The Methyltransferase Setd8 Is Essential for Erythroblast Survival and Maturation

Erythropoiesis is a highly regulated process that generates enucleate red blood cells from committed erythroidprogenitors. Chromatincondensation culminating in enucleation is a defining feature of this process. Setd8 is the sole enzyme that can mono-methylate histone H4, lysine 20 and is highly expressed in erythroblasts compared to most other cell types. Erythroid Setd8 deletion results in embryonic lethality from severe anemia due to impaired erythroblast survival and proliferation. Setd8 protein levels are also uniquely regulated in erythroblasts, suggesting a cell-type-specific role for Setd8 during terminal maturation. Consistent with this hypothesis, Setd8 Delta/Delta erythroblasts have profound defects in transcriptional repression, chromatin condensation, and heterochromatin accumulation. Together, these results suggest that Setd8, used by most cells to promote mitotic chromatin condensation, is an essential aspectof the transcriptional repression andchromatin condensation that are hallmarks of terminal erythroid maturation.