I'm All Thumbs

Science's STKE  15 Jun 2004:
Vol. 2004, Issue 237, pp. tw217-TW217
DOI: 10.1126/scisignal.2372004tw217

Studies of tetrapods have identified several of the factors that participate in vertebrate limb patterning. A major player in limb development, Sonic hedgehog (Shh), has a key function in organizing limb asymmetry, such as the difference between the thumb and index finger. Zákány et al. (see the Perspective by Deschamps) examined the genetic cascade leading to anterior-posterior polarity of the vertebrate limb. Early posterior Hox gene expression triggers Shh activation, which in turn induces a second phase of Hox gene expression in a posterior domain. Thus, Hox genes act both early and late in establishing anterior-posterior asymmetry of the limb by acting upstream and downstream of Shh signaling.

J. Zákány, M. Kmita, D. Duboule, A dual role for Hox genes in limb anterior-posterior asymmetry. Science 304, 1669-1672 (2004). [Abstract] [Full Text]

J. Deschamps, Hox gene in the limb: A play in two acts. Science 304, 1610-1611 (2004). [Summary] [Full Text]