Sox3^tm1Pqt

A 36 bp expansion of the first polyalanine tract expanded the tract from 14 to 26 alanines. Morula injection resulted in chimeras with up to 95% mutant cell contribution. In addition, an FRT flanked neo selection cassette was inserted downstream. Despite extensive breeding, none of these chimeras exhibited germline transmission of the mutant allele. (J:195300)