面肩肱型肌营养不良症的基因诊断

目的 对中国人面肩肱型肌营养不良症进行基因诊断。方法 用EcoRI以及EcoRI/BlnI消化基因组DNA,0.6%琼脂糖凝胶电泳,P13E11探针进行Southern印迹杂交。结果 患者所得EcoRI BlnI/P13E11DNA片段长度在15-33kb之间,而正常对照在41kb以上,发现两个症状前患者。结论 以P13E11探针通过Southern印迹杂交探测EcoRi/BlnI双酶消化的基因组DNA可对中国人绝大部分面肩肱型肌营养不良症进行基因诊断,并可进行症状前诊断。     

面肩肱型肌营养不良症基因诊断

目的 观察面肩肱型肌营养不良症(facioscapulohumeral muscular dystrophy，FSHD)患者p13E—11标记的4q35 EcoR Ⅰ／B1n Ⅰ片段分子量变化特点，对FSHD进行基因诊断。方法 提取基因组DNA，EcoR Ⅰ／B1n Ⅰ双酶切后进行脉冲凝胶电泳，用同位素标记的探针p13E—11进行Southern印迹，以小于38kb为诊断FSHD标准，观察4q35 EcoR Ⅰ／B1n Ⅰ片段分子量大小的分布。结果 FSHD组26例患者中，20例4q35 EcoR Ⅰ／B1n Ⅰ片段小于38kb，基因诊断阳性率为76．92％。FSHD亲属组12例，其中两例该片段小于38kb。对照组21人，该片段均大于38kb。结论 以小于38kb为诊断标准较满意，FSHD基因诊断阳性率与文献基本吻合。     

面肩肱型肌营养不良症的分子遗传学研究进展

面肩肱型肌营养不良症（factoscapulohumeral muscular dystrophy,FSHD)呈常染色体显性遗传。大多数致病基因定位于4q35,存在遗传异质性。发现与FSHD相关的DNA重组,即4q35上3．3kb串联重复单位呈不同拷贝数缺失。以p13E-11为探针检测EcoR I/Bln I双重消化的DNA片段,FSHD患者的消化片段通常小于正常人,从而进行有效的分子诊断。由于FSHD基因尚未鉴定与分子,FSHD的确切发病机理仍未阐明,提出有位置效应变异假说等。目前有一候选基因FRG1。与FSHD相关的DNA重组片段的大小与FSHD临床表型之间显著相关,可较好地解释FSHD患者广泛的临床变异性。     

面肩肱型肌营养不良症发病机制的研究进展

面肩肱型肌营养不良症,是一种常染色体显性遗传疾病,至今尚未找到其致病基因。大部分面肩肱型肌营养不良症患者和4q35区域3.3-kb的串联重复序列Z4D4的整倍缺失紧密连锁,几乎所有面肩肱型肌营养不良症患者,Southern杂交片段小于35 kb(少于11个D4Z4重复序列),而正常人群该片段为350 kb(11-150个D4Z4重复序列)。通过分子生物学研究与生物信息学分析,在4q35区域内,排除了FRG1、FRG2、ALP、ANT1、DUX4、YY I、HMGB2及Nu-c lolin等几个可能的候选基因;有关肩肱型肌营养不良症发病机制的位置变异效应假说,需要更多的证据支持;另一假说认为,面肩肱型肌营养不良症患者,D4Z4区域内类似沉默子的序列与转录抑制复合物相结合,由于D4Z4的缺失,该复合物不能形成并导致D4Z4上游基因的过表达,有关基因的过表达通过某种不明机制导致FSHD疾病的发生;D4Z4的缺失使4qter在细胞核内的定位异常,使许多基因的表达不正常,从而引起一系列的病理变化,并最终导致FSHD疾病的发生,也是FSHD发病的可能性机制之一。FSHD的发病相关基因和发病机制的研究有待深入。     

