KATP channel gain-of-function leads to increased myocardial ... - PNAS

2 downloads 0 Views 3MB Size Report
Jun 14, 2016 - University of Washington, Seattle, WA 98195-7280. Contributed by William ..... enhanced contractility and maintained APD is explained by en-.
KATP channel gain-of-function leads to increased myocardial L-type Ca2+ current and contractility in Cantu syndrome Mark D. Levina,b, Gautam K. Singha,b, Hai Xia Zhanga,c, Keita Uchidaa,c, Beth A. Kozela,b, Phyllis K. Steind, Atilla Kovacsd, Ruth E. Westenbroeke, William A. Catteralle,1, Dorothy Katherine Grangea,b, and Colin G. Nicholsa,c,1 a Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110; bDepartment of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110; cDepartment of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110; dDepartment of Medicine, Washington University School of Medicine, St. Louis, MO 63110; and eDepartment of Pharmacology, University of Washington, Seattle, WA 98195-7280

Cantu syndrome (CS) is caused by gain-of-function (GOF) mutations in genes encoding pore-forming (Kir6.1, KCNJ8) and accessory (SUR2, ABCC9) KATP channel subunits. We show that patients with CS, as well as mice with constitutive (cGOF) or tamoxifen-induced (icGOF) cardiac-specific Kir6.1 GOF subunit expression, have enlarged hearts, with increased ejection fraction and increased contractility. Whole-cell voltage-clamp recordings from cGOF or icGOF ventricular myocytes (VM) show increased basal L-type Ca2+ current (LTCC), comparable to that seen in WT VM treated with isoproterenol. Mice with vascularspecific expression (vGOF) show left ventricular dilation as well as less-markedly increased LTCC. Increased LTCC in KATP GOF models is paralleled by changes in phosphorylation of the pore-forming α1 subunit of the cardiac voltage-gated calcium channel Cav1.2 at Ser1928, suggesting enhanced protein kinase activity as a potential link between increased KATP current and CS cardiac pathophysiology. KATP

| transgenic | cardiovascular system | KCNJ8 | Kir6.1

C

antu syndrome (CS), characterized by hypertrichosis, osteochondrodysplasia, and multiple cardiovascular abnormalities (1), is caused by gain-of-function (GOF) mutations in the genes encoding the pore-forming (Kir6.1, KCNJ8) and regulatory (SUR2, ABCC9) subunits of the predominantly cardiovascular isoforms of the KATP channel (2–5). Because the same disease features arise from mutations in either of these subunits, it is concluded that CS arises from increased KATP channel activity, as opposed to any nonelectrophysiologic function of either subunit. However, this conclusion does not provide immediate explanation for many CS features. In the myocardium, for example, acute activation of KATP channels results in shortening of the action potential (AP), with concomitant reduction of both calcium entry and contractility (6). The naïve prediction in CS would therefore be that KATP GOF mutations should shorten the AP, reduce contractility, and reduce cardiac output. We previously reported high cardiac output with low systemic vascular resistance in CS (7). Cantu syndrome cardiac pathology is therefore opposite to prediction, and also unlike classical hypertrophic or dilated cardiomyopathies, in that the ventricle is dilated, but there is increased cardiac output. Here we characterize CS cardiac pathology in patients, and explore the mechanistic basis using mice that express KATP GOF mutant subunits in the heart and vasculature. Results Low Blood Pressure in CS Patients. Eleven CS individuals (five male, six female, aged 17 mo to 47 y), all harboring ABCC9 mutations (Table S1), participated in CS research clinics at St. Louis Children’s Hospital. Five had been previously followed at this institution (7) and the remainder were enrolled via the CS Interest Group (www.cantu-syndrome.org). Patient demographic data, genotype, and available cardiac historical, physical, and test information are summarized in Table S1. Most patients had no recalled cardiac www.pnas.org/cgi/doi/10.1073/pnas.1606465113

