Linkage Mapping of the Bra, Brb and Brg Genes for Rat Protein Phosphatase 2A 55 kDa B‐Regulatory Subunit Isotypes

We previously identified the rat Bra, Brb and Brg genes, which encode α, β and γ isotypes of the 55 kDa B‐regulatory subunit of protein phosphatase 2A. Polymerase chain reaction‐single strand conformation polymorphism analysis in the present study identified polymorphisms in Bra, Brb and Brg between the ACI and BUF, ZI and TM, and BN and WTC strains, respectively. Linkage analysis using mapping panels composed of F2 or back‐crosses of these strains allowed Bra, Brb and Brg to be assigned to chromosomes 15, 18 and 14, respectively. Furthermore, it was revealed that Bra is located close to the Rb1 locus. Using polymorphism in Bra, loss of heterozygosity (LOH) was analyzed for rat mammary tumors induced in (SDxF344) F1 female rats by a food‐borne carcinogen, 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine, and a typical mammary carcinogen, 7,12‐dimethylbenz[a]anthracene. No LOH was detected at the Bra locus.