Understanding HNF-1A function is potentially clinically relevant, as numerous genetic variants within the HNF1A gene can cause the hereditary diabetes type “maturity onset diabetes of the young” (HNF1A-MODY), be associated with HNF1A-MODY with reduced penetrance, or act as polygenic risk factors for type 2 diabetes (Flannick et al., 2016; Najmi et al., 2017; Krentz and Gloyn, 2020; Zhang et al., 2021). This evidence concerns the gene HNF1A and type 2 diabetes mellitus.