| Myotonia Congenital is an inherited disease with the disorders in the chloride channel of muscular cell membrane .The disease has two different types:Thomsen' s disease which is an autosomal dominant disorder and Beck' s disease which is an autosomal recessive disorder. The two diseases share some similar clinical features, such as muscle myotonia and stiffness. Muscle Chloride Channel (CLC1) is coded by muscle Chloride Channel Gene(CLCNl) which locates at 7q35 in homo-sapiens chromosome. CLCN1 gene is organized into 23 exons and code 988 amino acids. Mutation in CLCN1 gene leads to the disorder of CLC1 , increasing the membrane excitability, and allowing myocyte membrane to fire myotonic potentials .Up to now about 60 CLCN1 mutations and 10 polymorphisms have been identified in myotonia congenitia patients. Those mutations and polymorphisms disperse in the whole CLCN1 which there is no hot spot in. It was nearly 1/3 patients who were not found mutations and the pathogenic mechanism is unknown at present. Moreover, there are only several family cases reported about this disease in China, and no relative research on this disease by molecular biology. Through the study of a Myotonia Congenital family of 24 infected members, the project analysised and summarized all theclinical features in details. Then through the way of Polymerase chain reaction - Single nucleotide polymorphism (PCR-SSCP), the whole 23 exon of CLCN1 were screed to find the mutation, and the pathogenic mechanism of myotonia congenital was investigated. Material and methodThe family members was checked by detailed inquirement and medical examination, and the auxiliary examination of creatase, electrolyte, electromyogram and muscle biopsy pathology were also carry out on those patients. In the end, heredity law and clinical features according to onset characteristic of this family were summarized.Firstly, 3 patients were selected from this family as experiment objects: II s x IIIis > IV 4, who are 2 females and 1 male( 7K 35and 16 years old respectively).Meanwhile 2 healthy people (male 23years old, female 20 years old) were random selected in contrast with the experimental samples. Secondly, genome DNA was extracted , 24 pairs primes were designed, Thirdly destination genes were amplified by PCR , and analyzed by SSCP after polyacrylamide gel electrophoresis(PAGE). Lastly abnormal band was sequenced . Results:This family's inheritance characters accord with the autosomal dominant inheritance ones. Infected members of this family showed myotonia, movement awkward, and most of them accompanied with hypermyotrophy and percussion at the same time. Myotonia symptom aggravated in cold environment or movement starting, but under the conditions of warm environment or repeat movement the symptom could be lessened. The creatase and electrolyte were normal. Electromyogram showed that typical repetitive discharge had the characters of attenuating in low frequency stimulant and facilitated under cold water. Pathology of muscle biopsy showed that (1) accrementition and hypertrophy were found in some muscle fibers, (2) slight degeneration fibers were seen somewhere, (3)a few inflammation cells wereinfiltrated in the periphery. Cold stimulation and potassium loading experiment were negative.When the 23 exon of CLCN1 were screed by PCR-SSCP, an abnormal band was found in the 18th exon of patient of III 15 .The following sequence verified the transition of C to T in 2267 nucleotide of the CLCN1.After all patients and other 50 normal controls were screed, the abnormal band were also found in other two normal controls but was not appearance in other patients. So it was confirmed as the single nucleotide polymorphism and the new finding compare to the Gene bank. But no mutation, which led to myotonia, was found in the whole exons. Conclusions:1. Myotonia Congenital is a rare heredity disease, and has special clinical features in patients of the family.2. By PCR-SSCP, a new SNP was found when the 23 exons was screed i...
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