Dnase1^tm1Tmo

All 9 exons of Dnase1 were removed and replaced with a neomycin resistance cassette via homologous recombination. Subsequently, sequencing identified an additional mutation in Trap1. Trap1 is located at the opposite DNA strand to the Dnase1 gene and both genes overlap within their 3'-UTR. Due to the replacement of the entire Dnase1 gene with a neo cassette, the 3'-end of the last Trap1 exon coding for 18 C-terminal amino acids and containing the 3'-UTR is deleted and fused to the cassette. The fusion of the truncated Trap1 exon 18 to the neo cassette leads to an extended reading frame with addition of 48 unrelated amino acids. Northern blot analysis of RNA from parotids, kidney, and small intestine from homozygous mutant animals, using a rat cDNA probe, did not detect Dnase1 gene expression. Zymograms of cell extracts from parotids, small intestines, kidneys, urine, and serum of homozygous animals demonstrated the absence of Dnase1 enzyme activity. Almost complete lack of the mutant Trap1 and no wild-type Trap1 protein is seen in homozygotes. (J:62549, J:209292)