XB-ART-24951Development April 1, 1991; 111 (4): 1045-55.
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Xwnt-8, a Xenopus Wnt-1/int-1-related gene responsive to mesoderm-inducing growth factors, may play a role in ventral mesodermal patterning during embryogenesis.
In amphibian embryos, formation of the basic body plan depends on positional differences in the mesoderm. Although peptide growth factors involved in mesoderm induction have tentatively been identified, additional signals are required to generate pattern in this tissue. We have isolated a Xenopus cDNA for a Wnt-1 related gene, designated Xwnt-8, which is activated in response to mesoderm-inducing growth factors. Xwnt-8 transcripts are transiently expressed, being most abundant during gastrulation at which time expression is confined primarily to ventral mesodermal cells. Embryos dorsoanteriorized by exposure to lithium exhibit greatly reduced levels of Xwnt-8 mRNA, supporting a correlation between Xwnt-8 expression and a ventral mesodermal cell fate. Surprisingly, ectopic expression of Xwnt-8 in embryos causes a dorsoanterior-enhanced phenotype. These findings suggest that Xwnt-8 may be a secondary signalling agent which is produced in response to mesoderm-inducing factors and is involved in the early steps of mesodermal patterning.
PubMed ID: 1879349
Species referenced: Xenopus laevis
Genes referenced: wnt1 wnt8a
Article Images: [+] show captions
|Fig. 4. Localization of Xwnt-8 transcripts in gastrula stage embryos by in situ hybridization. Sections of gastrulae (stage 10-11) hybridized with 35S-labelled single-stranded Xwnt-8 RNA probes. (A,B,C) Sagittal sections; (D,E) para-equatorial section; plane of section indicated by black line in panel A. Arrows in A denote dorsal blastopore lip (open arrow) and deep ventral mesoderm, which expresses high levels of Xwnt-8 RNA (filled arrow). (B,C,E) Dark-field micrographs; (A,D) Light-field micrographs corresponding to B and E. The section in C was hybridized with a sense-strand probe, the remaining sections were hybridized with an antisense strand probe, an, animal; vg, vegetal; d, dorsal; v, ventral.|
|Fig. 7. Duplication of dorsal axial structures following injection of Xwnt-8 mRNA into embryos. Approximately 30 pg (B) or 100 pg (C) of Xwnt-8 mRNA was injected into the animal hemisphere of a fertilized egg, or 30 pg of RNA was injected into one ventral blastomere of a 16 cell embryo (D). A control (uninjected) embryo is shown in A. All embryos were grown to the tailbud stage.|