symptomatology, although prior office notes revealed episodes of chest pain, fatigue, shortness of breath, and exercise intolerance associated with pericardial effusion. Additionally, three patients (cs002, cs004, cs005) reported palpitations and exercise intolerance. One of these (cs004) also had symptoms with orthopnea, resulting from “idiopathic” high-output state and atrial fibrillation. Five patients had patent ductus arteriosus that required surgical ligation or catheter-based closure, two had significant pericardial effusions, three had been diagnosed with pulmonary hypertension, and five had histories of lower extremity edema. All patients had full but noncollapsing peripheral pulses. All but one patient (cs004, who was on several medications; Table S1) had supine systolic and diastolic blood pressure (BP) that was well below mean for age (Table S1) [mean age: 16.6 ± 13.5; systolic BP: 90.5 ± 12.8 mmHg; diastolic BP: 58.2 ± 6.2 mmHg; heart rate (HR): 85 ± 17 beats per minute (bpm)] (8). Despite these low BP values, no patient demonstrated orthostatic HR or BP changes. There were relatively few cardiac findings on physical examination, with the exception of one patient with a diastolic murmur (cs004) at the apex. Electrocardiograms revealed first-degree atrioventricular (AV) block in four patients, fascicular block in two, and T-wave abnormalities (T-wave axis 180° displaced from QRS axis and morphologic abnormalities) in seven patients, but no evidence of QT shortening or correct QT (QTc) prolongation (Table S2). Significance ATP-sensitive potassium (KATP) channels are present in cardiac and smooth muscle; when activated, they relax blood vessels and decrease cardiac action potential duration, reducing cardiac contractility. Cantu syndrome (CS) is caused by mutations in KATP genes that result in overactive channels. Contrary to prediction, we show that the myocardium in both CS patients and in animal models with overactive KATP channels is hypercontractile. We also show that this results from a compensatory increase in calcium channel activity, paralleled by specific alterations in phosphorylation of the calcium channel itself. These findings have implications for the way the heart compensates for decreased excitability and volume load in general and for the basis of, and potential therapies for, CS specifically. Author contributions: M.D.L., G.K.S., H.X.Z., K.U., B.A.K., P.K.S., A.K., R.E.W., W.A.C., D.K.S., and C.G.N. designed research; M.D.L., G.K.S., H.X.Z., K.U., B.A.K., A.K., and R.E.W. performed research; R.E.W. contributed new reagents/analytic tools; M.D.L., G.K.S., H.X.Z., K.U., B.A.K., P.K.S., A.K., R.E.W., W.A.C., D.K.G., and C.G.N. analyzed data; and M.D.L., G.K.S., R.E.W., W.A.C., and C.G.N. wrote the paper. Reviewers: D.M.B., University of California, Davis; R.S.K., Columbia University; and M.C.S., University of Utah. The authors declare no conflict of interest. 1

To whom correspondence may be addressed. Email: [email protected] or [email protected].

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. 1073/pnas.1606465113/-/DCSupplemental.

PNAS | June 14, 2016 | vol. 113 | no. 24 | 6773–6778

PHYSIOLOGY

Contributed by William A. Catterall, April 26, 2016 (sent for review November 13, 2015; reviewed by Donald M. Bers, Robert S. Kass, and Michael C. Sanguinetti)

Circadian Abnormalities and Low Vagal Function in CS Patients.

* P = 0.0357

300 200 100

LVPW (cm) Shortening (%)

P =NS

1.0 0.5 0.0

* P =0.0014

50 45 40 35 30

Global LV strain long (%)

Control

-20 -30

4 2 0

* P < 0.0001

100 80 60 40 20 0

* P < 0.0001

10 8 6 4 2 0

Control

Cantu

0 -10

P 6 mo of age. (B) Representative Ca2+ currents obtained from either control (Left) or vGOF (Right) cardiomyocytes. Protocols as in Fig. 4. Peak ICa amplitude and ICa density plotted as a function of voltage (mean ± SEM). (Inset) Mean capacitance in each case. (Scale bars, 500 pA and 20 ms.)

Levin et al.

B 100

*

1.5

Control

Relative intensity (arb.)

0 Total Cav1.2

Distal C-term

Processed C-term *

* 3

Percent survival

1 0.5

80

60

40

2

icGOF 20

1 0

phospho S1700

0

phospho S1928

0

5 10 15 20 25 days after implantation

C Cardiac KATP overactivity

Vascular KATP overactivity

-

Heart rate

APD

+

+

Electrical activity

-

2+

Cardiomyocyte [Ca ]I

+

+

VSM [Ca2+]I

Cav1.2 S1928 phosphorylation

-

-

Central autonomic activity

Stress signalling

Cardiomyocyte contractility

VSM contractility

Baroreceptor drive

Cardiac output

-

BP

Peripheral resistance

Fig. 7. Cellular and molecular basis of Cantu syndrome. (A) Quantitation of Western blot analysis of isolated total Cav1.2a subunit protein, distal C terminus, and processed C-terminal fragments, normalized to WT protein levels in cGOF, Kir6.1[AAA], and vGOF cardiac samples, as well as relative levels of phosphoS1700 and phospho-S1928 residues. (B) Kaplan–Meier survival curve for male icGOF (n = 7) and littermate control mice (n = 6) transplanted with slow-release propranolol pellets (5 mg/21-d release) on day 0, and then induced (both icGOF and control) with tamoxifen starting on days 2–7 (gray bar). (C) Proposed mechanistic basis of Cantu syndrome. GOF mutations in either the pore-forming (KCNJ8) or accessory (ABCC9) KATP subunits will directly cause action potential (AP) shortening and reduced heart rate in cardiomyocytes and reduced excitability in smooth muscle myocytes, which will result in diminished calcium uptake, decreased contractility, and decreased cardiac output, as well as decreased peripheral resistance. Combined, these reactions would reduce blood pressure, stimulating baroreceptors and triggering PKA- or PKC-dependent stress-signaling pathways in the heart and potentially in smooth muscle. These pathways lead to phosphorylation of LTCC, specifically the Cav1.2 subunit, resulting markedly enhanced basal activity of the LTCC, enhanced contractility of the myocyte, and restored APD. In vascular smooth muscle cell, the diminished peripheral resistance will result in diminished effective tissue perfusion, giving rise to long-standing volume load on the heart, and chamber dilation.

