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Gene Review

HOXA2  -  homeobox A2

Gallus gallus

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High impact information on HOXA2

  • In addition to conservation of binding sites critical for Krox-20 activity in the chicken Hoxa-2 and pufferfish Hoxb-2 genes, the r3/r5 enhancers are also characterized by the presence of a number of identical motifs likely to be involved in cooperative interactions with Krox-20 during the process of hindbrain patterning in vertebrates [1].
  • In addition, r4 gene expression is also partially altered by RA; within 6 hours of r4 exposure to RA, ectopic expression of Krox-20 is seen in r4 and Hoxb-1 expression is lost while Hoxa-2 expression continues normally [2].
  • Expression of certain Hox genes (Hoxa-2, Hoxa-3 and Hoxb-4) was recorded in the branchial arches of chick and quail embryos at embryonic days 3 (E3) and E4 [3].
  • Grafting experiments in which pairs of rhombomeres were transplanted to ectopic sites at the time of rhombomere boundary formation reveal a prepatterning of the neural crest with respect to Hoxa-2 expression [4].
  • Conversely, at the level of r4, both the neural tube and the neural crest cells, which migrate out of this rhombomere to populate the second branchial arch, express Hoxa-2 [4].

Biological context of HOXA2

  • Hoxa-2 is thus unusual in demonstrating separate anterior expression limits in neural tube and neural crest; this allowed us to test whether Hox gene expression patterns in neural crest are determined by migratory pathways or are prespecified by the site of origin in the neuroepithelium [4].


  1. The conserved role of Krox-20 in directing Hox gene expression during vertebrate hindbrain segmentation. Nonchev, S., Maconochie, M., Vesque, C., Aparicio, S., Ariza-McNaughton, L., Manzanares, M., Maruthainar, K., Kuroiwa, A., Brenner, S., Charnay, P., Krumlauf, R. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  2. Late effects of retinoic acid on neural crest and aspects of rhombomere. Gale, E., Prince, V., Lumsden, A., Clarke, J., Holder, N., Maden, M. Development (1996) [Pubmed]
  3. The regeneration of the cephalic neural crest, a problem revisited: the regenerating cells originate from the contralateral or from the anterior and posterior neural fold. Couly, G., Grapin-Botton, A., Coltey, P., Le Douarin, N.M. Development (1996) [Pubmed]
  4. Hoxa-2 expression in normal and transposed rhombomeres: independent regulation in the neural tube and neural crest. Prince, V., Lumsden, A. Development (1994) [Pubmed]
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