High impact information on Xombi

• We show that this pattern of expression of the transgene in gastrulae is not dependent on the T-box sites [1].
• A region of the promoter containing the T-box sites and the Wnt sites is sufficient to drive expression of a reporter gene in a dorsal domain in transgenic Xenopus at the gastrula stage [1].
• We recently reported that the upstream regulatory region of the homeobox-containing gene Bix4 contains T-box binding sites [2].
• Caudalward migration of the node depends on the presence of the most posterior region, which is closely apposed to the anterior portion of the primitive streak as defined by expression of the T-box gene Ch-Tbx6L [3].
• Remarkably, a single T-box binding site is able to act as a mesoderm-specific enhancer when placed upstream of a minimal promoter [2].

Biological context of Xombi

• We show that the regulatory hierarchy among spadetail, no tail and a third T-box gene, tbx6, are substantially different during trunk and tail mesoderm formation, and propose a genetic model that accounts for the regional phenotypes of spadetail and no tail mutants [4].
• T-box genes have diverse functions during embryogenesis and are implicated in several human congenital disorders [5].
• The results suggest that T-box proteins are involved in the specification of myogenic mesoderm and muscle development [6].
• Here, we report the identification, sequence analysis, and developmental expression patterns of four members of the T-box gene family in the diploid frog Xenopus tropicalis [5].

Anatomical context of Xombi

• Maternal Xombi transcript is first localized to the oocyte's vegetal cortex and cytoplasm, early sources of mesoderm and endoderm-inducing signals [7].
• Expression cloning of a Xenopus T-related gene (Xombi) involved in mesodermal patterning and blastopore lip formation [7].
• Soon after zygotic transcription begins, there is a wave of Xombi expression, beginning in dorsal mesoderm and then extending to lateral and ventral mesoderm, that precedes and parallels blastopore lip formation at the border between the mesoderm and endoderm [7].
• We have used a functional assay to identify a putative T-box transcription factor (Xombi) that has the ability to induce sites of invagination in the ectoderm of Xenopus embryos that resemble the blastopore lip [7].
• Brachyury, a member of the T-box gene family, is required for posterior mesoderm and notochord differentiation in vertebrate development, and mis-expression of Xenopus Brachyury causes ectopic mesoderm formation [8].

Other interactions of Xombi

• Expression of luciferase from the minimal promoter is dorsal-specific and requires two T-box half sites and a functional beta-catenin/XTcf-3 pathway [9].
• Conserved expression control and shared activity between cognate T-box genes Tbx2 and Tbx3 in connection with Sonic hedgehog signaling during Xenopus eye development [10].
• We have used differential display to identify genes inducible by activin and isolated a novel member of the T-box gene family that includes the Xenopus genes Xbrachyury and Eomesodermin [11].

References