扩张性心肌病的分子遗传学

扩张性心肌病可以常染色体显性、常染色体隐性及Ｘ染色体连锁方式遗传，家族性扩张性心肌病约占特发性扩张性心肌病的２０％，与家族性扩张心肌病有关的基因尚未发现。扩张性心肌病是进行性肌营养不良的常见临床表现，心力衰竭是该病常见的死亡原因。引起进行性肌营养不良的基因是位于Ｘ染色体上的抗肌营养不良蛋白基因。强直性营养不良是常染色体显性遗传性疾病，常累及心肌及传导组织，其基因是位于１９号染色体上的肌强直蛋白基因     

扩张性心肌病的分子遗传学

扩张性心肌病可以常染色体显性、常染色体隐性及Ｘ染色体连锁方式遗传。家族性扩张性心肌病约占特发性扩张性心肌病的２０％。与家族性扩第性心肌病有关的基因沿未发现．扩张性心肌病是进行性肌营养不良的常见临床表现，心力衰竭是该病常见的死亡原因。引起进行性肌营养不良的基因是位于Ｘ染色体上的抗肌营养不良蛋白基因。强直性肌营养不良是常染色全显性遗传性疾病，常累及心肌及传导组织，其基因是位于１９号染色体上的肌强直蛋白基因。另有一些扩张性心肌病可能与线粒体ＤＮＡ突变有关，呈母系遗传。     

Stargardt病的分子遗传学研究进展

Stargardt病(STGD)是一组进行性眼底黄斑营养不良的遗传性疾病，多于青少年期发病，表现为进行性中心视力减退，黄斑与色素上皮萎缩，常伴随后极部斑点，尚无有效治疗方法。STGD多呈常染色体隐性遗传，少数为常染色体显性遗传或X-连锁隐性遗传。目前已发现4个染色体区段与本病相关，并因此将本病分为STGD1、STGD2、STGD3和STGD4。其中，STGD1与STGD3的致病基因已被克隆，已通过体外表达研究相关蛋白突变体的性质，对于致病基因的结构、突变功能、蛋白突变体及其发病机制的研究目前已有了新的进展。     

Stargardt病的分子遗传学研究进展

Stargardt病(STGD)是一组进行性眼底黄斑营养不良的遗传性疾病,多于青少年期发病,表 现为进行性中心视力减退,黄斑与色素上皮萎缩,常伴随后极部斑点,尚无有效治疗方法。STGD多呈常 染色体隐性遗传,少数为常染色体显性遗传或X-连锁隐性遗传。目前已发现4个染色体区段与本病相 关,并因此将本病分为STGD1、STGD2、STGD3和STGD4。其中,STGD1与STGD3的致病基因已被克隆, 已通过体外表达研究相关蛋白突变体的性质,对于致病基因的结构、突变功能、蛋白突变体及其发病机 制的研究目前已有了新的进展。     

用X染色体失活分析检出X-连锁重症联合免疫缺陷病携带者

重症联合免疫缺陷病(SCID)是一类以X-连锁或常染色体隐性方式遗传的异质性病症。在常染色体隐性SCID中约有20%的病例是由于缺乏嘌呤降解酶和腺苷脱氨酶所致,这种类型易区别。就所有类型的SCID而言,受累男性与受累女性之比约为4∶1。所以,有60%的病例必属X-连锁型。由于在X-连锁型家系中,肯定携带者女性无免疫学异常,故一直无法将X-连锁遗传和常染色体遗传区别开来。     

两兄弟患一新型肌营养不良:应用DNA探针分析提示为常染色体隐性遗传

常见的肌营养不良为X连锁的DMD,另一X连锁类型为BMD。应用DNA探针的连锁分析已证实DMD、BMD为位于Xp21的等位突变基因引起。第三种X连锁的肌营养不良为罕见的Emery-Dreifuss型(E-DMD),其特点为早期发生挛缩和心肌病变,该基因已被定位于Xq27-q28。另外有一种临床症状与DMD相似的儿童肌营养不良,为常染色体隐性遗传病。本文作者报导了一个两兄弟同时患有肌营养不良症的家系,其临床所见不能确定为常染色体隐性遗传或X连锁隐性遗传,并进行了RFLP连锁分析。     

