Hume CR and Dodd J (1993), Cwnt-8C: a novel Wnt gene with a potential role...

XB-ART-21968

Development 1993 Dec 01;1194:1147-60.

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Cwnt-8C: a novel Wnt gene with a potential role in primitive streak formation and hindbrain organization.

Hume CR , Dodd J .

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To begin to examine the possibility that Wnt proteins act as cell signalling molecules during chick embryogenesis, PCR was used to identify Wnt genes expressed in Hensen's node. We have identified a novel member of the Wnt gene family, Cwnt-8C, which is expressed prior to gastrulation in the posterior marginal zone, the primitive streak and Hensen's node. Injection of Cwnt-8C mRNA into Xenopus embryos caused axis duplication and dorsalization of mesodermal tissues. During neurulation, Cwnt-8C is expressed transiently in a restricted domain of the prospective hindbrain neurectoderm that will give rise to rhombomere 4. This domain is defined prior to the formation of rhombomere boundaries and also precedes the up-regulation and restriction of expression of Hox B1 in the same region. Thus, Cwnt-8C is potentially involved in the regulation of axis formation and hindbrain patterning.

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Species referenced: Xenopus laevis
Genes referenced: myc wnt8a wnt8b

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	Fig. 1. Predicted amino acid sequence of CWnt-8C and comparison with Xwnt-8. Cysteine residues conserved in known Wnt genes are indicated in bold type. Asterisks mark the positions at which two cysteines found in other Wnt genes are not conserved in either CWnt-8C or Xwnt-8. Arrows above the amino acid sequence indicate the regions used for making degenerate PCR primers. Wnt-5¢ and Wnt-3¢ prime all known Wnt genes, while W8-1 and W8-2 are predicted to be relatively specific for genes related to Cwnt- 8C and Xwnt-8.
	Fig. 2. Comparison of Cwnt-8C with Xwnt-8 and Xwnt-8B over the 115 amino acids of overlapping sequence available for Xwnt-8B.
	Fig. 6. Xenopus embryos injected with Cwnt-8C RNA. Embryos were injected with 250 pg of either Cwnt-8C sense mRNA (A-C) or control, inactive, Cwnt-8C-myc (D) RNA. Cwnt-8C sense mRNA was injected at the 8-cell stage into ventral (A) or dorsal (B) animal blastomeres or at the 32-cell stage into a ventral marginal blastomere (tier c) (C). Embryos shown represent the most common phenotypes observed at stage 38. Injections of sense mRNA into ventral blastomeres resulted in double axes including duplication of cement glands (c in A and C) and eyes. Injection into a dorsal blastomere caused partial duplication without extra cement glands or eyes (B).
	Fig. 7. Injection of Cwnt-8C mRNA causes duplication of the notochord. 8 mm paraffin section through a stage 28 Xenopus embryo injected with Cwnt-8C mRNA into a ventral animal blastomere at the 8-cell stage. The section passes through the region of the rostral spinal cord/hindbrain and shows a duplicated notochord (black horizontal arrows) and neural tube (white vertical arrows). Stained with Giemsa. Magnification, ´200.