2011 Annual Report 1a.Objectives (from AD-416) Our proposed experiments are designed to evaluate the impact of myoepithelial cells in prepubertal bovine mammogenesis and investigate ovariectomy-induced changes in gene expression that lead to myoepithelial differentiation. The project has two primary objectives. Objective 1 is to investigate the ontogeny of myoepithelial cells in the prepubertal bovine mammary gland. This will include (a) developing validated protocols for a panel of immunohistochemically defined markers of myoepithelial cells in bovine mammary tissues; (b) performing an analysis of myoepithelial differentiation in archived samples of prepubertal bovine mammary parenchyma and (c) investigating the ontogeny of myoepithelial cells between birth and 42d of age. Objective 2 is to test whether ovariectomy during the early postnatal development window alters the expression of genes involved in myoepithelial cell differentiation in the prepubertal bovine mammary gland. 1b.Approach (from AD-416) Our proposed experiments are designed to evaluate the impact of myoepithelial cells in prepubertal bovine mammogenesis and investigate ovariectomy-induced changes in gene expression that lead to myoepithelial differentiation. Co-localization studies will allow us to delineate stages of differentiation through myoepithelial ontogeny. Analysis of myoepithelial differentiation and ontogeny in archived tissue samples will yield insight into physiologic regulation of myoepithelial differentiation, and analysis of myoepithelial ontogeny from birth to 42d of age will fill a substantial knowledge gap related to peri-natal bovine mammary development. Finally, we will use laser microdissection and microarrays to assay changes in gene expression that underlie the observed effect of ovariectomy on myoepithelial differentiation. Data from these studies will provide new insights into mechanisms that control mammogenesis in prepubertal heifers and therefore aid in efforts to develop therapies to improve mammary development and milk production. Additionally, knowledge of cell lineage and mammary gland development is key for future studies designed to promote repair of mammary tissue that has been damaged by mastitis. 3.Progress Report This project was funded through an NRI grant. Microarrays have been purchased for surveying changes in gene expression on a global level. Embedded and frozen tissues have been sent to Beltsville for sectioning and laser microdissection, which is scheduled to be initiated in August. Additionally, paraffin sections will be sent from Beltsville to Clemson University for quantitative immunohistochemical analysis of myoepithelial cell markers. As per grant objective #1, an impact of ovariectomy on myoepithelial cell differentiation in prepubertal bovine mammary gland has been demonstrated and a manuscript has been submitted for publication. Monitoring activities associated with this project include frequent (~monthly) telephone and email exchanges to coordinate and monitor activities at the multiple sites, and annual updates presented to NIFA-APHIS NPS at the ADSA/ASAS National Meeting and submission of an annual progress report to NIFA-NRI.