Liu, J.X., Hu, B., Wang, Y., Gui, J.F., and Xiao, W. (2009) Zebrafish eaf1 and eaf2/u19 mediate effective convergence and extension movements through the maintenance of wnt11 and wnt5 expression. The Journal of biological chemistry. 284(24):16679-16692.
Studies have attributed several functions to the Eaf family, including tumor suppression and eye development. Given the potential association between cancer and development, we set forth to explore Eaf1 and Eaf2/u19 activity in vertebrate embryogenesis, using zebrafish. In situ hybridization revealed similar eaf1 and eaf2/u19 expression patterns. Morpholino (MO)-mediated knockdown of either eaf1 or eaf2/u19 expression produced similar morphological changes that could be reversed by ectopic expression of target or reciprocal-target mRNA. However, combination of Eaf1 and Eaf2/u19 (Eafs)-MOs increased the severity of defects, suggesting that Eaf1 and Eaf2/u19 only share some functional redundancy. The Eafs-knockdown phenotype resembled that of embryos with defects in convergence and extension (C & E) movements. Indeed, knockdown caused expression pattern changes for C & E movement markers while cell tracing experiments using kaeda mRNA showed a correlation between Eafs knockdown and cell migration defects. Cardiac and pancreatic differentiation markers revealed that Eafs knockdown also disrupted midline convergence of heart and pancreatic organ precursors. We found that Eaf1 and Eaf2/u19 maintained expression levels of wnt11 and wnt5. Moreover, wnt11 or wnt5 mRNA partially rescued the C & E movement defects occurring in eafs morphants. Wnt11 and Wnt5 converge on rhoA, and so not surprisingly, rhoA mRNA more effectively rescued defects than either wnt11 or wnt5 mRNA alone. However, the ectopic expression of wnt11 and wnt5 did not affect eaf1 and eaf2/u19 expression. These data indicate that eaf1 and eaf2/u19 act upstream of non-canonical Wnt signaling to mediate convergence and extension movements.