夏科-马里-图斯病2A2型一家系的临床病理特点

目的 报道一个早发型夏科-马里-图斯病(CMT)2A2家系,探讨其临床和病理特点.方法 该家系共有5例患者,呈常染色体显性遗传,先证者为36岁女性,6岁开始出现下肢进行性无力,8岁出现双足内翻.家族中另有2例男性和2例女性发病,发病年龄3～7岁,主要表现为缓慢进展的四肢远端肌肉无力、萎缩,伴随四肢远端感觉减退、腱反射减退及关节挛缩.先证者和其儿子的上肢感觉神经、下肢感觉和运动神经诱发电位波幅不能引出.对先证者左侧腓肠神经进行活体组织病理检查.对先证者和其他4例家系患者、3名无症状家系成员行MFN2基因测序.结果 病理检查可见腓肠神经有髓纤维数目重度减少,以大有髓神经纤维减少为主,伴随个别有髓神经纤维再生簇结构以及不典型的洋葱球样结构.电镜下可见轴索中线粒体聚集,未发现线粒体结构异常.5例患者存在MFN2基因R94W突变,无症状家系成员无此突变.结论 我国存在早发型CMT2A2家系,患者周围神经缺乏有髓神经纤维再生改变,提示MFN2基因突变对神经元的损害更大.     

X连锁腓骨肌萎缩症Cx32基因的突变、临床和电生理特点

目的 分析X连锁腓骨肌萎缩症（CMTX）患者Cx32基凶的突变及其临床表现和电生理特点、方法应用多聚酶链反应一单链构象多态性分析结合DNA直接测序的方法,对24例无周围髓鞘蛋白（PMP）22基因大片段重复突变,家系中无男传男的腓骨肌萎缩症（CMT）先证者进行Cx32基因的突变分析;对先证者及其家系内患者进行临床和电生理检查。结果 在6个X连锁遗传家系和1例散发患者中发现了7个不同的Cx32基因突变,其中4个家系临床分型为CMTI型,2个家系为CMT中间型,散发病例为CMT1型检测到有Cx32基因突变的家系成员共38例,其巾男性20例,全部为CMTX患者;女性18例,其中6例为CMTX患者,12例为无临床症状的携带者;26例患者均为周围神经轻、中度受累。结论 CMTX的遗传方式可为X连锁显性、X连锁隐性遗传,也可为散发。根据临床和电生理特点分为CMTI型或CMT中间型,多为周围神经轻、中度受累,男性患者的症状通常较女性重。在没有检测到PMP22基因大片段重复突变和无男传男的CMT家系中应首先进行Cx32基因突变分析。     

腓骨肌萎缩症CMTX1型的间隙连接蛋白32基因突变检测

目的检测无基因重复的腓骨肌萎缩症患者间隙连接蛋白32(connexin32,Cx32)基因的突变情况。方法应用变性高效液相色谱(DHPLC)结合混合样品池法和脱氧核糖核酸(DNA)序列测定对1个临床可疑的X连锁显性遗传的腓骨肌萎缩症CMTX1型家系的先证者和15名家庭成员及60名家系外健康对照者进行Cx32基因外显子2的基因编码区突变检测,分3个片段扩增其基因编码区全长。结果先证者在片段2的DHPLC中发现杂合双峰,经DNA序列测定证实其Cx32外显子2发生Leu89Pro(266T→C)错义突变;家系内其他4例发病者和5名未发病者Cx32外显子2都有与先证者一致的DHPLC杂合双峰。60名健康对照者中未发现上述改变。结论Leu89Pro是该家系的致病性突变。该突变体的致病机制如何,有待于做进一步研究。     

腓骨肌萎缩症X1型1个家系的临床、电生理和Connexin32基因突变分析

目的观察腓骨肌萎缩症(CMT)X1型的临床、电生理特点和Connexin32(Cx32)基因突变情况.方法对1个无基因重复的临床可疑的CMTX1家系中的3例患者进行详尽的临床和神经电生理检查,并应用变性高效液相色谱结合混和样品池法和DNA序列测定对包括先证者在内的3名成员的Cx32基因进行突变检测.结果 该家系中的病人发生了Gly12Ser,50名正常人中未发现上述改变,提示该突变为致病性突变.家系中男性病人临床症状重于女性;电生理特点为脱髓鞘改变;同一病人的不同神经间存在异质性.结论 Gly12Ser突变可能导致原发性脱髓鞘性神经病,不伴有特殊的临床表现.     

