Targeted generation of ADAM17^ex/ex mice. (A) Scheme for targeting the ADAM17 gene. Open arrowheads denote FLP recombinase sites, and LoxP sites are indicated by closed arrowheads. The altered allele contains an artificial exon starting with an in-frame translational stop codon placed downstream of exon 11. The artificial exon (E11a, yellow) containing the stop codon is flanked by noncanonical splice donor and acceptor sites (see Materials and methods). The black bar indicates the hybridization probe used for Southern blotting. (B) mRNA from liver and brain was analyzed by RT-PCR. (C) ADAM17 and ADAM10 Western blots of skin and heart tissues. (D and E) Shedding of L-selectin from B cells (D) and TNF from spleen cells (E) was analyzed by FACS and ELISA, respectively. (F) Serum levels of sTNF-R_II were measured by ELISA. Data in D–F are shown as mean values ± SD. (G) Formation of milk ducts in mice at the age of 12 wk. Representative pictures from four animals are shown. Bars, 500 µm.