enhanced basal LTCC in the ambulatory ECG data: higher than normal heart rates, as well as blunted heart rate variability and T-wave abnormalities (Fig. 2). In the presence of ISO, LTCC densities in cGOF or icGOF myocytes are not significantly different from control (Figs. 4 and 5) (12). This lack of ISO response is consistent with chronic in vivo activation of signaling pathways that result in prestimulation. This prestimulation must be a consequence of the initial defect; that is, the gain of KATP conductance, which we suggest will indeed be a reduced cardiac output, but that this results in activation of adrenergic or parallel signaling pathways. We previously showed that basal and ISO-stimulated cAMP concentrations are not altered in transgenic Kir6.2 GOF hearts that also show prestimulation (12). Cardiac LTCC can be increased by PKA activation (28–30), but also by PKC in response to α-adrenergic and endothelin-1–dependent Levin et al.

signaling (31–35). PKC overexpression may result in diminished LTCC current in some circumstances (36), although dialysis of critical LTCC-associated proteins may confound results in wholecell patch-clamp experiments (32). Both PKA and PKC modulation of LTCC (22, 37) are mediated by phosphorylation of CaV1.2 serine residues on the pore or accessory subunits (18–20, 38). The identity of relevant residues phosphorylated in response to adrenergic signaling remains an active area of investigation. Ser1700 and Ser1928 phosphorylation of Cavα1.2 have both been demonstrated, but Ser1928 may also be phosphorylated by PKC (35, 39), and Ser1700 may also be a target of CaMKII (18, 40). Our analysis implicates Ser1928 phosphorylation as a marker of the response to KATP GOF but not Ser1700. Though Ser1928 phosphorylation may not itself be directly involved in the enhancement of LTCC, it is suggestive that PKC or PKA pathways may ultimately be activated. Feedback Response to Vascular Defects in CS. Two distinct effects were observed on cGOF and icGOF LTCC: left-shift in activation and increased current density. We also observed a left-shift of voltage dependence of LTCC in vGOF, but only a mild increase in current density, and a nonsignificant increase in Ser1928 phosphorylation. In contrast, older vGOF animals exhibited increased diastolic volume, as observed in CS patients. Vascular KATP GOF results in increased smooth muscle KATP current and diminished BP (9), providing a potentially direct explanation for the markedly lowfor-age BPs in CS patients; this also provides a systemic mechanism that may link the primary vGOF phenotype to secondary consequences in the heart: vascular KATP GOF expression results in vasodilation that will ultimately result in a long-standing volume load, evidenced by LV chamber dilation. Early after transgene induction (6 wk), vGOF hearts exhibit increased contractility and increased ejection fraction (Fig. 6), but end diastolic volume is increased in older vGOF animals, potentially reflecting dilation manifesting after prolonged exposure to volume overload (26). Conclusions and Implications. CS can arise from GOF in either Kir6.1 or SUR2 proteins of the cardiovascular KATP channel (2–5). A distinct CS cardiac pathology is characterized by high output state with enhanced cardiac contractility and enhanced chamber volume, associated with decreased vascular pulse wave velocity and low BP. Our animal studies suggest that CS cardiac pathology emerges from combined cardiac and vascular KATP GOF mutation expression (Fig. 7C). The vascular findings are readily explained by the expected molecular consequences, but KATP GOF mutations in the myocardium will tend to reduce cardiac action potential duration (APD) and decrease pacemaker activity, both of which would reduce cardiac contractility and output. The counter observation of enhanced contractility and maintained APD is explained by enhanced LTCC, with left-shifted activation and increased basal conductance, associated with enhanced phosphorylation of the PKA/PKC target residue Ser1928. These findings are consistent with compensatory chronic signaling, potentially involving adrenergic stimulation, through pathways that converge on the LTCC. This consistent explanation for CS cardiac features raises the question of whether or how to treat them. The dramatic difference in response of icGOF and control animals to β-blockade (Fig. 7B) is consistent with adrenergic signaling being involved in at least the early compensation to KATP GOF, further suggesting that β-blockade could be a dangerous approach to treating Cantu patients. Alternately, appropriate therapies should target KATP channels directly, and the success of sulphonylurea drugs in treating neonatal diabetes, which results from GOF in the pancreatic KATP isoforms, gives promise that similar or more selective KATP antagonists may reverse some or all CS disease features.

Methods Human studies were carried out on CS patients recruited to an annual research clinic at St. Louis Children’s Hospital. Written informed consent was provided by all patients. The study was approved by the Human Research Protection Office of Washington University School of Medicine and performed at St. Louis Children’s Hospital in St. Louis. Echocardiographic and electrocardiographic studies were

PNAS | June 14, 2016 | vol. 113 | no. 24 | 6777

PHYSIOLOGY

A

performed. All animal studies complied with the standards for the care and use of animal subjects as stated in the NIH Guide for the Care and Use of Laboratory Animals (41) and were reviewed and approved by the Washington University Institutional Animal Care and Use Committee. Mouse strains used included cGOF (10), αMHC-Cre (42), icGOF (tamoxifen-inducible Kir6.1[G343D] transgenic), MerCre-Mer-α-MHC (43), and vGOF (9). Transgene expression was induced by 5× daily injections of 10 mg/kg tamoxifen (44). Isolated myocyte studies and

isolated tissue Western blot analyses were carried out as previously described (45–48). Detailed methods are available in SI Methods.

