title: Interferon-gamma inhibits cell cycle exit in differentiating oligodendrocyte progenitor cells.
abstract: The developmental processes of the oligodendrocyte progenitor cell (OPC) lineage that are targeted by interferon-gamma (IFN-gamma) were studied in primary rat OPC cultures. Under conditions of thyroid hormone-mediated oligodendrocyte differentiation, IFN-gamma produced a dose-dependent apoptotic response in OPCs. The lowest dose tested (15 ng/ml or 75 U/ml) was nonapoptotic, but activated detectable STAT1 DNA-binding. At this dose, IFN-gamma reduced the percentage of mature O1+ cells and increased the percentage of immature A2B5+ OPCs. This was observed without significant change in total cell number and cytotoxicity, and was accompanied by an increase in BrdU-labeled A2B5+ and O4+ cells. FACS analysis confirmed a lack of apoptotic sub-G1 cells and revealed a greater percentage of S- and G2/M-phase OPCs with IFN-gamma treatment. Dual immunostaining with Ki-67 and Olig2 showed a smaller percentage of Olig2+ cells in G0 phase in IFN-gamma-treated OPCs, indicating loss of G1 control. Instead, increased levels and phosphorylation of the checkpoint protein p34cdc2 by IFN- suggested increased partial arrest in G2. IFN-gamma not only sustained expression of PCNA and the G1-S regulators retinoblastoma protein, cyclin D1, cyclin E, and cdk2, but also decreased p27 levels. In addition to changes in cell proliferation and differentiation, IFN-gamma attenuated myelin basic protein (MBP) expression significantly, which was associated with decreased expression of both MBP and Sox10 RNAs. These findings indicate that IFN-gamma not only maintains cell cycle activity that could predispose OPCs to apoptosis, but also overrides G1-G0 signals leading to thyroid hormone-mediated terminal differentiation and myelin gene expression.
authors.affiliation: Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA. lchew@cnmcresearch.org
authors.forename: Li-Jin
authors.initials: LJ
authors.lastname: Chew
authors.forename: William C
authors.initials: WC
authors.lastname: King
authors.forename: Ann
authors.initials: A
authors.lastname: Kennedy
authors.forename: Vittorio
authors.initials: V
authors.lastname: Gallo
mesh_terms: D000818:Animals; D000963:Antimetabolites; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001973:Bromodeoxyuridine; D002453:Cell Cycle / Q000187:drug effects*; D016923:Cell Death / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007371:Interferon-gamma / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009186:Myelin Sheath / Q000187:drug effects / Q000648:ultrastructure; D009836:Oligodendroglia / Q000187:drug effects*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D013963:Thyroid Hormones / Q000378:metabolism
chemical_list: D000963:Antimetabolites; D010982:Platelet-Derived Growth Factor; D013778:Tetrazolium Salts; D013844:Thiazoles; D013963:Thyroid Hormones; D007371:Interferon-gamma; D004247:DNA; D007770:L-Lactate Dehydrogenase; C022616:thiazolyl blue; D001973:Bromodeoxyuridine