The Condensin II Complex Regulates the Expression of Essential Gene Expression Programs During Erythropoiesis

Erythropoiesis is characterized by dramatic changes in gene expression in the context of a cell that is rapidly proliferating while simultaneously condensing its nucleus in anticipation of enucleation. The mechanisms that maintain high level expression of erythroid genes and promote nuclear condensation remain poorly understood. Condensin II is a ring-like complex that promotes mitotic chromatin condensation and has roles in regulating interphase chromatin architecture and gene expression. We interrogated the role of Condensin II in erythropoiesis using an erythroid-specific deletion of the Condensin II subunit, Ncaph2. Ncaph2 loss resulted in severe embryonic anemia with lethality at embryonic day 13.5. Ncaph2 mutant erythroid cells had dysregulated maturation and disrupted cell cycle progression, but surprisingly Ncaph2 was dispensable for nuclear condensation. Genomic studies revealed that Ncaph2 occupied the promoter of key erythroid and cell cycle genes that were downregulated following Ncaph2 loss. Together, our results demonstrate an essential role for Ncaph2 in the gene expression programs that regulate cell cycle progression and erythroid differentiation, and identify a key role for the Condensin II complex in the regulation of a lineage-specific differentiation program. Summary StatementThe Condensin II complex regulates cell cycle progression and erythroid differentiation, but is dispensable for nuclear condensation during terminal erythroid maturation.