先天性小眼球致病基因的研究进展

先天性小眼球是一种先天发育异常性眼科疾病,遗传方式有常染色体显性遗传,常染色体隐性遗传和X连锁隐性遗传。迄今为止,用连锁分析和细胞遗传学方法对小眼球相关基因进行了基因定位并进一步对候选基因进行突变分析。本文就近年来先天性小眼球致病基因研究方面作一综述。     

Dysferlin缺陷:肢带2B型肌营养不良与Miyoshi肌病的致病原因

目的　对临床怀疑为常染色体隐性遗传性肌营养不良一家系进行分析 ,以明确肌病类型并寻找其致病基因的分子缺陷。方法　用与 8种常染色体隐性遗传性肌营养不良基因连锁的短串联重复序列标记进行连锁分析 ,用与 5种肌营养不良相关的单克隆抗体作多重免疫印迹分析检测相应致病基因的编码产物 ;通过逆转录 - PCR扩增先证者致病基因的编码序列并测序 ,确定基因突变。结果　家系连锁分析显示在 DYSF基因附近的 D2 S337位点的优势对数记分值为 1.85 ,提示致病基因与 D2 S337连锁 ;免疫印迹分析提示患者DYSF基因的编码产物 dysferlin缺陷 ;测序证明先证者DYSF基因的c DNA第 6 4 2 9位发生纯合性del G突变。结论　综合研究结果和临床资料 ,这一家系中的先证者被诊断为 Miyoshi肌病 ,由DYSF基因纯合性缺失突变所导致。     

Xp21/常染色体易位:病例报告和DMD风险

Duchenne型肌营养不良(DMD)是一种X-连锁隐性遗传疾病,通常只有男性受累,在少数女性病例观察到与男性相同的受累程度。在8例报道的病例中,发现受累女性有X/常染色体易位,X染色体的断裂点在Xp21。根据在这些女性中新发生的结构重排和DMD的表现,表明DMD位点在X染     

一个常染色体显性遗传Emery-Dreifuss型肌营养不良家系的基因突变分析

目的 探讨一个常染色体显性遗传Emery-Dreifuss型肌营养不良(Emery-Dreifuss muscular dystrophy,EDMD)家系的临床、病理及遗传学特点.方法 收集家系中2例患者(先证者及女儿)的临床资料及骨骼肌标本,行组织化学染色病理分析;收集先证者及家系成员(3代7人)血液DNA标本,采用聚合酶链反应和DNA直接测序方法 对LMNA基因进行突变检测;明确基因变异位点后对家系行单倍型分析.结果 先证者具有典型的EDMD临床表现:关节挛缩、进行性加重的肌无力和肌萎缩、心脏传导异常;骨骼肌活检病理示肌源性合并轻度神经源性改变;2例患者LMNA基因第9外显子发现杂合错义突变1583(C→G)(T528R),表型正常的其他家系成员未发现该突变;单倍型分析显示先证者及女儿具有相同的致病单倍型.结论 报道了中国人常染色体显性遗传EDMD患者的表现型及基因型.     

Cardiac dysrhythmias,cardiomyopathy and muscular dystrophy in patients with Emery-Dreifuss muscular dystrophy and limb-girdle muscular dystrophy type 1B

Emery-Dreifuss muscular dystrophy (EDMD) and limb-girdle muscular dystrophy type 1B (LGMD1B) are characterized by cardiac dysrhythmias, late-onset cardiomyopathy, slowly progressive skeletal myopathy and contractures of the neck, elbows and ankles. The causative mutation is either in the emerin gene (X-linked recessive EDMD) or lamin A/C gene (autosomal dominant EDMD2 or LGMD1B). We report three cases of EDMD, EDMD2 and LGMD1B. A 14-yr-old boy showed limitation of cervical flexion and contractures of both elbows and ankles. Sinus arrest with junctional escape beats was noted. He was diagnosed as X-linked recessive EDMD (MIM 310300). A 28-yr-old female showed severe wasting and weakness of humeroperoneal muscles. Marked limitation of cervical flexion and contractures of both elbows and ankles were noted. Varying degrees of AV block were noted. She was diagnosed as autosomal dominant EDMD2 (MIM 181350). A 41-yr-old female had contractures of both ankles and limb-girdle type muscular dystrophy. ECG revealed atrial tachycardia with high grade AV block. She was diagnosed as autosomal dominant LGMD1B (MIM 159001). Cardiac dysrhythmias in EDMD and LGMD1B include AV block, bradycardia, atrial tachycardia, atrial fibrillation, and atrial standstill, causing sudden death necessitating pacemaker implantation. Cardiologists should know about these unusual genetic diseases with conduction defects, especially in young adults.     

