Abstract：
Distal myopathies are a group of rare heterogeneous diseases that are mostly caused by genetic factors. At least 20 genes have been associated with distal myopathies. We performed whole-exome sequencing to identify the genetic cause of disease in a family with distal myopathy. Following the American College of Medical Genetics and Genomics (ACMG) guidelines, we analyzed the sequencing results and screened suspicious mutations based on mutation frequency, functional impact, and disease inheritance pattern. The harmfulness of the mutations was predicted using bioinformatics methods, and the pathogenic mutations were determined. We identified a novel amino acid mutation (NP_005467.1:p.S663L) on the GNE gene that may cause familial distal myopathy. This mutation is the result of the simultaneous mutation of two adjacent nucleotides (c.1988C > T, c.1989C > A) in the codon. First, we measured the mRNA and protein expression of the GNE gene in the lymphoblastoid cell lines (LCLs) of the probands and their family members. Second, GNE vectors carrying the novel mutation, two other known pathogenic mutations, and the wild-type gene were constructed and transfected into HEK293T cells. The enzymatic activity of these GNE variants was investigated and showed that the p.S663L mutation significantly reduced the activity of the bifunctional GNE enzyme without altering the expression level of the GNE protein. Furthermore, the mutation may also alter the immunogenicity of the 3\' end of the GNE protein, potentially affecting its oligomer formation. In this study, a novel GNE gene mutation that may cause distal myopathy was identified, expanding the spectrum of genetic mutations associated with this disease.
摘要：
远端肌病是一组罕见的异质性疾病，主要由遗传因素引起。至少有20个基因与远端肌病有关。我们进行了全外显子组测序，以确定患有远端肌病的家庭中疾病的遗传原因。遵循美国医学遗传学和基因组学学院（ACMG）的指导方针，我们分析了测序结果，并根据突变频率筛选了可疑突变，功能影响，和疾病遗传模式。使用生物信息学方法预测突变的危害性，并确定致病突变。我们鉴定了一个新的氨基酸突变(NP_005467.1:p.S663L）对可能引起家族性远端肌病的GNE基因。此突变是两个相邻核苷酸同时突变的结果（c.1988C>T，c.1989C>A）在密码子中。首先,我们测量了先证者及其家族成员的淋巴母细胞样细胞系（LCLs）中GNE基因的mRNA和蛋白质表达。第二,携带新突变的GNE载体，另外两个已知的致病突变，构建野生型基因并转染HEK293T细胞。研究了这些GNE变体的酶活性,表明p.S663L突变显著降低了双功能GNE酶的活性,而不改变GNE蛋白的表达水平。此外，突变还可能改变GNE蛋白3'末端的免疫原性，可能影响其低聚物的形成。在这项研究中,发现了一种可能导致远端肌病的新的GNE基因突变，扩大与这种疾病相关的基因突变谱。