腓骨肌萎缩症X型临床、电生理及Connexin 32新突变一例

目的报告1例X连锁型腓骨肌萎缩症(CMTX),探讨其临床表现、电生理特点和连接蛋白32(Cx32)基因突变特点。方法对1例临床诊断CMT患者进行详细的病史采集和临床查体,分析其电生理和神经活检检查结果,同时进行周围髓鞘结构蛋白22(PMP22)基因重复和Connexin32(Cx32)基因突变检测。结果患者临床表现为经典的遗传性感觉运动神经病,肌电图检查提示脱髓鞘损害伴轴索损害,同时出现传导阻滞;神经活检示脱髓鞘性周围神经损害;基因检测发现Cx32基因编码序列第414位碱基发生单碱基错义突变(414C>G),造成其编码的第138位的氨基酸由丝氨酸突变为精氨酸(Ser138Arg)。结论 414C>G突变为Cx32基因新突变,国内外文献未见报道。该基因型没有产生特殊的临床表现,但电生理表现为脱髓鞘为主的混合性周围神经病变,且具有传导阻滞的特点。Cx32基因不同的突变位点和形式可能是导致CMTX临床异质性的原因之一。     

结蛋白基因S12F新突变导致的结蛋白病一家系

目的 报道1个结蛋白基因新突变导致的结蛋白病家系,介绍其临床和病理改变特点.方法 1个常染色体显性遗传家系内共有8例患者,男7例,女1例.发病年龄20～50岁.其中7例有心脏损害,3例有肢体近端无力,1例伴慢性腹泻.先证者和其兄行左肱二头肌活体组织检查,进行组织学、酶组织化学、电镜观察及抗结蛋白等免疫组织化学染色.先证者和3例患者、5名无症状家系成员及50名健康人行结蛋白基因测序.结果 先证者的骨骼肌出现肌纤维直径变异加大伴结缔组织增生,少数肌纤维出现嗜酸性改变伴镶边空泡,其兄的骨骼肌仅在许多肌纤维内出现小圆状嗜酸性包涵体.肌纤维内包涵体和肌纤维膜下结蛋白阳性.电镜显示先证者肌纤维内颗粒物质沉积.4例患者存在结蛋白基因S12F突变,无症状家系成员和健康对照无此突变.结论 结蛋白S12F新突变导致的结蛋白病多出现在男性,以心脏病多见.病理改变在家系不同患者之间存在差异.     

骨骼肌钠通道α1亚基基因R1129Q新突变导致正常钾和低钾性周期性瘫痪一家系

目的 报道1个骨骼肌钠通道α1亚基(SCN4A)基因新突变导致的正常钾和低钾性周期性瘫痪家系的临床和病理改变特点.方法 本家系为常染色体显性遗传,共有9例患者,男性4例,女性5例,发病年龄7～25岁.5例患者为正常钾性周期性瘫痪,其中4例伴随肌强直症状;3例患者为低钾性周期性瘫痪;1例发作时血钾浓度不详.对先证者进行左肱二头肌活体组织检查.先证者和7例家系患者、3名无症状家系成员以及50名健康人行SCN4A基因测序.结果 先证者的肌纤维出现轻度肥大和萎缩,伴随核内移和肌纤维内空泡,部分肌纤维内氧化酶分布异常.所有患者均存在SCN4A基因的R1129Q突变,3名无症状家系成员以及50名健康对照无此突变.结论 SCN4A基因R1129Q新突变在同一家系内可以导致低血钾性和正常血钾性周期性瘫痪共存.     

骨骼肌钠通道α1亚基基因R1129Q新突变导致正常钾和低钾性周期性瘫痪一家系

目的 报道1个骨骼肌钠通道α1亚基(SCN4A)基因新突变导致的正常钾和低钾性周期性瘫痪家系的临床和病理改变特点.方法 本家系为常染色体显性遗传,共有9例患者,男性4例,女性5例,发病年龄7～25岁.5例患者为正常钾性周期性瘫痪,其中4例伴随肌强直症状;3例患者为低钾性周期性瘫痪;1例发作时血钾浓度不详.对先证者进行左肱二头肌活体组织检查.先证者和7例家系患者、3名无症状家系成员以及50名健康人行SCN4A基因测序.结果 先证者的肌纤维出现轻度肥大和萎缩,伴随核内移和肌纤维内空泡,部分肌纤维内氧化酶分布异常.所有患者均存在SCN4A基因的R1129Q突变,3名无症状家系成员以及50名健康对照无此突变.结论 SCN4A基因R1129Q新突变在同一家系内可以导致低血钾性和正常血钾性周期性瘫痪共存.     

