The molecular basis of dendrite-substrate interactions in vivo and the implications for dendrite morphogenesis remain incompletely understood. As dendrites elaborate, one important step in their patterning is the proper spacing of branches from the same cell, or sister dendrites, via repulsive dendrite-dendrite interactions (Grueber and Sagasti, 2010 and Jan and Jan, 2010). Self-avoidance, which ensures complete and nonredundant coverage of sensory or synaptic inputs, is most clearly observed in neurons that grow in a planar pattern, such as retinal ganglion cells, leech sensory neurons, and Drosophila dendritic arborization (da) neurons ( Grueber and

Sagasti, 2010, Jan and Jan, 2010 and Kramer and Stent, 1985). Although self-avoidance is probably not limited to two-dimensional arbors ( Zhu et al., 2006), the robustness of self-avoidance click here in such processes implies that molecules and substrates that restrict growth to a plane may influence repulsive interactions. The extent of this influence, and the impact on current molecular models of self-avoidance, is not known. Drosophila dendritic arborization (da) neurons have proven useful for studies of dendritic

morphogenesis and self-avoidance. da neurons can be Selleck C59 wnt segregated into four classes (classes I–IV) distinguished both by dendritic morphology and central axon projections ( Grueber et al., 2002 and Grueber et al., 2007). Numerous molecules have been implicated in control of dendrite-dendrite repulsion. For example, the Down syndrome cell adhesion molecule 1 (Dscam1) family of Astemizole homophilic adhesion molecules permits selective recognition between the surfaces of sister dendrites and initiation of repulsive responses between them ( Corty et al., 2009,

Hattori et al., 2008, Hughes et al., 2007, Matthews et al., 2007 and Soba et al., 2007). Dscam1 endows different neurons with unique surface identities via extensive alternative splicing to permit self versus nonself discrimination ( Corty et al., 2009, Jan and Jan, 2010 and Millard and Zipursky, 2008). Several genes have been found to promote repulsion between branches of class IV neurons, including tricornered (trc), which encodes a serine threonine kinase, furry (fry), and turtle (tutl), encoding an immunoglobulin superfamily member, however these appear to function independently of Dscam1 ( Emoto et al., 2004, Long et al., 2009 and Soba et al., 2007). Consequently, how Dscam1 and other factors combine to support self-avoidance is not currently known. One notable distinction is that Dscam1 is required for self-avoidance in all classes of neurons ( Hughes et al., 2007, Matthews et al., 2007 and Soba et al., 2007), whereas action of other molecules appears to be limited to the highly complex class IV neurons. It is not clear how self-repulsion mechanisms might differ between different classes of neurons, but understanding this distinction should begin to extend current models.