Mutant mice express full length mouse Foxf1 under the control of the CMV promoter. 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)