Brca1 and Brca2 protein expression patterns in different tissues of murineorigin

We have analyzed by immunohistochemistry Brca1 and Brca2 protein expression in mouse during embryonic development, in adult tissues, and during postna tal mammary gland development. Our observations confirm previous localizati on of Brca1 and Brca2 mRNA on frozen sections by in situ hybridization, and demonstrate that Brca1 and Brca2 proteins are expressed in rapidly prolife rating cell types undergoing differentiation. These results imply that Brca 1 and Brca2 proteins are involved in the process of proliferation and diffe rentiation in multiple tissues, notably in the mammary gland during pregnan cy and lactation.