【作者】 王建锋；

【导师】 张学军； 杨森；

【作者基本信息】 安徽医科大学 ， 皮肤病与性病学， 2008， 硕士

【摘要】 研究背景多发性脂囊瘤(steatocystoma multiplex,SM,OMIM:184500)是一种少见的皮肤附属器良性肿瘤,临床特征为多发性半球形肤色或淡黄色皮肤囊性损害,好发于躯干部和四肢近心端,常在青春期或成人早期发病,皮疹数目和大小可随年龄增长而不同程度增加。本病多呈常染色体显性遗传,尽管也有诸多散发病例的报道。目前认为该病主要是由KRT17基因的突变所致,同时KRT17基因也是先天性厚甲症2型(Pachyonychia congenital-2,PC-2)的一个致病基因。角蛋白K17常表达于甲床、毛囊外根鞘、皮脂腺和其它附属器,角蛋白有一个由310个氨基酸残基构成的α-螺旋杆状结构域,该结构域由1A、1B、2A和2B四个片段组成。位于1A螺旋起始和2B螺旋末端的序列是高度保守区,对体内10nm中间丝的装配至关重要。KRT17基因定位于17q12-q21,全长5kb,由8个编码蛋白的外显子组成。迄今为止,国内外学者在不同SM家系中共检测到3种不同的突变,目前尚未发现基因型与表型之间的明确相关性。本研究收集了中国汉族人两个多发性脂囊瘤家系,并通过直接测序的方法对这两个家系的成员进行KRT17基因的突变检测。目的检测中国汉族人两个多发性脂囊瘤家系的KRT17基因的致病性突变。方法调查两个中国汉族人多发性脂囊瘤家系情况,收集整理家系资料并采集家系成员血样。提取家系成员和100名正常对照的外周血白细胞基因组DNA,设计覆盖KRT17基因所有外显子编码区的7对引物,采用PCR反应扩增所有外显子编码区及其侧翼序列,通过对PCR扩增产物直接测序进行序列分析。结果通过对中国汉族人多发性脂囊瘤两家系进行突变检测,检测到一个国外曾经报道过的突变c.281G＞A(p.R94H)和一个国内外在多发性脂囊瘤家系中未见报道的突变c.275 A＞G(p.N92S)。而这两个家系中表型正常个体及100个无关正常对照均不存在这样的突变。结论本研究证实错义突变c.281G＞A(p.R94H)和c.275 A＞G(p.N92S)是引起中国汉族人多发性脂囊瘤两家系临床症状的致病性突变,而不是正常多态性,为将来该家系的遗传咨询、产前诊断及基因治疗打下了基础。更多还原

【Abstract】 Background Steatocystoma multiplex is a rare benigh shin appendage tumor characterized by multiple hemispheroid,yellow to skin-colored cystic lesions,which are principally on the trunk and proximal parts of the limbs.The papules can increase in number and size throughout adult life.Onset of the disease tends to occur during adolescence or early adult life.It is thought to be inherited in an autosomal dominant fashion,although many sporadic cases have also been reported.It is demonstrated that steatocystoma multiplex is caused by mutation in KRT17 gene,which is also responsible for Pachyonychia congenital-2.KRT17 is expressed in the nail bed,hair. follicle,sebaceous gland and other epidermal appendages.Each keratin polypeptide possesses a 310-amino acid residueα-helical rod domain that consists of four helical segments named 1A,1B,2A and 2B.The sequences at the beginning of the helix 1A and at the end of the helix 2B are highly conserved and are the most critical for the assembly of the 10-nm intermediate filaments in vivo.KRT17 gene which is 5kb long with 8 exons was mapped to chromosome 17q12-q21.Up to date,there have been 3 germline mutations described in the KRT17 gene in cases of SM,no clear correlation between phenotype and genotypes has been established.In the present study,we have ascertained two Chinese kindreds with steatocystoma multiplex and examined KRT17 gene in these families by direct sequencing.Objective To identify pathogenic mutations of the KRT17 gene in two Chinese kindreds with steatocystoma multiplex. Methods We investigated two Chinese families with SM,collected clinical datas and blood samples from them.Genomic DNA was extracted from peripheral blood of members in two families and 100 unrelated normal controls.All the coding exons and their flanking sequences of KRT17 gene were amplified by polymerase chain reaction (PCR).The PCR products were directly sequenced to detect the mutation.Results One novel KRT17 gene mutation(c.275 A＞G) and one mutation(c.281G＞A) previously described were identified in two Chinese kindreds with steatocystoma multiplex.The two mutations were not found in the healthy members of families and in 100 unrelated control individuals.Conclusions These two missense mutations(c.275A＞G and c.281G＞A) may be the pathogenic mutations in these two Chinese families,not common polymorphism.This study should be useful for genetic counseling,prenatal diagnosis and gene therapy for the patients.更多还原