TCF7L2 and diabetes mellitus: Furthermore, several genes involved in the endocrine specification and diabetes development were significantly downregulated, such as HES1, INSM1, HNF1A, NEUROD1, NGN3, NKX2.2, GIPR, MNX1, PROX1, TCF7L2, and HHEX (Fig. 4C and Supplementary Table S4).