Characterization of Src*/SD transgenic mice. (A) Messenger RNA expression analysis of the transgene in L 67 and L 63 by reverse transcription–PCR (top panel). MG, mammary gland (lactating); LV, liver; KD, kidney; SP, spleen; SA, salivary gland; FVB, FVB control mouse; –DNA, PCR control; control, ribosomal subunit S15 (bottom panel). DNA molecular weight markers (M) are indicated. (B) Protein expression in mammary gland tissue of virgin (V) and lactating (L) animals of L 67, L 63 and WT FVB mice analyzed by IB of whole-tissue lysates (20 μg) with CasB. β-actin is used as a loading control (bottom panel). (C) Mammary gland development in transgenic Src*/SD versus WT FVB animals. Whole-mount preparations of gland number 4 of virgin animals at 6 and 10 weeks and at day 4 of involution are presented. Insets are presented at higher magnification for each gland. Black region represents a lymph node.