School of Medicine, The University of Adelaide, Adelaide 5005, Australia; Robinson Research Institute, The University of Adelaide, Adelaide 5006, Australia; School of Biological Sciences, The University of Adelaide, Adelaide 5005, Australia.
Bioinformatics Hub, School of Biological Sciences, The University of Adelaide, Adelaide, 5005, Australia.
Neurobiol Dis. 2018 Aug;116:106-119. doi: 10.1016/j.nbd.2018.05.004. Epub 2018 May 12.
PCDH19-Girls Clustering Epilepsy (PCDH19-GCE) is a childhood epileptic encephalopathy characterised by a spectrum of neurodevelopmental problems. PCDH19-GCE is caused by heterozygous loss-of-function mutations in the X-chromosome gene, Protocadherin 19 (PCDH19) encoding a cell-cell adhesion molecule. Intriguingly, hemizygous males are generally unaffected. As PCDH19 is subjected to random X-inactivation, heterozygous females are comprised of a mosaic of cells expressing either the normal or mutant allele, which is thought to drive pathology. Despite being the second most prevalent monogeneic cause of epilepsy, little is known about the role of PCDH19 in brain development. In this study we show that PCDH19 is highly expressed in human neural stem and progenitor cells (NSPCs) and investigate its function in vitro in these cells of both mouse and human origin. Transcriptomic analysis of mouse NSPCs lacking Pcdh19 revealed changes to genes involved in regulation of neuronal differentiation, and we subsequently show that loss of Pcdh19 causes increased NSPC neurogenesis. We reprogramed human fibroblast cells harbouring a pathogenic PCDH19 mutation into human induced pluripotent stem cells (hiPSC) and employed neural differentiation of these to extend our studies into human NSPCs. As in mouse, loss of PCDH19 function caused increased neurogenesis, and furthermore, we show this is associated with a loss of human NSPC polarity. Overall our data suggests a conserved role for PCDH19 in regulating mammalian cortical neurogenesis and has implications for the pathogenesis of PCDH19-GCE. We propose that the difference in timing or "heterochrony" of neuronal cell production originating from PCDH19 wildtype and mutant NSPCs within the same individual may lead to downstream asynchronies and abnormalities in neuronal network formation, which in-part predispose the individual to network dysfunction and epileptic activity.
PCDH19 相关女性癫痫（PCDH19-GCE）是一种儿童期癫痫性脑病，其特征是存在一系列神经发育问题。PCDH19-GCE 是由 X 染色体基因 Protocadherin 19（PCDH19）的杂合功能丧失突变引起的，该基因编码一种细胞间黏附分子。有趣的是，半合子男性通常不受影响。由于 PCDH19 受到随机 X 染色体失活的影响，杂合子女性由表达正常或突变等位基因的细胞镶嵌体组成，这被认为是导致病理学的原因。尽管 PCDH19 是第二大常见的单基因癫痫病因，但人们对其在大脑发育中的作用知之甚少。在这项研究中，我们表明 PCDH19 在人类神经干/祖细胞（NSPCs）中高度表达，并研究了其在来自小鼠和人类的这些细胞中的体外功能。缺乏 Pcdh19 的小鼠 NSPCs 的转录组分析显示，与神经元分化调节相关的基因发生变化，随后我们表明 Pcdh19 的缺失导致 NSPC 神经发生增加。我们将携带致病性 PCDH19 突变的人成纤维细胞重编程为人类诱导多能干细胞（hiPSC），并对这些细胞进行神经分化，以将我们的研究扩展到人类 NSPCs。与小鼠一样，PCDH19 功能的丧失导致神经发生增加，此外，我们还表明这与人类 NSPC 极性的丧失有关。总的来说，我们的数据表明 PCDH19 在调节哺乳动物皮质神经发生方面具有保守作用，这对 PCDH19-GCE 的发病机制具有重要意义。我们提出，源自同一个体中 PCDH19 野生型和突变型 NSPCs 的神经元细胞产生的时间或“异时性”的差异可能导致下游神经元网络形成的不同步和异常，这在一定程度上使个体易发生网络功能障碍和癫痫活动。
