Exons 4 through 11 were replaced with a neomycin selection cassette. The deleted region encoded a proline-rich central domain and the proximal region of the EVH2 domain. Transcript was undetected in the spleens and large intestines of homozygous mutant mice. Immunoblot analysis using antibodies and antiserum raised against untargeted regions showed the absence of both normal and truncated protein.