Fig. 2
From: Strategies for assembling columns and layers in the Drosophila visual system
Alternative splicing of Dscam1 and Dscam2 regulates synaptic exclusion. (a) Properties of Dscam1 and Dscam2 alternative splicing are very different, but allow both to exclude processes from the same cell at tetrad synapses. (b) A schematic of a tetrad synapse (variable components not shown). A random array of Dscam1 isoforms are expressed in L1 and L2. Since these isoforms are not identical between the two cells, homophilic repulsion does not occur. L1 and L2 express distinct isoforms of Dscam2. This allows for self-repulsion, but not repulsion between the two different cells. Through this indirect mechanism of excluding inappropriate partners at synapses, postsynaptic specificity is achieved