Tasheva, S.Nieto Guil, A.F.Homan, C.C.Gecz, J.Thomas, P.Q.2021-02-042021-02-042021Molecular Neurobiology, 2021; 58(5):2005-20180893-76481559-1182http://hdl.handle.net/2440/129726Published: 07 January 2021PCDH19-Clustering Epilepsy (PCDH19-CE) is an infantile onset disorder caused by mutation of the X-linked PCDH19 gene. Intriguingly, heterozygous females are affected while hemizygous males are not. While there is compelling evidence that this disorder stems from the coexistence of WT and PCDH19-null cells, the cellular mechanism underpinning the neurological phenotype remains unclear. Here, we investigate the impact of Pcdh19 WT and KO neuron mosaicism on synaptogenesis and network activity. Using our previously established knock-in and knock-out mouse models, together with CRISPR-Cas9 genome editing technology, we demonstrate a reduction in excitatory synaptic contacts between PCDH19-expressing and PCDH19-null neurons. Significantly altered neuronal morphology and neuronal network activities were also identified in the mixed populations. In addition, we show that in Pcdh19 heterozygous mice, where the coexistence of WT and KO neurons naturally occurs, aberrant contralateral axonal branching is present. Overall, our data show that mosaic expression of PCDH19 disrupts physiological neurite communication leading to abnormal neuronal activity, a hallmark of PCDH19-CE.en© The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature 2021Protocadherin 19PCDH19PCDH19-Clustering Epilepsy (PCDH19-CE)EpilepsySynapsesJournal article100003279410.1007/s12035-020-02242-40006073595000102-s2.0-85099104463561555Tasheva, S. [0000-0002-1394-580X]Nieto Guil, A.F. [0000-0002-9787-3486]Homan, C.C. [0000-0003-2847-8586]Gecz, J. [0000-0002-7884-6861]