In vertebrates, the genes encoding the class of transcription factors called homeobox genes are found in clusters named A, B, C, and D on four separate chromosomes. Expression of these proteins is spatially and temporally regulated during embryonic development. This gene is part of the A cluster on chromosome 7 and encodes a DNA-binding transcription factor which may regulate gene expression, morphogenesis, and differentiation. This gene is involved in the regulation of uterine development and is required for female fertility. Mutations in this gene can cause radio-ulnar synostosis with amegakaryocytic thrombocytopenia.