1. Nichols CG, Singh GK, Grange DK (2013) KATP channels and cardiovascular disease: Suddenly a syndrome. Circ Res 112(7):1059–1072. 2. Harakalova M, et al. (2012) Dominant missense mutations in ABCC9 cause Cantú syndrome. Nat Genet 44(7):793–796. 3. van Bon BW, et al. (2012) Cantú syndrome is caused by mutations in ABCC9. Am J Hum Genet 90(6):1094–1101. 4. Cooper PE, et al. (2014) Cantú syndrome resulting from activating mutation in the KCNJ8 gene. Hum Mutat 35(7):809–813. 5. Brownstein CA, et al. (2013) Mutation of KCNJ8 in a patient with Cantú syndrome with unique vascular abnormalities - support for the role of K(ATP) channels in this condition. Eur J Med Genet 56(12):678–682. 6. Nichols CG (2006) KATP channels as molecular sensors of cellular metabolism. Nature 440(7083):470–476. 7. Grange DK, Lorch SM, Cole PL, Singh GK (2006) Cantu syndrome in a woman and her two daughters: Further confirmation of autosomal dominant inheritance and review of the cardiac manifestations. Am J Med Genet A 140(15):1673–1680. 8. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents (2004) The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediatrics 14(2 Suppl 4th report):555–576. 9. Li A, et al. (2013) Hypotension due to Kir6.1 gain-of-function in vascular smooth muscle. J Am Heart Assoc 2(4):e000365. 10. Levin MD, et al. (2015) Electrophysiologic consequences of KATP gain of function in the heart: Conduction abnormalities in Cantu syndrome. Heart Rhythm 12(11):2316–2324. 11. Razani B, et al. (2011) Fatty acid synthase modulates homeostatic responses to myocardial stress. J Biol Chem 286(35):30949–30961. 12. Flagg TP, et al. (2004) Remodeling of excitation-contraction coupling in transgenic mice expressing ATP-insensitive sarcolemmal KATP channels. Am J Physiol Heart Circ Physiol 286(4):H1361–H1369. 13. Tong X, et al. (2006) Consequences of cardiac myocyte-specific ablation of KATP channels in transgenic mice expressing dominant negative Kir6 subunits. Am J Physiol Heart Circ Physiol 291(2):H543–H551. 14. Agah R, et al. (1997) Gene recombination in postmitotic cells. Targeted expression of Cre recombinase provokes cardiac-restricted, site-specific rearrangement in adult ventricular muscle in vivo. J Clin Invest 100(1):169–179. 15. Catterall WA (2011) Voltage-gated calcium channels. Cold Spring Harb Perspect Biol 3(8):a003947. 16. De Jongh KS, et al. (1996) Specific phosphorylation of a site in the full-length form of the α1 subunit of the cardiac L-type calcium channel by adenosine 3′,5′-cyclic monophosphate-dependent protein kinase. Biochemistry 35(32):10392–10402. 17. Hulme JT, Yarov-Yarovoy V, Lin TW, Scheuer T, Catterall WA (2006) Autoinhibitory control of the CaV1.2 channel by its proteolytically processed distal C-terminal domain. J Physiol 576(Pt 1):87–102. 18. Fuller MD, Emrick MA, Sadilek M, Scheuer T, Catterall WA (2010) Molecular mechanism of calcium channel regulation in the fight-or-flight response. Sci Signal 3(141):ra70. 19. Fu Y, Westenbroek RE, Scheuer T, Catterall WA (2014) Basal and β-adrenergic regulation of the cardiac calcium channel CaV1.2 requires phosphorylation of serine 1700. Proc Natl Acad Sci USA 111(46):16598–16603. 20. Fu Y, Westenbroek RE, Scheuer T, Catterall WA (2013) Phosphorylation sites required for regulation of cardiac calcium channels in the fight-or-flight response. Proc Natl Acad Sci USA 110(48):19621–19626. 21. Lemke T, et al. (2008) Unchanged β-adrenergic stimulation of cardiac L-type calcium channels in CaV 1.2 phosphorylation site S1928A mutant mice. J Biol Chem 283(50):34738–34744. 22. Kamp TJ, Hell JW (2000) Regulation of cardiac L-type calcium channels by protein kinase A and protein kinase C. Circ Res 87(12):1095–1102. 23. Flagg TP, Enkvetchakul D, Koster JC, Nichols CG (2010) Muscle KATP channels: recent insights to energy sensing and myoprotection. Physiol Rev 90(3):799–829. 24. Simmons BE, et al. (1988) Sickle cell heart disease. Two-dimensional echo and Doppler ultrasonographic findings in the hearts of adult patients with sickle cell anemia. Arch Intern Med 148(7):1526–1528. 25. Moss AJ, Allen HD (2008) Moss and Adams’ Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult (Lippincott Williams & Wilkins, Philadelphia), 7th Ed. 26. McCullagh WH, Covell JW, Ross J, Jr (1972) Left ventricular dilatation and diastolic compliance changes during chronic volume overloading. Circulation 45(5):943–951. 27. Ross J, Jr, McCullagh WH (1972) Nature of enhanced performance of the dilated left ventricle in the dog during chronic volume overloading. Circ Res 30(5):549–556. 28. Daaka Y, Luttrell LM, Lefkowitz RJ (1997) Switching of the coupling of the β2-adrenergic receptor to different G proteins by protein kinase A. Nature 390(6655):88–91. 29. Kuznetsov V, Pak E, Robinson RB, Steinberg SF (1995) β2-adrenergic receptor actions in neonatal and adult rat ventricular myocytes. Circ Res 76(1):40–52. 30. Weiss S, Oz S, Benmocha A, Dascal N (2013) Regulation of cardiac L-type Ca2+ channel CaV1.2 via the β-adrenergic-cAMP-protein kinase A pathway. Circ Res 113(5):617–631. 31. Tseng GN, Boyden PA (1991) Different effects of intracellular Ca and protein kinase C on cardiac T and L Ca currents. Am J Physiol 261(2 Pt 2):H364–H379.

