Research ArticlesNeuroscience

Pcdhαc2 is required for axonal tiling and assembly of serotonergic circuitries in mice

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Science  28 Apr 2017:
Vol. 356, Issue 6336, pp. 406-411
DOI: 10.1126/science.aal3231

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Pattern formation in the brain

Neurons in the developing brain cooperate to build circuits. Mountoufaris et al. found that ∼50 variable protocadherin genes support a combinatorial identity code that allows millions of olfactory neuron axons to sort into ∼2000 glomeruli. Sharing olfactory receptors drives axons to one glomerulus, and protocadherin diversity allows the multiple axons to touch each other as they converge. On the other hand, Chen et al. found that a single C-type protocadherin underlies the tiled distribution of serotonergic neurons throughout the central nervous system. These neurons, which share protocadherin identity, enervate broad swaths evenly without touching neighboring neurons.

Science, this issue p. 411, p. 406

Abstract

Serotonergic neurons project their axons pervasively throughout the brain and innervate various target fields in a space-filling manner, leading to tiled arrangements of their axon terminals to allow optimal allocation of serotonin among target neurons. Here we show that conditional deletion of the mouse protocadherin α (Pcdhα) gene cluster in serotonergic neurons disrupts local axonal tiling and global assembly of serotonergic circuitries and results in depression-like behaviors. Genetic dissection and expression profiling revealed that this role is specifically mediated by Pcdhαc2, which is the only Pcdhα isoform expressed in serotonergic neurons. We conclude that, in contrast to neurite self-avoidance, which requires single-cell identity mediated by Pcdh diversity, a single cell-type identity mediated by the common C-type Pcdh isoform is required for axonal tiling and assembly of serotonergic circuitries.

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