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Fig. 2. Comparison of hindlimb digital morphologies in wild-type (+/+),
Tg-Hoxd12;Gli3+/- and Gli3-/-
embryos by Gdf5 expression at E14.5 (A-C), and skeletal staining at
E18.5 (D-F). Anterior is top, posterior bottom for all panels. At E14.5, bands
of Gdf5 expression in digits prefigure sites of future segmentation
forming phalangeal joints (Storm and
Kingsley, 1996). Both wild type (+/+; A) and
Tg-Hoxd12;Gli3+/- (B) display one strong band of
expression within digit I, and two bands in each of the more posterior digits
(II-V). By contrast, Gli3-/- (C) has only one distinct
band of expression and a second `abortive' zone, which never forms a complete
band across the digit (evaluated at multiple stages, data not shown). Note
that, by E14.5, the proximal-most Gdf5 expression band marking the
phalangeal-metatarsal joint region in wild-type embryos has already declined.
At E18.5, wild type (D) and Tg-Hoxd12;Gli3+/- (E)
have distinguishable digits of varying size, with recognizable identities
based on size, shape and number of phalanges. By contrast,
Gli3-/- digits (F) are all short, similar in appearance,
and have ill-defined phalanges with only a single ossification center. Arrows
show ossification centers for digit I (single) compared with digit II-V (two
centers), and brackets show phalangeal segments for digit I (2 segments) and
digit II (3 segments) in wild type.
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