Mutant mice express a dominant negative version of mouse Foxf1 under the control of the CMV promoter. The chimeric gene was constructed by fusing the open reading frame of this transcriptional activator to a cDNA fragment harboring the strong transcriptional repression domain of the Drosophila engrailed protein. This coding region was followed by a fragment harboring an IRES-GFP sequence to allow visualization of misexpressing cells. The bicistronic transgene cassette was integrated in the ubiquitously expressed X-chromosomal Hypoxanthine guanine phosphoribosyl transferase (Hprt) locus. (J:244068)