title: Phenotype-based identification of mouse chromosome instability mutants.
abstract: There is increasing evidence that defects in DNA double-strand-break (DSB) repair can cause chromosome instability, which may result in cancer. To identify novel DSB repair genes in mice, we performed a phenotype-driven mutagenesis screen for chromosome instability mutants using a flow cytometric peripheral blood micronucleus assay. Micronucleus levels were used as a quantitative indicator of chromosome damage in vivo. Among offspring derived from males mutagenized with the germline mutagen N-ethyl-N-nitrosourea (ENU), we identified a recessive mutation conferring elevated levels of spontaneous and radiation- or mitomycin C-induced micronuclei. This mutation, named chaos1 (chromosome aberration occurring spontaneously 1), was genetically mapped to a 1.3-Mb interval on chromosome 16 containing Polq, encoding DNA polymerase theta. We identified a nonconservative mutation in the ENU-derived allele, making it a strong candidate for chaos1. POLQ is homologous to Drosophila MUS308, which is essential for normal DNA interstrand crosslink repair and is unique in that it contains both a helicase and a DNA polymerase domain. While cancer susceptibility of chaos1 mutant mice is still under investigation, these data provide a practical paradigm for using a forward genetic approach to discover new potential cancer susceptibility genes using the surrogate biomarker of chromosome instability as a screen.
authors.affiliation: The Jackson Laboratory, Bar Harbor, Maine 04609, USA.
authors.forename: Naoko
authors.initials: N
authors.lastname: Shima
authors.forename: Suzanne A
authors.initials: SA
authors.lastname: Hartford
authors.forename: Ted
authors.initials: T
authors.lastname: Duffy
authors.forename: Lawriston A
authors.initials: LA
authors.lastname: Wilson
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Schimenti
authors.forename: John C
authors.initials: JC
authors.lastname: Schimenti
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D002875:Chromosomes / Q000187:drug effects / Q000235:genetics*; D003433:Crosses, Genetic; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics*; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D005038:Ethylnitrosourea / Q000633:toxicity*; D005260:Female; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H / Q000235:genetics*; D008810:Mice, Inbred C57BL / Q000235:genetics*; D015162:Micronucleus Tests; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009153:Mutagens / Q000633:toxicity; D010641:Phenotype; D014158:Transcription, Genetic; D000097462:DNA Polymerase theta
chemical_list: D004259:DNA-Directed DNA Polymerase; D005038:Ethylnitrosourea; D009153:Mutagens; D000097462:DNA Polymerase theta