Characterization of an Ihx1a transgenic reporter in zebrafish

The LIM-domain containing transcription factor, Lhx1, is involved in the regulation of early gastrulation cell movements, kidney organogenesis and other processes in vertebrate model organisms. To follow the expression of this gene in live embryos, we created transgenic zebrafish expressing enhanced green fluorescent protein (EGFP) under the control of Ihx1a regulatory regions. Tg(Ihx1a:EGfP) super(pt303) recapitulates the expression of endogenous Ihx1a beginning at early gastrula stages through 72 hours of development with only few exceptions. In addition, over-expression of the Nodal ligand, ndr1, results in the concomitant expansion of the transgene and endogenous Ihx1a expression. Treatment of Tg(Ihx1a:EGFP) super(pt303) embryos with the small molecule SB-431542, an inhibitor of Nodal signaling, results in the loss of both transgene and endogenous Ihx1a expression. These experiments suggest that Tg(Ihx1a:EGFP) super(pt303) is regulated in a manner similar to endogenous Ihx1a. Therefore, this reporter can be utilized not only for monitoring Ihx1a expression, but also for numerous applications, including chemical genetics screening.