Novel and recurrent mutations in lamin A/C in patients with Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by slowly progressive muscle wasting and weakness; early contractures of the elbows, Achilles tendons, and spine; and cardiomyopathy associated with cardiac conduction defects. Clinically indistinguishable X-linked and autosomal forms of EDMD have been described. Mutations in the STA gene, encoding the nuclear envelope protein emerin, are responsible for X-linked EDMD, while mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found in patients with autosomal dominant, autosomal recessive, and sporadic forms of EDMD. We report mutations in LMNA found in four familial and seven sporadic cases of EDMD, including seven novel mutations. Nine missense mutations and two small in-frame deletions were detected distributed throughout the gene. Most mutations (7/11) were detected within the LMNA exons encoding the central rod domain common to both lamins A/C. All of these missense mutations alter residues in the lamin A/C proteins conserved throughout evolution, implying an essential structural and/or functional role of these residues. One severely affected patient possesed two mutations, one specific to lamin A that may modify the phenotype of this patient. Mutations in LMNA were frequently identified among patients with sporadic and familial forms of EDMD. Further studies are needed to identify the factors modifying disease phenotype among patients harboring mutations within lamin A/C and to determine the effect of various mutations on lamin A/C structure and function.     

Activation of MAPK in hearts of EMD null mice: similarities between mouse models of X-linked and autosomal dominant Emery Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is an inherited disorder characterized by slowly progressive skeletal muscle weakness in a humero-peroneal distribution, early contractures and prominent cardiomyopathy with conduction block. Mutations in EMD, encoding emerin, and LMNA, encoding A-type lamins, respectively, cause X-linked and autosomal dominant EDMD. Emerin and A-type lamins are proteins of the inner membrane of the nuclear envelope. Whereas the genetic cause of EDMD has been described and the proteins well characterized, little is known on how abnormalities in nuclear envelope proteins cause striated muscle disease. In this study, we analyzed genome-wide expression profiles in hearts from Emd knockout mice, a model of X-linked EDMD, using Affymetrix GeneChips. This analysis showed a molecular signature similar to that we previously described in hearts from Lmna H222P knock-in mice, a model of autosomal dominant EDMD. There was a common activation of the ERK1/2 branch of the mitogen-activated protein kinase (MAPK) pathway in both murine models, as well as activation of downstream targets implicated in the pathogenesis of cardiomyopathy. Activation of MAPK signaling appears to be a cornerstone in the development of heart disease in both X-linked and autosomal dominant EDMD.     

Multiple roles for emerin: implications for Emery-Dreifuss muscular dystrophy

X-linked Emery-Dreifuss muscular dystrophy (X-EDMD) is inherited through mutations in EMD, which encodes a nuclear membrane protein named emerin. Emerin is expressed in most cells, but EDMD strikes specific tissues. This review summarizes growing evidence that emerin has roles in both tissue-specific gene regulation and the mechanical integrity of the nucleus and discusses how these roles might impact EDMD.     

Mutations in Emery-Dreifuss muscular dystrophy and their effects on emerin protein expression

