Assessing the contributions of gene products to the form-shaping events of neurulation: a transgenic approach in chick

Most of our current knowledge on the tissue and cellular basis of neurulation in amniotes has been gained using the chick embryo as an experimental model system. Gene manipulation during chick neurulation has been difficult, greatly limiting our ability to assess the contribution of gene products to the tissue and cellular behaviors of neurulation. Using electroporation, we have developed a simple and reliable method for expressing transgenes in the ectoderm of the neural folds of chick embryos developing in whole-embryo culture. Sense- or antisense-expressing plasmids are electroporated, resulting in gain or loss of gene function, respectively. The morphogenesis of transgenic tissues was compared to the morphogenesis of contralateral wildtype tissues as neurulation was taking place. As a proof of principle, we present a functional analysis of the chick gene encoding Cartilage Linking Protein 1 (CRTL1), identified as a candidate neurulation gene using subtractive hybridization. This experimental approach provides a much-needed innovation for studying the mechanisms by which genes influence neurulation and reveals here important contributions of CRTL1 to the formation of the neural folds.