Recombineered Xenopus tropicalis BAC expresses a GFP reporter under the control of Arx transcriptional regulatory elements in transgenic Xenopus laevis embryos.

The aristaless-related homeobox (Arx) gene is expressed in a dynamic pattern in the developing vertebrate forebrain. We identified a bacterial artificial chromosome (BAC) containing the Xenopus tropicalis Arx gene and replaced a portion of the first coding exon with a green fluorescent protein (GFP) expression cassette by homologous recombination in bacteria (recombineering). Transgenic X. laevis embryos obtained by microinjecting the modified BAC expressed GFP in the developing forebrain in a pattern identical to that of the endogenous Arx gene. Thus, this BAC contains transcriptional regulatory elements necessary for regulating proper expression in transgenic frogs. This work demonstrates that transgenesis using recombineered BACs is a viable technique in Xenopus. Copyright (c) 2005 Wiley-Liss, Inc.