家族性筋萎縮性側索硬化症における Cu/Zn superoxide dismutase遺伝子変異に関する研究
家族性筋萎縮性側索硬化症における Cu/Zn superoxide dismutase遺伝子変異に関する研究
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Original abstract
Several missense mutations in Cu/Zn superoxide dismutase gene (SOD1) have recently been reported as a putative cause of chromosome-21q-linked familial amyotrophic lateral sclerosis (FALS). I discovered a novel missense mutation (substitution of Thr for Ala^4) in exon 1 (GCC to ACC) in two FALS patients from one Japanese FALS family. No mutations were found in 17 sporadic ALS, 2 ALS of Guam or 7 Parkinson-dementia complex of Guam. The enzyme activity of recombinant Cu/Zn superoxide dismutase (SOD) with the Ala^4 to Thr mutation was significantly reduced in the expression system in E.coli. In this system, the recombinant protein is produced as a fusion protein connected by a histidinerich polypeptide containing 20 amino acid residues. On the other hand, in the expression system in insect cells using baculovirus, the mutant SOD, which was nonfused protein, expressed as high enzyme activity as wild-type SOD. These results suggest that the stability of SOD with Ala^4 to Thr mutation is disrupted especially if it is expressed as the fusion protein. Autopsy was carried out for one of the two patients, and the pathological findings were typical for FALS with posterior column involvement. These results raise the possibility that mutation of the SOD1 is responsible for FALS with broader pathological involvement.