Down syndrome cell adhesion molecule is important for early development in Xenopus tropicalis

The Down syndrome cell adhesion molecule (DSCAM) is an Ig containing cell adhesion molecule with remarkable structural conservation throughout metazoans. In insects, DSCAM has 38,000 potential isoforms that convey axon guidance, fasciculation, and dendrite morphogenesis during neurodevelopment. In vertebrates, DSCAM is expressed throughout the nervous system and seems to also mediate proper axonal guidance and synaptogenesis without the isoform diversity found in insects. Differences in DSCAM function among several vertebrate species complicate the understanding of an evolutionarily conserved role during embryogenesis. We take advantage of the frog developmental model Xenopus tropicalis to study DSCAM function in early development by expression analysis and morpholino-mediated knockdown. Our results indicate that DSCAM is expressed early in development and restricted to the head and nervous system. Knockdown of protein expression results in early morphogenetic phenotypes characterized by failed gastrulation and improper posterior neural tube closure. Our results reveal a specific, fundamental role of DSCAM in early morphogenetic movements, presumably through its well-known role in homophilic cell adhesion.