July 1, 1999;
A conserved 30 base pair element in the Wnt-5a promoter is sufficient both to drive its'' early embryonic expression and to mediate its'' repression by otx2.
We have characterised a short (30 base pair) element from the Xenopus Wnt-5a
promoter which is nearly identical to one located in the human Wnt-5a
promoter, and has the same position relative to the transcription start site. When placed in front of a LacZ gene, this element can reproduce the same expression pattern observed for Wnt-5a
at the late gastrula stage
. Further we show that gastrula stage Wnt-5a
expression is repressed by otx2
, something which is reflected by the mutually exclusive expression patterns of these two genes. The isolated promoter sequence contains an OTX- consensus binding site and its'' activity in embryos is repressed by ectopically expressed otx2
[+] show captions
Fig. 4. (A-D) LacZ expression driven by W5aE. Zygotes were injected with W5aELacZ and embryos were cultured until stage 12.5 (late gastrula) and stained for LacZ. Of 102 embryos treated, 92 showed an almost identical expression pattern to the one shown. (A) Dorsal view anterior to left. (B) Anterior view. (C) Section through lateral edge of embryo to reveal staining in the outer ectodermal cells but not other cell layers. (D) Five fold magnification of top left corner of (C). (E-F) In situ hybridisation for XWnt-5a on untreated embryos at stage 12.5. E, dorsal view anterior to left. (F) Anterior view. (G) Section through lateral edge of embryo to reveal staining in the outer ectodermal cells but not other cell layers. (H) Five-fold magnification of top left corner of (G). (I,J) In situ hybridisation for Xotx2 on untreated embryos at stage 12.5. (I) Dorsal view anterior to left. (J) Anterior view. (K) LacZ staining of a stage 12.5 embryo injected zygotically with W5aE-Delta-OTXLacZ, anterior view (62 of the 74 injected embryos showed this pattern). (L) LacZ staining of a stage 12.5 embryo injected zygotically with the LacZ reporter construct containing only the basal promoter element.