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Homeobox protein Hox-A3 is a protein that in humans is encoded by the HOXA3 gene.[1][2][3]


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. Three transcript variants encoding two different isoforms have been found for this gene.[3]

During normal fetal development, HoxA3 is expressed in mesenchymal neural crest cells and endodermal cells found in the third pharyngeal pouch.[4] Expression of HoxA3 in these cells affects the proper formation of the thymus, thyroid, and parathyroid organs.[5][6] While the gene does not seem to affect the proliferation or migration of the pharyngeal neural crest cells, it does appear to trigger cellular differentiation events required to form these organs.[5] Knockout of HoxA3 leads to failure in forming the thymus (athymia) and parathyroid gland (aparthyroidism).[6] Mutant HoxA3 also causes a reduction in thyroid size. While the follicular and parafollicular cells still differentiate, their numbers are reduced and they are not evenly distributed throughout the gland.[5] Mutant HoxA3 models show similar phenotypes as those seen in DiGeorge’s Syndrome, and it is possible that the two are linked.[5]


The HOXA3 gene is repressed by the microRNA miR-10a.[7]

See also


  1. McAlpine PJ, Shows TB (July 1990). "Nomenclature for human homeobox genes". Genomics. 7 (3): 460. doi:10.1016/0888-7543(90)90186-X. PMID 1973146.
  2. Scott MP (November 1992). "Vertebrate homeobox gene nomenclature". Cell. 71 (4): 551–3. doi:10.1016/0092-8674(92)90588-4. PMID 1358459.
  3. 3.0 3.1 "Entrez Gene: HOXA3 homeobox A3".
  4. Hunt P, Gulisano M, Cook M, Sham MH, Faiella A, Wilkinson D, Boncinelli E, Krumlauf R (October 1991). "A distinct Hox code for the branchial region of the vertebrate head". Nature. 353 (6347): 861–4. doi:10.1038/353861a0. PMID 1682814.
  5. 5.0 5.1 5.2 5.3 Manley NR, Capecchi MR (July 1995). "The role of Hoxa-3 in mouse thymus and thyroid development". Development. 121 (7): 1989–2003. PMID 7635047.
  6. 6.0 6.1 Chojnowski JL, Masuda K, Trau HA, Thomas K, Capecchi M, Manley NR (October 2014). "Multiple roles for HOXA3 in regulating thymus and parathyroid differentiation and morphogenesis in mouse". Development. 141 (19): 3697–708. doi:10.1242/dev.110833. PMC 4197593. PMID 25249461.
  7. Han L, Witmer PD, Casey E, Valle D, Sukumar S (August 2007). "DNA methylation regulates MicroRNA expression". Cancer Biology & Therapy. 6 (8): 1284–8. doi:10.4161/cbt.6.8.4486. PMID 17660710.

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.