ABSTRACT: Sheep scrapie (Sc) is the classical transmissible spongiform encephalopathy (prion disease). The conversion of normal cellular prion protein (PrPC) to disease-associated prion protein (PrPSc) is a fundamental component of prion disease pathogenesis. The molecular mechanisms contributing to prion diseases and the impact of PrPSc accumulation on cellular biology are not fully understood. To define the molecular changes associated with PrPSc accumulation, primary sheep microglia were inoculated with PrPSc and then the transcriptional profile of these PrPSc-accumulating microglial cells was compared to the profile of PrPSc-lacking microglial cells using the Affymetrix Bovine Genome Array. The experimental design included three biological replicates, each with three technical replicates, and samples that were collected at the point of maximal PrPSc accumulation levels as measured by ELISA. The array analysis revealed 19 upregulated genes and 30 downregulated genes in PrPSc-accumulating microglia. Three transcripts (CCL2, SGK1, and AASDHPPT) were differentially regulated in a direction similar to previous reports from mouse or human models, whereas the response of three other transcripts (MT1E, NR4A1, PKP2) conflicted with previous reports. Overall, the results demonstrated a limited transcriptional response to PrPSc accumulation, when compared to microglia and macrophage cultures infected with other agents such as viruses and bacteria. This is the first microarray-based analysis of prion accumulation in primary cells derived from a natural TSE-host. Experiment Overall Design: Primary sheep microglial cells were either inoculated with PrPSc (Inoc) or sham-inoculated (Mock) Experiment Overall Design: Three biological replicates per treatment. Experiment Overall Design: Three technical replicates per biological replicate. Experiment Overall Design: biological replicate: Inoc12A, Inoc12B.2, Inoc12C Experiment Overall Design: biological replicate: Mock12A, Mock12B.2, Mock12C Experiment Overall Design: technical replicate - extract: Inoc12A.1, Inoc12A.2, Inoc12A.3 Experiment Overall Design: technical replicate - extract: Inoc12B.2.1, Inoc12B.2.2, Inoc12B.2.3 Experiment Overall Design: technical replicate - extract: Inoc12C.1, Inoc12C.2, Inoc12C.3 Experiment Overall Design: technical replicate - extract: Mock12A.1, Mock12A.2, Mock12A.3 Experiment Overall Design: technical replicate - extract: Mock12B.2.1, Mock12B.2.2, Mock12B.2.3 Experiment Overall Design: technical replicate - extract: Mock12C.1, Mock12C.2, Mock12C.3
