Proteomic analysis of the developing mammalian brain links PCDH19 to the Wnt/β-catenin signalling pathway

Clustering Epilepsy (CE) is a neurological disorder caused by pathogenic variants of the Protocadherin 19 (PCDH19) gene. PCDH19 encodes a protein involved in cell adhesion and Estrogen Receptor α mediated-gene regulation. To gain further insights into the molecular role of PCDH19 in the brain, we investigated the PCDH19 interactome in the developing mouse hippocampus and cortex. Combined with a meta-analysis of all reported PCDH19 interacting proteins, our results show that PCDH19 interacts with proteins involved in actin, microtubule, and gene regulation. We report CAPZA1, αN-catenin and, importantly, β-catenin as novel PCDH19 interacting proteins. Furthermore, we show that PCDH19 is a regulator of β-catenin transcriptional activity, and that this pathway is disrupted in CE individuals. Overall, our results support the involvement of PCDH19 in the cytoskeletal network and point to signalling pathways where PCDH19 plays critical roles.