title: Methyl binding domain protein 2 mediates gamma-globin gene silencing in adult human betaYAC transgenic mice.
abstract: The genes of the vertebrate beta-globin locus undergo a switch in expression during erythroid development whereby embryonic/fetal genes of the cluster are sequentially silenced and adult genes are activated. We describe here a role for DNA methylation and MBD2 in the silencing of the human fetal gamma-globin gene. The gamma-globin gene is reactivated upon treatment with the DNA methyltransferase inhibitor 5-azacytidine in the context of a mouse containing the entire human beta-globin locus as a yeast artificial chromosome (betaYAC) transgene. To elucidate the mechanism through which DNA methylation represses the gamma-globin gene in adult erythroid cells, betaYAC/MBD2-/- mice were generated by breeding betaYAC mice with MBD2-/- mice. Adult betaYAC/MBD2-/- mice continue to express the gamma-globin gene at a level commensurate with 5-azacytidine treatment, 10- to 20-fold over that observed with 1-acetyl-2-phenylhydrazine treatment alone. In addition, the level of gamma-globin expression is consistently higher in MBD2-/- mice in 14.5- and 16.5-days postcoitus fetal liver erythroblasts suggesting a role for MBD2 in embryonic/fetal erythroid development. DNA methylation levels are modestly decreased in MBD2-/- mice. MBD2 does not bind to the gamma-globin promoter region to maintain gamma-globin silencing. Finally, treatment of MBD2-null mice with 5-azacytidine induces only a small, nonadditive induction of gamma-globin mRNA, signifying that DNA methylation acts primarily through MBD2 to maintain gamma-globin suppression in adult erythroid cells.
authors.affiliation: Massey Cancer Center and Departments of Internal Medicine, Microbiology and Immunology, and Human Genetics, Virginia Commonwealth University, Richmond, VA 23298-0037, USA.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Rupon
authors.forename: Shou Zhen
authors.initials: SZ
authors.lastname: Wang
authors.forename: Karin
authors.initials: K
authors.lastname: Gaensler
authors.forename: Joyce
authors.initials: J
authors.lastname: Lloyd
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Ginder
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000494:pharmacology; D001665:Binding Sites / Q000235:genetics; D018244:Chromosomes, Artificial, Yeast / Q000235:genetics*; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D044127:Epigenesis, Genetic; D004900:Erythroblasts / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D005914:Globins / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011247:Pregnancy; D011401:Promoter Regions, Genetic
chemical_list: D004268:DNA-Binding Proteins; C489326:Mbd2 protein, mouse; D005914:Globins; D001374:Azacitidine