Accumulation of proteinase K-resistant prion protein (PrP) is restricted by the expression level of normal PrP in mice inoculated with a mouse-adapted strain of the Creutzfeldt-Jakob disease agent

Abstract

Creutzfeldt-Jakob disease (CJD) is a transmissible neurodegenerative disease of humans caused by an unidentified infectious agent, the prion. To determine whether there was an involvement of the host-encoded prion protein (PrP c) in CJD development and prion propagation, mice heterozygous (PrP ؉/؊) or homozygous (PrP ؊/؊) for a disrupted PrP gene were established and inoculated with the mouse-adapted CJD agent. In keeping with findings of previous studies using other lines of PrP-less mice inoculated with scrapie agents, no PrP ؊/؊ mice showed any sign of the disease for 460 days after inoculation, while all of the PrP ؉/؊ and control PrP ؉/؉ mice developed CJD-like symptoms and died. The incubation period for PrP ؉/؊ mice, 259 ؎ 27 days, was much longer than that for PrP ؉/؉ mice, 138 ؎ 12 days. Propagation of the prion was barely detectable in the brains of PrP ؊/؊ mice and was estimated to be at a level at least 4 orders of magnitude lower than that in PrP ؉/؉ mice. These findings indicate that PrP c is necessary for both the development of the disease and propagation of the prion in the inoculated mice. The proteinase-resistant PrP (PrP res) was undetectable in the brain tissues of the inoculated PrP ؊/؊ mice, while it accumulated in the affected brains of PrP ؉/؉ and PrP ؉/؊ mice. Interestingly, the maximum level of PrP res in the brains of PrP ؉/؊ mice was about half of the level in the similarly affected brains of PrP ؉/؉ mice, indicating that PrP res accumulation is restricted by the level of PrP c .

Grafting mouse brains: from neurocarcinogenesis to neurodegeneration

“…But how to detect spread of infectivity to the nervous system if one uses PrP-deficient mice? Such mice are, as repeatedly shown by several groups (Büeler et al, 1993;Manson et al, 1994;Sakaguchi et al, 1995), totally resistant to scrapie and cannot replicate the agent. We resorted to introducing a neural graft, which in this case would act as an indicator of neuroinvasion.…”

Prion protein genes and prion diseases: studies in transgenic mice

“…Once aggregates of PrP Sc form, they promote the conversion of PrP C by binding to and stabilizing the otherwise unfavoured PrP Sc conformation. mouse blastocysts and knockout mice were established [8,32,49]. Unlike wild-type mice, the resultant homozygous null mice (Prnp 0/0 ), which express no PrP C , fail to develop the characteristic clinical and neuropathological symptoms of scrapie after inoculation with mouse prions and do not propagate prion infectivity [9,33,43,49].…”

“…mouse blastocysts and knockout mice were established [8,32,49]. Unlike wild-type mice, the resultant homozygous null mice (Prnp 0/0 ), which express no PrP C , fail to develop the characteristic clinical and neuropathological symptoms of scrapie after inoculation with mouse prions and do not propagate prion infectivity [9,33,43,49]. Mice that are hemizygous for PrP gene ablation, and therefore express half the normal level of PrP C , have prolonged incubation times [10,33,43].…”

Prions: Pathogenesis and Reverse Genetics

“…In a third PrP c knockout line created by Sakaguchi and colleagues the whole PrP c ORF and about 250 bp of the 5′ intron and 452 bp of 3′ untranslated sequences were replaced with a drug-resistance gene. 31 Both the Büeler and Sakaguchi mice were on a mixed genetic (129/Sv × C57BL) background whereas the Manson mice were bred on a pure 129/Ola background. According to the terminology which has become customary in the literature, and by which we abide in this manuscript, the Zurich mice have been designated Prnp o/o while the Edinburgh and the Japanese mice are termed Prnp −/− .…”

“…40 This observation was confirmed using different PrP c null mice with different mouse-adapted scrapie inocula. 31,41 Mice hemizygous for the disrupted Prnp gene (Prnp 0/+ ) showed partial resistance to scrapie infection as manifested by prolonged incubation times of about 290 days as compared to about 160 days in the case of Prnp +/+ mice. The incubation times until the first scrapie symptoms appear seem to correlate with levels of PrP c in the host, whereas the severity of the disease in terms of neuropatholgical changes in the brain and levels of prion infectivity were not dependent on the PrP c level.…”