High impact information on XANF-1

• We show that the expression of Ras-dva begins during gastrulation throughout the anterior ectoderm and is activated by the homeodomain transcription factor Otx2; however, later on, Ras-dva expression is inhibited in the anterior neural plate by another homeodomain factor Xanf1 [1].
• This expression is essential for normal forebrain development and ectopic expression of Xenopus Anf, Xanf1 (also known as Xanf-1), results in severe forebrain abnormalities [2].
• Overexpression of normal and dominant-negative versions of these factors, as well as inhibition of their mRNA translation by antisense morpholinos, show that they actually function as transcriptional repressors of Xanf1 just behind its posterior expression limit [2].
• Other effects of the ectopic Xanf-1 include cyclopic phenotype and inhibition of the cement gland, both by Otx-2-dependent and -independent mechanisms [3].
• The homeobox-containing gene XANF-1 may control development of the Spemann organizer [4].

Biological context of XANF-1

• To identify transcriptional regulators that are responsible for the Xanf-1 inhibition, we have used the yeast one-hybrid system and identified a novel Xenopus homeobox gene X-nkx-5.1 that belongs to a family of Nkx-5.1 transcription factors [5].
• Two elements, highly conserved in Xenopus, chick and human, were identified within the Xanf-1 promoter region [6].

Anatomical context of XANF-1

• Such preferential localization of XANF-1 mRNA is established from its initially homogenous distribution in ectoderm of early gastrula [7].
• This change in the expression pattern is conditioned by a differential influence of various mesoderm regions on ectoderm: anterior mesoderm activates XANF-1 expression in the overlying ectoderm, whereas posterior axial and ventral mesoderm areas inhibit it [7].
• At the beginning of gastrulation the homeobox-containing gene, XANF-1, is expressed at a low level throughout the animal hemisphere of Xenopus laevis embryos, with a local maximum of expression in the region of the dorsal blastopore lip [4].
• We have investigated the functions of this gene by microinjecting XANF-1 mRNA in the blastomeres of the 32-cell stage embryo and have observed the following effects [4].
• The homeodomain-containing transcription factor X-nkx-5.1 inhibits expression of the homeobox gene Xanf-1 during the Xenopus laevis forebrain development [5].

References