BRCA1 expression during prenatal development of the human mammary gland

Germ-line alterations of BRCA1 are associated with elevated risk of breast cancer. Evidence for the involvement of Brca1 in cellular differentiation a nd morphogenesis has been obtained in mouse models during embryogenesis, Al though the presence of well-conserved functional domains might suggest a si milar function for both human and mouse genes, very few data on BRCA1 expre ssion in human fetal tissues are available. We have, therefore, investigate d the expression of BRCA1 in the mammary gland from human female fetuses ag ed between 15 and 33 weeks, Quantification of BRCA1 transcripts, using a co mpetitive reverse transcriptase PCR method, indicates a progressive decreas e in BRCA1 expression with increasing fetal age between the 15th and 30th w eek of gestation. Subsequently, the amount of BRCA1 transcripts becomes sim ilar to that found in adult mammary gland. Analysis of BRCA1 protein reveal ed, in fetal samples, a 220 kDa band corresponding to the 220 kDa BRCA1 pro tein described in human cell lines. These later experiments confirm that th e relative level of the 220 kDa BRCA1 protein is highest in the early stage s of mammary gland development. The temporal patterns of BRCA1 expression i n human fetuses suggest a role for BRCA1 in the morphogenesis and different iation of the human mammary gland.