A novel PRNP-P105S mutation associated with atypical prion disease and a rare PrPSc conformation

Anle138b prevents PrP plaque accumulation in Tg(PrP-A116V) mice but does not mitigate clinical disease

Anle138b is an anti-aggregating compound previously shown to delay the onset of scrapie, a transmissible prion disease, although its in vivo efficacy against other prion disease subtypes has not been fully assessed. TgGSS mice that model Gerstmann-Sträussler-Scheinker disease (GSS) via expression of mouse PrP^A116V accumulate PrP amyloid plaques in their brains and develop progressive ataxia leading to death in ~160 days. When allowed to feed on food pellets containing anle138b from weaning until death, the brains of TgGSS mice displayed significant reductions in PrP plaque burden, insoluble PrP, and proteinase K-resistant PrP^Sc at end stage, compared with TgGSS mice allowed to feed on placebo food pellets. Despite these effects on biological markers of disease, there was no difference in the onset of symptoms or the age at death between the two treatment groups. In contrast, scrapie-inoculated wild-type mice treated with anle138b survived nearly twice as long (254 days) as scrapie-inoculated mice fed placebo (~136 days). They also displayed greater reductions in insoluble and PK-resistant PrP^Sc than TgGSS mice. Although these results support an anti-aggregating effect of anle138b, the discordance in clinical efficacy noted between the two prion disease models tested underscores the pathophysiological differences between them and highlights the need to consider differences in susceptibilities among prion subtypes when assessing potential therapies for prion diseases.

Clinical and neuropathological phenotype associated with the novel V189I mutation in the prion protein gene

Prion diseases are neurodegenerative disorders which are caused by an accumulation of the abnormal, misfolded prion protein known as scrapie prion protein (PrPSc). These disorders are unique as they occur as sporadic, genetic and acquired forms. Sporadic Creutzfeldt-Jakob Disease (CJD) is the most common human prion disease, accounting for approximately 85-90% of cases, whereas autosomal dominant genetic forms, due to mutations in the prion protein gene (PRNP), account for 10-15% of cases. Genetic forms show a striking variability in their clinical and neuropathological picture and can sometimes mimic other neurodegenerative diseases.We report a novel PRNP mutation (V189I) in four CJD patients from three unrelated pedigrees. In three patients, the clinical features were typical for CJD and the diagnosis was pathologically confirmed, while the fourth patient presented with a complex phenotype including rapidly progressive dementia, behavioral abnormalities, ataxia and extrapyramidal features, and the diagnosis was probable CJD by current criteria, on the basis of PrPSc detection in CSF by Real Time Quaking-Induced Conversion assay. In all the three patients with autopsy findings, the neuropathological analysis revealed diffuse synaptic type deposition of proteinase K-resistant prion protein (PrPres), and type 1 PrPres was identified in the brain by western blot analysis. So, the histopathological and biochemical profile associated with the V189I mutation was indistinguishable from the MM1/MV1 subtype of sporadic CJD.Our findings support a pathogenic role for the V189I PRNP variant, confirm the heterogeneity of the clinical phenotypes associated to PRNP mutations and highlight the importance of PrPSc detection assays as diagnostic tools to unveil prion diseases presenting with atypical phenotypes.

Impaired transmissibility of atypical prions from genetic CJDG114V

OBJECTIVE

To describe the clinicopathologic, molecular, and transmissible characteristics of genetic prion disease in a young man carrying the PRNP-G114V variant.

METHODS

We performed genetic, histologic, and molecular studies, combined with in vivo transmission studies and in vitro replication studies, to characterize this genetic prion disease.

RESULTS

A 24-year-old American man of Polish descent developed progressive dementia, aphasia, and ataxia, leading to his death 5 years later. Histologic features included widespread spongiform degeneration, gliosis, and infrequent PrP plaque-like deposits within the cerebellum and putamen, best classifying this as a Creutzfeldt-Jakob disease (CJD) subtype. Molecular typing of proteinase K-resistant PrP (resPrPSc) revealed a mixture of type 1 (∼21 kDa) and type 2 (∼19 kDa) conformations with only 2, rather than the usual 3, PrPSc glycoforms. Brain homogenates from the proband failed to transmit prion disease to transgenic Tg(HuPrP) mice that overexpress human PrP and are typically susceptible to sporadic and genetic forms of CJD. When subjected to protein misfolding cyclic amplification, the PrPSc type 2 (∼19 kDa) was selectively amplified.

CONCLUSIONS

The features of genetic CJDG114V suggest that residue 114 within the highly conserved palindromic region (113-AGAAAAGA-120) plays an important role in prion conformation and propagation.

