HOX genes play a fundamental role in the development of the vertebrate central nervous system, heart, axial skeleton, limbs, gut, urogenital tract and external genitalia. The homeobox gene HoxA1 is transcriptionally regulated by retinoic acid (RA) and encodes a transcription factor, which has been shown to play important roles in cell differentiation and embryogenesis.HoxA1 is also expressed in cancers, such as mammary tumors, though it is not expressed in normal gland or in precancerous mammary tissues. HoxA2 protein is predominantly expressed in the nuclei of cells in the ventral mantle region of the developing embryo.
