Pluto Bioinformatics

GSE143531: Local translation highlights novel properties of perisynaptic astrocytic processes, and is modulated by behavior involving the dorsal hippocampus

Bulk RNA sequencing

Local translation is a conserved molecular mechanism. It allows a cell with a complex shape to bypass somatic protein synthesis and transport, and thus to respond quickly to a local stimulus. Local translation also contributes to the establishment of molecular and functional polarity. In the brain, it has been extensively studied in neurons and has also been described more recently in astrocytes - a type of glial cell with specialized extensions that contact vessels and synapses. Here, we studied perisynaptic astrocytic processes (PAPs) in the dorsal hippocampus and showed that they contain RNAs, ribosomes, the endoplasmic reticulum-Golgi intermediate compartment, particles of the Golgi apparatus, and protein synthesis events. We used our recently refined polysome immunoprecipitation technique to characterize the pool of polysomal mRNAs in PAPs (which we refer to as the PAPome) from the dorsal hippocampus and compared it with the polysomal mRNAs found in the astrocyte as a whole. The polysomal transcripts that were enriched in the PAPome encoded mostly cytoplasmic proteins and defined an unexpected molecular repertoire with the most enriched transcripts coding for proteins involved in iron homeostasis, translation, cell cycle and cytoskeleton. Interestingly, among them Erz, Fth1, and Rplp1 were enriched in PAPs compared to perivascular astrocytic processes indicating that local translation differ at these two interfaces and may sustain distinct molecular properties. The PAP-enriched transcripts Flt1, Fth1, Ccnd2, Mdm2, Gnb2l1 and Eef1a1 code for proteins involved in memory and learning mechanisms. We therefore studied their local translation in the context of fear conditioning (i.e. behavior involving the dorsal hippocampus). We observed changes in the density and/or distribution of these mRNAs in astrocytes processes as well as a drop of their translation specifically in PAPs. Our results highlight unexpected molecular properties of hippocampal PAPs and suggest for the first time that local translation in this perisynaptic compartment is linked to fear-related memory. SOURCE: Stephane Le Crom IBENS

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