title: Disruption of Brca2 increases the spontaneous mutation rate in vivo: synergism with ionizing radiation.
abstract: The breast cancer predisposition gene BRCA2 encodes a protein involved in the repair of DNA double-strand breaks, which arise spontaneously and following exposure to ionizing radiation (IR). To develop a mouse model that examines the effect of BRCA2 mutation and IR exposure on in vivo somatic mutation acquisition, we crossed mice with targeted disruption of Brca2 with a LacZ transgenic mutation reporter strain. Loss of both wild-type Brca2 alleles caused a 2.3-fold increase, equivalent to an extra 100 mutations per cell, in the in vivo acquisition of spontaneous somatic mutation by 2 weeks gestation. IR (4 Gy) had a disproportionate effect on animals homozygous for Brca2 disruption, inducing 3.4-fold more mutations compared with wild-type animals. These data provide the first evidence that loss of Brca2 increases in vivo somatic mutation acquisition and synergizes with IR exposure, with potential attendant implications for mammographic screening and therapeutic IR in mutation carriers.
authors.affiliation: The Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, Fulham Road, London SW3 6JB, UK.
authors.forename: Andrew N J
authors.initials: AN
authors.lastname: Tutt
authors.forename: Conny Th M
authors.initials: CT
authors.lastname: van Oostrom
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Ross
authors.forename: Harry
authors.initials: H
authors.lastname: van Steeg
authors.forename: Alan
authors.initials: A
authors.lastname: Ashworth
mesh_terms: D000818:Animals; D005260:Female; D017353:Gene Deletion; D024522:Genes, BRCA2; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D016296:Mutagenesis / Q000235:genetics / Q000528:radiation effects; D011839:Radiation, Ionizing