Ckmt1^tm2Bew

A 0.6 kb segment of the gene containing exons 7 and 8 was replaced with a neo resistance cassette via homologous recombination resulting in elimination of a catalytically significant cysteine. Unexpected banding patterns were observed in Southern blot analysis of homozygous mutant animals and may be the result of integration of an aberrantly ligated targeting vector. Homozygous mutant animals lacked enzyme activity as demonstrated by enzyme staining assays of brain extracts. (J:27221)