Exon 2, which encodes the amino-terminal region and an essential component of its DNA-binding domain, was replaced with a neomycin selection cassette inserted by homologous recombination. The deleted exon encoded the N-terminal region and a zinc finger domain. Northern blot analysis of renal RNA and Western blot analysis of intestinal protein indicated an absence of normal gene product in homozygous mutant mice. (J:86433)