缝隙连接蛋白B1基因I20T新突变导致伴有短暂性脑白质损害的X连锁Charcot-Marie-Tooth病1型

目的 报道1个伴有短暂性脑白质损害的X连锁Charcot-Marie-Tooth病1型(CMT1x)家系的临床、影像学和基因改变特点.方法 先证者为14岁男孩,出现短暂发作性言语不能和轻度肢体麻木无力2年5个月.其母亲存在弓形足.对先证者进行头颅MRI、神经电生理检查和腓肠神经活体组织检查;对先证者及其父母,50名女性无周围神经病及脑病对照者进行缝隙连接蛋白B1(GJB1)基因检测.结果 先证者周围神经的运动神经动作电位波幅显著下降,传导速度轻度减慢.听觉和体感诱发电位潜伏期明显延长.MRI显示胼胝体和大脑后部白质对称性异常信号,6个月后病变显著减轻.病理检查提示慢性轴索性周围神经病,电镜检查还可见有髓神经纤维的髓鞘施兰切迹加宽.先证者及其母亲GJB1基因存在I20T突变,其父和50名女性对照者无此突变.结论 伴短暂性脑白质损害的CMT1X可能与GJB1基因I20T新突变有关,其大脑白质的MR1改变具有可逆性.     

腓骨肌萎缩症伴神经性耳聋一家系临床和分子遗传学分析

目的探讨一个X连锁腓骨肌萎缩症(CMTX)伴常染色体隐性遗传的神经性耳聋家系的临床特点并研究其分子遗传学病因。方法对9名家系成员进行详细的临床检查，先证者进行了神经肌电图、听觉诱发电位和神经活检，3名耳聋患者进行电测听检查。运用聚合酶链反应一单链构象多态性分析技术(PCR-SSCP)结合直接测序法进行间隙连接蛋白32(eonnexin32)的突变分析，直接测序法进行间隙连接蛋白26(connexin26)的突变分析。结果家系中3名腓骨肌萎缩症患者为X连锁显性遗传，3名神经性耳聋患者为常染色体隐性遗传，其中1名患者同时出现腓骨肌萎缩症和神经性耳聋的临床症状。CMTX由connexin32错义突变C223T(Arg75Trp)引起。耳聋症状与connexin32点突变无共分离现象，对connexin26直接测序亦未发现突变，耳聋的致病基因有待进一步探讨。结论该家系腓骨肌萎缩症和耳聋分别由不同基因突变引起，这种在一个家系中同时出现两种不同遗传方式，不同致病基因的遗传病罕有报道。     

Charcot-Marie Tooth type X (CMTX) disease: clinical and genetic characteristics of eleven patients

Charcot-Marie-Tooth type X disease (CMTX) is the second most frequent inherited neuropathy, after CMT1A type associated with 17p11.2-p12 duplication. CMTX is inherited as X dominant trait and is caused by point mutations in Cx32 gene. In the study the first Polish group of 11 patients with CMTX from 4 families is presented. The following four mutations were found in Cx32 gene: Gly110Asp, Val 152 Asp, Arg 183 His and Glu 208 Gly. CMTX is characterized by X dominant trait of inheritance, a mild clinical course in affected females and slowly progressive atrophy and weakness of distal limb muscles. Both electrophysiological and sural nerve biopsy studies show axonal changes with secondary demyelination.     

Phenotypic expression of a Pro 87 to Leu mutation in the connexin 32 gene in a large Swiss family with Charcot-Marie-Tooth neuropathy

BACKGROUND: The clinical manifestations of CMTX have been well described but the natural history has not yet been studied in detail. We studied phenotype variability in a family with a Pro 87 to Leu mutation of the connexin 32 (Cx32) gene. METHODS: A total of 32 family members, of which 19 patients were affected, underwent clinical, electrophysiological, and genetic studies. RESULTS: Onset was in the second decade. Clinical features were similar in both sexes when quantitative scores were compared, but more males had a steppage gait and skeletal deformities. All adult patients had a predominant involvement of the thenar muscles. The median values of nerve conduction velocities (NCVs) were not statistically different in men and in women. The correlation coefficients were low between motor NCVs within the same extremities, indicating nonuniform slowing between nerves, the ulnar nerve being the least affected. When disability was rated, a strong correlation was seen in male patients between severity of motor axonal loss and duration of the disease. The main pathological features were axonal loss, clusters of regenerating fibers and paranodal demyelination, the hallmark of a Schwann cell pathology. CONCLUSIONS: Our data support the hypothesis that clinical disability in CMTX is caused by loss of large myelinated axons in men. Furthermore, this study shows that the nerves are not uniformly affected in terms of axonal loss. Preventing axonal degeneration and promoting axonal regeneration in the most affected nerves might be the best therapeutic approaches to ameliorate disability in CMTX.     

