INS and type 1 diabetes mellitus: Here, we reported the conversion of D cells into functional beta-like cells upon the misexpression of Pax4. It is worth considering that the neo-generated gastrointestinal insulin-producing cells are (1) directly exposed to the ingested food, (2) continuously replaced, and (3) scattered in an immune-tolerogenic environment, which altogether renders the aforementioned conversion of great interest in the context of type 1 diabetes research.