Part of exon 2, exons 3-5, and part of exon 6 were replaced with a lacZ-neo cassette via homologous recombination. The targeted mutation deletes exons encoding the DNA binding domains. Absence of gene expression was confirmed by Northern blot analysis of midbrain/forbrain and cerebellum RNA from P10 and P13 homozygous mutant animals. (J:60839)