Cysteine to alanine mutations were inserted at position 609 and 612 (C609A and C612A; TGCACTCTATGT to GCTACTCTAGCT) in exon 7 and a floxed neo cassette was inserted at position chr10:18726067 (NCBI37/mm9) via homologous recombination. Cre mediated recombination removed the neo cassette. The mutations disrupt the structure of the ZnF4 ubiquitin binding motif. (J:228302)