[Pathogenesis of Parkinson's disease, a molecular genetic approach]

In juvenile parkinsonism (JP), unlike naturally occurring Parkinson's disease, high frequency of familial onset is observed, which suggests the involvement of some genetic factor(s) in the pathogenesis of the disease. In an attempt to conduct a molecular genetic approach to JP, we tried to isolate tyrosine hydroxylase (TH) cDNA from human pheochromocytoma, and demonstrated the existence of four types of cDNA (type 1, 2, 3 and 4), differing in the 5'-terminal region. All four cDNAs had the same sequence in common from ATG of the translation start codon to 90th nucleotide. However, in types 2, 3 and 4, characteristic sequences were inserted between 90th and 91 st nucleotides of type 1 cDNA. TH genomic DNA cloning showed that the multiple form of mRNA were produced from a single gene through alternative splicing. Four types of cDNA was expressed in COS cells. They exhibited different homospecific activities: type 1 TH having the highest activity, others less than 40% of type 1 TH. The question whether possible change in TH gene is related to the pathogenesis of JP is now being pursued based on these molecular biological understanding of TH gene.