The 13.7-kb BamHI DNA fragment covering exons 2 – 20 of the Adam11 gene was amplified from C57BL/6 genomic DNA by the PCR using Expand Hi-Fidelity polymerase mix (Roche Diagnostics KK, Tokyo, Japan). To generate a mutation in the mouse Adam11 gene, we inserted a PGKneo cassette into exons 5 – 7 of the Adam11 gene. The final targeting construct consisted of a 10.1-kb genomic DNA fragment that was interrupted by the insertion of the PGKneo cassette and contained a MC1/TK cassette as a negative selection marker against random integration [39].