Genetic PrP Prion Diseases

Genetic prion diseases (gPrDs) caused by mutations in the prion protein gene (PRNP) have been classified as genetic Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker disease, or fatal familial insomnia. Mutations in PRNP can be missense, nonsense, and/or octapeptide repeat insertions or, possibly, deletions. These mutations can produce diverse clinical features. They may also show varying ancillary testing results and neuropathological findings. Although the majority of gPrDs have a rapid progression with a short survival time of a few months, many also present as ataxic or parkinsonian disorders, which have a slower decline over a few to several years. A few very rare mutations manifest as neuropsychiatric disorders, with systemic symptoms that include gastrointestinal disorders and neuropathy; these forms can progress over years to decades. In this review, we classify gPrDs as rapid, slow, or mixed types based on their typical rate of progression and duration, and we review the broad spectrum of phenotypes manifested by these diseases.

Genetic PrP Prion Diseases

Genetic prion diseases (gPrDs) caused by mutations in the prion protein gene (PRNP) have been classified as genetic Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker disease, or fatal familial insomnia. Mutations in PRNP can be missense, nonsense, and/or octapeptide repeat insertions or, possibly, deletions. These mutations can produce diverse clinical features. They may also show varying ancillary testing results and neuropathological findings. Although the majority of gPrDs have a rapid progression with a short survival time of a few months, many also present as ataxic or parkinsonian disorders, which have a slower decline over a few to several years. A few very rare mutations manifest as neuropsychiatric disorders, with systemic symptoms that include gastrointestinal disorders and neuropathy; these forms can progress over years to decades. In this review, we classify gPrDs as rapid, slow, or mixed types based on their typical rate of progression and duration, and we review the broad spectrum of phenotypes manifested by these diseases.

Dominantly inherited prion protein cerebral amyloidoses - a modern view of Gerstmann-Sträussler-Scheinker

Among genetically determined neurodegenerative diseases, the dominantly inherited prion protein cerebral amyloidoses are characterized by deposition of amyloid in cerebral parenchyma or blood vessels. Among them, Gerstmann-Sträussler-Scheinker disease has been the first to be described. Their clinical, neuropathologic, and molecular phenotypes are distinct from those observed in Creutzfeldt-Jakob disease (CJD) and related spongiform encephalopathies. It is not understood why specific mutations in the prion protein gene (PRNP) cause cerebral amyloidosis and others cause CJD. A significant neurobiologic event in these amyloidoses is the frequent coexistence of prion amyloid with tau neurofibrillary pathology, a phenomenon suggesting that similar pathogenetic mechanisms may be shared among different diseases in the sequence of events occurring in the cascade from amyloid formation to tau aggregation. This chapter describes the clinical, neuropathologic, and biochemical phenotypes associated with each of the PRNP mutations causing an inherited cerebral amyloidosis and emphasizes the variability of phenotypes.

Genetic prion disease: Experience of a rapidly progressive dementia center in the United States and a review of the literature

Although prion diseases are generally thought to present as rapidly progressive dementias with survival of only a few months, the phenotypic spectrum for genetic prion diseases (gPrDs) is much broader. The majority have a rapid decline with short survival, but many patients with gPrDs present as slowly progressive ataxic or parkinsonian disorders with progression over a few to several years. A few very rare mutations even present as neuropsychiatric disorders, sometimes with systemic symptoms such as gastrointestinal disorders and neuropathy, progressing over years to decades. gPrDs are caused by mutations in the prion protein gene (PRNP), and have been historically classified based on their clinicopathological features as genetic Jakob-Creutzfeldt disease (gJCD), Gerstmann-Sträussler-Scheinker (GSS), or Fatal Familial Insomnia (FFI). Mutations in PRNP can be missense, nonsense, and octapeptide repeat insertions or a deletion, and present with diverse clinical features, sensitivities of ancillary testing, and neuropathological findings. We present the UCSF gPrD cohort, including 129 symptomatic patients referred to and/or seen at UCSF between 2001 and 2016, and compare the clinical features of the gPrDs from 22 mutations identified in our cohort with data from the literature, as well as perform a literature review on most other mutations not represented in our cohort. E200K is the most common mutation worldwide, is associated with gJCD, and was the most common in the UCSF cohort. Among the GSS-associated mutations, P102L is the most commonly reported and was also the most common at UCSF. We also had several octapeptide repeat insertions (OPRI), a rare nonsense mutation (Q160X), and three novel mutations (K194E, E200G, and A224V) in our UCSF cohort. © 2016 Wiley Periodicals, Inc.

