CACNA1Ahaploinsufficiency leads to reduced synaptic function and increased intrinsic excitability

Abstract

AbstractHaploinsufficiency of theCACNA1Agene, encoding the pore-forming α1 subunit of P/Q-type voltage-gated calcium channels, is associated with a clinically variable phenotype ranging from cerebellar ataxia, to neurodevelopmental syndromes with epilepsy and intellectual disability.To understand the pathological mechanisms ofCACNA1Aloss-of-function variants, we characterized a human neuronal model forCACNA1Ahaploinsufficiency, by differentiating isogenic induced pluripotent stem cell lines into glutamatergic neurons, and investigated the effect ofCACNA1Ahaploinsufficiency on mature neuronal networks through a combination of electrophysiology, gene expression analysis, andin silicomodeling.We observed an altered network synchronization inCACNA1A+/−networks alongside synaptic deficits, notably marked by an augmented contribution of GluA2-lacking AMPA receptors. Intriguingly, these synaptic perturbations coexisted with increased non-synaptically driven activity, as characterized by inhibition of NMDA and AMPA receptors on micro-electrode arrays. Single-cell electrophysiology and gene expression analysis corroborated this increased intrinsic excitability through reduced potassium channel function and expression. Moreover, we observed partial mitigation of theCACNA1A+/−network phenotype by 4-aminopyridine, a therapeutic intervention for episodic ataxia type 2.In summary, our study pioneers the characterization of a human induced pluripotent stem cell-derived neuronal model forCACNA1Ahaploinsufficiency, and has unveiled novel mechanistic insights. Beyond showcasing synaptic deficits, this neuronal model exhibited increased intrinsic excitability mediated by diminished potassium channel function, underscoring its potential as a therapeutic discovery platform with predictive validity.