Sporadic Jakob-Creutzfeldt disease (sCJD) and dementia with Lewy bodies (DLB) have overlapping clinical symptoms that can lead to their misdiagnosis. We delineated the clinical overlap between sCJD and DLB, and assessed the value of MRI to differentiate between them.
Medical records, MRI, EEG and CSF were reviewed from 56 sCJD and 30 DLB subjects.
46% of sCJD subjects met probable DLB criteria and 40% of DLB subjects met probable CJD criteria. A greater proportion of sCJD subjects had cerebellar signs (66% vs. 10%, p<0.001), myoclonus (64% vs. 30%, p=0.002), and visual symptoms (other than hallucinations) (61% vs. 7%, p<0.001), whereas more DLB subjects had hallucinations (70% vs. 39%, p=0.007) and fluctuations (57% vs. 23%, p=0.002). Cortical and/or basal ganglia MRI DWI hyperintensities consistent with sCJD were seen in 96% of sCJD subjects but in none with DLB. Logistic regression in sCJD revealed that those meeting probable DLB criteria were more likely to have occipital lobe involvement on MRI (OR 1.4, p=0.058, model p=0.022). Parietal lobe involvement on MRI was a predictor of “Other Focal Cortical signs” (OR 1.9, p=0.021) in sCJD. EEG and CSF assessments lacked sensitivity for sCJD as 48% of sCJD patients had a negative EEG and 67% of the 36 sCJD patents with a CSF evaluation, had a negative or inconclusive result. Too few DLB patients had EEG or CSF to assess their utility.
Sporadic CJD and DLB have significant symptom overlap. MRI helps differentiate these diseases and is related to the signs/symptoms observed in sCJD.
Creutzfeldt-Jakob disease; Lewy body disease; Lewy body dementia; diffusion-weighted imaging; DWI
Behavioral variant frontotemporal dementia (bvFTD) erodes complex social–emotional functions as the anterior cingulate cortex (ACC) and frontoinsula (FI) degenerate, but the early vulnerable neuron within these regions has remained uncertain. Previously, we demonstrated selective loss of ACC von Economo neurons (VENs) in bvFTD. Unlike ACC, FI contains a second conspicuous layer 5 neuronal morphotype, the fork cell, which has not been previously examined. Here, we investigated the selectivity, disease-specificity, laterality, timing, and symptom relevance of frontoinsular VEN and fork cell loss in bvFTD. Blinded, unbiased, systematic sampling was used to quantify bilateral FI VENs, fork cells, and neighboring neurons in 7 neurologically unaffected controls (NC), 5 patients with Alzheimer's disease (AD), and 9 patients with bvFTD, including 3 who died of comorbid motor neuron disease during very mild bvFTD. bvFTD showed selective FI VEN and fork cell loss compared with NC and AD, whereas in AD no significant VEN or fork cell loss was detected. Although VEN and fork cell losses in bvFTD were often asymmetric, no group-level hemispheric laterality effects were identified. Right-sided VEN and fork cell losses, however, correlated with each other and with anatomical, functional, and behavioral severity. This work identifies region-specific neuronal targets in early bvFTD.
Alzheimer's disease; behavioral variant frontotemporal dementia; fork cell; frontoinsula; von Economo neuron
Degeneration of nigrostriatal neurons in Parkinson's disease (PD) causes progressive loss of aromatic l-amino acid decarboxylase (AADC), the enzyme that converts levodopa (l-DOPA) into dopamine in the striatum. Because loss of this enzyme appears to be a major driver of progressive impairment of response to the mainstay drug, l-DOPA, one promising approach has been to use gene therapy to restore AADC activity in the human putamen and thereby restore normal l-DOPA response in patients with PD. An open-label phase I clinical trial of this approach in patients with PD provided encouraging signs of improvement in Unified Parkinson's Disease Rating Scale scores and reductions in antiparkinsonian medications. However, such improvement was modest compared with the results previously reported in parkinsonian rhesus macaques. The reason for this discrepancy may have been that the relatively small volume of vector infused in the clinical study restricted the distribution of AADC expression, such that only about 20% of the postcommissural putamen was covered, as revealed by l-[3-18F]-α-methyltyrosine-positron emission tomography. To achieve more quantitative distribution of vector, we have developed a visual guidance system for parenchymal infusion of AAV2. The purpose of the present study was to evaluate the combined magnetic resonance imaging-guided delivery system with AAV2-hAADC under conditions that approximate the intended clinical protocol. Our data indicate that this approach directed accurate cannula placement and effective vector distribution without inducing any untoward effects in nonhuman primates infused with a high dose of AAV2-hAADC.
