COL6A3基因新突变导致的Bethlem肌病家系研究

Study of a Bethlem myopathy pedigree resulted from a novel mutation of COL6A3 gene

目的应用遗传性肌病基因芯片捕获测序对一个肌营养不良家系进行分子遗传学检测，从基因水平确定其病因，进而分析其临床特点，为遗传咨询和产前诊断提供依据。方法针对一个肌营养不良家系，首先通过表型进行临床诊断，检测特定的基因。在未能找到致病突变情况下，采用遗传性肌病目标捕获测序芯片，应用高通量目标区域捕获测序结合Sanger测序和生物信息学分析，确定该家系患者的致病突变。利用PolyPhen网站与NCBI网站对突变类型进行致病性与保守性分析，预测突变位点致病性。结果基因芯片捕获测序方式提示先证者COL6A3基因存在C．3353A〉C杂合突变，进一步的Sanger测序证实该家系中4例患者均存在同样的突变，而家系中正常成员则无此突变。生物信息学分析该突变导致编码氨基酸由组氨酸变成了脯氨酸，该位点区高度保守，突变后具有高度致病性。患者智力正常，肌活检提示肌源性损害，血清肌酸激酶轻度升高，疾病进展缓慢，亦符合Bethlem肌病临床特征。结论目标区域捕获测序是一种高效的基因诊断方法，应用该技术在一个遗传性肌病家系中发现COL6A3基因第8外显子c3353A〉C杂合突变，该突变可能导致Bethlem肌病，呈常染色体显性遗传方式。

Objective To determine the molecular etiology for a muscular dystrophy pedigree with target region sequencing platform using hereditary myopathy capture array. Methods Specific gene testing was performed based on the clinical diagnosis. Since no pathogenic mutation was found, target region sequencing with hereditary myopathy capture array combined with Sanger sequencing and bioinformatics analysis were employed in turn. PolyPhen and NCBI were used to evaluate the pathogenicity of identified mutation and conservation of the gene. Results Target region sequencing indicated the proband has carried a heterozygous c. 3353 A〉C mutation of COL6A3 gene, which was confirmed by Sanger-sequencing in 4 affected individuals from the family. The same mutation was not detected in healthy members of the pedigree. Bioinformatics analysis suggested that the mutation has caused a highly pathogenic amino acid substitution from Histidine to Proline. The affected patients featured normal intelligence with mild myogenic damage by muscle biopsy, slightly increased serum creatine kinase and slow disease progression, which was consistent with Bethlem myopathy. Conclusion Target region sequencing is an effective and efficient method for genetic testing. The heterozygous c. 3353A〉C mutation in exon 8 of the COL6A3 gene probably underlies the Bethlem myopathy with autosomal dominant inheritance.