面肩肱型肌营养不良症一例大家系20年随访报告

目的了解面肩肱型肌营养不良症一例大家系的发展形势,寻求防治方法。方法实际访查该家系所有成员,重绘家系谱图。结果该家系出现第Ⅶ代;现共418人:第Ⅵ代新发病3人:现存患者9人:因先天性疾病早死产15人。结论本病尚无法治疗,危害严重,应依据产前诊断和有效措施,终止本病的继续传递。     

伴腓肠肌假肥大的面肩肱型肌营养不良症一家系三例

先证者（Ⅱ4）女，31岁，因“自幼吹哨不能，双上肢无力16年伴双下肢无力10年”于2006年6月到我院门诊就诊。患者自幼不能吹口哨，6岁时发现鼓腮漏气，15岁左右发现双肩肌肉萎缩，随后胸大肌也逐渐出现萎缩，21岁左右发现双下肢萎缩，以近端明显，病情进展缓慢，目前自己梳头困难，能刷牙、行走。查体：神志清楚，心肺等内科检查未见异常。双侧额纹基本对称消失，双眼睑闭合无力，眼球各方向运动灵活、到位，口仑匝肌假性肥大而嘴唇微翘（猫脸），吹哨不能，鼓腮无力、漏气，鼻唇沟浅，表情运动无力、减少。双侧肩胛带肌、胸锁乳突肌、三角肌、肱二、三头肌、股四头肌和胫骨前肌萎缩，翼状肩胛，胸大肌上部萎缩，锁骨与第一肋骨突出，未见三角肌假性肥大，腓肠肌轻度假性肥大，未见弓形足、脊柱畸形。     

面肩肱型肌营养不良症的遗传早现现象三家系14例

家系１先证者（Ⅲ３），男，３２岁。因双上肢进行性无力，面部表情少１４年，伴双下肢无力１０年就诊。患者约１８岁时发现右肩肌肉少，随后发现鼓腮漏气，右上肢抬举无力，以后发展到左上肢，４～５年后双下肢也无力，上坡时明显，四肢近端肌肉萎缩，１０年后蹲下不能站...     

面肩肱型肌营养不良一家系26例

先证者(Ⅴ10)男，53岁。因双上肢进行性无力38年，伴双下肢无力23年就诊。患者15岁左右发现嘴唇逐渐增厚，吹口哨无力，鼓腮困难。18岁左右开始出现右肩胛带肌萎缩，右肩胛骨向后凸出，随后左肩胛带肌，胸大肌也逐渐出现萎缩。30岁左右出现双下肢近端肌肉萎缩，下蹲起立时困难。40岁开始不能承担较重体力劳动。目前行走尚无困难，但穿衣裤时上肢活动受限。查体：神清合作，智力正常，心肺未见异常。     

一例以智力低下为首发症状的面肩肱型肌营养不良患儿D4Z4区的变异分析

目的鉴定一例以智力障碍为首发症状的面肩肱型肌营养不良(facioscapulohumeral muscular dystrophy,FSHD)患儿4q35上D4Z4区域的致病变异。方法对患儿进行韦氏智力检测,并收集其临床资料进行综合分析。提取患儿及其父母的外周血DNA,先采用医学外显子组二代测序和拷贝数变异检测,之后应用分子梳法鉴定其D4Z4重复单元的缩短情况并鉴定其来源。结果患儿总体智商估计值为41,言语理解指数估计值为45,知觉推理指数估计值为520医学外显子组测序和拷贝数变异检测未发现患儿携带致病变异,分子梳检测结果表明患儿D4Z4区的长度为5.2kb,重复单元数为2,患儿的父母均未检测到相同的变异。结论D4Z4重复单元只有2个可能是患儿智力低下和FSHD的致病原因。分子梳检测能够鉴定此重复单元的数目和来源,有助于明确诊断。     

