Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, China.
Genesis. 2021 Apr;59(4):e23415. doi: 10.1002/dvg.23415. Epub 2021 Mar 7.
VPS4B (vacuolar protein sorting 4B), a member of the ATPase associated with diverse cellular activities (AAA) protein family, is a component of the endosomal sorting complexes required for transport machinery which regulates the internalization and lysosomal degradation of membrane proteins. We previously reported that VPS4B is one of the pathogenic genes related to dentin dysplasia type I, although its function was largely unknown. To investigate the role of VPS4B in tooth development, we deleted the Vps4b gene in mice. We found that heterozygous knockout mice (Vps4b ) developed normally and were fertile. However, homozygous deletion of the Vps4b gene resulted in early embryonic lethality of Vps4b mice at approximately embryonic day 9.5 (E9.5). To investigate the underlying molecular mechanisms, we examined the molecular functions of VPS4B in vivo and in vitro. Cell experiments showed that VPS4B influenced the proliferation, apoptosis, and cell cycle of transfected human neuroblastoma cells (IMR-32 cells) with over-expression or knockdown of VPS4B. Moreover, qRT-PCR detection showed that the mRNA expression levels of apoptosis-, cell cycle-, and endocytosis-related genes was significantly down or up-regulated in RNA interference-mediated knockdown of VPS4B in IMR-32 cells and Vps4b E12.5 embryos. We accordingly speculated that signal transduction disorders of cell endocytosis are a contributing factor to the prenatal lethality of Vps4b mice.
VPS4B（液泡蛋白分选 4B）是 ATP 酶相关的多种细胞活动（AAA）蛋白家族的成员，是内体分选复合物所必需的组成部分，该复合物负责运输调节膜蛋白内化和溶酶体降解的机器。我们之前报道 VPS4B 是与牙本质发育不全 I 型相关的致病基因之一，尽管其功能尚不清楚。为了研究 VPS4B 在牙齿发育中的作用，我们在小鼠中敲除了 Vps4b 基因。我们发现杂合子敲除小鼠（Vps4b ）正常发育并且具有生育能力。然而，Vps4b 基因的纯合缺失导致 Vps4b 小鼠在大约胚胎第 9.5 天（E9.5）出现早期胚胎致死。为了研究潜在的分子机制，我们在体内和体外研究了 VPS4B 的分子功能。细胞实验表明，VPS4B 影响转染人神经母细胞瘤细胞（IMR-32 细胞）的增殖、凋亡和细胞周期，而过表达或敲低 VPS4B 会产生不同的效果。此外，qRT-PCR 检测显示，在 IMR-32 细胞和 Vps4b E12.5 胚胎中，RNA 干扰介导的 VPS4B 敲低会显著下调或上调凋亡、细胞周期和内吞作用相关基因的 mRNA 表达水平。因此，我们推测细胞内吞信号转导障碍是导致 Vps4b 小鼠产前致死的一个因素。