San Sebastian and colleagues evaluate a magnetic resonance imaging-guided delivery system for CNS parenchymal infusion of adeno-associated viral type 2 (AAV2) vector encoding human aromatic l-amino acid decarboxylase (hAADC), a key enzyme lost during Parkinson's disease progression. This visual guidance approach directs accurate cannula placement and allows for effective distribution of a high AAV2-hAADC dose in nonhuman primates without any adverse effects.
Prion diseases are rare but invariably fatal neurodegenerative disorders. They are associated with spongiform encephalopathy, a histopathology characterized by the presence of large, membrane-bound vacuolar structures in the neuropil of the brain. While the primary cause is recognized as conversion of the normal form of prion protein (PrPC) to a conformationally distinct, pathogenic form (PrPSc), the cellular pathways and mechanisms that lead to spongiform change, neuronal dysfunction and death are not known. Mice lacking the Mahogunin Ring Finger 1 (MGRN1) E3 ubiquitin ligase develop spongiform encephalopathy by 9 months of age but do not become ill. In cell culture, PrP aberrantly present in the cytosol was reported to interact with and sequester MGRN1. This caused endo-lysosomal trafficking defects similar to those observed when Mgrn1 expression is knocked down, implicating disrupted MGRN1-dependent trafficking in the pathogenesis of prion disease. As these defects were rescued by over-expression of MGRN1, we investigated whether reduced or elevated Mgrn1 expression influences the onset, progression or pathology of disease in mice inoculated with PrPSc. No differences were observed, indicating that disruption of MGRN1-dependent pathways does not play a significant role in the pathogenesis of transmissible spongiform encephalopathy.
Scrapie of sheep and chronic wasting disease (CWD) of cervids are transmissible prion diseases. Milk and placenta have been identified as sources of scrapie prions but do not explain horizontal transmission. In contrast, CWD prions have been reported in saliva, urine and feces, which are thought to be responsible for horizontal transmission. While the titers of CWD prions have been measured in feces, levels in saliva or urine are unknown. Because sheep produce ∼17 L/day of saliva and scrapie prions are present in tongue and salivary glands of infected sheep, we asked if scrapie prions are shed in saliva. We inoculated transgenic (Tg) mice expressing ovine prion protein, Tg(OvPrP) mice, with saliva from seven Cheviot sheep with scrapie. Six of seven samples transmitted prions to Tg(OvPrP) mice with titers of −0.5 to 1.7 log ID50 U/ml. Similarly, inoculation of saliva samples from two mule deer with CWD transmitted prions to Tg(ElkPrP) mice with titers of −1.1 to −0.4 log ID50 U/ml. Assuming similar shedding kinetics for salivary prions as those for fecal prions of deer, we estimated the secreted salivary prion dose over a 10-mo period to be as high as 8.4 log ID50 units for sheep and 7.0 log ID50 units for deer. These estimates are similar to 7.9 log ID50 units of fecal CWD prions for deer. Because saliva is mostly swallowed, salivary prions may reinfect tissues of the gastrointestinal tract and contribute to fecal prion shedding. Salivary prions shed into the environment provide an additional mechanism for horizontal prion transmission.
scrapie; chronic wasting disease; saliva; horizontal transmission; titers
We report here the transmission of human prions to 18 new transgenic (Tg) mouse lines expressing 8 unique chimeric human/mouse prion proteins (PrP). Extracts from brains of two patients, who died of sporadic Creutzfeldt-Jakob disease (sCJD), contained either sCJD(MM1) or sCJD(VV2) prion strains and were used for inocula. Mice expressing chimeric PrP showed a direct correlation between expression level and incubation period for sCJD(MM1) prions irrespective of whether the transgene encoded methionine (M) or valine (V) at polymorphic residue 129. Tg mice expressing chimeric transgenes encoding V129 were unexpectedly resistant to infection with sCJD(VV2) prions, and when transmission did occur, it was accompanied by a change in strain type. The transmission of sCJD(MM1) prions was modulated by single amino acid reversions of each human PrP residue in the chimeric sequence. Reverting human residue 137 in the chimeric transgene from I to M prolonged the incubation time for sCJD(MM1) prions by more than 100 days; structural analyses suggest a profound change in the orientation of amino acid side chains with the I→M mutation. These findings argue that changing the surface charge in this region of PrP greatly altered the interaction between PrP isoforms during prion replication. Our studies contend that strain-specified replication of prions is modulated by PrP sequence-specific interactions between the prion precursor PrPC and the infectious product PrPSc.
