Comparative prion disease gene expression profiling using the prion disease mimetic, cuprizone

Abstract

Identification of genes expressed in response to prion infection may elucidate biomarkers for disease, identify factors involved in agent replication, mechanisms of neuropathology and therapeutic targets. Although several groups have sought to identify gene expression changes specific to prion disease, expression profiles rife with cell population changes have consistently been identified. Cuprizone, a neurotoxicant, qualitatively mimics the cell population changes observed in prion disease, resulting in both spongiform change and astrocytosis. The use of cuprizone-treated animals as an experimental control during comparative expression profiling allows for the identification of transcripts whose expression increases during prion disease and remains unchanged during cuprizone-triggered neuropathology. In this study, expression profiles from the brains of mice preclinically and clinically infected with Rocky Mountain Laboratory (RML) mouse-adapted scrapie agent and age-matched controls were profiled using Affymetrix gene arrays. In total, 164 genes were differentially regulated during prion infection. Eighty-three of these transcripts have been previously undescribed as differentially regulated during prion disease. A 0.4% cuprizone diet was utilized as a control for comparative expression profiling. Cuprizone treatment induced spongiosis and astrocyte proliferation as indicated by glial fibrillary acidic protein (Gfap) transcriptional activation and immunohistochemistry. Gene expression profiles from brain tissue obtained from cuprizone-treated mice identified 307 differentially regulated transcript changes. After comparative analysis, 17 transcripts unaffected by cuprizone treatment but increasing in expression from preclinical to clinical prion infection were identified. Here we describe the novel use of the prion disease mimetic, cuprizone, to control for cell population changes in the brain during prion infection.

Could Intracrine Biology Play a Role in the Pathogenesis of Transmissable Spongiform Encephalopathies Alzheimer’s Disease and Other Neurodegenerative Diseases?

“…2 At first blush, this notion of PrP c upregulation in TSEs seems wrong on its face-PrP c messenger RNA (mRNA) steady state levels do not appear to be appreciably altered in TSE brains nor in chronically prion-infected cultured cells. 41,42 It is true that PrP c is upregulated in scrapie-infected Peyer's patch lymph cells compared with noninfected cells, and in this model, higher PrP c synthesis in host animals was associated with increased susceptibility to infection. 43 But, overall, there is no clear evidence in favor of continuous PrP c gene upregulation in TSE.…”

“…The loss of cells secondary to apoptotic death would mask PrP c upregulation consistent with near normal steady state PrP c mRNA levels in scrapie-infected cells and animals. 41,42 Tau and PrP c are required for AB excitotoxicity, and although PrP c could lead to apoptosis, the role of tau is unclear. 4 In 1 model of tauopathy, enhancing autophagy reduces cell toxicity, suggesting tau fibrils are toxic and lowering the intracellular concentration of these fibrils is beneficial (Figure 2).…”

Upregulation Of Interferon-Gamma-Induced Genes During Prion Infection

“…Total RNA purification, preparation, and hybridization to Affymetrix Mouse Genome 430 2.0 arrays was previously described by Moody et al (2009). Each time point was performed in triplicate.…”

“…Several groups, including our own, employed these techniques to identify gene expression changes in a variety of tissues in response to different prion strains throughout prion infection (Duguid et al, 1988, 1989; Duguid & Dinauer, 1990; Diedrich et al, 1991, 1993; Duguid & Trzepacz, 1993; Dandoy-Dron et al, 1998; Riemer et al, 2000, 2004; Baker & Manuelidis, 2003; Baker et al, 2004; Booth et al, 2004a, 2004b; Brown et al, 2004, 2005; Xiang et al, 2004, 2007; Skinner et al, 2006; Moody et al, 2009). A consistent feature of these studies is the overrepresentation of transcripts related to astrocytes and microglia, the cells proliferating in the brain during disease.…”

“…Many of these transcripts are associated with the Gene Ontology (GO) term “immune response.” Prion diseases do not elicit a humoral immune response (Porter et al, 1973); therefore, the transcripts related to the “immune response” GO term are likely related to microglia, the CNS-specific immune cells or immune system mediators produced by astrocytes (Gehrmann et al, 1995; Farina et al, 2007). Moody et al (2009) analyzed this subset of our data looking for transcripts expressed through similar signaling pathways to gain a better understanding of the molecular signaling events that are occurring in the prion-infected brain. Unexpectedly, 11 transcripts upregulated were identified in both preclinical and clinical prion-infected brain tissue whose induction is postulated to be stimulated by interferon (IFN)- γ , a cytokine recently identified as upregulated in prion-infected brain (Tribouillard-Tanvier et al, 2009).…”