Quantifying prion disease penetrance using large population control cohorts

More than 100,000 genetic variants are reported to cause Mendelian disease in humans, but the penetrance-the probability that a carrier of the purported disease-causing genotype will indeed develop the disease-is generally unknown. We assess the impact of variants in the prion protein gene (PRNP) on the risk of prion disease by analyzing 16,025 prion disease cases, 60,706 population control exomes, and 531,575 individuals genotyped by 23andMe Inc. We show that missense variants in PRNP previously reported to be pathogenic are at least 30 times more common in the population than expected on the basis of genetic prion disease prevalence. Although some of this excess can be attributed to benign variants falsely assigned as pathogenic, other variants have genuine effects on disease susceptibility but confer lifetime risks ranging from <0.1 to ~100%. We also show that truncating variants in PRNP have position-dependent effects, with true loss-of-function alleles found in healthy older individuals, a finding that supports the safety of therapeutic suppression of prion protein expression.

Hereditary Human Prion Diseases: an Update

Prion diseases in humans are neurodegenerative diseases which are caused by an accumulation of abnormal, misfolded cellular prion protein known as scrapie prion protein (PrP^Sc). Genetic, acquired, or spontaneous (sporadic) forms are known. Pathogenic mutations in the human prion protein gene (PRNP) have been identified in 10-15 % of CJD patients. These mutations may be single point mutations, STOP codon mutations, or insertions or deletions of octa-peptide repeats. Some non-coding mutations and new mutations in the PrP gene have been identified without clear evidence for their pathogenic significance. In the present review, we provide an updated overview of PRNP mutations, which have been documented in the literature until now, describe the change in the DNA, the family history, the pathogenicity, and the number of described cases, which has not been published in this complexity before. We also provide a description of each genetic prion disease type, present characteristic histopathological features, and the PrP^Sc isoform expression pattern of various familial/genetic prion diseases.

Atypical parkinsonism caused by Pro105Leu mutation of prion protein: A broad clinical spectrum

Objective:

To delineate molecular and clinical characteristics of 3 families with PRNP P105L mutation, a variant of Gerstmann-Sträussler-Scheinker syndrome whose main motor symptoms were parkinsonism and/or involuntary movements.

Methods:

The causative mutation was first determined in the affected patients of family 1 using whole-exome sequencing, and then mutational analysis was extended to families 2 and 3. The clinical features of the patients of these 3 families were summarized. Haplotype analysis was performed using high-density single nucleotide polymorphism array.

Results:

The whole-exome sequencing revealed that the heterozygous mutation c.314C>T (p.P105L) in PRNP was the only known pathogenic mutation shared by the 3 patients of the family with autosomal dominant parkinsonism. We further identified the same mutation in patients of the other 2 families with autosomal dominant parkinsonism and/or involuntary movements. The clinical features of our patients with PRNP P105L mutation included various motor symptoms such as parkinsonism and involuntary movements in addition to progressive dementia. The clinical features in part overlapped with those of other forms of inherited prion diseases, such as fatal familial insomnia and Huntington disease-like type 1. The patients with PRNP P105L mutation shared a haplotype spanning 7.1 Mb around PRNP, raising the possibility that the mutations in the patients originated from a common founder.

Conclusion:

Most of the patients presented with parkinsonism in addition to progressive dementia. Although spastic paraparesis has been emphasized as the main clinical feature, the clinical spectrum of patients with PRNP P105L is broader than expected.

The pathogenesis of soluble PrP fragments containing Aβ binding sites

Prion protein (PrP) has proven to bind amyloid beta (Aβ) oligomers with high affinity, changing our understanding of both prion diseases (PD) and Alzheimer's disease (AD) at the molecular and phenotypic levels, although the latter currently lacks sufficient attentions. Transgenic mice expressing anchorless PrP developed unusual diseases reminiscent of AD with tremendous amyloid plaque formation. In this review, we described two interesting observations at the phenotypic level. First, common pathogenic mutations of the PRNP gene in Gerstmann-Sträussler-Scheinker (GSS) syndrome were clustered at PrP95-105. Meanwhile, all nonsense PRNP mutations that generated soluble PrP 95-105 exhibited phenotypes with abundant amyloid formations. We speculate that PrP-Aβ oligomers binding might be the underlying mechanism of the predominant amyloid phenotypes. Second, soluble PrP-Aβ oligomer complexes might exist in the extracellular space at the beginning of both PD and AD and subserve an initial neuroprotective function. Thus, the diseases would only present after long-term accumulation. This might be the central common pathogenic event of both PD and AD.

