Kennedy病两个家系的临床表型、基因型和遗传特征分析

目的 分析两个Kennedy病家系的临床表型、基因型和家系特征.方法 收集Kennedy病患者的临床资料,用基因分析的方法 ,明确患者及家族成员雄激素受体基因第1外显子CAG序列的重复数.结果 A家系4代共58人,先证者39岁隐袭起病.B家系5代共61人,有两例患者分别于39岁、41岁缓慢起病.3例患者均以下运动神经元损害为特征,都出现了雄激素不敏感综合征的相关表现.血清肌酶呈轻中度升高;肌电图呈广泛前角损害;肌肉活检示神经源性肌萎缩;雄激素受体基因第1外显子中CAG重复数分别为49、48、47.两个家系的遗传方式均为X连锁隐性遗传.结论 Kennedy病多为中年男性隐袭起病,主要表现为延髓肌和脊髓肌的萎缩和无力,基因分析有助于对本病的确诊,并可明确携带者,以进行遗传咨询及产前诊断.     

Kennedy病两个家系的临床表型、基因型和遗传特征分析

目的 分析两个Kennedy病家系的临床表型、基因型和家系特征.方法 收集Kennedy病患者的临床资料,用基因分析的方法 ,明确患者及家族成员雄激素受体基因第1外显子CAG序列的重复数.结果 A家系4代共58人,先证者39岁隐袭起病.B家系5代共61人,有两例患者分别于39岁、41岁缓慢起病.3例患者均以下运动神经元损害为特征,都出现了雄激素不敏感综合征的相关表现.血清肌酶呈轻中度升高;肌电图呈广泛前角损害;肌肉活检示神经源性肌萎缩;雄激素受体基因第1外显子中CAG重复数分别为49、48、47.两个家系的遗传方式均为X连锁隐性遗传.结论 Kennedy病多为中年男性隐袭起病,主要表现为延髓肌和脊髓肌的萎缩和无力,基因分析有助于对本病的确诊,并可明确携带者,以进行遗传咨询及产前诊断.     

Kennedy病两个家系的临床表型、基因型和遗传特征分析

目的 分析两个Kennedy病家系的临床表型、基因型和家系特征.方法 收集Kennedy病患者的临床资料,用基因分析的方法 ,明确患者及家族成员雄激素受体基因第1外显子CAG序列的重复数.结果 A家系4代共58人,先证者39岁隐袭起病.B家系5代共61人,有两例患者分别于39岁、41岁缓慢起病.3例患者均以下运动神经元损害为特征,都出现了雄激素不敏感综合征的相关表现.血清肌酶呈轻中度升高;肌电图呈广泛前角损害;肌肉活检示神经源性肌萎缩;雄激素受体基因第1外显子中CAG重复数分别为49、48、47.两个家系的遗传方式均为X连锁隐性遗传.结论 Kennedy病多为中年男性隐袭起病,主要表现为延髓肌和脊髓肌的萎缩和无力,基因分析有助于对本病的确诊,并可明确携带者,以进行遗传咨询及产前诊断.     

三个Fabry病家系GLA基因突变与临床表型

目的 分析3个Fabry病家系GLA基因突变及其与临床表型的关系.方法 应用PCR结合DNA测序技术,检测先证者及相关成员GLA基因编码序列与剪切位点DNA序列变异,分析致病性突变与临床表型关系.结果 在家系1先证者GLA基因第5外显子中发现1个未经报道的错义突变c.797A＞C(D266A),家系2先证者GLA基因第5外显子中发现1个错义突变c.644A＞G(N215S),家系3先证者GLA基因第2外显子中发现1个无义突变c.355C＞T(Ql19X).家系1与家系3先证者主要表现为皮肤损害和慢性肾功能不全,家系2先证者临床则以肥厚性心肌病为特点.结论 首次发现的GLA基因c.797A＞C(D266A)突变是第266位密码子第6个被证实的错义突变,已报道的另5种突变均有致病性,在正常非相关对照中未发现该突变,提示GLA基因c.797A＞C突变很可能是该家系的致病原因.N215S和Q119X系首次发现于中国Fabry病家系的突变.GLA基因不同位点的突变具有较为显著的表型差异.     

