How do dominant PMP2 mutations cause demyelinating neuropathy?

周围神经病是美国最常见的神经退行性疾病之一，具有 总患病率为1.66%，60岁以上人群患病率为6.6%。尽管它很普遍，但一个 在相当一部分患者中无法确定原因，除非有可治疗的原因 确诊后，治疗仅限于症状。这些发人深省的统计数据一直笼罩着这一领域 几十年。然而，如果一个人接受神经病的遗传原因(这是 以惊人的速度被发现)将可能是信息性的，然后利用这些丰富的信息来源 应该提供解开病因的钥匙，从而找到治疗神经疾病的新方法， 不仅是特定的遗传原因，还有更常见的原因所涉及的途径， 比如糖尿病神经病变。在这种观点下，CMT的每一项新事业都有助于完成 分子缺陷是如何导致神经病的，有许多意想不到的惊喜。 我们最近描述了一种新的遗传性脱髓鞘神经病的遗传原因 人类-从头开始，PMP2的显性突变。PMP2编码髓鞘蛋白P2，它是一种 与脂肪酸和胆固醇结合的胞浆蛋白。它是致密髓鞘的次要成分； PNS髓鞘比CNS髓鞘丰富。所描述的与疾病相关的突变 到目前为止，在蛋白质的相似区域发现了p.Ile43Asn、p.Thr51Pro和p.Ile52Thr，给出了 产生了这样的想法，即突变体在髓鞘雪旺细胞中分享了共同的毒性功能获得 这会导致脱髓鞘。我们使用CRISPR-Cas9对小鼠进行了一种突变，p.Ile52Thr， 并建议从以下几个具体目标来分析这一小鼠模型。 目的1：P.Ile52Thr突变小鼠会患上脱髓鞘神经病吗？ 我们产生了四个携带p.Ile52Thr突变的独立小鼠系，并有生殖系 在其中的三条线路上传输。我们将进行病理和电生理分析 在三个品系中的每一个上，比较纯合子(p.Ile52Thr/p.Ile52Thr)和杂合子(P.Ile52Thr) (p.Ile52Thr/+)和野生型(WT)(+/+)小鼠。尽管杂合子小鼠更准确地建立了 人类疾病，我们包括纯合子小鼠，因为它们可能有更明显的 表型。 目的2.P.Ile52Thr突变小鼠的三叉神经节髓鞘是否发生改变？ 由于P2与脂肪酸和胆固醇结合，我们将调查P.Ile43Asn 突变改变了髓鞘的脂质成分，通过脂类组学分析神经和通过执行 致密髓鞘的电子显微镜观察。

Peripheral neuropathy is one of the most common neurodegenerative diseases in America, with an overall prevalence of 1.66%, and 6.6% in persons older than 60 years. In spite of its prevalence, a cause cannot be identified in a substantial fraction of patients, and unless a treatable cause is identified, treatment is limited to symptoms. These sobering statistics have hung over the field for decades. However, if one accepts the idea that the genetic causes of neuropathy (which are being found at an astounding rate) will likely be informative, then exploiting this rich source of information should provide the keys to unlocking the causes and thus finding new treatments of neuropathies, not only the specific genetic causes, but also the pathways involved in the more common cause, such as diabetic neuropathy. In this view, each new cause of CMT helps to complete the “puzzle” of how molecular defects cause neuropathy, with many unanticipated surprises. We recently described a new genetic cause of dominantly inherited demyelinating neuropathy in humans – de novo, dominant mutations in PMP2. PMP2 encodes the myelin protein P2, which is a cytosolic protein that binds to fatty acids and cholesterol. It is minor component of compact myelin; more abundant in the PNS myelin than in CNS myelin. The disease-associated mutations described to date - p.Ile43Asn, p.Thr51Pro, and p.Ile52Thr – are found in a similar region of the protein, giving rise to the idea that the mutants share a common toxic gain of function in myelinating Schwann cells that results in demyelination. We have made one mutation in mice, p.Ile52Thr, using CRISPR-Cas9, and propose to analyze this mouse model in the following specific aims. Aim 1: Do p.Ile52Thr mutant mice develop a demyelinating neuropathy? We generated four, independent lines of mice harboring the p.Ile52Thr mutation, and have germ line transmission in three of these lines. We will perform pathological and electrophysiological analysis on each of the three lines, comparing homozygous (p.Ile52Thr/p.Ile52Thr), heterozygous (p.Ile52Thr/+), and wild type (WT) (+/+) mice. Although heterozygous mice more accurately model the human disease, we included homozygous mice because they might have a more pronounced phenotype. Aim 2. Are PNS myelin sheaths altered in p.Ile52Thr mutant mice? Because P2 binds to fatty acids and cholesterol, we will investigate the possibility that the p.Ile43Asn mutation alters the lipid composition of myelin, by analyzing nerves by lipidomics and by performing electron microscopy of compact myelin.