Identification of Upregulated Genes in Scrapie-Infected Brain Tissue

Abstract

The pathogenesis of scrapie, and of neurodegenerative diseases in general, is still insufficiently understood and is therefore being intensely researched. There is abundant evidence that the activation of glial cells precedes neurodegeneration and may thus play an important role in disease development and progression. The identification of genes with altered expression patterns in the diseased brain may provide insight on the molecular level into the process which ultimately leads to neuronal loss. Differentially expressed genes in scrapie-infected brain tissue were enriched by the suppression subtractive hybridization technique, molecularly cloned, and further characterized. Northern blotting and nucleotide sequencing confirmed the identities of 19 upregulated genes, 11 of which were unknown to be affected by scrapie. A considerable number of these 19 genes, namely those encoding interferon-inducible protein 10 (IP-10), 2,5-oligo(A) synthetase, Mx protein, IIGP protein, major histocompatibility complex classes I and II, complement, and ␤ 2 -microglobulin, were inducible by interferons (IFNs), suggesting that an IFN response is a possible mechanism of gene activation in scrapie. Among the newly found genes, that coding for 2,5-oligo(A) synthetase is of special interest because it could contribute to the apoptotic loss of neuronal cells via RNase L activation. In addition, upregulation of the chemokine IP-10 and B-lymphocyte chemoattractant mRNAs was seen at relatively early stages of the disease and was sustained throughout disease development.

Microglia from Creutzfeldt-Jakob Disease-Infected Brains Are Infectious and Show Specific mRNA Activation Profiles

“…3B), consistent with previously described results in scrapie-infected brains (36). However, we detected no differences in MIP-1␣ or MIP-1␤ expression between control and CJD-infected microglial cultures on a per-cell basis (Fig.…”

Microglia in prion diseases

“…However, depletion of CXCR3 resulted in reduced production of proinflammatory cytokines, which could explain the prolonged incubation time. The chemokine CXCL13 is also upregulated in prion disease (42,71); however, knockout of its receptor, CXCR5, did not alter prion pathogenesis after intracerebral inoculation of RML prions (73). (55).…”

“…CXCL9 and CXCL10, which recognize and bind to CXCR3, are also increased in prion infection (64,71). After intracerebral inoculation of 139A prion, Cxcr3 -/-mice accumulated more PrP Sc in their brains compared with WT mice, but succumbed to disease with a prolonged incubation time (72).…”

Role of Interleukin-1 in Prion Disease-Associated Astrocyte Activation

“…The GFAP-specific probe was obtained from a cDNA library enriched for up-regulated genes in scrapie-infected brain tissue as previously described, 6 all other DNAs used as hybridization probes were amplified by polymerase chain reaction (PCR) starting from murine spleen cDNA. Applied oligonucleotides for the PCR amplifications were: IL-1␤(ϩ) CCTGTGTCTTTCCCGTG; IL-1␤(Ϫ) GAGTGCTGCCTAATGTCC; IL-1RI(ϩ) GGGACTC-CAGGATTCATCAG; IL-1RI(Ϫ) GCTCTTCAGCCACATTCC; ICE(ϩ) CGTGGAGAGAAACAAGGAG; ICE(Ϫ) CAGCAGT-GGGCATCTGTAG; actin(ϩ) AAGGCCAACCGTGAAAA-GAT; actin(Ϫ) CGCTCGTTGCCAATAGTGAT.…”