NDRG1突变导致腓骨肌萎缩症4D型周围神经脱髓鞘的机制研究

Charcot-Marie-Tooth disease type 4D (CMT4D) is an autosomal-recessive demyelinating form of peripheral neuropathies. NDRG1 is the causative gene for CMT4D. To date, the pathogenic mechanism of NDRG1 mutation causing demyelination in CMT4D remains to be further explored. We previously identified for the first time two homozygous missense variants in NDRG1, p.L146P and p.R234Q, in two CMT4D families. Mutant NDRG1 carrying these two variants degraded faster than wild-type NDRG1, resulting in lower protein levels. Recently we found that NDRG1 interacted with β4-integrin in HEK293T cells. Knockdown the expression of NDRG1 in HeLa cell results in the lower expression level of β4-integrin in plasma membrane. So, we speculated that β-integrin may be implicated in the demyelination of CMT4D. Here, by the use of cell lines, primary Schwann cell and in vitro myelination model, we will evaluate the interaction between NDRG1 and β4-integrin. We will explore the effect of mutant NDRG1 on the endosomal trafficking of β4-integrin and the β4-integrin mediated signaling in regulation of myelination. We will investigate the role of endosomal trafficking of β-integrin in NDRG1 participating myelination. This investigation will be helpful to elucidate the pathologic mechanism of CMT4D and provide new strategy and therapy target for CMT4D.

腓骨肌萎缩症4D型（CMT4D）是遗传性周围神经病，病理改变为周围神经脱髓鞘，致病基因为NDRG1。目前，NDRG1突变引起CMT4D周围神经脱髓鞘的机制并不清楚。我们前期在CMT4D病人首次报道了NDRG1致病性错义突变（p.L146P和p.R234Q），并发现携带突变的NDRG1蛋白稳定性下降。我们近期研究发现，NDRG1蛋白与β4整合素结合，敲低细胞NDRG1导致膜表面β4整合素水平降低。因此，我们推测β4整合素在NDRG1突变引起的周围神经脱髓鞘中起重要作用。本项目将利用细胞系、雪旺细胞和体外髓鞘形成模型，明确NDRG1蛋白与β4整合素的相互作用，探讨NDRG1突变后蛋白对β4整合素内体运输及其与髓鞘形成和维持有关的下游信号通路的影响，并阐明β4整合素内体运输在NDRG1参与的髓鞘形成中的作用。上述研究有助于揭示NDRG1突变引起周围神经脱髓鞘的机制，为治疗CMT4D提供新策略。

腓骨肌萎缩症4D型（CMT4D）是遗传性周围神经病，病理改变为周围神经脱髓鞘，致病基因为NDRG1。目前，NDRG1突变引起CMT4D周围神经脱髓鞘的机制并不清楚。我们前期研究发现，致病性突变导致NDRG1蛋白稳定性下降，并且，NDRG1蛋白调节雪旺细胞膜受体β4-integrin的水平。我们在前期研究的基础上，构建了Ndrg1基因敲除小鼠，通过行为学、组织病理、电镜检查、电生理记录等一系列实验，明确了Ndrg1基因敲除小鼠具有典型的CMT4D表型，证实了NDRG1蛋白缺失导致周围神经脱髓鞘改变。进一步研究发现，NDRG1蛋白主要表达在周围神经雪旺细胞，参与调控雪旺细胞膜表面受体的内体运输；NDRG1蛋白缺失导致雪旺细胞β4-integrin和ErbB2表达分布及其下游与髓鞘形成和维持相关的信号通路异常。本研究阐明了CMT4D周围神经脱髓鞘的病理特征，揭示了β4-integrin和ErbB2在CMT4D发病中的作用，为研发CMT4D治疗药物提供了理论依据和新的干预模型。