Absence of spontaneous disease and comparative prion susceptibility of transgenic mice expressing mutant human prion proteins

Abstract

Approximately 15 % of human prion disease is associated with autosomal-dominant pathogenic mutations in the prion protein (PrP) gene. Previous attempts to model these diseases in mice have expressed human PrP mutations in murine PrP, but this may have different structural consequences. Here, we describe transgenic mice expressing human PrP with P102L or E200K mutations and methionine (M) at the polymorphic residue 129. Although no spontaneous disease developed in aged animals, these mice were readily susceptible to prion infection from patients with the homotypic pathogenic mutation. However, while variant Creutzfeldt-Jakob disease (CJD) prions transmitted infection efficiently to both lines of mice, markedly different susceptibilities to classical (sporadic and iatrogenic) CJD prions were observed. Prions from E200K and classical CJD M129 homozygous patients, transmitted disease with equivalent efficiencies and short incubation periods in human PrP 200K, 129M transgenic mice. However, mismatch at residue 129 between inoculum and host dramatically increased the incubation period. In human PrP 102L, 129M transgenic mice, short disease incubation periods were only observed with transmissions of prions from P102L patients, whereas classical CJD prions showed prolonged and variable incubation periods irrespective of the codon 129 genotype. Analysis of disease-related PrP (PrP(Sc)) showed marked alteration in the PrP(Sc) glycoform ratio propagated after transmission of classical CJD prions, consistent with the PrP point mutations directly influencing PrP(Sc) assembly. These data indicate that P102L or E200K mutations of human PrP have differing effects on prion propagation that depend upon prion strain type and can be significantly influenced by mismatch at the polymorphic residue 129.

Fig. 1.

Immunoblot analysis highlighting the PrP^Sc types propagated in brains of transgenic mice. Mice were inoculated with classical CJD and prions from patients with IPD P102L and E200K. (a) Immunoblots comparing transmission of IPD P102L prions and classical CJD to 102LL 129M Tg27 and Tg33 transgenic mice. (b) Immunoblots comparing transmission of human isolates from E200K-129MM, E200K-129VV and classical CJD to 200KK 129M Tg23 transgenic mice. (c) Immunoblots comparing transmission of IPD E200K-129MM, P200K-129VV and classical CJD prions to 200KK 129M Tg49 transgenic mice. (d) Immunoblots comparing transmission of vCJD prions to transgenic lines expressing human PrP. The provenance of each brain sample is designated above each lane. Immunoblots were analysed by enhanced chemiluminescence with anti-PrP antibody 3F4.

Fig. 2.

Neuropathological analysis of transgenic mouse brain by PrP immunohistochemistry. Anti-PrP monoclonal antibody ICSM 18 was used for the 102LL transgenic brains, and ICSM 35 was used for the 200KK transgenic brains because ICSM 35 does not detect mutant 102L PrP (Wadsworth et al., 2006). Upper panels (a–c and g–i) show regional distributions of PrP plaque deposition in 102LL 129M Tg27 and 200KK 129M Tg49 transgenic mice challenged with the various human prion inocula with the aetiologies indicated above each panel; synaptic type PrP deposits (pink), discrete PrP plaque deposits (red), blue box in the sketch denotes the area from which the PrP stained sections are derived. Panels (d), (e) and (f) represent PrP monoclonal antibody ICSM 18 immunohistochemical staining in 102LL 129M Tg27 transgenic mice challenged, respectively, with sporadic CJD, P102L and vCJD prions. Panels (j), (k) and (l) represent PrP monoclonal antibody ICSM 35 immunohistochemical staining in 200KK M129 Tg49 transgenic mice challenged, respectively, with IPD E200K-129MM, E200K-129VV and vCJD inocula. Inserts in panels (f) and (l) show examples of florid plaques associated with the neuropathology of vCJD prion transmissions in these mutant mice. Bar, panels (d)–(f) and (j)–(l)=200 μm.