Hind III site causing Proinsulin Kyoto and Pst I site polymorphism of the insulin gene in Japanese: its lack of association with either IDDM or NIDDM.

The gene encoding Proinsulin Kyoto has been isolated and characterized by DNA sequencing, indicating that the molecular basis of the disorder is a G-T point mutation in the insulin gene which creates a Hind III site. In addition, in the 3'-untranslated region of the mutant insulin gene, a Pst I site negative, alpha type allele was found, and in the normal gene, a Pst I site positive, beta type allele was found. In order to clarify the frequency of the mutation and to determine whether this mutation is associated with diabetes mellitus or not, we have investigated Hind III polymorphism in 91 normal Japanese subjects and patients with IDDM and NIDDM. No cases with the Proinsulin Kyoto gene were found among the subjects examined. Secondly, to determine whether this alpha type allele is associated with DM in Japanese, we investigated Pst I polymorphism in the same subjects. The frequencies of the alpha type and beta type alleles were 92% and 8%, respectively. No significant difference in genotypic frequency was found among normal, NIDDM, and IDDM. We conclude that the Proinsulin Kyoto gene is not a common cause of DM and the occurrence of the alpha type insulin gene in Japanese diabetes is more frequent than in other races, so this Pst I polymorphism is not a marker for diabetes mellitus in Japanese.