The LIM-domain protein zyxin binds the homeodomain factor Xanf1/Hesx1 and modulates its activity in the anterior neural plate of Xenopus laevis embryo

The question of how subdivision of embryo into cell territories acquiring different fates is coordinated with morphogenetic movements shaping the embryonic body still remains poorly resolved. In the present report, we demonstrate that a key regulator of anterior neural plate patterning, the homeodomain transcriptional repressor Xanf1/Hesx1, can bind to the LIM-domain protein Zyxin, which is known to regulate cell morphogenetic movements via influence on actin cytoskeleton dynamics. Using a set of deletion mutants, we found that the Engrailed-type repressor domain of Xanf1 and LIM2-domain of Zyxin are primarily responsible for interaction of these proteins. We also demonstrate that Zyxin overexpression in Xenopus embryos elicits effects similar to those observed in embryos with downregulated Xanf1. In contrast, when the repressor-fused variant of Zyxin is expressed, the forebrain enlargements typical for embryos overexpressing Xanf1 develop. These results are consistent with a possible role of Zyxin as a negative modulator of Xanf1 transcriptional repressing activity.