Patients with corticobasal degeneration (CBD) pathology present with diverse clinical syndromes also associated with other neuropathologies, including corticobasal syndrome, progressive nonfluent aphasia, and an Alzheimer’s-type dementia. Some present with behavioral variant frontotemporal dementia (bvFTD), though this subtype still requires more detailed phenotypic characterization. All patients with CBD pathology and clinical assessment were reviewed (N=17) and selected if they initially met criteria for bvFTD [bvFTD(CBD): N=5]. Available bvFTD patients with Pick’s [bvFTD(Pick’s): N=5] were selected as controls. Patients were also compared to healthy older controls [N=53] on neuropsychological and neuroimaging measures. At initial presentation, bvFTD(CBD) showed few neuropsychological or motor differences from bvFTD(Pick’s). Neuropsychiatrically, they were predominantly apathetic with less florid social disinhibition and eating disturbances, and were more anxious than bvFTD(Pick’s) patients. Voxel-based morphometry revealed similar patterns of predominantly frontal atrophy between bvFTD groups, though overall degree of atrophy was less severe in bvFTD(CBD), who also showed comparative preservation of the frontoinsular rim, with dorsal > ventral frontal atrophy, and sparing of temporal and parietal structures relative to bvFTD(Pick’s) patients. Despite remarkable overlap between the two patient types, bvFTD patients with underlying CBD pathology show subtle clinical features that may distinguish them from patients with Pick’s disease neuropathology.
Corticobasal degeneration; frontotemporal dementia; behavior; neuropsychiatry; neuropsychology; neuropathology
The prion protein (PrP) is capable of folding into multiple self-replicating prion strains that produce phenotypically distinct neurological disorders. Although prion strains often breed true upon passage, they can also transform or “mutate” despite being devoid of nucleic acids. To dissect the mechanism of prion strain transformation, we studied the physicochemical evolution of a synthetic prion strain (MoSP1) after repeated passage in mice and cultured cells. We show that MoSP1 gradually adopted shorter incubation times and lower conformational stabilities. These changes were accompanied by a structural transformation as indicated by a shift in the molecular mass of the protease-resistant core of MoSP1 from approximately 19 kDa [MoSP1(2)] to 21 kDa [MoSP1(1)]. We show that MoSP1(1) and MoSP1(2) can breed with fidelity when cloned in cells, but when present as a mixture, MoSP1(1) preferentially proliferated, leading to the disappearance of MoSP1(2). In culture, the rate of this transformation process can be influenced by the nature of the culture media and the presence of polyamidoamines. Our findings demonstrate that prions can exist as a conformationally diverse population of strains, each capable of replicating with high fidelity. Rare conformational conversion, followed by competitive selection among the resulting pool of conformers, provides a mechanism for the adaptation of the prion population to their host environment.
To characterize cognitive and behavioral features, physical findings and brain atrophy patterns in pathology-proven corticobasal degeneration (CBD) and corticobasal syndrome (CBS) with known histopathology.
We reviewed clinical and MRI data in all patients evaluated at our center with either an autopsy diagnosis of CBD (n=18) or clinical CBS at first presentation with known histopathology (n=40). Atrophy patterns were compared using voxel-based morphometry.
CBD was associated with four clinical syndromes: progressive nonfluent aphasia (5), behavioral variant frontotemporal dementia (5), executive-motor (7), and posterior cortical atrophy (1). Behavioral or cognitive problems were the initial symptoms in 15/18 patients; less than half exhibited early motor findings. Compared to controls, CBD patients showed atrophy in dorsal prefrontal and peri-rolandic cortex, striatum and brainstem (p<0.001 uncorrected). The most common pathologic substrates for clinical CBS were CBD (35%), Alzheimer’s disease (AD, 23%), progressive supranuclear palsy (13%), and frontotemporal lobar degeneration (FTLD) with TDP inclusions (13%). CBS was associated with perirolandic atrophy irrespective of underlying pathology. In CBS due to FTLD (tau or TDP), atrophy extended into prefrontal cortex, striatum and brainstem, while in CBS due to AD, atrophy extended into temporoparietal cortex and precuneus (p<0.001 uncorrected).
