Role of Dscam mediated self-avoidance and tiling in neural branching

Abstract

Dscams (down syndrome cell adhesion molecules) play an important role in the formation of neural circuits. Various studies have highlighted the role of dscams in two major wiring strate- gies, self-avoidance and tiling, leading to broad and uniform branching. The Drosophila dscam1 protein, which has thousands of isoforms formed by alternative splicing, has been shown to confer unique identities to cells and mediate homotypic recognition, homophilic repulsion and consequently self-avoidance behavior between neurites of a single neuron. The Drosophila dscam2 protein mediates homophilic repulsion between projections from the same class of cells, in a process called tiling. The vertebrate dscam has been shown to mediate both tiling
and self-avoidance. however, the mechanisms by which this is accomplished in the absence of homotypic recognition are unclear. This review provides an overview of functional similarities and differences between dscam homologues in invertebrate and vertebrate species, and describes some mechanisms proposed to account for these differences.