X染色体连锁显性遗传先天性眼球震颤家系的致病基因突变研究

目的对4个X染色体连锁显性遗传先天性眼球震颤(XL-CIN)家系进行候选致病基因FRMD7突变筛查。方法采集家系成员外周血5 ml,提取基因组DNA;以4个家系的先证者基因组DNA为模板,聚合酶链反应(PCR)扩增FRMD7基因的全部外显子及其外显子-内含子拼接部的序列,DNA直接测序筛查突变位点;一旦发现突变致病性位点,则采用DNA双向测序方法在其他家系成员进行疾病与致病突变共分离分析,以及进一步确认突变,将患者的FRMD7基因外显子8和10的扩增产物克隆至TA克隆载体测序。结果 4个XL-CIN家系皆为X染色体连锁显性遗传伴外显不全,其中2个家系携带FRMD7基因已知致病性突变:XL-CIN 02家系存在c.G886C/GGT>CGT(p.G296R)错义突变,位于FRMD7基因外显子8;XL-CIN 03家系存在c.C910T/CGA>TGA(p.R304X)无义突变,位于外显子10。结论 FRMD7 G296R和R304X是导致XL-CIN 02和XL-CIN 03家系致病的主要原因。

Study of Molecular Genetics of X-Linked Congenital Idiopathic Nystagmus in Four Chinese Families

Objective To identify the molecular defect of candidate gene FRMD7 in four Chinese families with X-linked Congenital Idiopathic Nystagmus(XL-CIN).Methods 5 ml of peripheral blood from the families with XL-CIN was collected and their Genomic DNA was extracted.The genomic DNA of the proband was used as the template to amplify all the exons and exon-intron splicing sequence of gene FRMD7 together with polymerase chain reaction(PCR).The mutation sites were sorted out by detecting the sequence of DNA and once the mutation site was determined,the bidirectional sequencing was used to have both disease and causative mutation segregation analysis in other family members.The superimposed mutant PCR products were subcloned into TA cloning vector to detect sequence,and then were sequenced to further confirm the mutation.Results FRMD7 mutations were found in 2 of 4 families with XL-CIN: a missense mutation c.G886C(p.G296R) in exon 8 of FRMD7 was detected in Family XL-CIN 02,and a nonsense mutation c.C910T(p.R304X) in exon 10 of FRMD7 gene in Family XL-CIN 03.Conclusion FRMD7 G296R and R304X were identified as the main factors for XL-CIN 02 and XL-CIN 03 in Chinese XL-CIN families.