The binary Gal4–UAS system has been used to drive the tissue-specific expression of transgenes in a number of animal models. In the February 5 issue of Proceedings of the National Academy of Sciences, Katharine Hartley and colleagues at the Wellcome/CRC Institute Cambridge, UK, report application of the Gal4–UAS system to create transgenic Xenopus (Proc Natl Acad Sci USA 2002, 99:1377-1382).

The authors generated Xenopus lines expressing constructs for the 'activator', the yeast transcription factor Gal4, or 'effector', tandem repeats of the yeast Gal4-binding motif (UAS). In this way they could drive tissue-specific, or stage-specific, transgene expression. Hartley et al. used the Gal4–UAS system to regulate expression of the ventralizing homeobox gene Xvent-2, resulting in severe developmental and microcephalic phenotypes. They propose that such misexpression studies will be useful for extensive gain-of-function experiments in Xenopus.