XIer2 is required for convergent extension movements during Xenopus development
Original Article | Published: 10 January 2012
Sung-Kook Hong1,2, Kosuke Tanegashima1,3 and Igor B. Dawid*,1
1Laboratory of Molecular Genetics, Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child and Human Development, NIH, USA, 2Molecular Genetics Branch, National Human Genome Research Institute, NIH, Bethesda, MD, USA and 3Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
Immediate early response 2 (Ier2) is a downstream target of fibroblast growth factor (FGF) signaling. In zebrafish, Ier2 is involved in left-right asymmetry establishment and in convergent extension movements. We isolated the Xenopusier2 gene based on sequence similarity searches using multiple vertebrate species. Xenopus Ier2 has high homology in the N-terminal region to other vertebrate Ier2 proteins, and Xier2 transcripts were observed from oocytes through larval stages. Except for the maternal expression of xier2, the expression of this gene in the marginal region at gastrulation and in somites and the notochord at later stages is similar to the expression pattern of zebrafish ier2. XIer2 knockdown using antisense morpholinos resulted in defects of convergent extension leading to severe neural tube defects; overexpression of Ier2 showed similar, albeit milder phenotypes. Assays in animal cap explants likewise showed inhibition of elongation after blocking XIer2 expression. These results indicate that Xenopus Ier2 is essential for the execution of convergent extension movements during early Xenopus development.