Frontal lobe involvement is characteristic of CBD, and in many patients frontal, not parietal or basal ganglia symptoms, dominate early-stage disease. CBS is driven by medial peri-rolandic dysfunction, but this anatomy is not specific to one single underlying histopathology. Antemortem prediction of CBD will remain challenging until clinical features of CBD are redefined, and sensitive, specific biomarkers are identified.
The lipophilic cationic compound quinacrine has been used as an antimalarial drug for over 75 years but its pharmacokinetic profile is limited. Here, we report on the pharmacokinetic properties of quinacrine in mice. Following an oral dose of 40 mg/kg/day for 30 days, quinacrine concentration in the brain of wild-type mice was maintained at a concentration of ∼1 µM. As a substrate of the P-glycoprotein (P-gp) efflux transporter, quinacrine is actively exported from the brain, preventing its accumulation to levels that may show efficacy in some disease models. In the brains of P-gp–deficient Mdr10/0 mice, we found quinacrine reached concentrations of ∼80 µM without any signs of acute toxicity. Additionally, we examined the distribution and metabolism of quinacrine in the wild-type and Mdr10/0 brains. In wild-type mice, the co-administration of cyclosporin A, a known P-gp inhibitor, resulted in a 6-fold increase in the accumulation of quinacrine in the brain. Our findings argue that the inhibition of the P-gp efflux transporter should improve the poor pharmacokinetic properties of quinacrine in the CNS.
The first transmissions of human prion diseases to rodents used guinea pigs (Gps, Cavia porcellus). Later, transgenic (Tg) mice expressing human or chimeric human/mouse PrP replaced Gps, but the small size of the mouse limits some investigations. To investigate the fidelity of strain-specific prion transmission to Gps, we inoculated “type 1” and “type 2” prion strains into Gps: we measured the incubation times and determined the strain-specified size of the unglycosylated, protease-resistant (r) PrPSc fragment. Prions passaged once in Gps from cases of sporadic (s) Creutzfeldt–Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker (GSS) disease caused by the P102L mutation were used as well as human prions from a variant (v) CJD case, bovine prions from bovine spongiform encephalopathy (BSE), and mouse-passaged scrapie prions. Variant CJD and BSE prions transmitted to all the inoculated Gps with incubation times of 367 ± 4 d and 436 ± 28 d, respectively. On second passage in Gps, vCJD and BSE prions caused disease in 287 ± 4 d and 310 ± 4 d, while sCJD and GSS prions transmitted in 237 ± 4 d and 279 ± 19 d, respectively. Although hamster Sc237 prions transmitted to 2 of 3 Gps after 574 and 792 d, mouse-passaged RML and 301V prion strains, the latter derived from BSE prions, failed to transmit disease to Gps. Those Gps inoculated with vCJD or BSE prions exhibited “type 2” unglycosylated, rPrPSc (19 kDa) while those receiving sCJD or GSS prions displayed “type 1” prions (21 kDa), as determined by Western blotting. Such strain-specific properties were maintained in Gps as well as mice expressing a chimeric human/mouse transgene. Gps may prove particularly useful in further studies of novel human prions such as those causing vCJD.
BSE; vCJD; sCJD; GSS; prions; guinea pig
Frontotemporal dementia-amyotrophic lateral sclerosis (FTD-ALS) is a heritable form of FTD, but the gene(s) responsible for the majority of autosomal dominant FTD-ALS cases have yet to be found. Previous studies have identified a region on chromosome 9p that is associated with FTD and ALS.
The authors report the clinical, volumetric MRI, neuropathological and genetic features of a new chromosome 9p-linked FTD-ALS family, VSM-20.
Ten members of family VSM-20 displayed heterogeneous clinical phenotypes of isolated behavioural-variant FTD (bvFTD), ALS or a combination of the two. Parkinsonism was common, with one individual presenting with a corticobasal syndrome. Analysis of structural MRI scans from five affected family members revealed grey- and white-matter loss that was most prominent in the frontal lobes, with mild parietal and occipital lobe atrophy, but less temporal lobe atrophy than in 10 severity-matched sporadic bvFTD cases. Autopsy in three family members showed a consistent and unique subtype of FTLD-TDP pathology. Genome-wide linkage analysis conclusively linked family VSM-20 to a 28.3 cM region between D9S1808 and D9S251 on chromosome 9p, reducing the published minimal linked region to a 3.7 Mb interval. Genomic sequencing and expression analysis failed to identify mutations in the 10 known and predicted genes within this candidate region, suggesting that next-generation sequencing may be needed to determine the mutational mechanism associated with chromosome 9p-linked FTD-ALS.
