ALX4 and frontonasal dysplasia: Frontonasal dysplasia has been described as a consequence of loss of expression of certain transcription factors, including Alx3 and Alx4. Although alone, Alx3 null mice have no phenotype, severe midfacial clefting and truncation of the snout is observed when the mice are inter crossed with Alx4 null mice (Alx3+/−;Alx4−/− and Alx3−/−;Alx4−/−;[27]).