title: A role for N-cadherin in mesodermal morphogenesis during gastrulation.
abstract: Cell adhesion molecules mediate numerous developmental processes necessary for the segregation and organization of tissues. Here we show that the zebrafish biber (bib) mutant encodes a dominant allele at the N-cadherin locus. When knocked down with antisense oligonucleotides, bib mutants phenocopy parachute (pac) null alleles, demonstrating that bib is a gain-of-function mutation. The mutant phenotype disrupts normal cell-cell contacts throughout the mesoderm as well as the ectoderm. During gastrulation stages, cells of the mesodermal germ layer converge slowly; during segmentation stages, the borders between paraxial and axial tissues are irregular and somite borders do not form; later, myotomes are fused. During neurulation, the neural tube is disorganized. Although weaker, all traits present in bib mutants were found in pac mutants. When the distribution of N-cadherin mRNA was analyzed to distinguish mesodermal from neuroectodermal expression, we found that N-cadherin is strongly expressed in the yolk cell and hypoblast in the early gastrula, just preceding the appearance of the bib mesodermal defects. Only later is N-cadherin expressed in the anlage of the CNS, where it is found as a radial gradient in the forming neural plate. Hence, besides a well-established role in neural and somite morphogenesis, N-cadherin is essential for morphogenesis of the mesodermal germ layer during gastrulation.
authors.affiliation: Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008, USA.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Warga
authors.forename: Donald A
authors.initials: DA
authors.lastname: Kane
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology*; D004475:Ectoderm / Q000196:embryology / Q000502:physiology; D054262:Gastrulation / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008648:Mesoderm / Q000196:embryology / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D054259:Neural Tube / Q000196:embryology / Q000502:physiology; D054261:Neurulation / Q000502:physiology; D015027:Zebrafish / Q000196:embryology / Q000502:physiology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*