Figure 1.
The activity of Hedgehog proteins with differential lipid modification in transgenic animals. Fore- and hindlimb skeleton (stained with Alcian blue [cartilage] and Alizarin red [calcified tissue]) of 18.5-dpc wild-type (A,E) and transgenic mice expressing Shh (B,F), ShhC25S (C,G), and Shh-NC25S (D,H) in the limb mesenchyme under the Prx1 promoter/enhancer. Views are all dorsal. The axis for orientation of the specimens is posterior on the right, anterior on the left, proximal downward, and distal upward. Table 1 summarizes the distributions of digit duplication in both fore- and hindlimbs of nontransgenic and transgenic animals expressing various forms of Shh proteins in the limb. Digits from both left and right limbs were counted, with 10 digits in nontransgenic wild-type mice. Compared with the hindlimbs, the forelimbs are more sensitive in their response to varying activities of Shh. Although the integration site of the transgene could potentially affect its expression levels, a general trend of decreasing activity from Shh to Shh-NC25S could be obtained by examining multiple transgenic animals. The DNAs were quantified and adjusted to 0.5 ng/μL for pronuclear injection.