Division of Genetics, Children's Hospital Boston, Boston, MA 02115, USA.
BMC Med Genet. 2011 Jun 28;12:87. doi: 10.1186/1471-2350-12-87.
Many myopathies share clinical features in common, and diagnosis often requires genetic testing. We ascertained a family in which five siblings presented with distal muscle weakness of unknown etiology.
We performed high-density genomewide linkage analysis and mutation screening of candidate genes to identify the genetic defect in the family. Preserved clinical biopsy material was reviewed to confirm the diagnosis, and reverse transcriptase PCR was used to determine the molecular effect of a splice site mutation.
The linkage scan excluded the majority of known myopathy genes, but one linkage peak included the gene GNE, in which mutations cause autosomal recessive hereditary inclusion body myopathy type 2 (HIBM2). Muscle biopsy tissue from a patient showed myopathic features, including small basophilic fibers with vacuoles. Sequence analysis of GNE revealed affected individuals were compound heterozygous for a novel mutation in the 5' splice donor site of intron 10 (c.1816+5G>A) and a previously reported missense mutation (c.2086G>A, p.V696M), confirming the diagnosis as HIBM2. The splice site mutation correlated with exclusion of exon 10 from the transcript, which is predicted to produce an in-frame deletion (p.G545_D605del) of 61 amino acids in the kinase domain of the GNE protein. The father of the proband was heterozygous for the splice site mutation and exhibited mild distal weakness late in life.
Our study expands on the extensive allelic heterogeneity of HIBM2 and demonstrates the value of linkage analysis in resolving ambiguous clinical findings to achieve a molecular diagnosis.
许多肌病具有共同的临床特征，诊断通常需要进行基因检测。我们确定了一个家系，其中 5 名兄弟姐妹表现为病因不明的远端肌肉无力。
我们进行了高密度全基因组连锁分析和候选基因的突变筛查，以确定该家系的遗传缺陷。对保存的临床活检材料进行了复查以确认诊断，并采用逆转录 PCR 来确定剪接位点突变的分子效应。
连锁扫描排除了大多数已知的肌病基因，但一个连锁峰包括 GNE 基因，其突变导致常染色体隐性遗传性包涵体肌病 2 型（HIBM2）。一位患者的肌肉活检组织显示出肌病特征，包括带有空泡的小碱性纤维。GNE 的序列分析显示，受影响的个体为 10 号内含子 5'剪接供体位点（c.1816+5G>A）和先前报道的错义突变（c.2086G>A，p.V696M）的复合杂合子，证实诊断为 HIBM2。剪接位点突变与外显子 10 从转录本中排除相关，这预计会导致 GNE 蛋白激酶结构域中 61 个氨基酸的框内缺失（p.G545_D605del）。先证者的父亲为剪接位点突变的杂合子，在生命后期表现出轻度远端无力。
我们的研究扩展了 HIBM2 的广泛等位基因异质性，并证明了连锁分析在解决不明确的临床发现以实现分子诊断方面的价值。
