Cortexillin I is required for development in Polysphondylium.

The actin binding proteins cortexillin I and II play a major role in Dictyostelium cytokinesis, in which they are found localized to the membranes of the cleavage furrow. Here we report on cortexillin I mutants isolated by gene trapping in Polysphondylium. The original mutation and reconstructed versions of the original, as well as cortexillin I deletions, are unable to form aggregation streams under starvation conditions. The fruiting bodies that do form when cells are grown on bacterial lawns lack the one- and two-dimensional symmetries so apparent in wild type. These two phenotypes and the proposed structural basis for them suggest that cortexillin I functions in chemotaxis and morphogenesis in addition to its role in cytokinesis. Copyright 1999 Academic Press.