PDX1 and retinal disorder: Zebrafish lacking Pdx1 (pdx1−/− mutants) have reduced numbers of β cells as larvae, and the few fish that survive to adulthood display elevated blood glucose levels (Kimmel et al., 2015) and retinopathy (Wiggenhauser et al., 2020) However, it is hard to separate symptoms caused by chronic diabetes from developmental defects.