OLETF allele of hyperglycemic QTL Nidd3/of is dominant.

The OLETF rat is a well-established model for the study of type 2 diabetes associated with obesity and has been shown to possess multiple hyperglycemic alleles in its genome. Here we focused on and carefully characterized one of the previously reported congenic strains, F.O-Nidd3/of that carries the OLETF allele of the Nidd3/of locus (also known as Niddm21 in the Rat Genome Database) in the normoglycemic F344 genetic background. A prominent finding was that the F1 progeny between the congenic and the F344 stain, whose genotype is heterozygote at the Nidd3/of locus, showed mild hyperglycemia equal to the parental congenic rat, suggesting that the OLETF allele is dominant. To our knowledge, this is the first study in which a diabetic QTL has been directly demonstrated to be dominant by using congenic strains.