A critical neurodevelopmental role for L-type voltage-gated calcium channels in neurite extension and radial migration

In spite of many association studies linking gene polymorphisms and mutations of L-type Voltage-Gated Ca 2+ Channels (VGCC) in neurodevelopmental disorders, such as autism and schizophrenia, specific L-type VGCC roles during brain development remain unclear. Yet, calcium signaling has been shown to be essential for neurodevelopmental processes such as sculpting of neurites, functional wiring and fine tuning of growing networks. To bridge this gap, we performed submembraneous calcium imaging using a membrane-tethered genetically-encoded calcium indicator (GECI) Lck-G-CaMP7. We successfully recorded s pontaneous r egenerative ca lcium t ransient s (SRCaTs) in developing mouse excitatory cortical neurons prepared from both sexes, before synapse formation. SRCaTs originated locally in immature neurites, independently of somatic calcium rises, and were significantly more elevated in the axons than in dendrites. SRCaTs were not blocked by tetrodoxin, a Na + channel blocker, but strongly inhibited by hyperpolarization, suggesting a voltage-dependent source. Pharmacological and genetic manipulations revealed a critical importance of Ca v 1.2 (CACNA1C) pore-forming subunit of L-type voltage-gated calcium channels (VGCC), which were indeed expressed in immature mouse brains. Consistently, knocking out Ca v 1.2 resulted in significant alteration of neurite outgrowth. Furthermore, expression of a gain-of-function Ca v 1.2 mutant found in Timothy syndrome, an autosomal dominant multisystem disorder exhibiting syndromic autism, resulted in impaired radial migration of layer 2/3 excitatory neurons, while postnatal abrogation of Ca v 1.2 enhancement could rescue cortical malformation. Taken together, these lines of evidence suggest a critical role for spontaneous opening of L-type VGCC in neural development and corticogenesis, and indicate that L-type VGCC might constitute a perinatal therapeutical target for neuropsychiatric calciochannelopathies. SIGNIFICANCE STATEMENT In spite of many association studies linking gene polymorphisms and mutations of L-type Voltage-Gated Ca 2+ Channels (VGCC) in neurodevelopmental disorders, such as autism and schizophrenia, specific L-type VGCC roles during brain development remain unclear. We here combined the latest Ca 2+ indicator technology, quantitative pharmacology, and in utero electroporation, and found a hitherto unsuspected L-type VGCC role for determining the Ca 2+ signaling landscape of mouse immature neurons. We found that a malfunctional L-type VGCC in immature neurons prior to birth might cause errors in neuritic growth and in cortical migration. Interestingly, the retarded corticogenesis phenotype was rescued by postnatal correction of L-type VGCC signal aberration. These findings suggest that L-type VGCC might constitute a perinatal therapeutical target for neurodevelopment-associated psychiatric disorders.