A human iPSC-based model to investigate the effects of psychiatric risk gene CACNA1C on neuronal development and network activity

CACNA1C encodes the pore-forming subunit of the L-type voltage gated calcium channel Cav1.2. Genome wide association studies have consistently shown that variation in CACNA1C increases risk for psychiatric diseases, including bipolar disorder, schizophrenia, and autism spectrum disorder (ASD). In addition, de novo mutations in the gene cause Timothy Syndrome (TS), a multi-system disorder with symptoms that include ASD, developmental delay and epilepsy. This thesis investigates the role of CACNA1C on cortical neuronal development and neuronal network activity. CRISPR/Cas9 gene editing was used in human induced pluripotent stem cells (iPSCs) to derive homozygous CACNA1C knockout lines. In addition to this an iPSC line was derived from an atypical TS patient carrying a novel mutation in CACNA1C that was predicted to have a gain-of-function effect. Differentiation of these lines into cortical neurons demonstrated changes to the expression of neuronal markers and rosette numbers following alterations to CACNA1C expression/function. Alterations to CACNA1C also led to changes in the activation of downstream signalling pathways and the expression of enzymes responsible for GABA production. Functional analysis of neuronal network activity showed alterations to the pattern of neuron bursting behaviour in both the knockout and patient lines. These changes could be rescued using pharmacology targeting either L-type calcium channels or GABA-A receptors. Overall, this data demonstrates that CACNA1C plays a role in cortical neuronal development and neuronal network activity. The results suggest that changes to GABAergic signalling may be responsible for the changes seen to neuronal network activity