浙江沿海一家系脊髓小脑性共济失调的基因突变检测与临床表现

目的 探讨浙江沿海脊髓小脑性共济失调的基因突变检测与临床表现.方法 对该家系18例患者的临床表现、头颅MRI等辅助检查资料分析,并与10名家系中未发病成员及12名非血缘的健康人进行SCA31MJD基因CAG三核苷酸重复数目比较.结果 家系18例患者均为SCA3/MJD型,同时检测出家系中未发病对照组有2例为SCA31MJD型基因携带者.产物测序结果家系对照组与健康对照组CAG重复数为14～27次;SCA患者CAG重复数为67～82次;SCA3/MJD携带者CAG重复数为28～45次.在现存三代18例患者中,每代均有患者,男女均受累,起病年龄平均38岁,以行走不稳、动作笨拙和言语含糊为突出表现,MRI检测结果小脑、脑干明显萎缩.结论 在我国沿海存在SCA3/MJD家系遗传.临床均以共济失调和构音障碍为突出,CAG重复数目检测可为基因诊断和症状前诊断提供依据.     

两个斑驳病家系KIT基因突变研究

目的 对2个斑驳病家系进行致病基因突变分析,为患者及其家系成员提供遗传咨询和生育指导.方法 分别采集家系1两例患者(先证者及其父亲)、家系2先证者及3名表型正常家系成员的外周血,提取外周血DNA和RNA.应用PCR、逆转录PCR及测序等技术,从基因组水平和表达水平对此两家系先证者和患者进行KIT基因诊断,并初步探讨检测到的突变对KIT基因功能的影响.结果 家系l中两例患者KIT基因均存在IVS12+ 2_+7delinsACATCTTTA的杂合突变,该突变在cDNA水平导致KIT基因c.1765-1779del突变,在氨基酸水平导致p.Gly592Ala/del:E12突变,使得KIT基因剪切位点发生改变,即其中一条cDNA第12外显子被跨越、未转录.家系2中先证者KIT基因存在c.2401A＞C突变,3位表型正常的家系成员未见该突变.结论 确诊了两个斑驳病家系的致病原因.家系1患者KIT基因均存在IVS12+ 2_+ 7delinsACATCTTTA的杂合突变,该突变为人类基因突变数据库未记载的、新的剪切突变;家系2先证者KIT基因存在c.2401A＞C突变,结合3位表型正常的家系成员KIT基因未见c.2401A＞C突变,推测该突变为先证者患斑驳病的致病突变可能性大.为此两家系进行遗传咨询和产前诊断提供了理论依据.     

一个全面性癫痫伴热性惊厥附加症家系临床表型及GABRG2基因突变分析

目的 分析并确定一个全面性癫痫伴热性惊厥附加症(generalized epilepsy with febrile seizures plus,GEFS+)家系临床表型,并对其CABAA受体γ2哑单化基因(GABAA-receptor γ2 subunit,GABRG2)进行突变筛查及遗传特征分析.方法 收集先证者及其家系成员临床资料及外周血DNA,采用聚合酶链反应和DNA直接测序的方法进行GBRG2基因突变筛查,确定基因突变的位点,分析基因型与表型的关系.结果 该家系为典型GEFS+家系,3代共有7例受累成员,临床表型1例为热性惊厥(febrile seizures,FS),6例为热性惊厥附加症(febrile seizures plus,FS+).该家系先证者的GABRG2基因存在第9外显子的杂合无义突变c.1287G＞A(P.W390X),先证者之母和具有GEPS+表型的其他家系成员均携带该基因突变,1例携带该突变的家系成员临床表型正常,外显率约为87.5%(7/8).结论 该GEFS+家系GBRG2基因突变P.W390X为遗传性突变,家系符合常染色体显性遗传伴外显率小全.GABRG2基因突变也是中国GEFS+家系的致病基因之一.     

Wilson病双(多)胞胎家系的临床和基因突变研究

目的 观察双(多)胞胎Wilson病家系的临床和基因突变特点.方法 收集双(多)胞胎Wilson病家系的临床资料,留取其全血标本,提取基因组DNA,应用短串联重复(short tandem repeats,STR)分型判定双胞胎是否为同卵双生,用DNA测序法检测ATP7B基因各外显子的突变.结果 5个双胞胎家系的患者均符合Wilson病的诊断标准.STR分型提示4个家系为同卵双生,1个家系为异卵双生.3个双胞胎家系的患者均以肝症状起病,另外2个家系的患者以脑症状起病.在4个家系的患者中检出ATP7B基因的突变,均位于第8和(或)第13外显子,其中1个家系的患者同时携带第8外显子p.R778W杂合突变和第13外显子p.P992L纯合突变,其父母分别为p.R778W杂合突变和p.P992L杂合突变的携带者,因此该家系的患者发生了杂合丢失现象.有1个家系的2例患者及其父母亲各外显子均未检出突变.1个三胞胎家系中的1名女性成员为脑症状起病的Wilson病患者,1名男性为无症状的亚临床型Wilson病患者,另1例女性成员未患病,这3位成员及其母亲均检出第13外显子p.P992L杂合突变.结论 本研究结果进一步证实了遗传因素在Wilson病发病中的主要作用.杂合丢失现象是除点突变外Wilson病的另一种发病机制.     

