遗传性多发性外生骨疣的遗传学研究进展

遗传性多发性外生骨疣（ＥＸＴ）的基因克隆是９０年代以来医学遗传学基因克隆研究的热点之一,迄今在染色体上发现了３个与之相关的致病基因位点。其中,ＥＸＴ１,ＥＸＴ２基因已被克隆,并报道了许多致病突变。最近,又发现了３个与已知ＥＸＴ１、ＥＸＴ２基因具有相同羧基端编码产物的ＥＸＴ基因家族成员。本文就此作一综述。     

遗传性多发性外生骨疣的遗传学研究进展

遗传性多发性外生骨疣的基因克隆是９０年代以来医学遗传学基因克隆研究的热点之一。迄今在染色体上发现了３个与之相关的致病基因位点。其中，ＥＸＴ１，ＥＸＴ２基因已被克隆，并报道了许多致病突变。最近，又发现了３个与已条ＥＸＴ１，ＥＸＴ２基因具有相同羧基端编码产物的ＥＸＴ基因家族成员，本就此作一综述。     

遗传性多发性外生骨疣发病的分子机制

遗传性多发性外生骨疣发病的具体分子机制仍不清楚.国内外大量研究分别从EXT基因家族、产物蛋白、信号通路等不同角度进行探讨,认为该病可能由于EXT基因突变引起信号传导通路出现异常,影响软骨细胞增殖分化,导致骨疣形成.本文概述近年来对遗传性多发性外生骨疣发病机制的新进展,提出以后可能的研究方向和需要解决的关键问题.     

遗传性多发性外生骨疣－大家系的遗传与治疗研究

目的本文对遗传性多发性外生骨疣（hereditary multiple exostoses,简称EXT或HME）一大家系的家系调查、染色体、致病基因的定位以及中西医结合治疗研究进行了回顾总结。方法作者历时15年对一个HME大家系完成了家系调查,绘制了家系谱,对部分成员外周血淋巴细胞常规培养染色体核型G显带分析、致病基因的定位与测序分析,并对部分患者给予中西药物和手术治疗。结果共调查该家族7代1179人,具有亲缘关系成员646人,发现患者44人,37．32％o,男29人,女15人,男女之比1．933：1。8例患者染色体G显带核型均正常,40例成员致病基因测序分析后发现,有13例家系成员含有骨疣致病基因EXT2的突变。应用四环素、糖皮质激素、六味地黄丸治疗21例,有效率达80．95％,手术治疗12例,一次治愈无复发。结论对该HME家系研究已取得一定成果,针对基因异常的药物开发和积极优生学措施有待进一步研究。     

遗传性多发性骨外生疣一家系报告

我们在工作中遇一例遗传性多发性骨外生疣已恶变患者,进行了家系调查,呈常染色体显性遗传.现报告如下.     

应用变性高效液相色谱技术检测三个遗传性多发性外生骨疣家系的EXT1与EXT2基因突变

目的建立一种应用变性高效液相色谱(denaturing high performance liquid chromatograph,DHPLC)技术检测遗传性多发性外生骨疣(hereditary multiple exostosis,EXT)基因突变的新方法,并研究3个EXT家系的基因突变情况。方法扩增EXT致病基因的所有外显子区及部分内含子与外显子交界区,联合连锁分析、DHPLC筛查及测序的方法进行分析。结果3个EXT家系中,共检测到两处已知EXT2基因的剪接位点突变IVS2 1G>A、IVS7 1G>T,一处28C>A变异和一处EXT1基因的IVS4 66G>A变异。结论EXT2基因的2个剪接位点突变分别是引起相应EXT家系的致病原因,应用DHPLC技术检测遗传性疾病基因变突是一种自动化、高通量、灵敏、快速且简便经济的好方法。     

