Fig. 4. The yolk sac vasculature of the Tak1
/
embryos
fails to undergo angiogenesis. (A,B) E9.5 yolk sacs of
Tak1+/
and Tak1
/
embryos, respectively.
The yolk sac vascular plexus in A has undergone angiogenesis to create a
branched network of mature vitelline vessels (arrowhead). The yolk sac
vascular plexus in B has not remodeled but has retained its honeycomb-like
structure of blood islands (arrowhead). The vessels in B are also prone to
rupture, causing pooling of blood in the yolk sac (arrow). (C,D)
Cross-sections of Tak1+/
and Tak1
/
yolk
sacs, respectively, that are immunostained for vSMCs with an antibody to SMA
(brown). The Tak1+/
yolk sac in C contains a mature vitelline
vessel surrounded by a layer of smooth muscle (arrowhead). The
Tak1
/
yolk sac in D has no mature vitelline vessels,
the existing vessels are extremely dilated and have little SMA expression.