Exon 10 was replaced with a pgk-neo cassette via homologous recombination. This selectively deleted two of the isoforms (UT-A1 and UT-A3). Immunoblot analysis confirmed the absence of the UT-A1 and UT-A3 proteins and the presence of the UT-A2 protein. A fourth testis specific isoform, UT-A5, also contains exon 10 and is predicted to be deleted.