Overexpression of CAF1 encoding a novel Ca2+-binding protein stimulates the transition of Dictyostelium cells from growth to differentiation

Dev Growth Differ. 1998 Dec;40(6):677-83. doi: 10.1046/j.1440-169x.1998.t01-2-00012.x.


Among the expressed genes associated with the switch-over of Dictyostelium cells from cell proliferation to differentiation, the Calfumirin-1 (CAF1) gene has been shown to be preferentially expressed at the initial step of differentiation, encoding a novel Ca2+-binding protein (Abe & Maeda 1995). To analyze precisely the function of CAF1, transformants overexpressing the CAF1 mRNA at the vegetative growth phase and also CAF1-null mutants were prepared, and their developmental features were compared with those of parental wild-type cells. As a result, the CAF1-overexpression was found to promote cell differentiation, possibly through prompt induction of the cAMP receptor 1 (CAR1) gene expression. In addition, the CAF1-overexpressing cells were able to differentiate even under low external Ca2+ ([Ca2+]e) conditions around 10(-6) mol/L at which non-transformed wild-type cells never differentiated. Unexpectedly, however, the CAF1-null mutant produced by homologous recombination exhibited apparently normal development to form fruiting bodies on non-nutrient agar. These results seem to indicate that CAF1-overexpression has a stimulatory effect on differentiation, but that the CAF1 protein is not necessarily required for the phase-shift of cells from growth to differentiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Northern
  • Calcium / metabolism
  • Calcium-Binding Proteins / physiology
  • Cell Differentiation
  • Cell Division
  • Dictyostelium / genetics*
  • Fungal Proteins / genetics
  • Gene Expression
  • Genetic Vectors
  • Mutation
  • RNA / isolation & purification
  • Receptors, Cyclic AMP / genetics*
  • Transcription Factors / genetics*
  • Transformation, Genetic


  • Calcium-Binding Proteins
  • Fungal Proteins
  • Receptors, Cyclic AMP
  • Transcription Factors
  • cyclic AMP receptor cAR1
  • RNA
  • Calcium