Bradford, B.M.

Brown, D.A.

Clarke, A.

Kisielewski, Dorothy

Manson, J.C.

Marshall, A.S.

Perry, V.H.

Piccardo, Pedro

Tuzi, N.L.

It is known that expression of the host form of PrP protein (PrPC) is required for susceptibility to and the establishment of transmissible spongiform encephalopathies (TSEs). We have produced a Cre/LoxP conditional PrP knockout mouse model in which administration of tamoxifen results in the removal of PrPC expression from neurones only. Using this model we have previously demonstrated that removal of PrPC expression from neurones prior to infection with the ME7 mouse-adapted Scrapie strain dramatically altered pathology, preventing spongiosis and neuronal loss in specific neuronal populations, and greatly extended disease incubation period. As a further application of this model, neuronal PrP knockout was induced in groups of mice at various time-points post intra-cerebral ME7 infection to assess the impact upon disease pathogenesis. Results indicate that early in the incubation period there are time-points where neuronal PrPC expression is essential for ‘normal’ disease progression, but at later stages removal of neuronal PrPC no longer influenced disease incubation period. This critical time-point occurs after known pathologies such as synaptic loss have become established within the central nervous system.These results assist in informing us of the basic mechanisms in TSE neurodegeneration and also of a ‘time-window’ when potential therapeutic intervention involving the reduction of PrPC expression may be possible in TSE diseases. The findings and conclusions in this article have not been formally disseminated by the Food and Drug Administration and should not be construed to represent any Agency determination or policy

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     Edinburgh Research Explorer                                      Inducible neuronal PrP knockout mice reveal potentialtherapeutic window for TSE interventionCitation for published version:Bradford, BM, Marshall, AS, Brown, DA, Kisielewski, D, Tuzi, NL, Piccardo, P, Clarke, A, Perry, VH &Manson, JC 2010, 'Inducible neuronal PrP knockout mice reveal potential therapeutic window for TSEintervention' Prion, vol 4, no. 3, pp. 173.Link:Link to publication record in Edinburgh Research ExplorerDocument Version:Early version, also known as pre-printPublished In:PrionGeneral rightsCopyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s)and / or other copyright owners and it is a condition of accessing these publications that users recognise andabide by the legal requirements associated with these rights.Take down policyThe University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorercontent complies with UK legislation. If you believe that the public display of this file breaches copyright pleasecontact openaccess@ed.ac.uk providing details, and we will remove access to the work immediately andinvestigate your claim.Download date: 28. Apr. 2017Inducible Neuronal PrP Knockout Mice Reveal Potential Therapeutic Window for TSE Intervention.Barry M. BradfordThe Roslin Institute and R(D)SVS, The University of Edinburgh Neuropathogenesis Division Inducible neuronal PrP knockout• Tamoxifen-inducible neuronal Cre (NSECreER)– Neuron specific enolase promoter– Cre activity regulated by modified oestrogen receptor sensitive only to tamoxifen• Gene-targeted loxP sites flanking PrP gene (PrPfl)– Expresses PrP normally– No expression following Cre-mediated recombinationPrnp Exon 3CreCre ERTxNSEpromoter Fusion proteinCharacterizationIncubation period resultsNeuropathologyNeuropathologyCerebellumComparative PathologyNeuropathology ME7 ME7 Neuronal PrP KOHippocampal neuronal loss(pyramidal / granule cells)  Rescue*- MAP2 loss   disruption- Synaptophysin loss   disruptionVacuolation   Cornu ammonis Dentate gyrusPrPSc deposition   Patchy§ (Cornu ammonis / cortex) Smooth / Neuropil (Dentate gyrus)Reactive Astrocyte  - GFAP+ /  cytoskeletal Hypermorphy   extreme§Reactive Microglia   reduced- Iba1 +  - Infiltrate   rare around neuronesCerebellumGranule neurone loss minimal  Loss to extreme loss§§Increasing with incubation periodCerebellumPurkinje cell loss minimal  Extreme to minimal (rescue)**reduced with increasing incubation periodTimed neuronal PrP knockoutSummary• Induced knockout of neuronal PrP– Extends incubation period• Both prior to infection and at any point up until overt clinical phase of disease– Alters pathology• Involvement of astrocytes• Removes correlation between hallmark pathologies– White matter degeneration with aging• In absence of diseaseConclusions• Therapeutic PrP depletion strategies– Target both neurones and astrocytes for maximal effect– Avoid myelin degeneration phenotypeFurther work• Astrocytes– Differential susceptibilities to disease– Infection non-fatal to cell – Fundamental difference to neurones?AcknowledgementsThe Roslin InstituteJean MansonAlison MarshallDebbie BrownDot KisielewskiAnimal welfareKris HoganIrene McConnellSimon CummingsPathologyAnne CoghillSandra MackGillian McGregorUniversity of EdinburghNadia TuziUniversity of SouthamptonHugh PerryUniversity of CardiffAlan ClarkeUS Food and Drug AdministrationPedro PiccardoFunding: DOH 007/104 NIH-NIAID AI-4893-02FDA 224-05-1307"The findings and conclusions in this article have not been formally disseminated by the Food and Drug Administration and should not be construed to represent the Agency determination or policy". 

Inducible neuronal PrP knockout mice reveal potential therapeutic window for TSE intervention

Inducible neuronal PrP knockout mice reveal potential therapeutic window for TSE intervention

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