BglⅡ-BlnⅠ剂量检测方法在面肩肱型肌营养不良症1A基因诊断中的应用

目的 通过检测染色体4q35和10q26之间的易位情况，进一步提高面肩肱型肌营养不良症1A(hcioscapulohumeral muscular dystrophy，FSHD1A)基因诊断的准确性。方法 应用Bgl Ⅱ-Bln Ⅰ剂量检测方法，对7例基因诊断阳性的FSHD症状前患者和5例基因诊断阴性而临床诊断为散发性FSHD患者的染色体4q35和10q26的易位状况进行分析。用Bgl Ⅱ和Bin Ⅰ酶切基因组DNA后行琼脂糖凝胶电泳，制备p13E-11探针并以α^-32P dCTP标记，进行Southern杂交及放射自显影。应用图像分析系统和薄层扫描仪对4q与10q杂交片段的信号强度进行定量分析，判断4q35和10q26的易位情况。结果 在基因诊断阳性的7例FSHD症状前患者中，1例发生了4q35至10q26的易位，有可能为假阳性基因诊断。在基因诊断阴性的5例散发性FSHD患者中，1例发生了10q26至4q35的易位，可能为假阴性基因诊断。其余10例未发现4q35和10q26之间的易位．结论 应用Bgl Ⅱ-Bln Ⅰ剂量检测方法，可以检出染色体4q35和10q26之间的易位，能够进一步提高FSHD1A基因诊断的准确性。     

Common epigenetic changes of D4Z4 in contraction‐dependent and contraction‐independent FSHD

Facioscapulohumeral muscular dystrophy (FSHD), caused by partial deletion of the D4Z4 macrosatellite repeat on chromosome 4q, has a complex genetic and epigenetic etiology. To develop FSHD, D4Z4 contraction needs to occur on a specific genetic background. Only contractions associated with the 4qA161 haplotype cause FSHD. In addition, contraction of the D4Z4 repeat in FSHD patients is associated with significant D4Z4 hypomethylation. To date, however, the methylation status of contracted repeats on nonpathogenic haplotypes has not been studied. We have performed a detailed methylation study of the D4Z4 repeat on chromosome 4q and on a highly homologous repeat on chromosome 10q. We show that patients with a D4Z4 deletion (FSHD1) have D4Z4‐restricted hypomethylation. Importantly, controls with a D4Z4 contraction on a nonpathogenic chromosome 4q haplotype or on chromosome 10q also demonstrate hypomethylation. In 15 FSHD families without D4Z4 contractions but with at least one 4qA161 haplotype (FSHD2), we observed D4Z4‐restricted hypomethylation on chromosomes 4q and 10q. This finding implies that a genetic defect resulting in D4Z4 hypomethylation underlies FSHD2. In conclusion, we describe two ways to develop FSHD: (1) contraction‐dependent or (2) contraction‐independent D4Z4 hypomethylation on the 4qA161 subtelomere. Hum Mutat 30:1–11, 2009. © 2009 Wiley‐Liss, Inc.     

Distinguishing the 4qA and 4qB variants is essential for the diagnosis of facioscapulohumeral muscular dystrophy in the Chinese population

Facioscapulohumeral muscular dystrophy (FSHD) is the third most common inherited muscular dystrophy with markedly clinical variability and complex genetic cause. Several reports pertaining to the Caucasian population have confirmed that there are 4qA and 4qB variants of the 4qter subtelomere, and FSHD is uniquely associated with the 4qA variant. However, few data relevant to the Chinese population have been published. In present paper, detailed clinical and genetic re-evaluations were performed in members of four special families who had been initially diagnosed as atypical or asymptomatic FSHD based only on the D4Z4 repeat length analysis. The FSHD-sized D4Z4 repeats in the probands from families 1, 2 and 3 were identified as 4qB variants. These patients were further confirmed as limb-girdle muscular dystrophy (LGMD2) or myotonic dystrophy (DM1) by molecular analyses. Specifically, we identified a 4qB variant on chromosome 10 in the healthy members of the fourth FSHD family with complex D4Z4 rearrangements of two exchanged repeat arrays. For the first time, we demonstrated in the Chinese population that D4Z4 contractions on the 4qB variant do not cause FSHD and 4qB variant on chromosome 10 might also represent intermediate structures in the transition from 4q to 10q. Furthermore, our results emphasize that D4Z4 repeat length analysis alone is not sufficient for the diagnosis of FSHD, especially when used as an exclusion criterion. This analysis should be accompanied by 4qA/4qB variant determination and integrated chromosome assignments, especially in patients with obscure and unclassified myopathies similar to atypical forms of FSHD.     

