Transcriptomic determinants of scrapie prion propagation in cultured ovine microglia

Authors: MUÑOZ-GUTIÉRREZ, JUAN - Washington State University; PIERLÉ, SEBASTIÁN - Institut Pasteur - France; Schneider, David; BASZLER, TIMOTHY - Washington State University; STANTON, JAMES - University Of Georgia

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2016
Publication Date: 1/25/2016
Citation: Muñoz-Gutiérrez, J.F., Pierlé, S.A., Schneider, D.A., Baszler, T.V., Stanton, J.B. 2016. Transcriptomic determinants of scrapie prion propagation in cultured ovine microglia. PLoS One. 11(1):e0147727.

Interpretive Summary: The mechanisms by which prions infect cells are poorly understood. Though a cell must express adequate levels of a susceptible prion protein, other factors must also be important since not all such cells are permissive to infection. In this study, the expression of genes associated with permissiveness to scrapie prion infection were determined by Illumina RNA sequencing technology using clones of a cell type (microglia) derived from the brain of sheep and which are naturally infected during scrapie disease. Microglia clones expressed equivalent levels of prion protein but only one was permissive to scrapie infection. Comparative analyses identified twenty-two genes expressed at highly different levels between these clones. The data suggest that the permissiveness of microglia to infection by scrapie prions may be limited by relatively high expression of selenoprotein P, endolysosomal proteases, and proteins associated with extracellular matrix remodeling, and also relatively low expression of transforming growth factor ß–induced. Thus it may be possible to alter prion infection of microglia, and perhaps other cell types, by targeting expression of these genes and related functional pathways. Such confirmation would help in the development of a robust and highly sensitive culture system for prions as well as provide novel targets for therapeutic investigation.

Technical Abstract: While infection by scrapie prions is dependent on expression of cellular prion protein (PrP-C), other factors must play a role since not all cells that express equivalent levels of PrP-C are permissive to infection. The aim of this study was to determine the cellular factors associated with permissiveness to infection by scrapie prions. This was accomplished by comparing the global transcriptional profiles of two clones of an immortalized cell line of ovine microglia after inoculation with scrapie-positive or scrapie-naive sheep brain homogenate. The cultured cells and sheep from which the inocula were derived were all homozygous for the prion protein allele coding for valine at codon 136. Despite having similar levels of PrP-C expression, one clone was permissive and the other non-permissive to scrapie infection. The transcriptional profiles were sequenced using Illumina technology. Comparative transcriptional analyses identified twenty-two differentially transcribed genes, most of which were up-regulated in the non-permissive clone. These included genes encoding selenoprotein P, endolysosomal proteases, and proteins involved in extracellular matrix remodeling. Genes up-regulated in the permissive clone included transforming growth factor ß–induced, retinoic acid receptor response 1, and phosphoserine aminotranspherase 1. Gene Set Enrichment Analysis identified proteolysis, translation, and mitosis as the most affected pathways and supported the trends of up-regulation of several genes encoding for intracellular proteases and ribosomal proteins. We propose that prion cellular aggregation and replication may be inhibited by selenoprotein P, endolysosomal proteases, and proteins associated with extracellular matrix remodeling, and may be enhanced by the known amyloid aggregating properties of transforming growth factor ß–induced.