Laboratory of Neurobiology and Stem Cells, NeuroCellT, Department of Cellular Biology, Faculty of Biological Sciences, University of Concepcion, 4030000, Concepcion, Chile.
Department of Cell Biology, Genetics and Physiology, University of Malaga, IBIMA, Malaga, Spain.
Sci Rep. 2021 Sep 17;11(1):18537. doi: 10.1038/s41598-021-97948-3.
Ependymal cells have multiple apical cilia that line the ventricular surfaces and the central canal of spinal cord. In cancer, the loss of ependymal cell polarity promotes the formation of different types of tumors, such as supratentorial anaplastic ependymomas, which are highly aggressive in children. IIIG9 (PPP1R32) is a protein restricted to adult ependymal cells located in cilia and in the apical cytoplasm and has unknown function. In this work, we studied the expression and localization of IIIG9 in the adherens junctions (cadherin/β-catenin-positive junctions) of adult brain ependymal cells using confocal and transmission electron microscopy. Through in vivo loss-of-function studies, ependymal denudation (single-dose injection experiments of inhibitory adenovirus) was observed, inducing the formation of ependymal cells with a "balloon-like" morphology. These cells had reduced cadherin expression (and/or delocalization) and cleavage of the cell death marker caspase-3, with "cilia rigidity" morphology (probably vibrational beating activity) and ventriculomegaly occurring prior to these events. Finally, after performing continuous infusions of adenovirus for 14 days, we observed total cell denudation and reactive parenchymal astrogliosis. Our data confirmed that IIIG9 is essential for the maintenance of adherens junctions of polarized ependymal cells. Eventually, altered levels of this protein in ependymal cell differentiation may increase ventricular pathologies, such as hydrocephalus or neoplastic transformation.
室管膜细胞具有多个位于脑室表面和脊髓中央管的顶生纤毛。在癌症中，室管膜细胞极性的丧失促进了不同类型肿瘤的形成，如位于幕上的间变性室管膜瘤，在儿童中具有高度侵袭性。III G9（PPP1R32）是一种仅存在于成年室管膜细胞中的蛋白，位于纤毛和顶质体中，其功能未知。在这项工作中，我们使用共聚焦和透射电子显微镜研究了 IIIG9 在成年脑室管膜细胞黏着连接（钙粘蛋白/β-连环蛋白阳性连接）中的表达和定位。通过体内功能丧失研究，观察到室管膜脱落（抑制性腺病毒单次剂量注射实验），诱导具有“气球样”形态的室管膜细胞形成。这些细胞的钙粘蛋白表达减少（和/或定位改变），细胞死亡标记物 caspase-3 被切割，出现“纤毛僵硬”形态（可能是振动摆动活性），并且在这些事件发生之前出现脑室扩大。最后，在连续输注腺病毒 14 天后，我们观察到细胞完全脱落和反应性实质星形胶质细胞增生。我们的数据证实，III G9 对于极化室管膜细胞黏着连接的维持是必不可少的。最终，该蛋白在室管膜细胞分化中的水平改变可能会增加脑室病变，如脑积水或肿瘤转化。