Seventeen families with Emery-Dreifuss muscular dystrophy (EDMD) have been studied both by DNA sequencing and by emerin protein expression. Fourteen had mutations in the X-linked emerin gene, while three showed evidence of autosomal inheritance. Twelve of the 14 emerin mutations caused early termination of translation. An in-frame deletion of six amino acids from the C-terminal transmembrane helix caused almost complete absence of emerin from muscle with no localization to the nuclear membrane, although mRNA levels were normal. This shows that mutant emerin proteins are unstable if they are unable to integrate into a membrane. A 22 bp deletion in the promoter region was expected to result in reduced emerin production, but normal amounts of emerin of normal size were found in leucocytes and lymphoblastoid cell lines. This shows that DNA analysis is necessary to exclude emerin mutations in suspected X-linked EDMD. Emerin levels in female carriers often deviated from the expected 50% and this was due, in at least two families, to skewed emerin mRNA expression from the normal and mutated alleles. In one family with a novel deletion of the last three exons of the emerin gene, a carrier had a cardiomyopathy and very low emerin levels (<5% of normal) due to skewed X-inactivation. In the three autosomal cases of EDMD, emerin was normal on western blots of blood cells, which suggests that autosomal EDMD is not caused by indirect reduction of emerin levels.      

Novel and recurrent mutations in lamin A/C in patients with Emery‐Dreifuss muscular dystrophy

Emery‐Dreifuss muscular dystrophy (EDMD) is characterized by slowly progressive muscle wasting and weakness; early contractures of the elbows, Achilles tendons, and spine; and cardiomyopathy associated with cardiac conduction defects. Clinically indistinguishable X‐linked and autosomal forms of EDMD have been described. Mutations in the STA gene, encoding the nuclear envelope protein emerin, are responsible for X‐linked EDMD, while mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found in patients with autosomal dominant, autosomal recessive, and sporadic forms of EDMD. We report mutations in LMNA found in four familial and seven sporadic cases of EDMD, including seven novel mutations. Nine missense mutations and two small in‐frame deletions were detected distributed throughout the gene. Most mutations (7/11) were detected within the LMNA exons encoding the central rod domain common to both lamins A/C. All of these missense mutations alter residues in the lamin A/C proteins conserved throughout evolution, implying an essential structural and/or functional role of these residues. One severely affected patient possesed two mutations, one specific to lamin A that may modify the phenotype of this patient. Mutations in LMNA were frequently identified among patients with sporadic and familial forms of EDMD. Further studies are needed to identify the factors modifying disease phenotype among patients harboring mutations within lamin A/C and to determine the effect of various mutations on lamin A/C structure and function. © 2001 Wiley‐Liss, Inc.     

SPG4基因的遗传学研究

遗传性痉挛性截瘫(hereditary spastic paraplegia,HSP),又称为家族性Strümpell-Lorrain病,是一种具有临床及遗传高度异质性的神经系统遗传病,患病率为2/10万～9.6/10万,表现为缓慢进展的双下肢无力及痉挛性截瘫.根据遗传方式不同HSP可分为常染色体显性遗传、常染色体隐性遗传和X-连锁隐性遗传,以常染色体显性遗传最常见.目前已经发现40个HSP基因位点,已克隆19个疾病基因.其中spastin基因突变所致的遗传性痉挛性截瘫4型(spastic paraplegia-4,SPG4)约占常染色体显性遗传的HSP的40%.基因检测是诊断该病的金标准,有助于早期诊断、症状前诊断及产前诊断.动物模型的研究对揭示HSP的分子病理机制有重要作用,本文就SPG4基因的遗传学研究作一概述.     

腓骨肌萎缩症的遗传特征及致病机制的研究进展

腓骨肌萎缩症(Charcot-Marie-Tooth disease,CMT)是一类常见的遗传性周围神经病,发病率约为1/2500.该病主要呈AD遗传,也可呈AR遗传及XD或XR遗传.据统计,与CMT相关的基因有33个[1],已确定的致病基因至少有27个,其中外周髓鞘蛋白22(peripheral myelin protein 22,PMP22)、髓鞘蛋白零(myelin protein zero,MPZ)和间隙连接蛋白32(connexin-32,Cx32)异常最受关注.近年来在突变基因特征及其致病机制方面取得的研究进展为该病的基因诊断和基因治疗奠定了基础.本文主要就上述内容作一综述.     

Autosomal recessive form of connatal Pelizaeus-Merzbacher disease

We report on a brother and sister with the connatal form of Pelizaeus-Merzbacher disease. This rare degenerative disease of white matter is reported to be transmitted as an X-linked recessive with an occasional affected female. Some authors have suggested that an autosomal recessive form exists. When this family is analyzed with other families in the literature, both X-linked and autosomal recessive inheritance must be considered.