SMARCD2 subunit of SWI/SNF chromatin-remodeling complexes mediates granulopoiesis through a CEBPɛ dependent mechanism

Julie Lessard and colleagues report that ATP-dependent SWI/SNF chromatin-remodeling complex subunit SMARCD2 is essential for granulocyte development. They find that Smarcd2 -deficient mice fail to generate functioning neutrophils and eosinophils, and they determine that the divergent coiled-coil 1 and SWIB domains are responsible for functional specificity during granulocyte differentiation. Recent studies suggest that individual subunits of chromatin-remodeling complexes produce biologically specific meaning in different cell types through combinatorial assembly. Here we show that granulocyte development requires SMARCD2, a subunit of ATP-dependent SWI/SNF (BAF) chromatin-remodeling complexes. Smarcd2 -deficient mice fail to generate functionally mature neutrophils and eosinophils, a phenotype reminiscent of neutrophil-specific granule deficiency (SGD) in humans, for which loss-of-function mutations in CEBPE (encoding CEBPɛ) have been reported. SMARCD2-containing SWI/SNF complexes are necessary for CEBPɛ transcription factor recruitment to the promoter of neutrophilic secondary granule genes and for granulocyte differentiation. The homologous SMARCD1 protein (63% identical at the amino acid level) cannot replace the role of SMARCD2 in granulocyte development. We find that SMARCD2 functional specificity is conferred by its divergent coiled-coil 1 and SWIB domains. Strikingly, both CEBPE and SMARCD2 loss-of-function mutations identified in patients with SGD abolish the interaction with SWI/SNF and thereby secondary granule gene expression, thus providing a molecular basis for this disease.