychiatry and Human Development, 31, 165–182. Pletnikov, M. V., Rubin, S. A., Schwartz, G. J., Moran, T. H., Sobotka, T. J., & Carbone, K. M. (1999a). Persistent neonatal Borna disease

virus (BDV) infection of the brain causes chronic emotional abnormalities in adult rats. Physiology & Behavior, 66, 823–831. Pletnikov, M. V., Rubin, S. A., Vasudevan, K., Moran, T. H., & Carbone, K. M. (1999b). Developmental brain injury associated with abnormal play behavior in neonatally Borna disease virus-infected Lewis rats: a model of autism. Behavioural Brain Research, 100, 43–50. Pletnikov, M. V., Rubin, S. A., Schwartz, G. J., Carbone, K. M., & Moran, T. (2000). Effects of neonatal rat Borna disease virus (BDV) infection on the postnatal development of the brain monoaminergic systems. Developmental Brain Research, 119, 179–185. Pletnikov, M. V., Moran, T. H., & Carbone, K. M. (2001). Neonatal Borna disease virus infection (BDV)-induced damage to the cerebellum is associated with sensorimotor deficits in developing Lewis rats. Developmental Brain Research, 126, 1–12. Pletnikov, M. v., Moran, T. H., & Carbone, K. M. (2002). Borna disease virus infection of the neonatal rat: developmental brain injury model of autism spectrum disorders. Frontiers in Bioscience, 7, d593–607. Presti, M. F. (2003). Behavior-related alterations of striatal neurochemistry in a mouse model of stereotyped movement disorder. Pharmacology, Biochemistry, and Behavior, 77(3), 501–507. Rinaldi, T., Silberberg, G., & Markram, H. (2008). Hyperconnectivity of local neocortical microcircuitry induced by prenatal exposure to valproic acid. Cerebral Cortex, 18, 763–770. Ross, H. E., & Young, L. J. (2009). Oxytocin and the neural mechanisms regulating social cognition and affiliative behavior. Frontiers in Neuroendocrinology, 30, 534–547. Rossi, M. A., & Yin, H. H. (2012). Methods for studying habitual behavior in mice. Department of Psychology and Neuroscience and Department of Neurobiology. Center for Cognitive Neuroscience: Duke University, Durham, North Carolina. Rubin, S. A., Pletnikov, M., & Carbone, K. M. (1998). Comparison of the neurovirulence of a vaccine and a wild-type mumps virus strain in the developing rat brain. Journal of Virology, 72, 8037–42. Sago, H., Carlson, E. J., Smith, D. J., Kilbridge, J., Rubin, E. M., Mobley, W. C., Epstein, C. J., & Huang, T. T. (1998). Ts1Cje, a partial trisomy 16 mouse model for Down syndrome, exhibits learning and behavioural abnormalities. Proceedings of the National Academy of Sciences, 95, 6256–6261. Sandman, C. A. (1992). Various endogenous opioids and autistic behavior: a response to Gillberg (letter to the editor). Journal of Autism and Developmental Disorders, 22, 132–133. Sandman, C. A., Barron, J. L., Chicz-DeMet, A., & DeMet, E. (1991). Brief report: plasma b-endorphin and cortisol levels in autistic patients. Journal of Autism and Developmental Disorders, 21, 83–87. Schain, R. J., & Freedman, D. X. (1961). Studies on 5-hydroxyindole metabolism in autistic and other mentally retarded children. The Journal of Pediatrics, 58, 315–320. Schneider, T., Roman, A., Basta-Kaim, A., Kubera, M., Budziszewska, B., Schneider, K., & Przewłocki, R. (2008). Specific behavioural and immunological alterations in an animal model of autism induced by prenatalexposure to valproic acid. Psychoneuroendocrinology, 33, 728–740. Sebat, J., Lakshmi, B., Malhotra, D., Troge, J., Lese-Martin, C., Walsh, T., Yamrom, B., Yoon, S., Krasnitz, A., Kendall, J., et al. (2007). Strong association of de novo copy number mutations with autism. Science, 316, 445–449. Sher, L. (1997). Autistic disorder and the endogenous opioid system. Medical Hypotheses, 48, 413–414. Silverman, J. L., Yang, M., Lord, C., & Crawley, J. N. (2010). Behavioural phenotyping assays for mouse models of autism. Nature Reviews. Neuroscience, 11, 490–502. Slotkin, T. A., Tate, C. A., Cousins, M. M., & Seidler, F. J. (2001). Betaadrenoceptor signal-ing in the developing brain: sensitization or desensitization in response to ter-butaline. Brain Research. Developmental Brain Research, 131, 113–125.

