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Fig. 5. Tsg enhances BMP signaling and can act independently of Chordin. Wild-type
or din-/- embryos were injected with the indicated amounts
of tsg1-MO1, and photographed on the second day following injection
(A-F) or fixed and processed for in situ hybridization (G-M). Some wild-type
embryos injected with 3-4 ng of tsg1-MO1 (B,C) displayed a smaller
brain and increased blood in the ventral tail (arrows). However, none
displayed multiplication of the ventral fin fold, a prominent feature in
ventralized din mutants (unfilled arrowhead in D). (E,F) Injection of
tsg1-MO1 ameliorated some aspects of the din mutant
phenotype; the excess development of blood was reduced (compare arrows in
D-F), and in some embryos the multiplication of the fin fold was corrected
(black arrowhead in F). However, anterior nervous system development was not
rescued. All embryos in A-F are shown from the side, with anterior towards the
left. (G-M) Embryos were injected with the indicated amounts of
tsg1-MO1 or MO5, fixed at the 8- to 12-somite stage, and processed
for in situ hybridization. (I,J) In wild-type embryos, we observed features of
dorsalization: lateral expansion of krox20 expression (arrowhead) and
myod expression. (L,M) Injection of tsg1-MO1 also dorsalized
din-/- embryos. (N) Wild-type embryos injected with the
indicated amounts of tsg1-MO1 were fixed and processed for in situ
hybridization as above. They were sorted as having a narrowed krox20
expression domain (Narrow HB); as wild type; or as having a widened expression
domain for both markers (Dorsalized). The number of embryos is beneath each
bar. (O-D') Wild-type embryos were injected with indicated amounts of
tsg1-MOs, fixed at mid-gastrulation (80% epiboly) and processed by in
situ hybridization for markers of DV patterning. Expression of
chordin, a marker for dorsal ectoderm and mesoderm, was expanded in
embryos receiving higher amounts of tsg1-MOs (S,W), and unchanged in
embryos receiving a lower amount of MO1 (A'). By contrast, three
different markers of ventral territories (bmp4, eve1 and
gata2) were decreased (T-V,X,Z) or absent (there is a lack of
eve1 in Y) in embryos receiving high amounts of either MO. In the
most strongly dorsalized embryos, gsc expression, which marks the
dorsal midline tissue, was expanded (unfilled arrowheads in Y). In embryos
injected with 3 ng of tsg1-MO1, there was increased expression of
gata2, a marker for ventral ectoderm and hematopoetic cells in the
ventral mesoderm (D'); expression of the other markers of ventral
territories were unchanged (B',C'). Embryos in G-M are in dorsal
view, with anterior towards the left. (G,H and K,L) Two views of a single
embryo rotated to show the krox20 or myod expression. All
embryos in O-D' are shown from the animal pole, with dorsal towards the
right; arrowheads indicate the lateral limits of dorsal or ventral
markers.
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10-fold more potent than wild type in the rescue assay. CMA
was 