32. Steinberg SF (2012) Cardiac actions of protein kinase C isoforms. Physiology (Bethesda) 27(3):130–139. 33. Woo SH, Lee CO (1999) Role of PKC in the effects of α1-adrenergic stimulation on Ca2+ transients, contraction and Ca2+ current in guinea-pig ventricular myocytes. Pflugers Arch 437(3):335–344. 34. Kelso E, Spiers P, McDermott B, Scholfield N, Silke B (1996) Dual effects of endothelin-1 on the L-type Ca2+ current in ventricular cardiomyocytes. Eur J Pharmacol 308(3):351–355. 35. Yang L, et al. (2005) Ser1928 is a common site for CaV1.2 phosphorylation by protein kinase C isoforms. J Biol Chem 280(1):207–214. 36. Braz JC, et al. (2004) PKC-α regulates cardiac contractility and propensity toward heart failure. Nat Med 10(3):248–254. 37. Ter Keurs HE, Boyden PA (2007) Calcium and arrhythmogenesis. Physiol Rev 87(2):457–506. 38. Yang L, Katchman A, Samad T, Morrow JP (2013) β-Adrenergic regulation of the L-type Ca2+ channel does not require phosphorylation of β1C Ser1700. Circ Res 113(7):871–880. 39. Yang L, et al. (2009) Protein kinase C isoforms differentially phosphorylate CaV1.2 α1C. Biochemistry 48(28):6674–6683. 40. Hofmann F, Flockerzi V, Kahl S, Wegener JW (2014) L-type CaV1.2 calcium channels: From in vitro findings to in vivo function. Physiol Rev 94(1):303–326. 41. Committee on Care and Use of Laboratory Animals (1996) Guide for the Care and Use of Laboratory Animals (National Institutes of Health, Bethesda, MD), DHHS Publ No (NIH) pp 85–23. 42. Ray O (2004) How the mind hurts and heals the body. Am Psychol 59(1):29–40. 43. Sohal DS, et al. (2001) Temporally regulated and tissue-specific gene manipulations in the adult and embryonic heart using a tamoxifen-inducible Cre protein. Circ Res 89(1):20–25. 44. Wang Z, York NW, Nichols CG, Remedi MS (2014) Pancreatic β cell dedifferentiation in diabetes and redifferentiation following insulin therapy. Cell Metab 19(5):872–882. 45. Hell JW, et al. (1993) Identification and differential subcellular localization of the neuronal class C and class D L-type calcium channel α1 subunits. J Cell Biol 123(4):949–962. 46. Hell JW, et al. (1993) Differential phosphorylation of two size forms of the neuronal class C L-type calcium channel α1 subunit. J Biol Chem 268(26):19451–19457. 47. Hulme JT, Westenbroek RE, Scheuer T, Catterall WA (2006) Phosphorylation of serine 1928 in the distal C-terminal domain of cardiac CaV1.2 channels during β1-adrenergic regulation. Proc Natl Acad Sci USA 103(44):16574–16579. 48. Emrick MA, Sadilek M, Konoki K, Catterall WA (2010) β-adrenergic-regulated phosphorylation of the skeletal muscle CaV1.1 channel in the fight-or-flight response. Proc Natl Acad Sci USA 107(43):18712–18717. 49. Singh GK, et al. (2013) Alterations in ventricular structure and function in obese adolescents with nonalcoholic fatty liver disease. J Pediatr 162(6):1160–1168. 50. Lang RM, Mor-Avi V, Sugeng L, Nieman PS, Sahn DJ (2006) Three-dimensional echocardiography: The benefits of the additional dimension. J Am Coll Cardiol 48(10):2053–2069. 51. Devereux RB, et al. (1986) Echocardiographic assessment of left ventricular hypertrophy: Comparison to necropsy findings. Am J Cardiol 57(6):450–458. 52. Khoury PR, Mitsnefes M, Daniels SR, Kimball TR (2009) Age-specific reference intervals for indexed left ventricular mass in children. J Am Soc Echocardiogr 22(6):709–714. 53. Daniels SR, Loggie JM, Khoury P, Kimball TR (1998) Left ventricular geometry and severe left ventricular hypertrophy in children and adolescents with essential hypertension. Circulation 97(19):1907–1911. 54. Lang RM, et al.; American Society of Echocardiography’s Nomenclature and Standards Committee; Task Force on Chamber Quantification; American College of Cardiology Echocardiography Committee; American Heart Association; European Association of Echocardiography, European Society of Cardiology (2006) Recommendations for chamber quantification. Eur J Echocardiogr 7(2):79–108. 55. Lewis JF, Kuo LC, Nelson JG, Limacher MC, Quinones MA (1984) Pulsed Doppler echocardiographic determination of stroke volume and cardiac output: Clinical validation of two new methods using the apical window. Circulation 70(3):425–431. 56. Greenberg NL, et al. (2002) Doppler-derived myocardial systolic strain rate is a strong index of left ventricular contractility. Circulation 105(1):99–105. 57. Singh GK, et al. (2010) Accuracy and reproducibility of strain by speckle tracking in pediatric subjects with normal heart and single ventricular physiology: A twodimensional speckle-tracking echocardiography and magnetic resonance imaging correlative study. J Am Soc Echocardiogr 23(11):1143–1152. 58. Amundsen BH, et al. (2006) Noninvasive myocardial strain measurement by speckle tracking echocardiography: Validation against sonomicrometry and tagged magnetic resonance imaging. J Am Coll Cardiol 47(4):789–793. 59. Stein PK, Reddy A (2005) Non-linear heart rate variability and risk stratification in cardiovascular disease. Indian Pacing Electrophysiol J 5(3):210–20. 60. Subramaniam A, et al. (1991) Tissue-specific regulation of the alpha-myosin heavy chain gene promoter in transgenic mice. J Biol Chem 266(36):24613–24620. 61. Regan CP, Manabe I, Owens GK (2000) Development of a smooth muscle-targeted Cre recombinase mouse reveals novel insights regarding smooth muscle myosin heavy chain promoter regulation. Circ Res 87(5):363–369. 62. Fleming S, et al. (2011) Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: A systematic review of observational studies. Lancet 377(9770):1011–1018.

