Restriction-fragment-length-polymorphisms close to the human insulin gene on chromosome 11 and their possible relation to diabetes mellitus in a GDR population.

A polymorphic DNA sequence flanking the 5'-region of the human insulin gene was studied by means of Southern blot hybridization techniques in 92 diabetic and non-diabetic individuals in order to investigate the possible relation of their allelic variants to certain types of diabetes. DNA was isolated from nucleated blood cells and digested with the restriction endonucleases EcoRI or Bg1 I. Only two classes of alleles were found (U and L). The small L-allele was predominantly found with the following frequency: 0.64 in controls, 0.795 in insulin-dependent diabetics, and 0.625 in non-dependent patients. It could be demonstrated that the L-allele and IDDM are associated. These data suggest that this allele seems to be a genetic marker for insulin-dependent diabetes mellitus. The putative function of the polymorphic region in the aetiology of diabetes mellitus and the possible genes being in linkage disequilibrium with it are not known so far.