Homeobox Protein A3 (HOXA3)

HOXA3 is part of the A cluster on chromosome 7 and encodes a DNA-binding transcription factor which may regulate gene expression, morphogenesis, and differentiation. Three transcript variants encoding two different isoforms have been found for this gene.At embryonic day 17.5, homozygous null Hoxa3 embryos demonstrated complete absence of the thymus. However, replacement of one or both copies of the Hoxa3 protein with the Hoxd3 protein restored this organ. Alterations of the hyoid cartilage, which is characteristic of embryos homozygous for the null allele of Hoxa3, were reversed by expression of the Hoxd3 protein at the Hoxa3 locus. One conclusion from this data was that the Hoxd3 protein is functionally equivalent to the Hoxa3 protein if it is expressed in the context of the Hoxa3 gene.