Fig. 2A–B.

The influence of GLI3 on digit formation. This figure illustrates the range of GLI3 influence in the two most common models used in limb development, chick and mouse. In the chicken deletion mutant Oligozeugodactyly (ozd) (A), the limb-specific enhancer of SHH has been deleted. Without SHH, GLI3R function is unopposed and inhibits the formation of the ulna and digits. In contrast, in the GLI3 knockout mouse (B) that lacks GLI3 function, excessive digits are formed (note eight digits) and these digits lack specific AP (radioulnar) identity, most conspicuously the absence of the two phalangeal thumb identity. (Images courtesy of John F. Fallon, PhD, University of Wisconsin, and Maria A. Ros, MD, PhD, Instituto de Biomedicina y Biotechnologia de Cantabria; (A) adapted with permission from Ros et al. [25].).