Cloning and developmental expression of Xenopus Enabled (Xena)

Abstract

Regulation of actin dynamics, organization, and interaction with cell surface adhesion proteins is critical for tissue morphogenesis during development. The Ena/VASP family of actin-binding proteins function in several cellular processes that involve dynamic regulation of the actin cytoskeleton, including axon guidance, platelet aggregation, cell migration, and cell adhesion. The vertebrate Ena/VASP family is composed of three genes: Ena (Enabled), VASP (Vasodilator Stimulated Phosphoprotein), and Evl (Ena/VASP-Like). To better understand the role of Ena/VASP proteins during vertebrate development, we have cloned and characterized the developmental expression of Ena in Xenopus laevis. Analysis of the temporal expression of Xenopus Ena (Xena) demonstrates that multiple isoforms of Xena are detected throughout embryogenesis and that the presence of different isoforms is developmentally regulated. In situ hybridization analyses reveal that Xena is broadly expressed throughout development. During gastrulation and neurulation, Xena is detected in the neuroepithelium, notochord, and somites. In tadpoles, Xena expression is restricted to dorsal regions of the brain, whereas it is expressed at lower levels throughout the spinal cord. Xena expression is also detected in the notochord, myotome, heart, pronephros, and cranial placodes, including the olfactory and otic placodes. Analysis of the subcellular localization of Xena using a GFP fusion protein revealed that Xena localizes to adherens junctions and focal adhesions in Xenopus animal caps and NIH3T3 fibroblasts, respectively. These results define spatiotemporal windows in which Xena may function during early Xenopus development to modulate actin-dependent processes such as cell adhesion and migration.