The DNA rearrangement associated with facioscapulohumeral muscular dystrophy involves a heterochromatin-associated repetitive element: Implications for a role of chromatin structure in the pathogenesis of the disease

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant form of muscular dystrophy. The FSHD locus has been linked to the most distal genetic markers on the long arm of chromosome 4. Recently, a probe was identified that detects anEcoRI fragment length polymorphism which segregates with the disease in most FSHD families. Within theEcoRI fragment lies a tandem array of 3.2 kb repeats. In several familial cases and four independent sporadic FSHD mutations, the variation in size of theEcoRI fragment was due to a decrease in copy number of the 3.2 kb repeats. To gain further insight into the relationship between the tandem array and FSHD, a single 3.2 kb repeat unit was characterized. Fluorescencein situ hybridization (FISH) demonstrates that the 3.2 kb repeat cross-hybridizes to several regions of heterochromatin in the human genome. In addition, DNA sequence analysis of the repeat reveals a region which is highly homologous to a previously identified family of heterochromatic repeats, LSau. FISH on interphase chromosomes demonstrates that the tandem array of 3.2 kb repeats lies within 215 kb of the 4q telomere. Together, these results suggest that the tandem array of 3.2 kb repeats, tightly linked to the FSHD locus, is contained in heterochromatin adjacent to the telomere. In addition, they are consistent with the hypothesis that the gene responsible for FSHD may be subjected to position effect variegation because of its proximity to telomeric heterochromatin.     

A unique library of myogenic cells from facioscapulohumeral muscular dystrophy subjects and unaffected relatives: family, disease and cell function

To explore possible mechanisms of pathology in facioscapulohumeral muscular dystrophy (FSHD), we generated a novel library of myogenic cells composed of paired cultures derived from FSHD subjects and unaffected first-degree relatives. We prepared cells from biopsies of both biceps and deltoid muscles obtained from each of 10 FSHD and 9 unaffected donors. We used this new collection to determine how family background and disease affected patterns of growth and differentiation, expression of a panel of candidate, and muscle-specific genes, and responses to exogenous stressors. We found that FSHD and unaffected cells had, on average, indistinguishable patterns of differentiation, gene expression, and dose-response curves to staurosporine, paraquat, hydrogen peroxide, and glutathione depletion. Differentiated FSHD and unaffected cultures were both more sensitive to glutathione depletion than proliferating cultures, but showed similar responses to paraquat, staurosporine, and peroxide. For stress responses, the sample size was sufficient to detect a 10% change in effect at the observed variability with a power of >99%. In contrast, for each of these properties, we found significant differences among cells from different cohorts, and these differences were independent of disease status, gender, or muscle biopsied. Thus, though none of the properties we examined could be used to reliably distinguish between FSHD and unaffected cells, family of origin was an important contributor to gene-expression patterns and stressor responses in cultures of both FSHD and unaffected myogenic cells.     

Analysis of the tandem repeat locus D4Z4 associated with facioscapulohumeral muscular dystropothhy

The sequence of the tandem repeat sequence (D4Z4) associatedwith facioscapulohumeral muscular dystrophy (FSHD) has beendetermined: each copy of the 3.3 kb repeat contains two homeoboxesand two previously described repetitive sequences, LSau anda GC-rich low copy repeat designated hhspm3. By Southern blotting,FISH and isolation of cDNA and genomic clones we show that thereare repeat sequences similar to D4Z4 at other locations in thehuman genome. Southern blot analysis of primate genomic DNAindicates that the copy number of D4Z4-like repeats has increasedmarkedly within the last 25 million years. Two cDNA clones wereisolated and found to contain stop codons and frameshifts withinthe homeodomains. An STS was produced to the cDNAs and analysisof a somatic cell hybrid panel suggests they map to chromosome14. No cDNA clones mapping to the chromosome 4q35 D4Z4 repeatshave been Identified, although the possiblilty that they encodea protein cannot be ruled out. Although D4Z4 may not encodea protein, there is an association between deletions withinthis locus and FSHD. The D4Z4 repeats contain LSau repeats andare adjacent to 68 bp Sau3A repeats. Both of these sequencesare associated with heterochromatic regions of DNA, regionsknown to be involved in the phenomenon of position effect variegation.We postulate that deletion of D4Z4 sequences could produce aposition effect.     

