title: Targeted disruption of the cell-cycle checkpoint gene ATR leads to early embryonic lethality in mice.
abstract: Checkpoints of DNA integrity are conserved throughout evolution, as are the kinases ATM (Ataxia Telangiectasia mutated) and ATR (Ataxia- and Rad-related), which are related to phosphatidylinositol (PI) 3-kinase [1] [2] [3]. The ATM gene is not essential, but mutations lead to ataxia telangiectasia (AT), a pleiotropic disorder characterised by radiation sensitivity and cellular checkpoint defects in response to ionising radiation [4] [5] [6]. The ATR gene has not been associated with human syndromes and, structurally, is more closely related to the canonical yeast checkpoint genes rad3(Sp) and MEC1(Sc) [7] [8]. ATR has been implicated in the response to ultraviolet (UV) radiation and blocks to DNA synthesis [8] [9] [10] [11], and may phosphorylate p53 [12] [13], suggesting that ATM and ATR may have similar and, perhaps, complementary roles in cell-cycle control after DNA damage. Here, we report that targeted inactivation of ATR in mice by disruption of the kinase domain leads to early embryonic lethality before embryonic day 8.5 (E8.5). Heterozygous mice were fertile and had no aberrant phenotype, despite a lower ATR mRNA level. No increase was observed in the sensitivity of ATR(+/-) embryonic stem (ES) cells to a variety of DNA-damaging agents. Attempts to target the remaining wild-type ATR allele in heterozygous ATR(+/-) ES cells failed, supporting the idea that loss of both alleles of the ATR gene, even at the ES-cell level, is lethal. Thus, in contrast to the closely related checkpoint gene ATM, ATR has an essential function in early mammalian development.
authors.affiliation: MGC Department of Cell Biology and Genetics, Center for Biomedical Genetics, Erasmus University, Rotterdam, The Netherlands. deklein@gen.fgg.eur.nl
authors.forename: A
authors.initials: A
authors.lastname: de Klein
authors.forename: M
authors.initials: M
authors.lastname: Muijtjens
authors.forename: R
authors.initials: R
authors.lastname: van Os
authors.forename: Y
authors.initials: Y
authors.lastname: Verhoeven
authors.forename: B
authors.initials: B
authors.lastname: Smit
authors.forename: A M
authors.initials: AM
authors.lastname: Carr
authors.forename: A R
authors.initials: AR
authors.lastname: Lehmann
authors.forename: J H
authors.initials: JH
authors.lastname: Hoeijmakers
mesh_terms: D000483:Alleles; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D002678:Chimera; D002875:Chromosomes / Q000737:chemistry; D004247:DNA / Q000528:radiation effects; D004249:DNA Damage; D004268:DNA-Binding Proteins; D020964:Embryo Loss; D005720:Gamma Rays; D051379:Mice; D016685:Mitomycin / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000235:genetics; D013234:Stem Cells / Q000166:cytology; D025521:Tumor Suppressor Proteins; D014466:Ultraviolet Rays
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D016685:Mitomycin; D004247:DNA; C576897:Atr protein, mouse; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases