title: Rescue of Xrcc1 knockout mouse embryo lethality by transgene-complementation.
abstract: Xrcc1 knockout embryos show increased DNA breakage and apoptosis in tissues of the embryo proper prior to death at embryonic day E6.5. An additional deficiency in Trp53 allows Xrcc1(-/-) embryos to enlarge slightly and initiate gastrulation although ultimately death is delayed by less than 24h. Death presumably results from DNA damage that reaches toxic levels in the post-implantation mouse embryo. To investigate the level of XRCC1 protein needed for successful mouse development, we derived Xrcc1 transgene-complemented Xrcc1(-/-) mice that express Xrcc1 within the normal range or at a greatly reduced level (<10% normal). The greatly reduced XRCC1 protein level destabilized the XRCC1 partner protein DNA ligase III (LIG3) but still allowed for successful mouse development and healthy, fertile adults. Fibroblasts from these animals exhibited almost normal alkylation sensitivity measured by differential cytotoxicity. Thus, a large reduction of both XRCC1 and DNA ligase III has no observable effect on mouse embryogenesis and post-natal development, and no significant effect on cellular sensitivity to DNA alkylation. The presence of XRCC1, even at reduced levels of expression, is therefore capable of supporting mouse development and DNA repair.
authors.affiliation: Biology and Biotechnology Research Program, L441, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551-0808, USA. tebbs1@llnl.gov
authors.forename: Robert S
authors.initials: RS
authors.lastname: Tebbs
authors.forename: Larry H
authors.initials: LH
authors.lastname: Thompson
authors.forename: James E
authors.initials: JE
authors.lastname: Cleaver
mesh_terms: D000478:Alkylation; D000818:Animals; D002455:Cell Division; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D020964:Embryo Loss; D005314:Embryonic and Fetal Development / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology; D018507:Gene Expression Regulation, Developmental; D018390:Gene Targeting; D005816:Genetic Complementation Test; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D018345:Mice, Knockout / Q000196:embryology*; D000075223:Poly-ADP-Ribose Binding Proteins; D019076:Transgenes; D000076105:X-ray Repair Cross Complementing Protein 1; D029867:Xenopus Proteins
chemical_list: D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; D029867:Xenopus Proteins; C000619352:Xrcc1 protein, mouse; D011088:DNA Ligases; D000072481:DNA Ligase ATP; C000618816:DNA ligase III alpha protein, Xenopus; C000618818:Lig3 protein, mouse