Furthermore, also regardless of HNF4A mutation carrier status or diabetes status, the S7 cells displayed the same GSIS kinetics, the same ultrastructural features and the same levels of proteomics-based protein markers of a mature β-cell, including INS, PDX1, NKX6.1, MAFA, GLUT2, UCN3 and others. Here, HNF4A is linked to diabetes mellitus.