Recombination of Ptf1a/Ptf1aostm1Kymm exchanged the floxed neomycin resistance cassette with the CAG promoter driving ubiquitous expression of the first and second exons of Ptf1aos followed by an FRT site, puromycin resistance cassette and lox2272 site. This allele was generated in ES cells containing Etn2Sd.