遗传性多发性外生性骨疣（EXT）的遗传学研究

遗传性多发性外生性骨疣病的基因克隆是９０年代以来医学遗传传学基因克隆研究的热点之一，迄今在染色体上发现了３人上与之相关的致病基因位点，其中ＥＸＴ１基因已被克隆。     

先天性视网膜劈裂症基因突变分析

目的 阐明先天性视网膜劈裂症（X－linked juvenile retinoschisis,RS or XLRS)的发病机理,为建立基因诊断的方法提供理论依据。方法 采用聚合酶链反应－单链构象多态性分析,对6个独立XLRS病例进行了XLRS1基因突变筛选,并对发现的异常泳动带进行DNA测序,以明确突变位点;对发现的缺失突变进行Southern印迹证实。结果 在5个病例中发现基因突变。在家系1中发现缺失突变,家系中的4个患者均缺失了1、2和3外显子。在外显子4上检出3种异常泳动带,分别为3种突变,Glu72Lys,Glu72Gln,Gly70Ser。结论 XLRS1基因突变是导致中国人患RS的主要原因。本研究结果可直接应用于RS的遗传咨询和产前基因诊断。     

山西汉族遗传性多发性骨软骨瘤家系EXT1及EXT2基因突变研究

目的 对山西一个汉族遗传性多发性骨软骨瘤家系的EXT1和EXT2基因的全部外显子序列进行分析,以寻找致病突变.方法 用PCR扩增先证者EXT1和EXT2基因的全部外显子,将PCR产物送直接测序分析.结果 发现EXT1基因2种同义突变(P477P、E587E)、3种内含子突变(c.1537-48A＞G、c.1721 +203 A＞G、c.1722-103 C＞G).EXT2基因共发现5种内含子突变(c.-29-148 A＞T、c.1080-18 T＞A、c.1336-93 C＞T、c.1526-166 C＞T、c.1526-195C＞T).其中,EXT1 P477P、EXT1 E587E和EXT2 c.1080-18 T＞A为多发性骨软骨瘤突变数据库已收录的多态位点,其余7个位点尚未见报道.结论 对该家系EXT1、EXT2基因全部外显子的测序分析未发现明确的致病突变,该家系遗传性多发性骨软骨瘤的发生是否由除EXT1、EXT2外的其它EXT相关基因引起尚需进一步的连锁定位分析.     

一个遗传性多发性骨软骨瘤家系EXT1基因的突变分析CSCD

目的对1个遗传性多发性骨软骨瘤（hereditary multiple exostosis, HME）家系的先证者进行候选致病基因EXTI和EXT2的所有外显子检测,以寻找该HEM家系的致病性突变。方法应用PCR技术扩增EXT1、EXT2的全部外显子并进行直接Sanger测序分析。结果测序结果显示先证者EXT1基因第4外显子存在e．1202de1T（P．1401Tfs＊2）杂合缺失突变,该突变导致401位后的编码氨基酸发生移码,并在第402位引入终止密码,使EXTl编码的全长746氨基酸组成的蛋白质缩减至由402个氨基酸组成的截短型蛋白。该家系的其他6例患者均存在EXTle．1202delT的杂合移码突变,而表型正常家系成员未检测到该突变,符合基因型一表型共分离。未检测到EXT2基因的可疑突变。结论EXT1c．1202delT杂合移码突变是导致这个HME家系患者发病的分子机制。     

Germline mutations in the EXT1 and EXT2 genes in Korean patients with hereditary multiple exostoses

Hereditary multiple exostoses (EXT) is an autosomal dominantly inherited disease characterized by the formation of cartilage-capped prominences (exostoses) that develop from the juxtaepiphyseal regions of the long bones. Recently, EXT1 and EXT2 genes were cloned and germline mutations of EXT1 and EXT2 were identified in EXT families. In this study, we performed a mutational analysis of EXT1 and EXT2 genes in eight unrelated Korean EXT families by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis followed by direct DNA sequencing. As a result, we were able to identify one family (SNU-OC3) with the EXT1 mutation and another family (SNU-OC15) with the EXT2 mutation. The EXT1 mutation was a 10-bp deletion at the 3′ end of exon 5 (CTAATTTAGg) including the splice site of this exon. The EXT2 mutation identified in the SNU-OC15 family was a missense mutation at codon 85 of exon 2 (T_GC ? C_GC), resulting in an amino acid change from cysteine to arginine. This missense mutation cosegregated with the disease phenotype in this family, suggesting that it is the disease-causing mutation. These two mutations identified in EXT1 and EXT2 are novel ones.     

