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Fig. 4. Effects of Tbx3 and Tbx3EN misexpression on
dHand and Gli3 expression. (A-C) Schematics of the
limb-forming region. (A) At stage 16, dHand is present throughout the
limb forming region. (B) At stage 17, high levels of dHand expression
are observed in the posterior limb mesenchyme owing to repression by
Gli3, which is expressed at higher levels in the anterior. (C) At
stage 18, Gli3 is expressed in the anterior limb mesenchyme, while
dHand in the posterior is required for the establishment of
Shh expression in the ZPA. In medial limb mesenchyme, dHand
and Gli3 expression domains overlap. (D) At stage 17, dHand
is restricted in the posterior limb mesenchyme in the control side (left,
arrowhead shows rostral border of expression). Following Tbx3
misexpression, dHand is expressed throughout the limb-forming region (right,
arrowhead). At stage 19 (E) and stage 21 (F), when the alteration in limb
position is apparent, normal expression of dHand is observed within
the limb mesenchyme of the shifted limb. (G) At stage 17, following
Tbx3 misexpression, Gli3 is downregulated in the injected
side (right arrowhead) compared with the control side (left arrowhead). A
rostral shift in the graded Gli3 expression domain is observed
(compare left and right arrowhead levels). At stage 19 (H) and at later stages
(stage 21) (I), Gli3 is expressed normally within the mesenchyme of
the shifted limb. Shh expressed in cells of the ZPA in the posterior
of the limb is detected in more rostral locations in the shifted limb by stage
19 (J) and also at stage 21 (K). Hoxd12, a downstream target of
Shh, is similarly expressed in more rostral locations in the
Tbx3-injected limb by stage 19 (L) and also at stage 21 (M).
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