Elucidating the role Cav1.2 dysfunction in the pathogenesis of timothy syndrome using iPSC-derived neurons.

Abstract

The L-type Ca2+ channel (LTCC) is critical for normal function of the heart and brain, and mutations in this channel have been linked to severe cardiac and neurodevelopmental disorders. Specifically, single de novo point mutations within the CaV1.2 LTCC can cause a multi-system disorder known as Timothy Syndrome (TS). TS patients exhibit severe cardiac arrhythmias, long-QT syndrome, developmental delays, and autism spectrum disorder (ASD). TS is one of the most penetrant genetic forms of ASD, making it an ideal model system for understanding the role of Ca2+ dysfunction in ASD. Prior work has demonstrated that TS mutations can cause marked differences in channel gating, with a possible association between enhanced channel activation and the neurological features of TS. Here, we utilize human induced pluripotent stem cell (iPSC)-derived neurons harboring select CaV1.2 mutations to probe the effects of these gating changes on neuronal function. Voltage clamp recordings demonstrate measurable alterations to the biophysical properties of calcium channels within wildtype vs. TS iPSC- derived neurons. In addition, current clamp recordings reveal a difference in the pattern of electrical activity across the neuron populationsbetween distinct neuronal populations, demonstrating an effect of the TS mutations at the level of a single neuron. Overall, these cells enable evaluation of the role of CaV1.2 in the pathogenesis of ASD. Through the study of rare mutations such as TS we stand to gain further insight into ASD pathogenesis, especially as Ca2+ disruption may be a recurrent feature of ASD.