In humans, SOX2 mutations cause anophthalmia, defective hippocampal development and seizures. SOX2 is actively expressed in adult hippocampal neural ...
Molecular Mechanisms underlying SOX2 Function in Adult Neurogenesis Alejandro Amador-‐Arjona1, Flavio Cimadamore1, Chun-‐Teng Huang1, Rebecca Wright2, Susan Lewis1, Fred H. Gage2 and Alexey V. Terskikh1 2
Department of Stem Cells and Regeneration, Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Rd., La Jolla, California 92037, USA Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Rd., La Jolla, California 92037, USA
cell cycle hippocampus BrdU epigenetics differentiation
neurogenesis
mice
SOX2 NEUROD1 electrophysiology
retrovirus
knockout
neural stem cell
neuron
cell death
Adult hippocampal neurogenesis is reduced in SOX2cKO mice To quantify hippocampal neurogenesis, a 5 consecutive day BrdU injection protocol followed by 4 weeks was used in 2 month-old wild-type (WT) and SOX2cKO (cKO) mice. (A,B) Hippocampal neurogenesis is reduced in SOX2cKO mice. (C, D) SOX2 ablation in adult NSCs increases cell death in the subgranular zone (SGZ) of the dentate gyrus.
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Results SOX2 ablation reduces the number of NSCs and proliferation of amplifying neural progenitors Characterization of adult hippocampal NSCs in 2-month-old wild-type (WT) and SOX2cKO (cKO) mice. (A) SOX2 is ablated in neural stem cells (NSCs) in SOX2cKO mice. (B, C) Radial NSC and amplifying progenitor numbers are reduced in SOX2cKO mice. (D) A 2-hour pulse of BrdU was given to measure proliferation in adult NSCs. (E, F) SOX2 deletion decreases proliferation in amplifying progenitors without affecting the proliferation of radial NSCs.
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Wild-type
SOX2cKO
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NeuroD1 is a proneural gene involved in granule neuron survival and differentiation. (A, B) Reduced NEUROD1 expression in immature neurons of SOX2cKO mice. (C) ChIP analysis of the open-chromatin marker H3K9ac reveals reduced histone acetylation at the level of NeuroD1 promoter in neural progenitors with reduced level of SOX2 (shSOX2) under neurogenic cues (Wnt3a induction).
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NEUROD1-induced expression rescues neurogenesis in SOX2cKO mice
SOX2 deletion in NSCs leads to an altered dendritic maturation and electrophysiological properties of adultborn neurons Characterization of 6-week-old hippocampal adult-born neurons in SOX2cKO mice. GFP-expressing retrovirus was used to infect adult hippocampal NSCs. (A) Adult-born neurons from wild-type (WT) and SOX2cKO (cKO). (B) Reduced dendritic length and (C) branching points in SOX2cKO newborn neurons. (D) Dendritic spines from wild-type and SOX2cKO mice. (E) Reduced spine density, and (F) increased mushroom spine density in SOX2cKO mice. (G) Spontaneous excitatory post-synaptic currents (sEPSCs) in newborn neurons from wild-type and SOX2cKO mice. (H) Increased sEPSCs amplitude in newborn neurons from SOX2cKO mice, but (I) no effect in frequency.
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GFP
Methods
SOX2flox mice were bred with transgenic mice expressing Cre under control of the mouse glial fibrillary acidic protein promoter (mGFAPCre) and nestin-CFPnuc transgenic mice resulting in SOX2cKO mice.
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Introduction In humans, SOX2 mutations cause anophthalmia, defective hippocampal development and seizures. SOX2 is actively expressed in adult hippocampal neural stem cells (NSCs). Proliferating adult NSCs in the hippocampus decrease SOX2 levels before exiting cell cycle and initiating the expression of gene markers associated with neural differentiation. The function of SOX2 in adult neurogenesis and the molecular mechanisms underlying its role in human SOX2related brain abnormalities are largely unknown. We developed a genetic mouse model, SOX2cKO mice, in which fetal/perinatal brain development is unaffected, but SOX2 is conditional ablated in adult GFAP+ neural stem/progenitor cells.
Decrease of NEUROD1 expression and histone acetylation at NeuroD1 promoter under neurogenic cues
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Retroviral infection (GFP/mCherry, or ND1-GFP/mCherry) was performed in the dentate gyrus of SOX2cKO mice. (A) Labeling of 21-day-old (21dpi) infected newborn neurons was used A to analyze cell survival (B) Double (GFP/mCherry, top) and single (mCherry) –labeled immature neurons (DCX+). (C) Increased number of mCherry (red) cells in the ND1 infected side. (D) The number of ND1/ mCherry-double infected cells were increased in comparison with cells mCherry infected with GFP/mCherry. ND1 or GFP
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DCX/GFP/mCherry
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Conclusions F
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SOX2 regulates NSC proliferation and cell survival in the adult hippocampus Genetic disruption of Sox2 in adult NSCs leads to a reduction of neuronal differentiation, aberrant dendritic development and altered electrophysiological properties of newborn neurons SOX2 regulates the expression of NEUROD1, an essential proneural gene involved in neuronal differentiation and survival, via histone acetylation at NeuroD1 gene promoter NEUROD1-induced expression rescues granule cell-survival in SOX2cKO mice
Acknowledgements
Silvia Nicolis (Sox2flox mice) Michael V. Sofroniew (mGFAP-Cre mice) Grigori Enikolopov (nestin-CFPnuc mice)
