FKO and Pax3-Cre driven Utx phenotypes. (A) WT or FKO hearts were dissected at P2 and sectioned. Interventricular septum (IVS) appeared normal in FKO mice (n = 3/3). (B) Male Utxfl/y, Pax3-Cre mice demonstrate shortened snouts, narrow palpebral fissures, and a dome-shaped forehead. (C) Utxfl/y, Pax3-Cre mice are viable; however, female Utxfl/fl, Pax3-Cre mice die at birth and are not recovered at weaning (χ2 *P < 0.01). (D) Utxfl/fl, Pax3-Cre lungs fail to inflate at birth (n = 3) and float in PBS.