Family VSM-20 significantly reduces the region linked to FTD-ALS on chromosome 9p. A distinct pattern of brain atrophy and neuropathological findings may help to identify other families with FTD-ALS caused by this genetic abnormality.
Mice deficient for the cellular prion protein (PrPC) do not develop prion disease; accordingly, gene-based strategies to diminish PrPC expression are of interest. We synthesized a series of chemically modified antisense oligonucleotides (ASOs) targeted against mouse Prnp messenger RNA (mRNA) and identified those that were most effective in decreasing PrPC expression. Those ASOs were also evaluated in scrapie-infected cultured cells (ScN2a) for their efficacy in diminishing the levels of the disease-causing prion protein (PrPSc). When the optimal ASO was infused intracerebrally into FVB mice over a 14-day period beginning 1 day after infection with the Rocky Mountain Laboratory (RML) strain of mouse prions, a prolongation of the incubation period of almost 2 months was observed. Whether ASOs can be used to develop an effective therapy for patients dying of Creutzfeldt–Jakob disease remains to be established.
Human prion diseases can be caused by mutations in the prion protein gene PRNP. Prion disease with mutations at codon 188 has been reported in 6 cases, but only 1 had the T188R mutation and it was not pathologically confirmed. We report the clinical, neuropsychological, imaging, genetic, and neuropathological features of a patient with familial Creutzfeldt-Jakob Disease (CJD), associated with a very rare PRNP mutation at T188R. The patient presented with prominent behavioral changes in addition to the more typical cognitive and motor impairments seen in sporadic CJD. The autopsy confirmed prion disease pathology. This case supports the pathogenicity of the T188 PRNP mutation, demonstrates the variability of clinical phenotypes associated with certain mutations and emphasizes the importance of testing for genetic prion disease in cases of apparently sporadic atypical dementia.
Codon 188; Creutzfeldt-Jakob disease; Dementia; Genetic; Prion
During prion infections of the central nervous system (CNS) the cellular prion protein, PrPC, is templated to a conformationally distinct form, PrPSc. Recent studies have demonstrated that the Sprn gene encodes a GPI-linked glycoprotein Shadoo (Sho), which localizes to a similar membrane environment as PrPC and is reduced in the brains of rodents with terminal prion disease. Here, analyses of prion-infected mice revealed that down-regulation of Sho protein was not related to Sprn mRNA abundance at any stage in prion infection. Down-regulation was robust upon propagation of a variety of prion strains in Prnpa and Prnpb mice, with the exception of the mouse-adapted BSE strain 301 V. In addition, Sho encoded by a TgSprn transgene was down-regulated to the same extent as endogenous Sho. Reduced Sho levels were not seen in a tauopathy, in chemically induced spongiform degeneration or in transgenic mice expressing the extracellular ADan amyloid peptide of familial Danish dementia. Insofar as prion-infected Prnp hemizygous mice exhibited accumulation of PrPSc and down-regulation of Sho hundreds of days prior to onset of neurologic symptoms, Sho depletion can be excluded as an important trigger for clinical disease or as a simple consequence of neuronal damage. These studies instead define a disease-specific effect, and we hypothesize that membrane-associated Sho comprises a bystander substrate for processes degrading PrPSc. Thus, while protease-resistant PrP detected by in vitro digestion allows post mortem diagnosis, decreased levels of endogenous Sho may trace an early response to PrPSc accumulation that operates in the CNS in vivo. This cellular response may offer new insights into the homeostatic mechanisms involved in detection and clearance of the misfolded proteins that drive prion disease pathogenesis.
In prion infections of the nervous system the cellular prion protein, PrPC, changes to a distinct form, PrPSc. Recent studies have demonstrated that another glycoprotein Shadoo (Sho), which occupies a similar membrane environment as PrPC, is reduced in the brains of rodents with terminal prion disease. Our analyses of prion-infected mice revealed that reduction of Sho protein was not due to reductions in the corresponding messenger RNA. Reduction in Sho was clearly evident upon propagation of a variety of prion strains, but was not seen in mice with other types of neurodegenerative disease. Also, as prion-infected mice with only one copy of the PrP gene exhibited both accumulation of PrPSc and a reduction of Sho protein hundreds of days prior to onset of neurologic symptoms, the drop in Sho protein level can be excluded as an important trigger for clinical disease, or a non-specific consequence of brain cell damage. Instead, our studies define a effect restricted to prion disease and we hypothesize that Sho protein is a “bystander” for degradative processes aimed at destroying PrPSc.
