Fig. 6. Mesodermal patterning defects in Tcf3-/- embryos.
(A-L') In situ hybridization with wild-type (WT) or
Tcf3-/- (KO) E7.0 embryos using the probes indicated in
the upper right of each panel. The view displayed is indicated in the lower
right corner and embryos are positioned as indicated in the key EEX marks the
embryonic/extra-embryonic border. (A-D) Endodermal markers Cer1
(A-B') and Hex (C,D) are maintained in
Tcf3-/- (B,B',D) embryos. (E-F') Brachyury
marks the primitive streak and axial mesendoderm in the wild-type (E), and it
is maintained in Tcf3-/- embryos (F,F') but adopts a
bent or twisted pattern (arrows) consistent with multiple primitive streaks.
(G-H') Cripto expression is similar in wild-type (G) and
Tcf3-/- embryos (H,H'). (I-J') Foxa2
expression marks the axial mesoderm of the APS in the wild type (I). In
Tcf3-/- embryos, Foxa2 expression is either
expanded (J) or ectopically expressed such as shown circumferentially along
the EEX border in J'. (K) Lefty2 is expressed in the lateral
mesoderm and its pattern reveals a `notch' (outlined in red) at the distal tip
of the wild-type embryo, reflective of the axial mesoderm-mesendoderm.
(L,L') In Tcf3-/- embryos, Lefty2
expression is diminished and reveals a larger `notch' (outlined in red)
indicating the increased axial mesoderm in the mutant.