Rev J Autism Dev Disord Stanton, M. E., Peloso, E., Brown, K. L., & Rodier, P. (2007). Discrimination learning and reversal of the conditioned eyeblink reflex in a rodent model of autism. Behavioural Brain Research, 176(1), 133–140. Studer, M., Lumsden, A., Ariza-McNaughton, L., Bradley, A., & Krumlauf, R. (1996). Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1. Nature, 384, 630–634. Studer, M., Gavalas, A., Marshall, H., Ariza-McNaughton, L., Rijli, F. M., Chambon, P., & Krumlauf, P. (1998). Genetic interactions between Hoxa1 and Hoxb1 reveal new roles in regulation of early hindbrain patterning. Development, 125, 1025–1036. Sutcliffe, J. S., Delahanty, R. J., Prasad, H. C., McCauley, J. L., Han, Q., Jiang, L., Li, C., Folstein, S. E., & Blakely, R. D. (2005). Allelic heterogeneity at the serotonin transporter locus (SLC64) confers susceptibility to autism and rigid-compulsive behaviors. American Journal of Human Genetics, 77, 265–279. Szatmari, P., Paterson, A. D., Zwaigenbaum, L., Roberts, W., et al. (2007). Mapping autism risk loci using genetic linkage and chromosomal rearrangements. Nature Genetics, 39, 319–328. Takumi, T. (2010). A humanoid mouse model of autism. Brain and Development, 32, 753–758. Tao, H., Manak, J. R., Sowers, L., Mei, X., Kiyonari, H., Abe, T., Dahdaleh, N. S., Yang, T., Wu, S., Chen, S., Fox, M. H., Gurnett, C., et al. (2011). Mutations in prickle orthologs cause seizures in flies, mice, and humans. American Journal of Human Genetics, 88, 138–149. Tordjman, S., Anderson, G. M., McBride, P. A., Hetzig, M. E., Snow, M. E., Hall, L. M., Thompson, S. M., Ferrari, P., & Cohen, D. J. (1997). Plasma beta-endorphin, adrenocorticotropin hormone and cortisol in autism. Journal of Child Psychology and Psychiatry, 38, 705–716. Tropepe, V., & Sive, H. L. (2003). Can zebrafish be used as a model to study the 1622 neurodevelopmental causes of autism? Genes, Brain, and Behavior, 2, 268–281. Turner, C. A., Presti, M. F., Newman, H. A., Bugenhagen, P., Crnic, L., & Lewis, M. H. (2001). Spontaneous stereotypy in an animal model of Down syndrome: Ts65Dn mice. Behavior Genetics, 31, 393–400. Ushkaryov, Y. A., Petrenko, A. G., Geppert, M., & Sudhof, T. C. (1992). Neurexins: synaptic cell surface proteins related to the α-latrotoxin receptor and laminin. Science, 257, 50–56. Vernes, S. C., Newbury, D. F., Abrahams, B. S., Winchester, L., Nicod, J., Groszer, M., Alarcon, M., Oliver, P. L., Davies, K. E., Geschwind, D. H., Monaco, A. P., & Fisher, S. E. (2008). A functional genetic link between distinct developmental language disorders. The New England Journal of Medicine, 359, 2337–2345. Vesterlund, L., Jiao, H., Unneberg, P., Hovatta, O., & Kere, J. (2011). The zebrafish transcriptome during early development. BMC Developmental Biology. doi:10.1186/1471-213X-11-30. Vogel, H. G. (2002). Drug discovery and evaluation: pharmacological assays. new York: springer-verlag berlin heidlberg. Walf, A. A., & Frye, A. C. (2007). The use of the elevated plus maze as an assay of anxiety-related behavior in rodents. Nat proto, C, 2, 322–328.