The central event in prion diseases is the conformational conversion of the cellular prion protein (PrPC) into PrPSc, a partially protease-resistant and infectious conformer. However, the mechanism by which PrPSc causes neuronal dysfunction remains poorly understood. Levels of Shadoo (Sho), a protein that resembles the flexibly disordered N-terminal domain of PrPC, were found to be reduced in the brains of mice infected with the RML strain of prions , implying that Sho levels may reflect the presence of PrPSc in the brain. To test this hypothesis, we examined levels of Sho during prion infection using a variety of experimental systems. Sho protein levels were decreased in the brains of mice, hamsters, voles, and sheep infected with different natural and experimental prion strains. Furthermore, Sho levels were decreased in the brains of prion-infected, transgenic mice overexpressing Sho and in infected neuroblastoma cells. Time-course experiments revealed that Sho levels were inversely proportional to levels of protease-resistant PrPSc. Membrane anchoring and the N-terminal domain of PrP both influenced the inverse relationship between Sho and PrPSc. Although increased Sho levels had no discernible effect on prion replication in mice, we conclude that Sho is the first non-PrP marker specific for prion disease. Additional studies using this paradigm may provide insight into the cellular pathways and systems subverted by PrPSc during prion disease.
Shadoo is a protein that resembles the prion protein, which causes prion diseases such as Creutzfeldt-Jakob disease in humans and “mad cow” disease. In this paper, we demonstrate that during prion disease in animals, levels of Shadoo were reduced in the brain and correlated with levels of infectious prions. This phenomenon occurred following infection with 14 different prion strains but was not observed following the accumulation of other aggregated proteins, including those that cause Alzheimer's disease and Parkinson's disease. Thus, Shadoo levels in the brain are a specific indicator of prion disease status, and it may be possible to exploit this observation for diagnostic purposes. Although we show that Shadoo itself is unlikely to influence prion disease, using Shadoo as a tool to probe the biology of prions may be a useful strategy for deciphering how prions damage the brain.
Infectious prion diseases 1 – scrapie of sheep 2 and chronic wasting disease (CWD) of several species in the deer family 3,4 – are transmitted naturally within affected host populations. Although several possible sources of contagion have been identified in excretions and secretions from symptomatic animals 5–8, the biological importance of these sources in sustaining epidemics remains unclear. Here we show that asymptomatic CWD-infected mule deer (Odocoileus hemionus) excrete CWD prions in their feces long before they develop clinical signs of prion disease. Intracerebral (i.c.) inoculation of irradiated deer feces into transgenic (Tg) mice overexpressing cervid PrP revealed infectivity in 14 of 15 fecal samples collected from 5 deer at 7–11 months before the onset of neurological disease. Although prion concentrations in deer feces were considerably lower than in brain tissue from the same deer collected at the disease terminus, the estimated total infectious dose excreted in feces by an infected deer over the disease course may approximate the total contained in brain tissue. Prolonged fecal prion excretion by infected deer provides a plausible natural mechanism that might explain the high incidence and efficient horizontal transmission of CWD within deer herds 3,4,9, as well as prion transmission between susceptible deer species.
Transgenic (Tg) mice expressing chimeras of mouse and human prion proteins (PrP) have shorter incubation periods for Creutzfeldt-Jakob disease (CJD) prions than mice expressing full-length human PrP. Increasing the sequence similarity of the chimeric PrP to mouse PrP, by reverting human residues to mouse, resulted in a Tg line, denoted Tg22372, which was susceptible to sporadic (s) CJD prions in ~110 days 1. Reversion of one additional residue (M111V) resulted in a new Tg line, termed Tg1014, susceptible to sCJD prions in ~75 days. Tg1014 mice also has shorter incubation periods for variant (v) CJD prions, providing a more tractable model for studying this prion strain. Transmission of vCJD prions to Tg1014 mice resulted in two different strains, determined by neuropathology and biochemical analysis, which correlated with the length of the incubation time. One strain had the biochemical, neuropathological, and transmission characteristics including longer incubation times of the inoculated vCJD strain; the second strain produced a phenotype resembling that of sCJD prions including relatively shorter incubation periods. Mice with intermediate incubation periods for vCJD prions had a mixture of the two strains. Both strains were serially transmitted in Tg1014 mice, which led to further reduction in incubation periods. Conversion of vCJD-like to sCJD-like strains was favored in Tg1014 mice more than in the Tg22372 line. The single amino acid difference therefore appears to offer selective pressure for propagation of the sCJD-like strain. These two Tg mouse lines provide relatively rapid models to study human prion diseases as well as the evolution of human prion strains.
