The second most common form of Charcot-Marie-Tooth neuropathy (CMT), X-linked CMT type X1 (CMTX1), is caused by coding and non-coding mutations in the gap junction beta 1 (GJB1) gene. The non-coding GJB1 c.-103C > T mutation (NM_000166.5) has been reported to cause CMTX1 in multiple families. This study assessed the internal ribosomal entry site (IRES) activity previously reported for the rat Gjb1 P2 5’ untranslated region (UTR). Using a bicistronic assay and transfecting RT4 Schwann cells, IRES activity of the human GJB1 P2 5’ UTR was compared to the GJB1 P2 5’ UTR containing either the c.-103C > T mutation or the non-pathogenic c.-102G > A variant. No differences in GJB1 P2 5’ UTR IRES activity were observed between the negative control, the wild-type P2 5’ UTR, the c.-103C > T 5’ UTR or the c.-102G > A 5’ UTR, irrespective of the GJB1 intron being present (p = .429 with intron, and p = .865 without). A theoretical c.-131A > G variant was predicted to result in the same RNA secondary structure as the GJB1 c.-103C > T P2 5’ UTR. However, no significant difference was observed between expression from the wild-type GJB1 P2 5’ UTR and the GJB1 c.-131A > G variant (p = .688). Deletion of the conserved region surrounding the c.-103C > T mutation (c.-108_-103del) resulted in significantly higher expression than the c.-103C > T mutation alone (p = .019), suggesting that the conserved c.-108_-103 region was not essential for translation. The reporter assays in this study do not recapitulate the previously reported GJB1 IRES activity and suggest an alternate pathogenic mechanism for the c.-103C > T CMTX1 non-coding mutation.

Charcot-Marie-Tooth 神经病 (CMT) 的第二种最常见形式，即 X 连锁 CMT X1 型 (CMTX1)，是由间隙连接 β1 ( GJB1 ) 基因中的编码和非编码突变引起的。据报道，非编码GJB1 c.-103C > T 突变 (NM_000166.5) 在多个家族中引起 CMTX1。本研究评估了先前报道的大鼠Gjb1 P2 5' 非翻译区 (UTR)的内部核糖体进入位点 (IRES) 活动。使用双顺反子测定和转染RT4雪旺氏细胞，人的IRES活性GJB1 P2 5' UTR物相比GJB1 P2 5'包含任一C.-103C> T突变或所述非致病C.-102G>甲UTR变体。GJB1没有差异在阴性对照、野生型 P2 5' UTR、c.-103C > T 5' UTR 或 c.-102G > A 5' UTR 之间观察到 P2 5' UTR IRES 活性，无论GJB1内含子是存在（p  = .429 有内含子，p  = .865 没有）。预计理论上的 c.-131A > G 变体会产生与GJB1 c.-103C > T P2 5' UTR相同的 RNA 二级结构。然而，野生型GJB1 P2 5' UTR 和GJB1 c.-131A > G 变体的表达之间没有观察到显着差异（p = .688)。删除 c.-103C > T 突变 (c.-108_-103del) 周围的保守区域导致表达显着高于单独的 c.-103C > T 突变 ( p  = .019)，表明保守的 c. -108_-103 区域对于翻译不是必需的。本研究中的报告基因分析没有概括先前报道的GJB1 IRES 活性，并提出了 c.-103C > T CMTX1 非编码突变的替代致病机制。