6778 | www.pnas.org/cgi/doi/10.1073/pnas.1606465113

ACKNOWLEDGMENTS. We thank Theresa Harter for help with animal husbandry, as well as the patients and volunteer members of the Center for the Investigation of Membrane Excitability Diseases and the Department of Pediatrics for their participation in the Cantu research clinics.

Levin et al.

Supporting Information Levin et al. 10.1073/pnas.1606465113 SI Methods Human Study Design. Patients were recruited to an annual research

clinic through invitations from cardiology and genetic outpatient clinics at St. Louis Children’s Hospital, and through the CS interest group website (www.cantu-syndrome.org). After a detailed explanation of the study, and before enrollment, written informed consent was obtained from each subject or, if under 18, their parents. We included healthy age, gender, and body mass index (BMI)-matched subjects from a separate study (49). The study was approved by the Human Research Protection Office of Washington University School of Medicine and performed at St. Louis Children’s Hospital. Standard clinical histories and physical examinations, including height, weight, and head circumference measurements, were made. BP was measured by manual sphygmomanometer with appropriate cuff size and heart rate, in the resting supine position and after 2 min in the upright position, to ascertain orthostatic vital sign changes. BP measurements were repeated three times to confirm measurement accuracy, and were subsequently compared with published normative values by gender and age (www.nhlbi. nih.gov/files/docs/guidelines/child_tbl.pdf). Ventricular structure. Transthoracic complete M-mode, 2D, and color Doppler echocardiographic examinations were performed with a commercially available ultrasound imaging system with appropriate size-phased array transducer (Vivid 7 and 9; General Electric Medical Systems). M-mode imaging of the LV in the parasternal short axis view was used to measure LV end-diastolic diameter (LVEDD), LV end-systolic diameter (LVESD), end diastolic posterior wall thickness (PWT), relative wall thickness (RWT = 2 × PWT/LVEDD) (50) and LV mass. LV mass was calculated and indexed to height (LVMI) using the Devereux equation (51). To define ventricular structural phenotype, the 95th percentiles for LVMI for children older than 9 y of age (>40 g/height2.7 in females and >45 g/height2.7 in males) and the 95th percentile value for RWT for normal children and adolescents (RWT > 0.41) were used as cutoff values to categorize abnormal LV geometry (52, 53). Children categorized as having normal LV geometry had LVMI and RWT below the 95th percentiles. Concentric remodeling was defined as normal LVMI and elevated RWT, eccentric hypertrophy as elevated LVMI and normal RWT, and concentric hypertrophy as elevated LVMI and RWT (54). Ventricular function. Cardiac output was calculated from measured aortic valve annular diameter (D), time velocity integral (TVI) of pulse-wave Doppler velocity in LV outflow tract, and HR (beats per minute) using equation: π × (D/2)2 × TVI × HR × 100 (l per min), averaged for three consecutive cardiac cycles and indexed against body surface area (BSA) (l·min−1·m2) (55). In addition, M-mode imaging was used to measure LV fractional shortening [FS = (LVEDD – LVESD)/LVEDD], and 2D imaging was used to measure LV ejection fraction using the modified Simpson method. Myocardial mechanics were evaluated by measurement of strain (dimensionless measure of myocardial deformation) and strain rate (time derivative of strain), which correlates with LV peak elastance, reflecting contractile performance (56). Strain and strain rate were analyzed by 2D speckle-tracking echocardiography. This technique is noninvasive, minimally angle-dependent, and has been validated against sonomicrometry and tagged MRI (57, 58). LV global longitudinal strain (GLS) and rates (GLSR) were measured from grayscale 2D apical images of the LV (four-, three-, and two-chamber views) (57). The peak LV GLS, systolic GLSR, early diastolic GLSR, and Levin et al. www.pnas.org/cgi/content/short/1606465113

