Alx3-deficient mice33 were maintained in a C57BL/6 J × FVB/N background by heterozygote intercrosses and were genotyped using PCR as described35. Experimental protocols involving mice were approved by the institutional bioethics committees on research animal care (IIBM Committee on Human and Animal Experimentation and CSIC Ethics Committee), and are in accordance with the requirements of Spanish (RD 53/2013) and European Union (63/2010/EU) legislation.