Runx1^tm1Yg

A loxP-flanked neomycin resistance cassette was inserted, in opposite transcriptional orientation, at nucleotide 27675861 of the mouse Chr 16 genomic sequence (NCBI Ref Seq NT-039625), ~1 kb upstream of the transcription initiation site from the P2 (more proximal) transcriptional promoter in exon 2. In E16.5 kidney and P1.5 tongue, where transcription normally occurs from both the P1 (more distal) and P2 promoters, only P1-derived transcripts are detected by RT-PCR in homozygous mutant tissues; E16.5 stomach epithelium, which normally employs only the P2 promoter, expresses no Runx1 transcripts in homozygous mutants. In thymus, RT-PCR and immunohistochemistry confirm the lack of mRNA and protein expression in mutant embryos at E15.5 and its gradual recovery by E16.5-E17.5 as the transition from the P2 to the P1 promoter occurs. (J:125830)