late diastolic GLSR values were calculated using EchoPAC (General Electric Medical Systems) software, by averaging the GLS and GLSR measurements from the three apical views. Characterization of heart rate and rhythm. Cardiac rhythm and conduction were assessed by 15-lead surface ECG and rhythm strip, and two-lead 24-h ambulatory ECG recording. Data were loaded onto a MARS PC Holter Analyzer (GE Medical Systems) and analyzed using standard research Holter techniques. Time-domain HRV was used to measure the statistical properties of NN interval variation over various time scales (from beat-to-beat to 24 h). Frequency domain HRV using power spectral analysis (fast Fourier transforms) was used to quantify variance (power) of heart rate as a function of underlying physiological oscillations, reflecting different aspects of the regulatory action of the autonomic system on the heart (59). Animal Studies. Generation and strains of transgenic mice. All procedures complied

with the standards for the care and use of animal subjects as stated in the NIH Guide for the Care and Use of Laboratory Animals (41) and were reviewed and approved by the Washington University Institutional Animal Care and Use Committee. Animals used were as follows:: cGOF. Mice harboring a Kir6.1[G343D] mutation downstream of the β-chicken actin promoter fragment knocked into the ROSA26 locus as previously described (9) were crossed with tissue- and time-specific Cre-driver mice to yield experimental models. Germline cardiac-specific KATP GOF was achieved by crossing with αMHC-Cre mice, which express Cre recombinase under direction of an α-myosin heavy-chain promoter fragment (60). icGOF. Kir6.1[G343D] mice were crossed with Mer-Cre-Mer– regulated α-MHC promoter fragment mice (43) and transgene expression was induced in double-transgenic (TG) animals by 5× daily injections of tamoxifen (10 mg/kg) as detailed previously (44). Control single-TG littermates were treated the same way. vGOF. Kir6.1[G343D] mice were crossed with animals expressing CRE recombinase under control of a smooth muscle-myosin heavychain promoter fragment (61) (SM-MHC-Cre). Transgene expression was induced in double-TG animals by 5× daily injections of 10 mg/kg tamoxifen (44). Control single-TG littermates were treated the same way. Kir6.1[AAA]. TG mice carrying an inducible dominant-negative mutation in the pore-forming subunit of Kir6.1 were described previously (13). Double-TG animals were obtained by crossing with αMHC-Cre driver mice as described previously. Isolation of cardiac myocytes. Mice were anesthetized by subcutaneous injection with 2.5% (vol/vol) Avertin (10 mL/kg, i.p.). The heart was rapidly excised, and retrogradely perfused through the aorta with Ca2+-free solution for 5 min followed by perfusion with digestion solution containing 0.8 mg/mL collagenase (Type 2; Worthington Biochemical). LV myocytes were dispersed by manual trituration. Cells were stored at room temperature in WIM solution. Cellular electrophysiology. Isolated myocytes were transferred into a recording chamber containing Tyrode solution (below; 5.4 mM CsCl replaces KCl) and TTX (10 μM). ISO (1 μM) was added where indicated. Patch-clamp electrodes (1–3 MΩ when filled with electrode solution) were fabricated from soda lime glass microhematocrit tubes (Kimble 73813). Cell capacitance and series resistance were determined using 5–10 mV hyperpolarizing square pulse from a holding potential of –70 mV following establishment of whole-cell recording configuration. Series resistance was 1 of 9

electronically compensated by 60–80%. pCLAMP 9.0 software and Digidata 1200 converter were used to generate command pulses and collect data. Data were filtered at 1 kHz and recorded at 3 kHz. Single-cell contraction measurement. To assess contractility, unloaded cell length was measured using a video edge detection system (IonOptix). Myocytes were bathed with normal Tyrode solution and stimulated with bipolar-stimulating electrodes placed near the cell. Solutions. Wittenberg isolation medium. NaCl, 116 mM; KCl, 5.3 mM;

NaH2PO4, 1.2 mM; glucose, 11.6 mM; MgCl2, 3.7 mM; Hepes, 20 mM; L-glutamine, 2.0 mM; NaHCO3, 4.4 mM; KH2PO4, 1.5 mM; 1× essential vitamins (GIBCO catalog no. 12473-013); 1× amino acids (GIBCO catalog no. 11120-052); pH 7.3–7.4. Tyrode solution with CsCl substituted for KCl. NaCl, 137 mM; CsCl, 5.4 mM; NaH2PO4, 0.16 mM; glucose, 10 mM; CaCl2, 1.8 mM; MgCl2, 0.5 mM; Hepes, 5.0 mM; NaHCO3, 3.0 mM; pH 7.3–7.4. Krebs–Henseleit. NaCl, 118 mM; KCl, 4.7 mM; NaHCO3, 25 mM; NaH2PO4, 1.2 mM; MgSO4, 1.2 mM; CaCl2, 1.2 mM; glucose, 10 mM; saturated with a 95% O2–5% CO2 gas mixture; pH 7.3–7.4. KINT. KCl, 140 mM; K2ATP, 5 mM; Hepes, 10 mM; EGTA, 10 mM; pH 7.3–7.4.

