PCDH19-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.

PCDH19-Clustering Epilepsy (PCDH19-CE) 是一种由 X 连锁PCDH19基因突变引起的婴儿期发病疾病。有趣的是，杂合的雌性会受到影响，而半合的雄性则不会。虽然有令人信服的证据表明这种疾病源于 WT 和 PCDH19 无效细胞的共存，但支持神经表型的细胞机制仍不清楚。在这里，我们调查了Pcdh19的影响WT 和 KO 神经元嵌合对突触发生和网络活动的影响。使用我们之前建立的敲入和敲除小鼠模型，结合 CRISPR-Cas9 基因组编辑技术，我们证明了表达 PCDH19 的神经元和缺失 PCDH19 的神经元之间的兴奋性突触接触减少。在混合种群中也发现了显着改变的神经元形态和神经元网络活动。此外，我们显示在Pcdh19杂合小鼠中，WT 和 KO 神经元自然共存，存在异常的对侧轴突分支。总体而言，我们的数据显示 PCDH19 的镶嵌表达破坏了生理神经突通讯，导致神经元活动异常，这是 PCDH19-CE 的标志。