HOXA4(HOMEOBOX A4)，also known as HOX1D or HOMOLOG OF, is a protein that in humans is encoded by the HOXA4 gene, which is also part of the A cluster on chromosome 7. HOXA4 encodes a DNA-binding transcription factor which may regulate gene expression, morphogenesis, and differentiation. Its cytogenetic location is 7q15.2. 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.