title: GADD45A protein plays an essential role in active DNA demethylation during terminal osteogenic differentiation of adipose-derived mesenchymal stem cells.
abstract: Methylation and demethylation of DNA are the complementary processes of epigenetic regulation. These two types of regulation influence a diverse array of cellular activities, including the maintenance of pluripotency and self-renewal in embryonic stem cells. It was generally believed that DNA demethylation occurs passively over several cycles of DNA replication and that active DNA demethylation is rare. Recently, evidence for active DNA demethylation has been obtained in several cancer, neuronal, and embryonic stem cell lines. Studies in embryonic stem cell models, however, suggested that active DNA demethylation might be restricted to the early development of progenitor cells. Whether active demethylation is involved in terminal differentiation of adult stem cells is poorly understood. We provide evidence that active DNA demethylation does occur during terminal specification of stem cells in an adipose-derived mesenchymal stem cell-derived osteogenic differentiation model. The medium CpG regions in promoters of the Dlx5, Runx2, Bglap, and Osterix osteogenic lineage-specific genes were demethylated during the increase in gene expression associated with osteogenic differentiation. The growth arrest and DNA damage-inducible protein GADD45A was up-regulated in these processes. Knockdown of GADD45A led to hypermethylation of Dlx5, Runx2, Bglap, and Osterix promoters, followed by suppression of the expression of these genes and interruption of osteogenic differentiation. These results reveal that GADD45A plays an essential role in gene-specific active DNA demethylation during adult stem cell differentiation. They enhance the current knowledge of osteogenic specification and may also lead to a better understanding of the common mechanisms underlying epigenetic regulation in adult stem cell differentiation.
authors.affiliation: College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Rui-peng
authors.initials: RP
authors.lastname: Zhang
authors.forename: Jian-zhong
authors.initials: JZ
authors.lastname: Shao
authors.forename: Li-xin
authors.initials: LX
authors.lastname: Xiang
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D053687:Adult Stem Cells / Q000166:cytology / Q000378:metabolism; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics; D055785:Gene Knockdown Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010012:Osteogenesis / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D000097642:GADD45 Proteins
chemical_list: D000943:Antigens, Differentiation; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D000097642:GADD45 Proteins; C499072:Gadd45a protein, mouse; C490125:Gadd45b protein, mouse