Normal mammary gland development in cortactin transgene mice. (A) Expression of endogenous and transgenic cortactin in mouse mammary epithelium at different stages of mammary gland development as determined by Western blot analysis. Total protein was loaded from the abdominal mammary gland of non-transgenic (W) and transgenic mouse line 16 (T) of virgin female mice (V), mice at day 11 and 17 of pregnancy (P11, P17), day 4, 10 and 17 of lactation (L4, L10, L17) and day 4 and 8 of involution (I4, I8). Monoclonal antibody Esab157 was used to recognize specific human transgene expression, whereas monoclonal antibody 4F11 recognizes both human and mouse cortactin. Actin was used as a loading control. (B) Immunohistochemical detection of cortactin transgene in a 10-days lactating mammary gland (L10). WT, wild type; T16, transgenic mouse line 16. About 50% of epithelial cells from the transgenic section stained positive for cortactin. Arrows indicate cortactin localization at cell-cell contacts. Sections were counterstained with haematoxylin.