Transcription factor involved in skull and limb development. Binds DNA. Expressed in osteoblasts. Not expressed in brain, heart, intestine, kidney, liver, muscle, spleen and testis. Expressed from 8.25 dpc and confined to mesenchymal cells throughout the embryo development. Expression is seen at several sites including craniofacial region, first branchial arch and anterior aspect of the limb bud. Defects in Alx4 are the cause of Strong luxoid (lst) phenotype. At heterozygosity lst is characterized by preaxial abnormalities of the hindfeet and, very rarely, of the forefeet. Homozygotes show preaxial polydactyly of all four limbs, reductions and duplications of the radius, absence of the tibia, craniofacial defects, reduction of the pubis, and dorsal alopecia. Belongs to the paired homeobox family.