FOXF2 and cleft palate: Wang et al (2003) first showed cleft palate defect in the Foxf2-/- mutant mice, but suggested that the cleft palate phenotype might be secondary to defects in tongue muscle development because Foxf2 mRNAs are abundantly expressed in the muscle layers of the developing tongue in wildtype mouse embryos, and because they did not detect a significant difference in cell proliferation in the developing palate at E13.5 and E15.5 using BrdU labeling.