NDP基因c.361C>T错义变异致诺里病一家系

目的分析1个诺里病家系的致病基因变异,确定其遗传学病因。方法对先证者核心家系4名成员的DNA样本进行全外显子组检测,筛选变异位点,确定致病基因。通过Sanger测序对核心家系及7名其他家系成员进行验证。结果全外显子组检测及Sanger测序结果显示先证者及另外3例男性患者的NDP基因均存在c.361C>T(p.Arg121Trp)半合子错义变异,先证者母亲、外祖母和2个表妹均为c.361C>T杂合变异携带者,正常表型男性家系成员均未检测到该变异,符合X连锁隐性遗传病的特点。结论NDP基因c.361C>T错义变异是该诺里病家系的遗传学病因。     

一个单纯家族性嗜铬细胞瘤家系的VHL基因突变筛查

目的检测一个单纯家族性嗜铬细胞瘤家系的VHL基因突变情况。方法对一个单纯家族性嗜铬细胞瘤家系进行VHL基因突变检测，抽取该家系5例患者及15名血缘亲属外周血基因组DNA，对VHL基因3个外显子进行PCR，产物进行DNA测序。结果该家系5例患者均检测出VHL基因第2外显子上第587位核苷酸A—C突变，该突变导致第125位编码氨基酸由组氨酸（H）转变为脯氨酸（P）。15名家系成员中筛查出7名成员为该突变基因携带者，B超检查发现1例为双侧肾上腺肿瘤，1例为右肾囊肿。该突变为首次报道。结论该嗜铬细胞瘤家系中检测到可能的致病突变，VHL基因检测可早期发现致病基因携带者，建议对单纯家族性嗜铬细胞瘤患者常规进行VHL基因突变筛查。     

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

CAG repeat contraction in the androgen receptor gene in three brothers with mental retardation.

We report on three brothers with mental retardation and a contracted CAG repeat in the androgen receptor (AR) gene. It is known that expansion of the CAG repeat in this gene leads to spinal and bulbar muscular atrophy (SBMA or Kennedy disease); however, contracted repeats have not yet been implicated in disease. As the range of the length of CAG repeats in the AR gene, like those of other genes associated with dynamic mutations, follows a normal distribution, the theoretical possibility of disease at both ends of the distribution should be considered.     

Androgen receptor gene (CAG)n repeat analysis in the differential diagnosis between Kennedy disease and other motoneuron disorders

An increase in the number of (CAG)n repeats in the first coding exon of the androgen receptor (AR) gene has been strongly associated with Kennedy disease (KD) (spinal and bulbar muscular atrophy). This is an X-linked hereditary disorder characterized by motoneuron degeneration occurring in adults together with gynecomastia and hyperestrogenemia. We have performed AR gene molecular analysis in several members of a large family with KD as well as in 25 sporadic patients suffering from heterogeneous motoneuron disease (MND). An increase in the length of the (CAG)n repeats was detected, as expected, in all the affected males and in obligatory carrier females, some of which had minor signs of lower motoneuron involvement. There was only one possible exception, one young male with initial signs of the disease, who had an apparent normal length allele. An increased pathological allele was also found in 3 patients with MND. This indicates that the analysis of (CAG)n repeats of the AR gene plays a role in the differential diagnosis of this heterogeneous group of neurological diseases. © 1995 Wiley-Liss, Inc.     

