Molecular analysis in Japanese patients with Charcot-Marie-Tooth disease: DGGE analysis for PMP22, MPZ,and Cx32/GJB1 mutations

Charcot-Marie-Tooth disease (CMT) is a heterogeneous disorder and is traditionally classified into two major types, CMT type 1 (CMT1) and CMT type 2 (CMT2). Most CMT1 patients are associated with the duplication of 17p11.2-p12 (CMT1A duplication) and small numbers of patients have mutations of the peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), connexin 32 (Cx32/GJB1), and early growth response 2 (EGR2) genes. Some mutations of MPZ and Cx32 were also associated with the clinical CMT2 phenotype. We constructed denaturing gradient gel electrophoresis (DGGE) analysis as a screening method for PMP22, MPZ, and Cx32 mutations and studied 161 CMT patients without CMT1A duplication. We detected 27 mutations of three genes including 15 novel mutations; six of PMP22, three of MPZ, and six of Cx32. We finally identified 21 causative mutations in 22 unrelated patients and five polymorphic mutations. Eighteen of 22 patients carrying PMP22, MPZ, or Cx32 mutations presented with CMT1 and four of them with MPZ or Cx32 mutations presented with the CMT2 phenotype. DGGE analysis was sensitive for screening for those gene mutations, but causative gene mutation was not identified in many of the Japanese patients with CMT, especially with CMT1. Other candidate genes should be studied to elucidate the genetic basis of Japanese CMT patients.     

大鼠新基因PMP22CD的克隆以及多克隆抗体的制备

目的:通过PCR克隆PMP22CD基因,构建原核表达载体PET-32a(+)/PMP22CD,表达并纯化蛋白,制备多克隆抗体,为研究该基因的功能奠定基础.方法:通过PCR的方法克隆PMP22CD基因,选择抗原性较强的C-端,构建原核表达载体PET32a(+)/PMP22CD,在大肠杆菌BL21(DE3 Lysis)中诱导表达,SDS-PAGE分析重组蛋白以包涵体的形式存在,应用电洗脱的方式获得重组蛋白,免疫新西兰大白兔,获得抗血清,通过琼脂糖双扩和Western Blot检测抗血清效价和特异性.结果:经测序鉴定成功克隆PMP22CD基因,并构建PET-32a(+)/PMP22CD重组质粒,表达融合蛋白,免疫新西兰大白兔,获得PMP22CD多克隆抗体.结论:得到了纯化的PET-32a(+)/PMP22CD融合蛋白,获得了效价高、特异性强的抗体.     

妇科手术中发现的原发性阑尾癌5例分析

 目的  探讨阑尾癌与右侧附件肿瘤的异同点,以期提高阑尾癌术前诊断率。方法  本文就临床诊断附件肿瘤而行妇科手术中确诊为阑尾癌或伴发腹腔假黏液瘤(pseudomyxoma peritonei,PMP)的5例患者进行分析,总结临床症状、影像学检查、胃肠镜检查、血清肿瘤标志物、术中发现等方面的特征。结果  阑尾癌与右侧附件肿瘤在临床表现、影像学、生化指标等方面有很多共同点,但特异性不足。结论  虽然阑尾肿瘤非常罕见,但对于右侧盆腔肿块要充分考虑阑尾来源的可能性,从影像学等各方面入手可提高阑尾癌的术前诊断率。     

Variable phenotypes are associated with PMP22 missense mutations

Charcot-Marie-Tooth disease (CMT) is the commonest hereditary neuropathy encompassing a large group of clinically and genetically heterogeneous disorders. The commonest form of CMT, CMT1A, is usually caused by a 1.4 megabase duplication of chromosome 17 containing the PMP22 gene. Mutations of PMP22 are a less common cause of CMT. We describe clinical, electrophysiological and molecular findings of 10 patients carrying PMP22 missense mutations. The phenotype varied from mild hereditary neuropathy with liability to pressure palsies (HNPP) to severe CMT1. We identified six different point mutations, including two novel mutations. Three families were also found to harbour a Thr118Met mutation. Although PMP22 point mutations are not common, our findings highlight the importance of sequencing the PMP22 gene in patients with variable CMT phenotypes and also confirm that the PMP22 Thr118Met mutation is associated with a neuropathy albeit with reduced penetrance.     

