The oligodendrocyte "protrusiosome": Identification of compartmentalized enrichment of transcripts in newly-formed protrusions of oligodendrocyte precursor cells (OPC) by RNAseq. The oligodendrocyte "protrusiosome": Identification of compartmentalized enrichment of transcripts in newly-formed protrusions of oligodendrocyte precursor cells (OPC) by RNAseq

Like neurons, oligodendrocytes (OL) are cells with elaborate morphology that probably require asymmetrical spatial regulation of biological processes. Formation of membrane protrusions is critical for OL development and interaction with axons. We hypothesized that the enrichment of specific mRNAs in protrusions of oligodendrocyte precursor cells (OPC) is important for morphological differentiation, thus having an impact in myelination. To explore this hypothesis, we established a modified Boyden chamber system to physically separate soma from membrane protrusions of rat primary OPC cultured in vitro for 24h. We performed a whole transcriptome analysis (RNAseq) of primary rat OPC soma and membrane protrusion fractions and found a subcellular enrichment of mRNAs in these structures during initial protrusion formation. At the very initial stage of OPC protrusion extension, there is a significant subcellular enrichment of transcripts encoding proteins related to cellular component assembly and cytoskeleton organization, particularly of actin-related molecules. This suggests that the regulation of the cytoskeleton dynamics may be locally controlled in OPCs and probably relevant for their differentiation program. Overall design: Rat OPCs were plated on a modified Boyden chamber system for 24h consisting of a transwell with 1μm pore size with chemo- and haptotactic gradients to physically separate OPC soma and protrusion fractions for RNA sequencing. RNAseq was done on 2 samples for OPC soma and 2 samples of OPC protrusions. Due to very low RNA yields in OPC protrusions samples (typically 9ng per well), each sample consisted in a pool of several experiments.