Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2006
Publication Date: July 12, 2006
Citation: Connor, E.E., Meyer, M.J., Li, R.W., Van Amburgh, M.E., Boisclair, Y.R., Capuco, A.V. 2006. Regulation of gene expression in the bovine mammary gland by ovarian steroids [abstract]. J. Dairy Sci. 89(Suppl. 1):426.
It is well established that estrogen is required for mammary epithelial cell proliferation and ductal development in the growing animal, and that lobuloalveolar development during gestation is dependent upon progesterone. Effects of these steroid hormones on gene expression in the mammary gland are mediated primarily by their respective nuclear hormone receptors that function as hormone-bound transcription factors. To gain insight into how estrogen and progesterone regulate mammary gland growth and function in cattle, we and others have characterized the expression patterns of their cognate receptors in bovine mammary gland throughout development, pregnancy and lactation. This work has identified significant differences in estrogen receptor (ER) beta and progesterone receptor (PR) expression between bovine and other species. We speculate that interactions among the ER isoforms that regulate PR expression may contribute to these species differences. Further, demonstrated expression of substantial quantities of ER within the prepubertal bovine mammary fat pad, along with coordinated IGF-1 expression, suggests this tissue may modulate parenchymal growth via an estrogen-responsive paracrine mechanism. In addition, the recent availability of bovine genomic sequence information and microarray technologies has permitted the study of global gene expression in the mammary gland in response to the steroid environment. A comparison of estrogen-responsive genes in the mammary glands of humans, mice and cattle suggests considerable variation among species, as well as potential differences in regulatory elements in common ER gene targets. Continuing studies using advanced molecular techniques should assist in elucidating the complex regulation of mammary function at the transcript level.