Functional analysis of the epilepsy gene Pcdh19 using a novel conditional GFP-reporter mouse model

PCDH19 is a cell adhesion molecule belonging to the delta2-protocadherin subfamily that plays a critical role in brain development, neuronal migration, synaptic organisation, and neural circuit formation. Mutations in PCDH19 cause PCDH19-clustering epilepsy, an infantile-onset disorder characterized by seizures and intellectual disabilities. Despite the increasing development of constitutive cellular and murine models to investigate the effects of Pcdh19 knockout on cell-cell interactions and cellular function, the spatiotemporal consequences of its loss remain poorly understood. To address this gap, we generated and validated a novel conditional Pcdh19 knockout mouse model incorporating a GFP reporter (Pcdh19-cKO-GFP), enabling cell type-specific and temporally controlled gene deletion and direct visualization of recombination events. Using a neuronal Syn1-Cre driver, we demonstrate that targeted deletion of Pcdh19 in neurons results in altered hippocampal neurogenesis and mouse behaviour. We further demonstrate the versatility of this model using a doxycycline-inducible Cre system, enabling temporally controlled deletion of Pcdh19 and the modelling of disease-relevant phenotypes. Finally, we validate adeno-associated viral (AAV) vector-mediated recombination as a strategy for precise postnatal manipulation of Pcdh19 expression. Collectively, this Pcdh19-cKO-GFP model provides a powerful and flexible genetic tool to interrogate the cell type specific and temporary regulated functions of PCDH19 in the developing and postnatal brain under physiological and disease conditions.