title: Genomic instability in both wild-type and telomerase null MEFs.
abstract: To examine chromosome instability in the absence of telomerase, we established mouse embryonic fibroblast (MEF) lines from late generation mTR-/- and wild-type animals and examined metaphases using telomere fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY). In early passages, mTR-/- G6 cell lines showed more chromosome ends with no telomere signal, more chromosome end-to-end fusions and greater radiosensitivity than wild-type lines. At later passages, however, the rate of genomic instability in the wild-type MEFs increased to a level similar or higher than seen in the mTR-/- G6 cell lines. This high degree of instability in wild-type MEF lines suggests that post-crisis MEFs should not be considered genetically defined cell lines. Surprisingly, the increased radiosensitivity seen in early passage mTR-/- G6 cultures was lost after crisis. Both post-crisis mTR-/- G6 MEFs and wild-type MEFs showed loss of p53 and gamma-H2AX phosphorylation in response to irradiation, indicating a loss of DNA damage checkpoints.
authors.affiliation: Graduate Program in Human Genetics, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: Ling-Yang
authors.initials: LY
authors.lastname: Hao
authors.forename: Carol W
authors.initials: CW
authors.lastname: Greider
mesh_terms: D000818:Animals; D002460:Cell Line; D004249:DNA Damage / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D004622:Embryo, Mammalian / Q000166:cytology / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology*; D005720:Gamma Rays; D017353:Gene Deletion; D042822:Genomic Instability / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D006657:Histones / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D016615:Telomere / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D006657:Histones; D016159:Tumor Suppressor Protein p53; C475961:gamma-H2AX protein, mouse