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Gene Review

Rhox4b  -  reproductive homeobox 4B

Mus musculus

Synonyms: 5430432L21Rik, Ehox, Rhox4.2, Rhox4a
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High impact information on Rhox4b

  • ES cell self-renewal and differentiation assays reveal that inhibition of Ehox activity results in the maintenance of a stem cell phenotype in limiting concentrations of leukemia inhibitory factor and the almost complete impairment of the cardiomyocyte differentiation capacity of these cells [1].
  • We report here the identification and characterization of a novel paired-like homeobox-containing gene (Ehox) [1].
  • This has involved molecular and biological analyses of the effects of sense or antisense Ehox expression (using episomal vectors) on ES cell differentiation [1].
  • Cloning and characterization of Ehox, a novel homeobox gene essential for embryonic stem cell differentiation [1].
  • The data presented here is the first description of Ehox expression during embryogenesis and suggests a dual role for Ehox: (1) in trophoblast stem cells and compartments of the developing placenta, and (2) during development of the pharyngeal pouches, possibly delineating the area to become thymus [2].

Biological context of Rhox4b

  • Finally, no changes in Rhox4 expression were detected in mice with defects in thymus organogenesis, placing it upstream or outside of established transcriptional pathways [3].
  • No tissue-specific enhancer was identified in the 1.9-kb 5'-flanking region of the Ehox gene [4].
  • Transient transfection with a luciferase reporter gene under the control of serially deleted 5'-flanking sequences revealed that the nt -84 to -68 region contained a positive cis-acting element for efficient expression of the Ehox gene [4].
  • To understand the mechanisms of regulation of Ehox gene expression, the 5'-flanking region of the Ehox gene was isolated from a mouse BAC library [4].

Anatomical context of Rhox4b

  • In embryos at 6.5 days post coitum (dpc), Ehox expression was restricted to the extraembryonic ectoderm which correlates with high-level expression in cultures of trophoblast stem cells [2].
  • Ehox expression in the embryo proper first appears at 8.5 dpc in the anterior foregut endoderm and by 9.5 dpc is visible in pharyngeal pouches 2-4 [2].
  • Extraembryonic expression becomes further restricted to the chorion and by 15.5 dpc Ehox is expressed in chorionic trophoblast of the labyrinth and spongiotrophoblast layers of the placenta [2].
  • Ehox is an X-linked paired like homeobox gene identified from a differentiating embryonic stem (ES) cell cDNA library and is expressed at low levels in the preimplantation blastocyst and in ES cells in vitro [2].


  1. Cloning and characterization of Ehox, a novel homeobox gene essential for embryonic stem cell differentiation. Jackson, M., Baird, J.W., Cambray, N., Ansell, J.D., Forrester, L.M., Graham, G.J. J. Biol. Chem. (2002) [Pubmed]
  2. Expression of a novel homeobox gene Ehox in trophoblast stem cells and pharyngeal pouch endoderm. Jackson, M., Baird, J.W., Nichols, J., Wilkie, R., Ansell, J.D., Graham, G., Forrester, L.M. Dev. Dyn. (2003) [Pubmed]
  3. Identification of a tandem duplicated array in the Rhox alpha locus on mouse chromosome X. Morris, L., Gordon, J., Blackburn, C.C. Mamm. Genome (2006) [Pubmed]
  4. Cloning and characterization of the 5'-flanking region of the Ehox gene. Lee, W.K., Kim, Y.M., Malik, N., Ma, C., Westphal, H. Biochem. Biophys. Res. Commun. (2006) [Pubmed]
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