Genomically integrated transgenes are stably and conditionally expressed in neural crest cell-specific lineages

Neural crest cells (NCCs) are a transient embryonic structure that gives rise to a variety of cells including peripheral nervous system, melanocytes, and Schwann cells. To understand the molecular mechanisms underlying NCC development, a gene manipulation of NCCs by in ovo electroporation technique is a powerful tool, particularly in chicken embryos, the model animal that has long been used for the NCC research. However, since expression of introduced genes by the conventional electroporation method is transient, the mechanisms of late development of NCCs remain unexplored. We here report novel methods by which late-developing NCCs are successfully manipulated with electroporated genes. Introduced genes can be stably and/or conditionally expressed in a NCC-specific manner by combining 4 different techniques: Tol2 transposon-mediated genomic integration (Sato et al., 2007), a NCC-specific enhancer of the Sox10 gene (identified in this study), Cre/loxP system, and tet-on inducible expression (Watanabe et al., 2007). This is the first demonstration that late-developing NCCs in chickens are gene-manipulated specifically and conditionally. These methods have further allowed us to obtain ex vivo live-images of individual Schwann cells that are associated in axon bundles in peripheral tissues. Cellular activity and morphology dynamically change as development proceeds. This study has opened a new way to understand at the molecular and cellular levels how late NCCs develop in association with other tissues during embryogenesis.