Role of the GATA-1/FOG-1/NuRD pathway in the expression of human beta-like globin genes.
ABSTRACT 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.
Article: Mi2b Is Required for c-Globin Gene Silencing: Temporal Assembly of a GATA-1-FOG-1-Mi2 Repressor Complex in b-YAC Transgenic Mice[show abstract] [hide abstract]
ABSTRACT: Activation of c-globin gene expression in adults is known to be therapeutic for sickle cell disease. Thus, it follows that the converse, alleviation of repression, would be equally effective, since the net result would be the same: an increase in fetal hemoglobin. A GATA-1-FOG-1-Mi2 repressor complex was recently demonstrated to be recruited to the 2566 GATA motif of the A c-globin gene. We show that Mi2b is essential for c-globin gene silencing using Mi2b conditional knockout b-YAC transgenic mice. In addition, increased expression of A c-globin was detected in adult blood from b-YAC transgenic mice containing a T.G HPFH point mutation at the 2566 GATA silencer site. ChIP experiments demonstrated that GATA-1 is recruited to this silencer at day E16, followed by recruitment of FOG-1 and Mi2 at day E17 in wild-type b-YAC transgenic mice. Recruitment of the GATA-1–mediated repressor complex was disrupted by the 2566 HPFH mutation at developmental stages when it normally binds. Our data suggest that a temporal repression mechanism is operative in the silencing of c-globin gene expression and that either a trans-acting Mi2b knockout deletion mutation or the cis-acting 2566 A c-globin HPFH point mutation disrupts establishment of repression, resulting in continued c-globin gene transcription during adult definitive erythropoiesis.PLoS Genetics 12/2012; · 8.69 Impact Factor