Abnormalities in the axonal cytoskeleton induced by a connexin32 mutation in nerve xenografts

The X-linked form of Charcot-Marie-Tooth neuropathy is associated with mutations in the connexin32 (Cx32) gene. The functional role of Cx32 in Schwann cells and the relationship of these mutations to the progressive axonal loss and distal limb weakness seen in this disease have not been elucidated. To investigate the local influence of Schwann cells bearing the Cx32 gene defect on axonal cytoskeleton and the myelination process, the nerve xenograft model was used to transfer a Cx32 missense mutation (Glu102Gly) from human to an in vivo myelination system in nude mice. Twelve nerve grafts from two family members with Cx32 mutations and 17 grafts from three healthy individuals were generated by end-to-end anastomosis of approximately 6-mm sural nerve fascicles into the cut ends of the sciatic nerve in nude mice. Specimens were examined at 2, 4, 8, 12, and 16 weeks. Ultrastructural morphometric analysis showed Schwann cells with Cx32 mutation have a profound effect on the nude mice axons, resulting in an increase in neurofilament density, a depletion of microtubules associated with fragmentation of smooth axonal reticulum, and increased vesicles and mitochondria. At 16 weeks, axonal enlargement was evident within the proximal part of the graft; axonal atrophy, degeneration, and fiber loss were seen in distal-graft and host segments. The myelination process was not affected. We conclude that Cx32 mutation impairs a modulatory function of Schwann cells on axons, resulting in profound cytoskeletal alterations leading to distal axonal degeneration. These observations emphasize the role of impaired Schwann cell-axon interactions in the pathogenesis of hereditary neuropathies. J. Neurosci. Res. 51:174–184, 1998. © 1998 Wiley-Liss, Inc.     

MUTATIONS IN CONNEXIN 32: THE MOLECULAR AND BIOPHYSICAL BASES FOR THE X-LINKED FORM OF CHARCOT-MARIE-TOOTH DISEASE

The connexins are a family of homologous integral membrane proteins that form channels that provide a low resistance pathway for the transmission of electrical signals and the diffusion of small ions and non-electrolytes between coupled cells. Individuals carrying mutations in the gene encoding connexin 32 (Cx32), a gap junction protein expressed in the paranodal loops and Schmidt-Lantermann incisures of myelinating Schwann cells, develop a peripheral neuropathy—the X-linked form of Charcot-Marie-Tooth disease (CMTX). Over 160 different mutations in Cx32 associated with CMTX have been identified. Some mutations will lead to complete loss of function with no possibility of expression of functional channels. Some mutations in Cx32 lead to the abnormal accumulation of Cx32 proteins in the cytoplasm, particularly in the Golgi apparatus; CMTX may arise due to incorrect trafficking of Cx32 or to interference with trafficking of other proteins. On the other hand, many mutant forms of Cx32 can form functional channels. Some functional mutants have conductance voltage relationships that are disrupted to a degree which would lead to a substantial reduction in the available gap junction mediated communication pathway. Others have essentially normal steady-state g-V relations. In one of these cases (Ser26Leu), the only change introduced by the mutation is a reduction in the pore diameter from 7 Angstrom for the wild-type channel to less than 3 Angstrom for Ser26Leu. This reduction in pore diameter may restrict the passage of important signaling molecules. These findings suggest that in some, if not all cases of CMTX, loss of function of normal Cx32 is sufficient to cause CMTX.     

Clinical characterization and genetic analysis of Korean patients with X‐linked Charcot‐Marie‐Tooth disease type 1

Mutations in the gap junction protein beta 1 gene (GJB1) cause X‐linked Charcot‐Marie‐Tooth disease type 1 (CMTX1). CMTX1 is representative of the intermediate type of CMT, having both demyelinating and axonal neuropathic features. We analyzed the clinical and genetic characterization of 128 patients with CMTX1 from 63 unrelated families. Genetic analysis revealed a total of 43 mutations including 6 novel mutations. Ten mutations were found from two or more unrelated families. p.V95M was most frequently observed. The frequency of CMTX1 was 9.6% of total Korean CMT family and was 14.8% when calculated within genetically identified cases. Among 67 male and 61 female patients, 22 females were asymptomatic. A high‐arched foot, ataxia, and tremor were observed in 87%, 41%, and 35% of the patients, respectively. In the male patients, functional disability scale, CMT neuropathy score, and compound muscle action potential of the median/ulnar nerves were more severely affected than in the female patients. This study provides a comprehensive summary of the clinical features and spectrum of GJB1 gene mutations in Korean CMTX1 patients.     

