Disruption of the gene encoding the cell adhesion molecule DdCAD-1 leads to aberrant cell sorting and cell-type proportioning during Dictyostelium development

Development. 2002 Aug;129(16):3839-50.

Abstract

The cadA gene in Dictyostelium encodes the Ca2+-dependent cell adhesion molecule DdCAD-1, which is expressed soon after the initiation of development. To investigate the biological role of DdCAD-1, the cadA gene was disrupted by homologous recombination. The cadA-null cells showed a 50% reduction in EDTA-sensitive cell adhesion. The remaining EDTA-sensitive adhesion sites were resistant to dissociation by anti-DdCAD-1 antibody, suggesting that they were distinct adhesion sites. Cells that lacked DdCAD-1 were able to complete development and form fruiting bodies. However, they displayed abnormal slug morphology and culmination was delayed by approximately 6 hours. The yield of spores was reduced by approximately 50%. The proportion of prestalk cells in cadA(-) slugs showed a 2.5-fold increase over the parental strain. When cadA(-) cells were transfected with pcotB::GFP to label prespore cells, aberrant cell-sorting patterns in slugs became apparent. When mutant prestalk cells were mixed with wild-type prespore cells, mutant prestalk cells were unable to return to the anterior position of chimeric slugs, suggesting defects in the sorting mechanism. The wild-type phenotype was restored when cadA(-) cells were transfected with a cadA-expression vector. These results indicate that, in addition to cell-cell adhesion, DdCAD-1 plays a role in cell type proportioning and pattern formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / physiology
  • Cell Adhesion / drug effects
  • Cell Adhesion Molecules / genetics*
  • Cell Adhesion Molecules / physiology
  • Dictyostelium / cytology
  • Dictyostelium / genetics*
  • Dictyostelium / growth & development*
  • Edetic Acid / pharmacology
  • Gene Expression Regulation, Developmental
  • Gene Targeting
  • Genes, Protozoan*
  • Phenotype
  • Spores / cytology
  • Transfection

Substances

  • Calcium-Binding Proteins
  • Cell Adhesion Molecules
  • DdCAD-1 protein, Dictyostelium discoideum
  • Edetic Acid