Novel truncating mutations of the CHM gene in Chinesepatients with choroideremia

[摘要] Purpose: Choroideremia (CHM) is an X-linked retinal degenerativedisorder caused by mutations in the CHM gene. The mutations resultin malfunction of the Rab escort protein 1 (REP-1). In this study,mutational analysis of the CHM gene was performed on five Chinesefamilies clinically diagnosed with CHM.Methods: Denaturing high performance liquid chromatography was usedfor mutation screening for all 15 exons and flanking intron regions ofthe CHM gene. Mutations were confirmed and characterized with DNAsequencing. Second samples were later collected for extraction of mRNAand proteins from leukocytes. A non-radioactive protein truncation test(PTT) was developed and used to characterize the truncating nature ofthe mutations. Immunoblot analysis of proteins extracted from leukocyteswas also performed.Results: Five mutations were identified in these five families, eachwith one distinct mutation: three frameshift, one nonsense, and onesplicing. Two of these were novel mutations: c.627dupA in exon 5 andc.703-1G>C in intron 5. The truncating nature of the mutations wasexperimentally proved by PTT for four families with second samplescollected. In particular, c.703-1G>C spliced exon 5 directly to exon7 and deleted the entire exon 6 from the transcript. Direct immunoblotanalysis failed to detect REP-1 in males affected by CHM, butdemonstrated its presence in female carriers and homozygous normalfemales.Conclusions: This is the first study reporting mutations in theCHM gene in Chinese families. Mutational analysis was performed atthe DNA, mRNA and protein levels. Five truncating mutations were found,and two of these were novel.

[学科分类] 生物化学/生物物理