一个视网膜色素变性家系致病基因定位和CA4基因突变分析

目的通过对一个常染色体显性视网膜色素变性(autosomal dominant retinitis pigmentosa,adRP)家系致病基因的定位和基因突变分析,以确定该家系的致病基因及其突变形式。方法对15个已知的常染色体显性视网膜色素变性致病基因所在染色体位点进行连锁分析,以确定该家系与疾病连锁的染色体区域,对该区域附近候选基因进行直接序列分析。结果连锁分析提示在D17S701和D17S1604为正的连锁值(logofodds,LOD),分别为Zmax=2.107和Zmax=1.806。其余14个adRP染色体位点的微卫星标记两点LOD值均为负数。单倍型分析进一步将该家系致病基因定位于微卫星标记D17S916和D17S794之间的RP17位点,该位点adRP候选基因碳酸酐酶Ⅳ(carbonic anhydrase4,CA4)直接序列分析在其编码区未发现基因突变。结论将一个中国人常染色体显性视网膜色素变性家系的致病基因定位于RP17位点,但未发现该位点内的CA4基因突变,该家系是否存在CA4基因复杂突变或RP17位点是否存在新的视网膜色素变性致病基因有待于进一步研究。

Genotyping and CA4 gene analysis in a Chinese family with retinitis pigmentosa

OBJECTIVE:To illuminate pathogenic gene and mutation in a Chinese family with autosomal dominant retinitis pigmentosa (adRP). METHODS: Genetic linkage analysis was performed on the known genetic loci for adRP with a panel of polymorphic markers, and then all exons including exon-intron boundary, 5oUTR and 3oUTR of the candidate gene were sequenced directly. RESULTS: Two-point LOD scores were negative with all markers tested except D17S701 (Zmax=2.107, theta=0) and D17S1604 (Zmax=1.806, theta=0). The disease gene locus was confined to RP17 with further genetic linkage and haplotype analysis. Screening all exons including exon-intron boundary, 5oUTR and 3oUTR of carbonic anhydrase 4 (CA4) revealed no mutation in this family. CONCLUSION: The disease-causing gene of one Chinese family with adRP was first mapped to RP17, however no gene mutation of CA4 was detected in this family. Maybe there is a complex CA4 gene mutation in this family or a new disease-causing gene for this family in this locus, further study need to be done.