CsINT. CsCl, 120 mM; TEA-Cl, 20 mM; K2ATP, 5 mM; Hepes, 10 mM-; pH 7.3–7.4. Western blot analysis. Hearts were homogenized in buffer containing 50 mM Tris (pH 8.5), 5 mM EDTA, 150 mM NaCl, 10 mM KCl, 1% Triton X-100, 5 mM NaF, 5 mM β-glycerophosphate, 1 mM sodium-orthovanadate, plus protease inhibitors and membranes were solubilized in homogenization buffer for 2 h at 4 °C. Insoluble material was removed by centrifugation at 16,000 × g for 20 min. Proteins were separated by SDS/PAGE, transferred to nitrocellulose, and analyzed by immunoblotting. Polyclonal anti-CNC1 was generated against amino acid sequences in the intracellular loop between domains II and III of Cav1.2 (821–838) and detects both the long and short forms of Cav1.2 channels (45, 46). Polyclonal CH2 antibodies were generated against peptides corresponding to residues 2051–2066 in the distal C terminus of Cav1.2 (16) and were used to detect the distal C terminus and the processed C terminus. Anti-CH3P was generated against residues 1923–1932 and recognizes phosphorylated S1928 (47). Anti-Cav1.2-pS1700 phosphospecific antibody was generated against residues 1694– 7109 in the proximal C terminus (48). Data analysis. Unless indicated, data were analyzed using Clampfit, Microsoft Excel, and GraphPad Prism6 (GraphPad) software. Results are presented as mean ± SEM. Statistical tests and P values are denoted in figures.

Fig. S1. Human echocardiography. (Upper) Two-dimensional four-chamber view images of hearts from CS patient (cs001) and control individual at both end systole and end diastole. Note multicolor tag markings along the LV chamber for computing strain (deformation) measurements. (Lower) CS patient shows markedly greater strain (−22.3) than control (−16.8). Comparisons of pertinent echocardiographic measures from control and CS patients.

Levin et al. www.pnas.org/cgi/content/short/1606465113

2 of 9

Fig. S2. Cantu patient circadian rhythm and high-frequency power graphs.

Levin et al. www.pnas.org/cgi/content/short/1606465113

3 of 9

Fig. S3. Cantu patient circadian rhythm and high-frequency power graphs.

Levin et al. www.pnas.org/cgi/content/short/1606465113

4 of 9

Table S1. Patient genotype and history cs001 Age (y), gender 12.3 M Height (cm) 152.1 Height (%) for age 75 Weight (kg) 45.6 Amino acid R1154W substitution History Orthopnea — Exercise intolerance — Symptoms with — exertion Palpitations — Presyncope — Syncope — Fatigue — Headaches Rhythm No abnormalities PDA Yes Pericardial effusion No Pulmonary No hypertension Lower extremity No edema Medications

Physical HR (bpm) Supine Upright HR norms for age (10–90%) BP (mmHg) Supine Upright Orthostatic changes: BP Orthostatic changes: HR BP norms for age (50–99%) Age at which systolic BP represents 50th percentile CV findings

cs002

cs003

cs004

cs005

cs006

cs007

cs008

cs009

cs010

cs011

17.9 F 155.3 10 45.4 R1154Q

23.4 F 163.7 Adult 57.2 R1154Q

47.0 F 181.2 Adult 100.1 R1154Q

18.1 F 157.8 10–25 68.3 R1154W

12.8 M 139.8 95 39.7 R1116H

— — —

— — —

Yes Yes Yes

— — Occasionally

— — —

— — —

— — —

— — —

— — —

— — —

Yes — — — Yes No

— — — — Yes No

Yes — — — Yes AF

Yes — — — No No

— — — — No No

— — — — Yes No

— — — — — No

— — — — — No

— — — — — No

— — — — — No

No Yes Yes

No No No

No Yes No

Yes No No

No No No

Yes No No

Yes No Yes

No No No

Yes No No

Yes No Yes

Yes

Yes

Yes

Yes

No

Yes

No

No

No

No

Atenolol, Cardizem Lasix, spironolactone

Enalapril, Focalin

Sildenafil

78 84 62–96

72 88 62–96

74 88 60–80

92 92 60–80

66 76 62–96

100 104 62–96

75 83 60–80

126 120 98–135

90 102 86–123

90 112 81–117

72 96 74–111

92/62 96/66 No

88/52 92/58 No

92/70 88/62 No

116/60 108/70 No

88/50 98/62 No

74/56 74/50 No

106/64 102/60 No

72/50 94/64 No

84/56 74/56 No

85/60 72/54 No

98/60 100/62 No

No

No

No

No

No

No

No

No

No

No

Yes

120–140/ 80–90 Normal adult

120–140/ 80–90 4-y-old girl

Chronic venous changes

None

108–133/ 109–133/ 120–140/ 63–90 65–90 80–90 4-y-old 4-y-old 6-y-old boy girl girl

None

None

None

101–126/ 120–140/ 59–86 80–90