Overexpression of the recombined Spry2 IRES AP transgene in the lung. SPC-rtTA, Tet-o-Cre, SpryGOF triple transgenic adult mouse and a littermate control drank water supplemented with doxycycline for 1 week. Mice were then killed, and lungs were processed for alkaline phosphatase histochemical staining and then cryosectioned. (A) Littermate control lungs show no alkaline phosphatase staining. (B) In contrast, triple transgenic lungs show alkaline phosphatase staining in alveoli due to Cre-mediated recombination of the Spry2GOF transgene, which results in expression of both Spry2 and the AP reporter cDNAs. Magnification = ×200. (C) Western blot demonstrating doublet of Spry2 protein in lung homogenates from two Spry2 overexpressors (lanes 1 and 2) and littermate controls (lanes 3 and 4). Bracket marks doublet.