Vdr^tm1Rge

Exon 2 and part of intron 2 were replaced with a lacZ-PGK-neo cassette via homologous recombination. Unexpectedly, Northern blot analysis of homozygous mutant animals detected a transcript similar to wild-type transcript. RT-PCR and sequence analysis revealed the mutant transcript was deleted for exon 2 and is expressed in all tissues examined. A second start codon in exon 3 predicts a mutant protein lacking the first zinc finger (amino acids 1-51). Western blot analysis and immunohistochemistry revealed the presence of mutant protein in homozygous animals. Competitive binding assays demonstrated the vitamin D-binding ability of the mutant protein. However, the mutant protein lacks DNA-binding activity as shown by gel mobility shift assay. (J:77748)