一个进行性家族性心脏传导阻滞家系的致病基因筛查

Mutation screening for the causative gene in a four-generation Chinese pedigree with progressive cardiac conduction defect

目的对1例常染色体显性遗传性进行性家族性心脏传导阻滞（PCCD）家系进行外显子组测序分析来筛选该疾病的候选致病基因。方法2010至2015年，对来自湖南1个4代68人的大家系中共7例患者（5男2女），未能筛查出疾病相关致病基因，后对家系内2例患者和1名正常人进行了外显子组测序寻找致病基因，用在线数据库对这8个新发序列变异位点所在基因进行生物功能分析，并用Sanger测序方法对家系内成员进行共分离验证。结果对PCCD已知致病基因SCN5A、NKX2．5和LMNASanger测序验证未发现与疾病表型共分离的突变位点。选取家系中2例患者和1名正常人进行全外显子组测序，经过多个已知公共数据库对测序数据过滤，最后筛选出8个新发的单核苷酸变异位点：AQP7基因（exon5：c．T343C：p．Y115H）、CACNA1B基因（NM_001243812：exon19：c．A2986G：P．T996A）、CATSPERB基因（exon27：c．C3254G：p．P1085R）、CLCA2基因（exon11：c．G1725T：P．W575C）、CLCA3P基因（ncRNA—intronic）、MYLK-AS1基因（ncRNA—intronic）、TTN基因（ncRNA_UTR3）和LMNA基因（LMNA：NM_170708：exon5：c．C922T：p．Q308x）。CLCA2基因的C．G1725T杂合变异与表型共分离，从遗传学角度高度怀疑该突变位点是造成家系罹患PCCD的原因。结论CLCA2基因的c．1725G，T错义突变可能造成该家系成员罹患PCCD。CLCA2基因是新发现的可能与心脏传导阻滞关联的致病基因，CLCA2基因错义突变c．1725G，T是个新突变。

Objective To define the potential causative gene mutation in a Chinese pedigree with progressive cardiac conduction defect （PCCD）. Methods Sanger sequencing was performed to define potential causative gene mutation in a four-generation family with 68 members including seven PCCD patients （5 male） from 2010 to 2015. No causative gene was detected by screening known candidate genes related to PCCD including SCNSA, NKX2. 5 and LMNA. High-throughput sequencing technology on exon-enriched DNA was then used to search the causative genes in 2 patients and one normal family member. Results Eight new non-synonymous single nucleotide variants including AQP7 gene （ exon5 ： c. 3343 C ： p. Y115H）, CACNA1B gene （ NM 001243812 ： exonl9 ： e. A2986G ： p. T996A） , CATSPERB gene （ exon27 ： c. C3254G ： p. P1085R） , CLCA2 gene （ exonl 1 ： c. G1725T： p. W575C） , CLCA3P gene （ncRNA_intronic） , MYLK- AS1 gene （ncRNA_intronie） , TTN gene （ ncRNA_UTR3 ） , LMNA gene （ LMNA： NM_170708 ： exon5 ： c. C922T： p. Q308X ） were identified by comparing and filtering the results with known public databases. Then, more detailed biological analysis on these 8 genes was conducted. Traditional Sanger sequencing validated the exome sequencing results, and found that the mutation c. 1725G 〉 T in gene CLCA2 segregated with the phenotype of this PCCD pedigree. The mutation c. 1725G 〉 T in gene CLCA2 was thus be considered as the causative PCCD gene in this pedigree from the perspective of genetics and genomics.Conclusion The heterozygote mutation e. 1725G 〉 T in gene CLCA2 might be causative gene in this PCCD pedigree. This finding adds new gene mutation variant responsible for PCCD.