A cysteine to alanine mutation was inserted at position 103 (C103A; TGC to GCC) in exon 3 and a floxed neo cassette was inserted in intron 2 at position chr10:18729002 (NCBI37/mm9) via homologous recombination. Cre mediated recombination removed the neo cassette. The mutation inactivates OTU catalytic activity. (J:228302)