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].

References