Lastly, we addressed the question of whether cardiovascular abnormalities could be the primary cause of respiratory distress and cyanosis in KLEIP−/− mice as has been described for Foxc2- and Sema3c-deficient single-mutant mice (Feiner et al., 2001; Iida et al., 1997). This evidence concerns the gene FOXC2 and Abnormality of the skin.