Fig. 5. sp5l transcription is induced by ectopic Wnt and repressed by
interference with Wnt signaling. (A) Ectopic expression of sp5l at
the animal pole of embryos injected with 10 pg wnt8 RNA, 6 hours
after injection at shield stage (right panel, dorsal view), compared with
wild-type expression in embryos injected with equimolar amounts of GFP RNA (7
pg, left panel). (B) Overexpression of dominant-negative TCF rapidly abolishes
sp5l expression. Fish heterozygous for heat-shock-inducible
dominant-negative TCF-GFP [Tg (hsp70:
TCF-GFP)w26] were
outcrossed to wild type, the resulting embryos heat-shocked for 15 minutes or
30 minutes starting at the 1-somite stage and the whole clutch fixed
immediately. In situ hybridization for GFP (light brown) in addition to
sp5l (blue) was performed to identify transgenic embryos.
sp5l expression is severely reduced in 100% (n=21) of
transgenics 15 minutes after induction of the transgene (middle panel), and
completely abolished in 100% (n=24) of transgenic embryos after 30
minutes (right panel). (C-F) Expression of sp5l in WT, wnt3a,
wnt8 and wnt3a/wnt8 morphants at the 3-somite stage.