this gene cluster (Fig. 2b, front rows). The presence of these proteins in PSD preparations may represent a carry-over of glial fragments. Alternatively, they may be components of glutamatergic synapses between neurons and oligodendrocytes, which have been shown to share many properties with neuronal–neuronal synapses15. Overall, these data show remarkable regional variation in synaptic gene expression that probably underlies functional distinctions between regions.
