The skin and nervous tissue is derived from the ectoderm^. In Xenopus, ectodermal explants (animal caps) from blastula embryos show high tissue plasticity and can differentiate into a variety of tissues in vitro. Exploiting this property, we performed a functional screening for factors that can neuralize ectodermal explants, and isolated Xenopus Sox13 (XSox13), a member of the Sox (Sry-related high-mobility-group box) transcription factor family. During Xenopus embryogenesis, XSox13 mRNA is expressed in the entire ectoderm at blastula stages and in the organizer region at gastrula stages. Its expression becomes localized to the neural tube during neurulation and then to somites at tailbud stages. Mouse Sox13 mRNA shows similar expression patterns to the Xenopus homolog during embryogenesis : Sox13 is expressed in the node, an equivalent to the Xenopus organizer, at the neural fold stage, exclusively in the nervous tissue at early-mid somite stages, and then showed a segmental expression in the somites at the late somite stage. We next generated Sox13-LacZ-knock-in mice, and examined the expression of mouse Sox13 in adult tissues by X-gal staining. In contrast to the expression during embryogenesis, Sox13 is scarcely expressed in the central nervous system in adult. Moreover, Sox13-deficient mice showed no apparent abnormalities in neural development. These results suggest that Sox13 expression in early development is conserved in Xenopus and mouse and Sox13 plays a redundant role during mouse neural development
