This family consists of a region found within the alpha isoform and at the C-terminus of the beta isoform of the homeobox-containing transcription factor of HNF-1. Different isoforms of HNF-1 are generated by the differential use of polyadenylation sites and by alternative splicing. The C-terminal region of HNF-1 is responsible for the activation of transcription. Mutations and polymorphisms in HNF-1 cause the type 3 form of maturity-onset diabetes of the young (MODY3).