Wassif, C. A., Zhu, P., Kratz, L., Krakowiak, P. A., Battaile, K. P., Weight, F. F., Grinberg, A., Steiner, R. D., Nwokoro, N. A., Kelley, R. I., Stewart, R. R., & Porter, F. D. (2001). Biochemical, phenotypic, neurophysiological characterization of genetic mouse model of RSH/Smith-Lemli-Opitz syndrome. Human Molecular Genetics, 10, 555–564. Weis, J. S., & Analysis of the development of the nervous system of the zebrafish, Brachydanio rerio. (1968). The effect of nerve growth factor and its antiserum on the nervous system of the zebrafish. Journal of Embryology and Experimental Morphology, 19, 121–135. Weiss, L. A., Veenstra-Vanderweele, J., Newman, D. L., Kim, S. J., Dytch, H., McPeek, M. S., Cheng, S., Ober, C., Cook, E. H., Jr., & Abney, M. (2004). Genome-wide association study identifies ITGB3 as a QTL for whole blood serotonin. European Journal of Human Genetics, 12, 949–954. Weiss, L. A., Abney, M., Cook, E. H., Jr., & Ober, C. (2005). Sex-specific genetic architecture of whole blood serotonin levels. American Journal of Human Genetics, 76, 33–41. Wenk, G., Hepler, D., & Olton, D. (1984). Behavior alters the uptake of [3H] choline into acetylcholinergic neurons of the nucleus basalismagnocellularis and medial septal area. Behavioural Brain Research, 13, 129–138. Willemsen-Swinkels, S. H. N., Buitelaar, J. K., Nijhof, G. J., & van England, H. (1995). Failure of Naltrexone to reduce self-injurious and autistic behavior in mentally retarded adults: doubleblind placebo controlled studies. Archives of General Psychiatry, 52, 766–773. Wimersma Greidanus, T. B., van de, B. F., de Bruijckere, L. M., Pabst, P. H., Ruesink, R. W., Hulshof, R. L., Berckel, B. N. M. V., Arissen, S. M., De koning, E. J. P., & Donker, D. K. (1988). Comparison of bombesin, ACTH and beta-endorphin induced grooming: antagonism by haloperidol, naloxone and neurotensin. Annals of the New York Academy of Science, 525, 219–227. Winslow, J. T., Hearn, E. F., Ferguson, J., Young, L. J., Matzuk, M. M., & Insel, T. R. (2000). Infant vocalization, adult aggression, and fear behavior of an oxytocin null mutant mouse. Hormones and Behavior, 37, 145–155. Won, H., Lee, H. R., Gee, H. Y., Mah, W., Kim, J. I., Lee, J., Ha, S., Chung, C., Jung, E. S., Cho, Y. S., Park, S. G., Lee, J. S., Lee, K., Kim, D., Bae, Y. C., Kaang, B. K., Lee, M. G., & Kim, E. (2012). Autistic-like social behaviour in Shank2 mutant mice improved byrestoring NMDA receptor function. Nature, 486(7402), 261–5. Wu, C.-L., & Melton, D. W. (1993). Production of a model for LeschNyhan syndrome in hypoxanthine phosphoribosyltransferasedeficient mice. Nature Genetics, 3, 235–239. Yan, Q. J., Asafo-Adjei, P. K., Arnold, H. M., Brown, R. E., & Bauchwitz, R. P. (2004). A phenotypic and molecular characterization of the fmr1- tm1Cgr Fragile X mouse. Genes, Brain, and Behavior, 3, 337–359. Zahir, F. R., Baross, A., Delaney, A. D., Eydoux, P., Fernandes, N. D., Pugh, T., Marra, M. A., & Friedman, J. M. (2008). A patient with vertebral, cognitive and behavioural abnormalities and a de novo deletion of NRXN1 alpha. Journal of Medical Genetics, 45, 239–243.