The Role of Connexin32 in the Pathogenesis of CMTX

描述（申请人提供）：连接蛋白32（Cx 32）属于一种基因 一个至少有15个成员的家族（在哺乳动物中），所有成员都编码间隙连接 proteins.六个连接蛋白寡聚形成半通道（或连接子）， 当与相邻膜上的另一半通道并置时形成通道。 间隙连接允许离子和小分子的扩散，通常具有 分子量小于1000 Da。单个半通道可由以下组成： 一个以上的连接蛋白（异型连接蛋白），和半通道组成的 不同的连接蛋白也可以形成通道（异型间隙连接）。中 在一系列的论文中，我和我的同事们研究了基因突变是如何发生的， 人Cx 32基因引起X连锁型腓骨肌萎缩症（CMTX）。 这是第二个最常见的形式遗传性脱髓鞘神经病（CMT 类型1），一个遗传异质性的群体，集体是其中最 常见的遗传性神经系统疾病我们是第一个证明 突变导致CMTX，Cx 32定位于切口和旁阳极 （雪旺细胞（SC）髓鞘的区域，其组成于 非致密髓鞘），并且SC髓鞘含有功能间隙 交叉点与此特别相关的是，一些突变会导致损失 或改变运输，使突变蛋白不能到达 细胞膜。在到达细胞膜的突变体中，有些未能到达细胞膜， 形成功能性间隙连接（沟通能力不足），而其他人则是 沟通能力。我们已经制造出表达野生型或 两个不同的突变体Cx 32等位基因，并发现这两个突变体的贩运， 蛋白质与转染细胞中的蛋白质相似。其中一个变种人， Arg 142 Trp对野生型Cx 32具有显性负效应： 突变蛋白质“挂”在高尔基体，它也导致野生型蛋白质， 也在那里积累。这种竞争性更新的目标如下：（1） 以确定CMTX突变的影响是否是自主的， 髓鞘化雪旺细胞;（2）确定Cx 32突变体如何形成间隙 体外连接破坏髓鞘SC的功能;（3）确定 髓鞘形成SC是否表达其他连接蛋白以及其他连接蛋白是否可以 髓鞘SC中Cx 32的替代品。结果将阐明间隙如何 连接蛋白在髓鞘形成SC中组装并发挥功能， CMTX分子病理生理学的基本信息，以及 阐明其他间隙连接蛋白的突变如何导致疾病。

DESCRIPTION (provided by the applicant): Connexin 32 (Cx32) belongs to a gene family of at least 15 members (in mammals), all of which encode gap junction proteins. Six connexins oligomerize to form a hemi-channel (or connexon), which forms a channel when apposed to another hemi-channel on an adjacent membrane. Gap junctions allow the diffusion of ions and small molecules, typically with a molecular mass less than 1000 Da. Individual hemichannels can be composed of more than one connexin (heterotypic connexons), and hemichannels composed of different connexins can also form channels (heterotypic gap junctions). In a series of papers, my colleagues and I have investigated how mutations in the human Cx32 gene cause the X-linked form of Charcot-Marie-Tooth disease (CMTX). This is the second most common form of inherited demyelinating neuropathy (CMT type 1), a genetically heterogenous group that collectively is among the most common inherited neurological diseases. We were the first to show that mutations cause CMTX, that Cx32 is localized to incisures and paranodes (regions of the Schwann cell (SC) myelin sheath that are composed on non-compact myelin) and that the SC myelin sheath contains functional gap junctions. Of particular relevance to this grant, some mutations result in loss of the protein, or alter trafficking so that the mutant protein does not reach the cell membrane. Of the mutants that reach the cell membrane, some fail to form functional gap junctions (communication-incompetent), whereas others are communication-competent. We have made transgenic mice that express wild type or two different mutant Cx32 alleles and found that trafficking of the two mutant proteins was similar to that in transfected cells. One of the mutants, Arg142Trp, has a dominant-negative effect on wild type Cx32: not only does the mutant protein "hang up" in the Golgi, it also causes the wild type protein to accumulate there, too. The goals of this competing renewal are as follows: (1) to determine whether the effects of CMTX mutations are autonomous to myelinating Schwann cells; (2) to determine how Cx32 mutants that form gap junctions in vitro disrupt the function of myelinating SC; (3) to determine whether myelinating SC express other connexins and whether other connnexins can substitute for Cx32 in myelinating SC. The results will elucidate how gap junction proteins are assembled and function in myelinating SC, provide fundamental information on the molecular pathophysiology of CMTX, and illuminate how mutations in other gap junction proteins cause disease.