Objective To develop a method of studying fiber projecting in the spinal cord duiring chicken embryo development.Methods At embryonic incubation 3 day (E3), pCAGGS-green fluorescent protein (GFP) plasmid was injected into the spinal cord using in vivo electroporation.Three days after transfection (E6), GFP-positive embryos were collected under a stereo fluorescence microscope .Subsequently , the spinal cord was separated from the embryos and cut from the roof plate as an open book .After fixed with 4%paraformaldehyde ( PFA) for one hour , the opened spinal cords were used for immunohistochemistry with N-cadherin antibody and with DAPI for nuclei .Finally, the nerve fiber projecting was photographed and analyzed under a fluorescence microscope . Results Based on the opened spinal cord and immunostaining in the cryosection , we observed that the nerve fibers projected across the midline of the floor plate and reached to the sulcus terminalis along the white matter of the contra side .The immunoreaction against N-cadherin indicated that overexpression of GFP has no significant effect on chicken embryonic development .Conclusion A new method to study fiber projecting in the developing chicken spinal cord is established successfully in this study .

Objective:To explore the role of N-cadherin and β-catenin in the formation of spinal commissural axon projection during chicken embryonic development.Methods:Fertilized eggs were cultured for three days(stage22),N-cadherin orβ-catenin inter-ference plasmid was injected into the neural tube and in vivo electroporation was performed.Three days after the electroporation, embryos were collected,fixed with 4%PFA,embeded with OCT,and cut into frozen sections.Four groups ( knockdown of N-cadherin orβ-catenin or both of them,and control) were included in this study.Immunohistochemistry method was used to analyze the protein expression result of N-cadherin or β-catenin.The changes of spinal commissural projections were observed with GFP fluorescence.Results:During chicken embryonic development,knockdown of N-cadherin inhibited the expression of β-catenin in the spinal cord.The commissural nerve fibers projecting to the contralateral side of the spinal cord was impaired after knockdown of N-cadherin or β-catenin;this phenotype was similar after knocking down both of them.Conclusion: N-cadherin is implicated in the formation of spinal commissural projection in the developing spinal cord,possibly viaβ-catenin.