A nonsense mutation (Q268X) in exon 7 of the Nr2a1 gene that caused a deletion of 187 C-terminal amino acids of the HNF4α protein was indentified in patients with maturity-onset diabetes of the young type I (MODY1), an autosomal dominant, early-onset form of noninsulin-dependent diabetes mellitus (NIDDM) [62]. This evidence concerns the gene HNF4A and type 2 diabetes mellitus.