A mutation altering the function of a carbohydrate binding protein blocks cell–cell cohesion in developing Dictyostelium discoideum

Abstract
In D. discoideum, carbohydrate binding proteins (CBPs) or lectins are implicated in the molecular basis of cellular cohesion. To determine the role of these CBPs, structural gene mutants were isolated in which the CBPs have a defective affinity for carbohydrate ligands. The isolation of a spontaneous, cross-reacting material (CRM) mutant which is non-cohesive and fails to develop is reported. The mutant apparently has a defect in the structural gene for 1 of the 2 developmentally regulated carbohydrate binding proteins (CBP-26), which renders it unable to bind to galactose-containing ligands. The fact that wild-type cells interact with the mutant and carry it through development strongly supports a model of cell-cell interaction in which cohesion is mediated by complementary molecules.