Characterizing a rat Brca2 knockout model.

Evidence exists that BRCA2 carriers may have an elevated risk of breast, ovarian, colon, prostate, and pancreatic cancer. In general, carriers are defined as individuals with protein truncating mutations within the BRCA2 gene. Many Brca2 knockout lines have been produced and characterized in the mouse. We previously produced a rat Brca2 knockout strain in which there is a nonsense mutation in exon 11 between BRC repeats 2 and 3, and a truncated protein is produced. Interestingly, while such a mutation in homozygous mice would lead to limited survival of approximately 3 months, the Brca2-/- rats are 100% viable and the vast majority live to over 1 year of age. Brca2-/- rats show a phenotype of growth inhibition and sterility in both sexes. Aspermatogenesis in the Brca2-/- rats is due to a failure of homologous chromosome synapsis. Long-term phenotypes include underdeveloped mammary glands, cataract formation and lifespan shortening due to the development of tumors and cancers in multiple organs. The establishment of the rat Brca2 knockout model provides a means to study the role of Brca2 in increasing cancer susceptibility and inducing a novel ocular phenotype not previously associated with this gene.