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Fig. 4. Ectopic blood vessels inhibit muscle formation. (A)
VEGF/RCAS-expressing cells were grafted to the dorsal aspect of E4/HH22 chick
wings and the embryos were fixed at E8/HH32. Consecutive sections of the
manipulated wing (B,D,F,H,J) and of the
control left wing (C,E,G,I) were cut at the same
proximodistal level in order to allow comparison. Sections were hybridized
with Vegfa (B), Hif2
(C,D,G,H) and Fgfr4
(E,F,I,J) probes (blue), and then incubated with the MF20 antibody (brown)
that recognizes myosins. (B) Vegfa transcripts show the extent of the
infection in dorsal regions of the wings. Ectopic VEGFA leads to a dramatic
increase in the density of blood vessels, visualized by the expression of
Hif2 (D), compared with the normal vascular network of the
control wing (C). In the dorsal regions displaying an excess of blood vessels,
we observed a reduction of muscle size and even a loss of certain muscles (F),
as compared with the normal muscle pattern of the left control wing (E).
Asterisks label the control muscles (E) and their putative locations in the
VEGF-treated limbs (F). (G-J) High magnifications of the ANC (Anconeus) muscle
(arrowed in C-F) located in dorsal and posterior regions of the control and
manipulated limbs, showing that the hypervascularized muscles contain fewer
myogenic cells (J) than the corresponding control muscles (I). For all
sections, the top is dorsal and left is posterior. u, ulna; r, radius.
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