A Critical Neurodevelopmental Role for L-Type Voltage-Gated Calcium Channels in Neurite Extension and Radial Migration

Despite many association studies linking gene polymorphisms and mutations of L-type voltage-gated Ca²⁺ channels (VGCCs) in neurodevelopmental disorders such as autism and schizophrenia, the roles of specific L-type VGCC during brain development remain unclear. 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 investigate this relationship, we performed submembraneous calcium imaging using a membrane-tethered genetically encoded calcium indicator (GECI) Lck-G-CaMP7. We successfully recorded spontaneous regenerative calcium transients (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 were strongly inhibited by hyperpolarization, suggesting a voltage-dependent source. Pharmacological and genetic manipulations revealed the critical importance of the Ca_v1.2 (CACNA1C) pore-forming subunit of L-type VGCCs, which were indeed expressed in immature mouse brains. Consistently, knocking out Ca_v1.2 resulted in significant alterations of neurite outgrowth. Furthermore, expression of a gain-of-function Ca_v1.2 mutant found in Timothy syndrome, an autosomal dominant multisystem disorder exhibiting syndromic autism, resulted in impaired radial migration of layer 2/3 excitatory neurons, whereas postnatal abrogation of Ca_v1.2 enhancement could rescue cortical malformation. Together, these lines of evidence suggest a critical role for spontaneous opening of L-type VGCCs in neural development and corticogenesis and indicate that L-type VGCCs might constitute a perinatal therapeutic target for neuropsychiatric calciochannelopathies.

SIGNIFICANCE STATEMENT Despite many association studies linking gene polymorphisms and mutations of L-type voltage-gated Ca²⁺ channels (VGCCs) in neurodevelopmental disorders such as autism and schizophrenia, the roles of specific L-type VGCCs during brain development remain unclear. We here combined the latest Ca²⁺ indicator technology, quantitative pharmacology, and in utero electroporation and found a hitherto unsuspected role for L-type VGCCs in determining the Ca²⁺ signaling landscape of mouse immature neurons. We found that malfunctional L-type VGCCs in immature neurons before birth might cause errors in neuritic growth and cortical migration. Interestingly, the retarded corticogenesis phenotype was rescued by postnatal correction of L-type VGCC signal aberration. These findings suggest that L-type VGCCs might constitute a perinatal therapeutic target for neurodevelopment-associated psychiatric disorders.