Ylikallio Emil, Johari Mridul, Konovalova Svetlana, Moilanen Jukka S, Kiuru-Enari Sari, Auranen Mari, Pajunen Leila, Tyynismaa Henna
Research Programs Unit, Molecular Neurology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.
Department of Clinical Genetics, Oulu University Hospital and University of Oulu, Oulu, Finland.
Eur J Hum Genet. 2014 Apr;22(4):522-7. doi: 10.1038/ejhg.2013.190. Epub 2013 Aug 21.
Charcot-Marie-Tooth disease (CMT) is a group of hereditary peripheral neuropathies. The dominantly inherited axonal CMT2 displays striking genetic heterogeneity, with 17 presently known disease genes. The large number of candidate genes, combined with lack of genotype-phenotype correlations, has made genetic diagnosis in CMT2 time-consuming and costly. In Finland, 25% of dominant CMT2 is explained by either a GDAP1 founder mutation or private MFN2 mutations but the rest of the families have remained without molecular diagnosis. Whole-exome and genome sequencing are powerful techniques to find disease mutations for CMT patients but they require large amounts of sequencing to confidently exclude heterozygous variants in all candidate genes, and they generate a vast amount of irrelevant data for diagnostic needs. Here we tested a targeted next-generation sequencing approach to screen the CMT2 genes. In total, 15 unrelated patients from dominant CMT2 families from Finland, in whom MFN2 and GDAP1 mutations had been excluded, participated in the study. The targeted approach produced sufficient sequence coverage for 95% of the 309 targeted exons, the rest we excluded by Sanger sequencing. Unexpectedly, the screen revealed a disease mutation only in one family, in the HSPB1 gene. Thus, new disease genes underlie CMT2 in the remaining families, indicating further genetic heterogeneity. We conclude that targeted next-generation sequencing is an efficient tool for genetic screening in CMT2 that also aids in the selection of patients for genome-wide approaches.
夏科-马里-图斯病（CMT）是一组遗传性周围神经病。显性遗传的轴索性CMT2表现出显著的遗传异质性，目前已知有17个致病基因。大量的候选基因，加上缺乏基因型与表型的相关性，使得CMT2的基因诊断既耗时又昂贵。在芬兰，25%的显性CMT2由GDAP1奠基者突变或私有的MFN2突变所解释，但其余家族仍未得到分子诊断。全外显子组测序和基因组测序是寻找CMT患者疾病突变的有力技术，但它们需要大量测序才能可靠地排除所有候选基因中的杂合变异，并且会产生大量与诊断需求无关的数据。在此，我们测试了一种靶向新一代测序方法来筛查CMT2基因。共有15名来自芬兰显性CMT2家族的无关患者参与了该研究，这些患者已排除MFN2和GDAP1突变。靶向方法对309个靶向外显子中的95%产生了足够的序列覆盖，其余的通过桑格测序排除。出乎意料的是，筛查仅在一个家族的HSPB1基因中发现了一个疾病突变。因此，其余家族的CMT2存在新的致病基因，表明遗传异质性进一步存在。我们得出结论，靶向新一代测序是CMT2基因筛查的有效工具，也有助于为全基因组方法选择患者。