Increased (CTG/CAG)(n) lengths in myotonic dystrophy type 1 and Machado-Joseph disease genes in idiopathic azoospermia patients

BACKGROUND: An increase in CAG trinucleotide repeat length in the androgen receptor (AR) gene has been linked to idiopathic azoospermia. METHODS: In order to test whether other (CAG/CTG)(n) loci are also affected, the (CAG/CTG)(n) frequency distribution at myotonic dystrophy type 1 (DM1), Machado-Joseph disease (MJD), dentatorubral-pallidoluysian atrophy (DRPLA) and spinocerebellar ataxia type 8 (SCA8) loci, in addition to the AR gene, was investigated in 48 azoospermia patients and 47 controls. RESULTS: The median CAG repeat length in the AR gene was significantly longer in azoospermia patients than in controls (23 versus 21, P < 0.001). Significant differences were also noted in the upper tails of trinucleotide repeat length distributions at both DM1 and MJD loci between the two populations. At the DM1 locus, alleles of more than 18 repeats were observed only in azoospermia patients, and not in controls (P = 0.014). At the MJD locus, the frequency of normal alleles (ANs) with 29 or more CAG repeats was also much higher in azoospermia patients (29.2 versus 7.4%; P = 0.0001). However, the repeat length distribution at DRPLA and SCA8 loci did not differ in the two groups. CONCLUSIONS: These data indicated that, at least in a subset of azoospermia patients, there was an increase in the number of trinucleotide repeats in some disease loci. Thus, it is noteworthy to evaluate whether offspring of these azoospermia patients, if born by assisted reproductive technologies, have an increased risk of trinucleotide repeat diseases.     

Molecular chaperones enhance the degradation of expanded polyglutamine repeat androgen receptor in a cellular model of spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is one of a growing number of neurodegenerative diseases caused by a polyglutamine-encoding CAG trinucleotide repeat expansion, and is caused by an expansion within exon 1 of the androgen receptor (AR) gene. The family of polyglutamine diseases is characterized by the presence of ubiquitinated, intranuclear inclusions associated with molecular chaperones and 26S proteasome components, although the role of these inclusions in the pathogenesis of polyglutamine diseases remains unclear. The over-expression of molecular chaperones of the Hsp70 and Hsp40 families has been shown to modulate inclusion frequency and cellular toxicity. We developed a cell culture system which enables the quantitative analysis of the effects of molecular chaperones on the biochemical properties of an expanded repeat AR. Using this approach, we demonstrate that Hsp70 and its co-chaperone Hsp40 not only increase expanded repeat AR solubility, but function to enhance the degradation of expanded repeat AR through the proteasome. Furthermore, our studies indicate that these molecular chaperones significantly decrease the half-life of an expanded repeat AR. Molecular chaperone enhancement of protein degradation points to the modulation of molecular chaperones as a potential therapeutic target for polyglutamine diseases.     

Multiple founder effects in spinal and bulbar muscular atrophy (SBMA, Kennedy disease) around the world.

SBMA (spinal and bulbar muscular atrophy), also called Kennedy disease, is an X-chromosomal recessive adult-onset neurodegenerative disorder caused by death of the spinal and bulbar motor neurones and dorsal root ganglia. Patients may also show signs of partial androgen insensitivity. SBMA is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene on the X-chromosome. Our previous study suggested that all the Nordic patients with SBMA originated from an ancient Nordic founder mutation, but the new intragenic SNP marker ARd12 revealed that the Danish patients derive their disease chromosome from another ancestor. In search of relationships between patients from different countries, we haplotyped altogether 123 SBMA families from different parts of the world for two intragenic markers and 16 microsatellites spanning 25 cM around the AR gene. The fact that different SBMA founder haplotypes were found in patients from around the world implies that the CAG repeat expansion mutation has not been a unique event. No expansion-prone haplotype could be detected. Trinucleotide diseases often show correlation between the repeat length and the severity and earlier onset of the disease. The longer the repeat, the more severe the symptoms are and the onset of the disease is earlier. A negative correlation between the CAG repeat length and the age of onset was found in the 95 SBMA patients with defined ages at onset.     

Moderate instability of the trinucleotide repeat in spino bulbar muscular atrophy.

Increased length of a protein-coding CAG repeat within the androgen receptor gene appears to be the only type of mutation responsible for spino-bulbal muscular atrophy (SBMA or Kennedy disease). We have analysed a large 4-generation SBMA family and found that the mutant allele was unstable upon transmission from parent to child, with a documented variation from 46 to 53 repeats and a tendency to increase in size (7 increases and a single decrease in 17 events), which appeared stronger upon transmission from a male than from a female. Our results suggest also limited somatic instability of the abnormal allele, with observable variation of up to 2-3 repeats. This indicates that the behavior of the CAG repeat is similar to that observed for small premutations in the fragile X syndrome, or small abnormal alleles in myotonic dystrophy, two diseases which are caused by expansion of an unstable trinucleotide repeat.