Transgene, screening and expression. A, Transgene (Tg) structure, including WAP promoter, beta-globin intron to enhance Tg expression, Brk/PTK6 coding sequence, growth hormone poly A signal and BssHII restriction sites. B, PCR screening of founder mice and controls. (L-R: purified construct, water, wild-type FVB, and two WAP-Brk founders.) C, Whole cell lysates from wild type and Brk97 mammary glands were subjected to Western blotting for Brk or total p38 MAPK, after enrichment for epithelial cells. D, Brk IHC in FFPE mammary gland sections. Glands shown are from INV D1. Brown precipitate indicates positive staining. 200 × magnification.