Role of the GATA-1/FOG-1/NuRD pathway in the expression of human beta-like globin genes.

The human beta-globin genes are expressed in a developmentally controlled fashion. Studies on the molecular mechanisms underlying the stage-specific regulation of globin genes have been fueled by the clinical benefit of elevated fetal gamma-globin expression in patients with sickle cell anemia and thalassemia. Recent reports suggested a role of the hematopoietic transcription factor GATA-1, its cofactor FOG-1, and the associated chromatin remodeling complex NuRD in the developmental silencing of HBG1 and HBG2 gene expression. To examine whether FOG-1 via NuRD controls HBG1 and HBG2 silencing in vivo, we created mice in which the FOG-1/NuRD complex is disrupted (A. Miccio et al., EMBO J. 29:442-456, 2010) and crossed these with animals carrying the entire human beta-globin gene locus as a transgene. We found that the FOG-1/NuRD interaction is dispensable for the silencing of human HBG1 and HBG2 expression. In addition, mutant animals displayed normal silencing of the endogenous embryonic globin genes. In contrast, a significant reduction of adult-type human and murine globin gene expression was found in adult bone marrows of mutant animals. These results suggest that, unexpectedly, NuRD is required for FOG-1-dependent activation of adult-type globin gene expression but is dispensable for human gamma-globin silencing in vivo.