Prion diseases are fatal, neurodegenerative illnesses caused by the accumulation of PrPSc, an aberrantly folded isoform of the normal, cellular prion protein (PrPC). Detection of PrPSc commonly relies on immunochemical methods, a strategy hampered by the lack of antibodies specific for this disease-causing isoform. Here, we report the generation of 8 mAbs against PrP following immunization of Prnp-null mice with recombinant (rec) PrP. The 8 mAbs exhibited distinct differential binding to PrPC and PrPSc from different species as well as PrP-derived synthetic peptides. Five of the 8 mAbs exhibited binding discontinuous PrP epitopes, all of which were disrupted by addition of β-mercaptoethanol or dithiothreitol, which reduced the single disulfide bond found in PrP. One mAb F20-29 reacted only with human PrP while the F4- 31 mAb bound bovine PrP; the KD values for both mAbs F4-31 and F20-29 were ~500 pM. Binding of all five conformation-dependent mAbs to PrP was inhibited by β-mercaptoethanol in ELISA, Western blots and histoblots. One conformation-dependent mAb F4-31 was found to increase the sensitivity of an ELISA-based test by nearly 500-fold when it was used as the capture antibody. These new conformation-dependent mAbs were found be particularly useful in histoblotting studies, in which the low backgrounds after treatment with β-mercaptoethanol created unusually high signal-to-noise ratios.
Prion; monoclonal antibody; histoblot; bovine spongiform encephalopathy; conformation-dependent antibody; disulfide reduction
Sporadic corticobasal syndrome (CBS) has been associated with diverse pathological substrates, but frontotemporal lobar degeneration with TDP-43 immunoreactive inclusions (FTLD-TDP) has only been linked to CBS among progranulin mutation carriers. We report the clinical, neuropsychological, imaging, genetic, and neuropathological features of GS, a patient with sporadic corticobasal syndrome. Genetic testing revealed no mutations in the microtubule associated protein tau (MAPT) or progranulin (PGRN) genes, but GS proved homozygous for the T allele of the rs5848 PGRN variant. Autopsy showed ubiquitin and TDP-43 pathology most similar to a pattern previously associated with PGRN mutation carriers. These findings confirm that FTLD-TDP should be included in the pathological differential diagnosis for sporadic CBS.
corticobasal degeneration; TDP-43; frontotemporal lobar degeneration; progranulin
The objective of the study is to report 2 new genotypic forms of protease-sensitive prionopathy (PSPr), a novel prion disease described in 2008, in 11 subjects all homozygous for valine at codon 129 of the prion protein (PrP) gene (129VV). The 2 new PSPr forms affect individuals who are either homozygous for methionine (129MM) or heterozygous for methionine/valine (129MV).
Fifteen affected subjects with 129MM, 129MV, and 129VV underwent comparative evaluation at the National Prion Disease Pathology Surveillance Center for clinical, histopathologic, immunohistochemical, genotypical, and PrP characteristics.
Disease duration (between 22 and 45 months) was significantly different in the 129VV and 129MV subjects. Most other phenotypic features along with the PrP electrophoretic profile were similar but distinguishable in the 3 129 genotypes. A major difference laid in the sensitivity to protease digestion of the disease-associated PrP, which was high in 129VV but much lower, or altogether lacking, in 129MV and 129MM. This difference prompted the substitution of the original designation with “variably protease-sensitive prionopathy” (VPSPr). None of the subjects had mutations in the PrP gene coding region.
Because all 3 129 genotypes are involved, and are associated with distinguishable phenotypes, VPSPr becomes the second sporadic prion protein disease with this feature after Creutzfeldt-Jakob disease, originally reported in 1920. However, the characteristics of the abnormal prion protein suggest that VPSPr is different from typical prion diseases, and perhaps more akin to subtypes of Gerstmann-Sträussler-Scheinker disease.