A point mutation in the human connexin32 promoter P2 does not correlate with X-linked dominant Charcot-Marie-Tooth neuropathy in Germany

The sensorimotor neuropathy Charcot-Marie-Tooth disease (CMT) is the most common hereditary disorder of the peripheral nervous system. The X-linked dominant form of CMT (CMTX) is associated with mutations in the connexin32 gene (Cx32). The majority of CMTX cases harbour mutations in the coding region while a few cases have been reported to result from mutations in the promoter region. We found a G-713A transition of the nerve specific Cx32 promoter P2 in the Caucasian German population. The allele frequency reached 50%, both in CMT patients and in healthy control individuals. In contrast, in an earlier contribution to this journal [Brain Res. Mol. Brain Res.78 (2000) 146], the same base transition was reported to cause CMTX in a Taiwanese family. These divergent results are important for genetic counselling and require careful consideration of ethnic backgrounds and of diagnostic and experimental pitfalls.     

A NOVEL MUTATION OF CONNEXIN-32 GENE IN A CMTX ITALIAN FAMILY

X-linked Charcot-Marie-Tooth is an inherited motor and sensory neuropathy associated with mutations in GJB1, a gene on chromosome X coding for the gap junction protein "connexin 32" (Cx32). Cx 32 gene is expressed in both peripheral and central nervous system myelin.
We describe a family affected by X-linked CMT neuropathy with a novel point mutation in Cx32 gene, in which the mother, the putative carrier, and three affected sons were examined. The affected sons (32, 35, 38 yrs) presented a motor-sensory slowly progressive neuropathy mainly involving lower limbs. Nerve conduction study showed both axonal and demyelinating pattern of denervation. Evoked potentials indicated visual and brainstem auditory pathway involvement. The mother showed subclinical electrophysiological abnormalities in nerve conduction velocities.
By mutational analysis of GJB1 using SSCP and sequencing of candidate regions, a previously undescribed missense mutation in the exon 2, codon 151, was found. This mutation was due to a transversion (TAT-> TCT) leading to a Tyr->Ser substitution in the 2nd extracellular domain.
Our findings further stress the wide variability in the spectrum of Cx32 mutations associated to CMTX, making it worthwhile to deepen knowledge about genotypic–phenotypic interrelationship in this disease.     

Transient,recurrent, white matter lesions in X-linked Charcot-Marie-Tooth disease with novel connexin 32 mutation

BACKGROUND: X-linked hereditary demyelinating neuropathies (Charcot-Marie-Tooth Disease [CMTX]) caused by mutations in the connexin 32 (Cx32) gene account for approximately 10% to 20% of all hereditary demyelinating neuropathies. Mild subclinical central nervous system (CNS) involvement has been previously described, and CMTX patients with transient white matter lesions allied to CNS symptoms have very recently been described. This is of potential interest, as Cx32 is widely expressed in both peripheral nerve and the brain. PATIENTS: We describe a family with hereditary demyelinating neuropathy and transient CNS symptoms. For this study, family members underwent genotyping and detailed clinical, electrophysiological, and magnetic resonance imaging examination. RESULTS: We present a CMTX family with a novel mutation in the Cx32 gene. Affected family members show, in addition to the classic polyneuropathy, transient and reversible white matter lesions on magnetic resonance imaging scans, correlating similarly transient CNS symptoms. CONCLUSION: Patients with CMTX can present with transient CNS symptoms and marked white matter lesions on magnetic resonance imaging scans.     

Six novel connexin32 (GJB1) mutations in X-linked Charcot-Marie-Tooth disease

X-linked Charcot-Marie-Tooth disease (CMTX) is a clinically heterogeneous hereditary motor and sensory neuropathy with X-linked transmission. Common clinical manifestations of CMTX, as in other forms of Charcot-Marie-Tooth disease (CMT), are distal muscle wasting and weakness, hyporeflexia, distal sensory disturbance, and foot deformities. Motor nerve conduction velocity is reduced. In male patients it is often less than 38 m/s in the median nerve (a value often used to distinguish between "demyelinating" and "axonal" forms of CMT), but in female patients conduction velocity may be faster than this or normal. Mutations in the connexin32 (gap junction protein beta 1 (GJB1)) gene are responsible for the majority of CMTX cases. This report describes six British CMTX families with six novel mutations (four missense, one nonsense, and one frame shift) of the GJB1 gene. Affected members in these six families had typical signs of CMT but in some affected members of three families there was additional central nervous system involvement or deafness in the absence of any other explanation other than CMT.