Disruption of the function of zidh1/2 enzymes in zebrafish results in partial block of myeloid differentiation, whereas zidh1 also controls the emergence of definitive hematopoietic stem cells. Disease-associated mutations can recapitulate the mammalian phenotype but cannot rescue the mutant phenotypes. α-KG, α-ketoglutarate; 2-HG; 2-hydroxyglutarate; 5-hmC, 5-hydroxymethylcytosine; HSC, hematopoietic stem cell; WT, wild-type. Professional illustration by Patrick Lane, ScEYEnce Studios.