Local translation in neuronal processes is key to the alteration of synaptic strength necessary for long-term potentiation, learning, and memory. Here, we present evidence that regulated de novo protein synthesis occurs within distal, perisynaptic astrocyte processes. Astrocyte ribosomal proteins are found adjacent to synapses in vivo, and immunofluorescent detection of peptide elongation in acute slices demonstrates robust translation in distal processes. We have also developed a biochemical approach to define candidate transcripts that are locally translated in astrocyte processes. Computational analyses indicate that astrocyte-localized translation is both sequence-dependent and enriched for particular biological functions, such as fatty acid synthesis, and for pathways consistent with known roles for astrocyte processes, such as GABA and glutamate metabolism. These transcripts also include glial regulators of synaptic refinement, such as Sparc. Finally, the transcripts contain a disproportionate amount of a binding motif for the quaking RNA binding protein, a sequence we show can significantly regulate mRNA localization and translation in the astrocytes. Overall, our observations raise the possibility that local production of astrocyte proteins may support microscale alterations of adjacent synapses.astrocyte | local translation | synapse | TRAP | RNA-sequencing

Highlights d pnVTA Pnoc neurons project locally onto VTA dopamine neurons d pnVTA Pnoc neurons become active when animals are demotivated to seek rewards d Stimulation of pnVTA Pnoc neurons reduces breakpoint and promotes avoidance behavior d VTA dopamine neuron NOPR expression is necessary to limit reward-seeking behavior Authors

Precise spatiotemporal control of mRNA translation machinery is essential to the development of highly complex systems like the neocortex. However, spatiotemporal regulation of translation machinery in the developing neocortex remains poorly understood. Here, we show that an RNA-binding protein, Hu antigen R (HuR), regulates both neocorticogenesis and specificity of neocortical translation machinery in a developmental stage-dependent manner in mice. Neocortical absence of HuR alters the phosphorylation states of initiation and elongation factors in the core translation machinery. In addition, HuR regulates the temporally specific positioning of functionally related mRNAs into the active translation sites, the polysomes. HuR also determines the specificity of neocortical polysomes by defining their combinatorial composition of ribosomal proteins and initiation and elongation factors. For some HuR-dependent proteins, the association with polysomes likewise depends on the eukaryotic initiation factor 2 alpha kinase 4, which associates with HuR in prenatal developing neocortices. Finally, we found that deletion of HuR before embryonic day 10 disrupts both neocortical lamination and formation of the main neocortical commissure, the corpus callosum. Our study identifies a crucial role for HuR in neocortical development as a translational gatekeeper for functionally related mRNA subgroups and polysomal protein specificity.

21Local translation in neuronal processes is key to the alteration of synaptic strength that contributes 22

Background Studies in psychiatric genetics have identified over 100 loci associated with disease risk, yet many of these loci are distant from protein coding genes. Recent characterization of the transcriptional landscape of cell lines and whole tissues has suggested widespread transcription in both coding and non-coding regions of the genome, including differential expression from loci that produce regulatory non-coding RNAs which function within the nucleus; however, the nuclear transcriptome of specific cell types in the brain has not been previously investigated. Methods Here we have defined the nuclear transcriptional landscape of the three major cellular divisions of the nervous system using flow sorting of genetically labeled nuclei from bacTRAP mouse lines. This was followed by characterization of the unique expression of coding, non-coding and intergenic RNAs in the mature mouse brain with RNAseq and validation with independent methods. Results Our findings reveal diverse expression across the cell-types of all classes of RNAs, including long non-coding RNAs – several of which were confirmed as highly enriched in the nuclei of specific cell-types using anatomical methods. Finally, we also discovered several examples of cell-type specific expression of tandem gene fusions, and report the first cell-type specific expression of circular RNAs, notably a neuron-specific and nuclear-enriched RNA arising from the gene Hnrnpu. Conclusion These data will provide an important resource for studies evaluating the function of a variety of ncRNAs in the brain, including those that may play a role in psychiatric disease.