De novo variants and recombination at 4q35: Hints for preimplantation genetic testing in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) has been associated with the deletion of an integral number of 3.3 kb units of the polymorphic D4Z4 repeat array at 4q35. The prenatal identification of this defect can be carried out on chorionic villi or amniocytes, whereas preimplantation genetic testing for monogenic disorders (PGT-M) requires molecular markers linked to the D4Z4 allele of reduced size. In this context the reliability of this association is crucial. To test the informativeness of the nearby polymorphic markers we investigated recombination at 4q35 using the polymorphic markers D4S1523, D4S163 and D4S139 positioned at 0.55, 0.5 and 0.21 Mb proximal to the D4Z4 array respectively. We determined the probability of recombination events to occur in the D4Z4-D4S1523 interval considering 86 subjects belonging to 12 FSHD families and found a recombination frequency of 14% between D4Z4 and D4S1523. Our study also revealed the occurrence of de novo variants and germline mosaicism. These findings highlight the recombinogenic nature of the 4q subtelomere and indicate that caution should be taken when interpreting PGT-M results. It is advisable that a woman who underwent a PGT-M cycle undertakes a prenatal DNA analysis to confirm the size of the D4Z4 alleles carried by the fetus.     

Duchenne型肌营养不良症的产前基因诊断研究

应用Ｄｕｃｈｅｎｎｅ型肌营养不良症（Ｄｕｃｈｅｎｎｅ　ｍｕｓｃｕｌａｒ　ｄｙｓｔｒｏｐｙ，ＤＭＤ）基因的ｃＤＮＡｓ作为探针，以限制性片段长度多态（ＲＦＬＰ）分析为策略，采用Ｓｏｕｔｈｅｒｎ分子杂交方法，成功地对１例可疑ＤＭＤ的男性胎儿及１例ＤＭＤ患儿进行基因诊断。结果显示该胎儿ＤＭＤ基因正常，而患儿存在ＤＭＤ基因缺失（缺失２．１５ｋｂ）。在基因分析前，应用聚合酶链式反应（ｐｏｌｙｍｅｒａｓｅ　ｃｈａｉｎ　ｒｅａｃｔｉｏｎ，ＰＣＲ）技术鉴定胎儿性别为男性。胎儿出生后检查结果与与产前基因诊断相吻合。为了获得高灵敏度探针，本文采用地高辛配基标记ＤＮＡ探针的方法，通过酶联免疫法，使分子杂交的ＤＮＡ检测带出现颜色反应。实验结果表明，此方法适用于基因组单拷贝ＤＮＡ顺序的检测，具有快速、安全等优越性，可以替代同位素进行推广、应用。     

Intrafamilial variability of limb-girdle muscular dystrophy,LGMD1D type

LGMD1D is an autosomal dominant limb girdle muscular dystrophy caused by variants in the DNAJB6 gene. This is typically an adult-onset disorder characterized by moderately progressive proximal muscle weakness without respiratory or bulbar involvement; however phenotypic variability is often observed with some individuals having earlier onset and more severe symptoms. Here, we present a family with a novel NM_005494.2:c.271T > G p.(Phe91Val) variant in DNAJB6 with a late-onset, mild and slowly progressive form of the disease, including one individual, who in her 7th decade of life has subclinical LGMD1D with only mild features on muscle biopsy and MRI. Unlike previously reported cases where missense variants affecting the Phe91 amino acid residue are associated with a more severe form of the disease, this family represents the mild end of the LGMD1D clinical spectrum. Therefore, this family adds further complexity to the genotype-phenotype correlation in DNAJB6-associated muscular dystrophies.