Molecular basis of multiple exostoses: mutations in the EXT1 and EXT2 genes

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of exostoses, which are cartilage-capped bony protuberances mainly located on long bones. Two genes, EXT1 and EXT2, and at least one other unidentified gene, are known to be involved in the formation of exostoses. To date, 49 different EXT1 and 25 different EXT2 mutations have been found in EXT patients, and there is evidence that mutations in these two genes are responsible for over 70% of the EXT cases. Among the 49 EXT1 mutations there are 9 nonsense, 21 frameshift, and 5 splice site mutations; 2 in-frame deletions of 1 and 5 amino acids respectively; and 12 missense mutations. For EXT2, 8 nonsense, 11 frameshift, 3 splice site and 3 missense mutations are described. The majority of these mutations are mutations causing loss of function, which is consistent with the presumed tumor suppressor function of the EXT genes.     

Mutation analysis in 46 German families with familial hypercholesterolemia: Identification of 8 new mutations

In order to obtain a survey of the mutations being prevalent in Northern Germany and to enable molecular genetic testing for families with clinically diagnosed familial hypercholesterolemia (FH), we screened 46 unrelated German individuals with elevated LDL levels for mutations in the 18 exons and their flanking intron sequences including the promotor region of the LDL receptor (LDLR) gene. In addition, we tested all patients for the presence of mutations in the gene coding for apolipoprotein B‐100 (apoB‐100). We detected 15 mutations affecting the LDLR gene, 8 of which, designated A29S, 195insAT, 313+1insG, 553insG, 680insGGACAAATCTG, D200N, E267K and L411V have not yet been reported. One patient is heterozygous for the double mutant N543H and 2393del9Bp. Two patients carried the mutation R3500Q (Arg→Glu) within the apoB‐100 gene. © 1999 Wiley‐Liss, Inc.     

Mutation frequencies of EXT1 and EXT2 in 43 Japanese families with hereditary multiple exostoses

Hereditary multiple exostoses (EXT) is an autosomal dominant bone disease characterized by the formation of cartilage‐capped prominences. EXT is genetically heterogeneous with at least four chromosomal loci. Among the four loci, the exostosis type 1 gene (EXT1) and type 2 gene (EXT2) have been cloned. Previous studies have shown that disease‐type‐specific frequency of mutations is different among various ethnic populations. To determine those frequencies in the Japanese, we conducted a large‐scale mutation screening on both genes. In 23 of 43 Japanese families examined, we found 21 different mutations, of which 18 are novel. Seventeen (40%) of the 23 families had a mutation in EXT1 and six (14%) had a mutation in EXT2, suggesting that the former mutations are more frequent than the latter in Japanese EXT families. Of the 17 families with EXT1 mutations, 13 had those causing premature termination of the EXT1 protein and four showed missense mutations, whereas five of the six families with EXT2 mutations had those causing premature termination and one showed missense mutation. Interestingly, all four EXT1 missense mutations occurred in an arginine residue at codon 340 (R340) that is known as a critical site for expression of heparan sulfate glycosaminoglycans, suggesting that the region encompassing the arginine residue may play an important role in the function of the EXT1 protein. These results expand our knowledge of the ethnic difference of EXT and the structure‐function relationship of the EXT genes. © Wiley‐Liss. Inc.     

An optimized DHPLC protocol for molecular testing of the EXT1 and EXT2 genes in hereditary multiple osteochondromas

Hereditary multiple osteochondromas (MO) is an autosomal dominant bone disorder characterized by the presence of bony outgrowths (osteochondromas or exostoses) on the long bones. MO is caused by mutations in the EXT1 or EXT2 genes, which encode glycosyltransferases implicated in heparan sulfate biosynthesis. Standard mutation analysis performed by sequencing analysis of all coding exons of the EXT1 and EXT2 genes reveals a mutation in approximately 80% of the MO patients. We have now optimized and validated a denaturing high-performance liquid chromatography (DHPLC)-based protocol for screening of all EXT1- and EXT2-coding exons in a set of 49 MO patients with an EXT1 or EXT2 mutation. Under the optimized DHPLC conditions, all mutations were detected. These include 20 previously described mutations and 29 new mutations - 20 new EXT1 and nine new EXT2 mutations. The protocol described here, therefore, provides a sensitive and cost-sparing alternative for direct sequencing analysis of the MO-causing genes.