TCF7L2 and type 2 diabetes mellitus: In 2006, Grant et al. [6] identified one microsatellite DG10S478 within intron 3 of the transcription factor 7-like 2 gene (TCF7L2; formerly TCF4) was associated with type 2 diabetes (p = 2.1 × 10−9) in Icelandic individuals.