A 2.8 kb region of the gene encompassing part of exon 1, exon 2, and exon 3 was replaced with a PGK-neo cassette via homologous recombination. The targeted region encodes the translation initiation codon and the first of 3 zinc finger domains. Northern blot analysis and immunohistochemistry of skin sections from homozygous mutant animals verified the absence of gene expression. (J:56495)