Chronic wasting disease (CWD) is a transmissible, fatal prion disease of cervids and is largely confined to North America. The origin of CWD continues to pose a conundrum: does the disease arise spontaneously or result from some other naturally occurring reservoir? To address whether prions from sheep might be able to cause disease in cervids, we inoculated mice expressing the elk prion protein (PrP) transgene with two scrapie prion isolates. The SSBP/1 scrapie isolate transmitted disease to Tg(ElkPrP) mice with a median incubation time of ~270 days but a second isolate failed to produce neurologic dysfunction in these mice. Although prions from cattle with bovine spongiform encephalopathy (BSE) did not transmit to the Tg(ElkPrP) mice, they did transmit after being passaged through sheep. In Tg(ElkPrP) mice, the sheep-passaged BSE prions exhibited an incubation time of ~300 days. SSBP/1 prions produced abundant deposits of the disease-causing PrP isoform, denoted PrPSc, in the cerebellum and pons of Tg(ElkPrP) mice while PrPSc accumulation in Tg mice inoculated with sheep-passaged BSE prions was confined to the deep cerebellar nuclei, habenula and the brainstem. The susceptibility of “cervidized” mice to “ovinized” prions raises the question about why CWD has not been reported in other parts of the world where cervids and scrapie-infected sheep coexist.
Chronic wasting disease (CWD) is a transmissible, fatal prion disease of cervids and is largely confined to North America. The origin of CWD continues to pose a conundrum: does the disease arise spontaneously or result from some other naturally occurring reservoir? To address whether prions from sheep might be able to cause disease in cervids, we inoculated mice expressing the elk prion protein (PrP) transgene [Tg(ElkPrP) mice] with two scrapie prion isolates. The SSBP/1 scrapie isolate transmitted disease to Tg(ElkPrP) mice with a median incubation time of 270 days, but a second isolate failed to produce neurological dysfunction in these mice. Although prions from cattle with bovine spongiform encephalopathy (BSE) did not transmit to the Tg(ElkPrP) mice, they did transmit after being passaged through sheep. In Tg(ElkPrP) mice, the sheep-passaged BSE prions exhibited an incubation time of approximately 300 days. SSBP/1 prions produced abundant deposits of the disease-causing PrP isoform, denoted PrPSc, in the cerebellum and pons of Tg(ElkPrP) mice, whereas PrPSc accumulation in Tg mice inoculated with sheep-passaged BSE prions was confined to the deep cerebellar nuclei, habenula and the brainstem. The susceptibility of ‘cervidized’ mice to ‘ovinized’ prions raises the question about why CWD has not been reported in other parts of the world where cervids and scrapie-infected sheep coexist.
Seizures are relatively common in Alzheimer disease (AD) and other neurodegenerative disorders. To our knowledge, however, there have been no reports of seizures associated with corticobasal degeneration (CBD). We describe a patient with brain biopsy features suggestive of CBD whose course was complicated by complex partial seizures with secondary generalization. Thus, the occurrence of seizures in a patient with dementia should not exclude the diagnosis of CBD.
Gerstmann-Sträussler-Scheinker syndrome (GSS) is a genetic prion disease typified clinically by the development of progressive ataxia and dementia, and histopathologically by the presence of prion protein (PrP) amyloid plaques in the CNS, especially within the cerebellum. Several mutations of the PrP gene (PRNP) are associated with GSS, but only the P102L mutation has been convincingly modeled in transgenic (Tg) mice. To determine if other mutations carry specific GSS phenotypic information, we constructed Tg mice that express PrP carrying the mouse homolog of the GSS-associated A117V mutation. Tg(A116V) mice express ~6 times the endogenous levels of PrP, develop progressive ataxia by ~140 days, and death by ~170 days. Compared with a mouse model of transmissible Creutzfeldt-Jakob disease (CJD), the ataxia of Tg(A116V) mice is more prominent, and the course of disease is more protracted, paralleling that observed in human disease. Neuropathology includes mild scattered vacuolation and prominent, mainly cerebellar localized, thioflavin S positive PrP plaques comprised of full length PrPA116V. In some mice, more prominent vacuolation or a non-cerebellar distribution of PrP plaques was evident, suggesting some variability in phenotype. The biophysical properties of PrP from Tg(A116V) mice and human GSS(A117V) revealed a similarly low fraction of insoluble PrP and a weakly protease-resistant ~13 kDa mid-span PrP fragment, not observed in CJD. Overall, Tg(A116V) mice recapitulate many clinicopathologic features of GSS(A117V) that are distinct from CJD, supporting PrPA116V to carry specific phenotypic information. The occasional variation in histopathology they exhibit may shed light on a similar observation in human GSS(A117V).
prion; GSS; PrP; A117V; transgenic mouse; transmissible spongiform encephalopathy