念珠状发家系Ⅱ型毛发角蛋白基因突变的研究

Mutation analysis of type Ⅱ hair keratin gene in a pedigree with monilethrix

目的 探讨汉族念珠状发家系Ⅱ型毛发角蛋白（hHb）基因的突变情况.方法 采集该家系成员及50例毛发外观正常者外周血并提取基因组DNA.运用PCR扩增hHb1、hHb3、hHb6外显子1和外显子7,DNA直接测序检测突变位置.测序结果采用BLAST软件在互联网上进行比对.扫描电镜下观察毛干结构.结果 扫描电镜下,病发呈典型的念珠状表现,狭窄部见明显的纵嵴和纵沟,病发毛小皮厚薄不均,其中1例病发大部分皮质和髓质消失.经网上比对分析,该家系患者hHb6外显子7第1289位碱基鸟嘌呤（G）被腺嘌呤（A）取代,导致第430位精氨酸突变为谷氨酰胺（即R430Q）.而该家系中未患病者和50位正常对照组均未发现该突变,hHb1、hHb3外显子1和外显子7及hHb6的外显子1未发现突变.结论 hHb6外显子7的R430Q错义突变是一种新的突变,可能与该家系的发病有关.

Objective To investigate the mutation of type Ⅱ human hair basic keratin （hHb） gene in a family with monilethrix.Methods Scanning electron microscopy was used to observe the structure of hair shafts.With informed consent,blood samples were drawn from affected and unaffected membets in this family,as well as from 50 healthy controls.Genomic DNA was isolated from these samples.The exon 1 and exon 7 of hHb1,hHb3 and hHb6 were amplified by polymerase chain reaction （PCR）.All the PCR products were sequenced directly using ABI3730 automated sequencer.DNA sequence alignment was carried out with BLAST software.Results A typical beaded appearance was observed in affected hairs by using scanning electron microscopy.There were obvious longitudinal ridges and sulcuses in hair node.and hair cuticles were irregularly shaped.Most cortex and medullary substance were absent in affected hairs of a patient.After sequence alignment,a G1289A point mutation in exon 7 of hHb6 gene,which led to a substitution of arginine for glutamide at codon 430,was detected in affected members of this family,but not in unaffected family members or 50 unrelated human controls.No mutation was observed in exon 1 or exon 7 of hHb1 and hHb3 gene or exon 1 of hHb6 gene.Conclusion The missense mutation of R430Q is a novel mutation.which may be associated with the pathogenesis of monilethrix in this pedigree.