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Using induced pluripotent stem cells to investigate cardiac phenotypes in Timothy syndrome


Individuals with congenital or acquired prolongation of the QT interval, or long QT syndrome (LQTS), are at risk of life-threatening ventricular arrhythmia1,2. LQTS is commonly genetic in origin but can also be caused or exacerbated by environmental factors1,3. A missense mutation in the L-type calcium channel CaV1.2 leads to LQTS in patients with Timothy syndrome4,5. To explore the effect of the Timothy syndrome mutation on the electrical activity and contraction of human cardiomyocytes, we reprogrammed human skin cells from Timothy syndrome patients to generate induced pluripotent stem cells, and differentiated these cells into cardiomyocytes. Electrophysiological recording and calcium (Ca2+) imaging studies of these cells revealed irregular contraction, excess Ca2+ influx, prolonged action potentials, irregular electrical activity and abnormal calcium transients in ventricular-like cells. We found that roscovitine, a compound that increases the voltage-dependent inactivation of CaV1.2 (refs 6–8), restored the electrical and Ca2+ signalling properties of cardiomyocytes from Timothy syndrome patients. This study provides new opportunities for studying the molecular and cellular mechanisms of cardiac arrhythmias in humans, and provides a robust assay for developing new drugs to treat these diseases.

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Figure 1: Generation of cardiomyocytes from control and Timothy syndrome iPSCs.
Figure 2: Electrophysiological features of Timothy syndrome cardiomyocytes.
Figure 3: Ca 2+ signalling in Timothy syndrome and control cardiomyocytes.
Figure 4: Roscovitine rescues the cellular phenotypes of Timothy syndrome cardiomyocytes.


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We thank K. Timothy and the Timothy syndrome patients who participated in this study; U. Francke for discussion and for providing karyotyping expertise; A. Cherry and D. Bangs for fibroblast isolation; K. C. Chan for iPSC cultures; O. Shcheglovitov for help with electrophysiological recordings; and A. Olson for help with the confocal microscope. Funding was provided by grants from the Japan Society for the Promotion for Science and the American Heart Association Western States to M.Y., and a National Institutes of Health Director’s Pioneer Award, a grant from the Simons Foundation to R.E.D and gifts from L. Miller, B. and F. Horowitz and M. McCaffery.

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Authors and Affiliations



M.Y. and R.E.D. designed research and wrote the manuscript; J.A.B., J.H. and R.E.D recruited the Timothy syndrome patients; M.Y. and X.J. generated and characterized control and Timothy syndrome iPSCs; A.M.P. conducted karyotyping; M.Y. performed generation and characterization of human cardiomyocytes, whole-cell patch clamp, and Ca2+ imaging; M.Y. and B.H. analysed cardiomyocytes contraction rates.

Corresponding author

Correspondence to Ricardo E. Dolmetsch.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-8 with legends and Supplementary Tables 1-2. (PDF 1874 kb)

Supplementary Methods

This file contains Supplementary Materials and Methods. (PDF 149 kb)

Supplementary Movie 1

This movie shows control EBs (round) spontaneously contracting at d37. (MOV 9615 kb)

Supplementary Movie 2

This movie shows control EBs (flat) spontaneously contracting at d37. (MOV 9497 kb)

Supplementary Movie 3

This movie shows TS EBs (round) spontaneously contracting at d37. (MOV 10200 kb)

Supplementary Movie 4

This movie shows TS EBs (flat) spontaneously contracting at d37. (MOV 9497 kb)

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Yazawa, M., Hsueh, B., Jia, X. et al. Using induced pluripotent stem cells to investigate cardiac phenotypes in Timothy syndrome. Nature 471, 230–234 (2011).

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