title: Cell cycle and cell death regulation of neural progenitor cells in the 5-azacytidine (5AzC)-treated developing fetal brain.
abstract: In the developing brain, neural progenitor cells are susceptible to many extrinsic stresses, including DNA damage. We treated pregnant rats with 5-azacytidine (5AzC), a DNA demethylating and damaging agent, to investigate the cellular responses of the fetal brain, focusing on the regulation of proliferation and cell death. 5AzC first induced the accumulation of cells in abnormal mitosis, G2-phase accumulation, and then apoptosis of the neural progenitor cells. Most of the apoptotic cells were in G1 phase. Cell cycle transition studies suggested that G2/M progression was blocked, after which the cells moved to G1 phase or underwent apoptosis. p53, a key factor for response to DNA damage, and some of its target genes showed increased expression in Western blot and DNA microarray analyses. In 5AzC-treated fetal brains of p53-deficient mice, apoptosis did not occur, although G2/M accumulation was induced. These results suggest that, in the developing brain, apoptosis is p53-dependent but that another mechanism governs the G2/M checkpoint. The G2/M regulator, Cdc2, was activated by dephosphorylation through G2/M accumulation, suggesting accelerated entry into mitosis leading to accumulation of cells showing abnormal mitosis. Furthermore, some cells may have died due to mitotic catastrophe. Throughout brain development, various cell cycle and cell death regulation mechanisms provide neural progenitor cells with options for defense from DNA damage.
authors.affiliation: Department of Veterinary Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. ms-ueno@umin.ac.jp
authors.forename: Masaki
authors.initials: M
authors.lastname: Ueno
authors.forename: Kei-ichi
authors.initials: K
authors.lastname: Katayama
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yamauchi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakayama
authors.forename: Kunio
authors.initials: K
authors.lastname: Doi
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000494:pharmacology*; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000196:embryology; D001973:Bromodeoxyuridine / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D016923:Cell Death / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D046228:Microarray Analysis / Q000379:methods; D008954:Models, Biological; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D006657:Histones; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D001973:Bromodeoxyuridine; D001374:Azacitidine