XB-ART-49272Genesis October 31, 2017;
Down syndrome cell adhesion molecule (DSCAM) 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. © 2014 Wiley Periodicals, Inc.
PubMed ID: 25088188
Article link: Genesis
Species referenced: Xenopus tropicalis
Genes referenced: dscam
GO keywords: gastrulation with mouth forming second
Antibodies: Acta1 Ab3 Dscam Ab1
Disease Ontology terms: Down syndrome
OMIMs: DOWN SYNDROME
Article Images: [+] show captions
|FIG. 1. XtDSCAM is phylogenetically conserved and maintains synteny with the human genetic locus. A: A rooted Neighbor joining phylogenetic analysis of full-length amino acid sequences of DSCAM and DSCAML of vertebrates, Drosophila melanogaster using planarian DSCAM as an outgroup. B: Genetic structure of the genomic locus of human DSCAM (top) compared with corresponding locus in Xenopus tropicalis (bottom). Each triangle represents a gene and the direction of transcription. Colored triangles represent genes found in Xenopus. The diagram displays position but not relative distance of the genes.|
|FIG. 2. XtDSCAM is expressed in the nervous system during early development. A: RTPCR analysis of individual Xenopus embryos at different stages in development using primers specific for XtDSCAM and XtGAPDH. Results are shown for single embryos in triplicate. B–D: In situ hybridization staining of neurula (B, Stage 19), early tailbud (C, Stage 22), and tadpole stage (D, Stage 27) X. tropicalis embryos using an XtDSCAM-specific probe. Arrows point to areas with significant DSCAM staining, Nc, notochord; Hb, hindbrain; Op, olfactory placode; Tn, trigeminal nerve; Ep, epibranchial placodes. Scalebar5100 mm.|
|FIG. 3. XtDSCAM is important in early morphogenesis. A: A western blot analysis of a pool of stage 19 embryos that had been injected with 5 ng or 10 ng of control or DSCAM morpholinos at one cell stage. B: Gastrulation phenotypes observed at neurula stage (Stage 19) upon injection of 10 ng DSCAM morpholino (right) compared with control (left). C: Phenotypes of DSCAM-Mo injected embryos (right and center) at Stage 25 compared with control-Mo injected embryos (left). D, E: Representative experiment of cohorts at stage 26 injected with either (D) control Mo or (E) DSCAM Mo at 10 ng dose. The squares indicate the magnified insets, the yellow arrows indicate intermediate gastrulation phenotypes and the red arrows indicate severe gastrulation phenotypes. Note the difference in severity and overall morphology between Control Mo and DSCAM Mo embryos.|
|dscam (Down syndrome cell adhesion molecule) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 34, lateral view, anterior left, dorsal up.|