Peripheral Myelin Protein 22 gene duplication with atypical presentations: A new example of the wide spectrum of Charcot-Marie-Tooth 1A disease

Charcot-Marie-Tooth type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are both autosomal-dominant disorders linked to peripheral myelin anomalies. CMT1A is associated with a Peripheral Myelin Protein 22 (PMP22) duplication, whereas HNPP is due to a PMP22 deletion on chromosome 17. In spite of this crucial difference, we report three observations of patients with the 1.4 megabase CMT1A duplication and atypical presentation (electrophysiological, clinical or pathological): a 10 year-old girl with tomaculous lesions on nerve biopsy; a 26 year-old woman with recurrent paresthesiae and block conduction on the electrophysiological study; a 46 year-old woman with transient recurrent nerve palsies mimicking HNPP. These observations highlight the wide spectrum of CMT1A and the overlap between CMT1A and HNPP (both linked to the PMP22 gene), and finally illustrate the complexity of the genotype–phenotype correlations in Charcot-Marie-Tooth diseases.     

Co-segregation of LMNA and PMP22 gene mutations in the same family

We report here clinical, electrophysiological, and molecular findings in a family affected with two inherited genetic diseases: limb girdle muscular dystrophy type 1B (LGMD1B) and hereditary neuropathy with liability to pressure palsies (HNPP). Members of the family carry a novel missense mutation in the LMNA gene and a nonsense mutation in the PMP22 gene. Interestingly, the double LMNA/PMP22 mutations carriers showed clinical features more severe than usually seen in HNPP, and electrophysiological findings suggesting an axonal loss in addition to a typical myelinopathy. This study provides further insights into the relevance of lamin A/C in muscle and nerve.     

Application of multiplex ligation-dependent probe analysis to define a small deletion encompassing PMP22 exons 4 and 5 in hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies arises as a result of defects at the chromosome 17p11.2-12 locus and in 84% of cases a 1.5 Mb deletion containing the PMP22 gene is detected by analysis that utilises polymorphic (CA)_n repeat markers which flank this gene. We report the clinical and electrophysiological findings observed in a kindred with three members affected by HNPP due to a deletion containing exons 4 and 5 of the PMP22 gene. This small deletion cannot be detected using standard analysis with polymorphic (CA)_n repeat markers and a definitive diagnosis was made by multiplex ligation-dependent probe analysis of PMP22 exons 1A-5. MLPA can be readily utilised as a routine diagnostic laboratory test to detect the common HNPP 1.5 Mb deletion, as well as the reciprocal 1.5 Mb insertion observed in CMT1A, but has the advantage over other diagnostic techniques of being able to define single exon deletions.     

Dejerine-Sottas' neuropathy caused by the missense mutation PMP22 Ser72Leu

OBJECTIVE: To describe a patient with the Dejerine-Sottas' syndrome due to a de novo Ser72Leu amino acid substitution in the PMP22 protein and summarize the phenotype associated with this frequent mutation. CASE REPORT: The proband has a medical history of early onset, severe, and progressive demyelinating neuropathy, accompanied by mild ptosis and limitations of eye movements. Ulnar nerve motor conduction velocities were extremely reduced (2.6 and 2.2 m/s), and the sural nerve biopsy showed onion bulbs and thinly myelinated axons. Duplication of chromosome 17p11.2 was ruled out, and the Ser72Leu substitution was found upon sequencing the PMP22 gene. CONCLUSION: The Ser72Leu substitution is being confirmed as the most frequent point mutation in the PMP22 gene. This 'hot spot' should be considered in the strategy of looking for point mutations in the hereditary demyelinating neuropathies.