Prion Protein Prolines 102 and 105 and the Surrounding Lysine Cluster Impede Amyloid Formation

Human prion diseases can have acquired, sporadic, or genetic origins, each of which results in the conversion of prion protein (PrP) to transmissible, pathological forms. The genetic prion disease Gerstmann-Straussler-Scheinker syndrome can arise from point mutations of prolines 102 or 105. However, the structural effects of these two prolines, and mutations thereof, on PrP misfolding are not well understood. Here, we provide evidence that individual mutations of Pro-102 or Pro-105 to noncyclic aliphatic residues such as the Gerstmann-Straussler-Scheinker-linked leucines can promote the in vitro formation of PrP amyloid with extended protease-resistant cores reminiscent of infectious prions. This effect was enhanced by additional charge-neutralizing mutations of four nearby lysine residues comprising the so-called central lysine cluster. Substitution of these proline and lysine residues accelerated PrP conversion such that spontaneous amyloid formation was no longer slower than scrapie-seeded amyloid formation. Thus, Pro-102 and Pro-105, as well as the lysines in the central lysine cluster, impede amyloid formation by PrP, implicating these residues as key structural modulators in the conversion of PrP to disease-associated types of amyloid.

Genetic studies in human prion diseases

Human prion diseases are fatal neurodegenerative disorders that are characterized by spongiform changes, astrogliosis, and the accumulation of an abnormal prion protein (PrP(Sc)). Approximately 10%-15% of human prion diseases are familial variants that are caused by pathogenic mutations in the prion protein gene (PRNP). Point mutations or the insertions of one or more copies of a 24 bp repeat are associated with familial human prion diseases including familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome, and fatal familial insomnia. These mutations vary significantly in frequency between countries. Here, we compare the frequency of PRNP mutations between European countries and East Asians. Associations between single nucleotide polymorphisms (SNPs) of several candidate genes including PRNP and CJD have been reported. The SNP of PRNP at codon 129 has been shown to be associated with sporadic, iatrogenic, and variant CJD. The SNPs of several genes other than PRNP have been showed contradictory results. Case-control studies and genome-wide association studies have also been performed to identify candidate genes correlated with variant and/or sporadic CJD. This review provides a general overview of the genetic mutations and polymorphisms that have been analyzed in association with human prion diseases to date.

Report about four novel mutations in the prion protein gene

BACKGROUND/AIMS

Since detection of the prion protein gene (PRNP) more than 30 mutations have been discovered. Some have only been found in single case reports without known intrafamilial accumulation or neuropathological proof so that the causal connection between mutation and disease could not be proved. Those patients often present atypical clinical phenotypes, and it is not unusual that they are classified as diseases other than Creutzfeldt-Jakob disease (CJD).

METHODS

Cases of suspected CJD have been reported to the national reference center for prion diseases. Clinical and diagnostic data were collected, and a classification of definite, possible or probable prion disease was made. Molecular analysis of PRNP was performed by capillary sequencing.

RESULTS

We have described 4 cases with atypical clinical and diagnostic findings and unknown mutations in PRNP so far.

CONCLUSION

Three patients fulfilled the criteria of probable CJD, and 1 patient fulfilled the criteria of possible CJD but the clinical picture in none of the patients was typical CJD; hence, it remained questionable whether the mutations were causal of the disease.

The prion diseases

The prion diseases are a family of rare neurodegenerative disorders that result from the accumulation of a misfolded isoform of the prion protein (PrP), a normal constituent of the neuronal membrane. Five subtypes constitute the known human prion diseases; kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal insomnia (FI), and variant CJD (vCJD). These subtypes are distinguished, in part, by their clinical phenotype, but primarily by their associated brain histopathology. Evidence suggests these phenotypes are defined by differences in the pathogenic conformation of misfolded PrP. Although the vast majority of cases are sporadic, 10% to 15% result from an autosomal dominant mutation of the PrP gene (PRNP). General phenotype-genotype correlations can be made for the major subtypes of CJD, GSS, and FI. This paper will review some of the general background related to prion biology and detail the clinical and pathologic features of the major prion diseases, with a particular focus on the genetic aspects that result in prion disease or modification of its risk or phenotype.

Atypical prion protein conformation in familial prion disease with PRNP P105T mutation

Protease-resistant prion protein (PrP(Sc) ) is diagnostic of prion disease, yet its detection is frequently difficult. Here, we describe a patient with a PRNP P105T mutation and typical familial prion disease. Brain PrP(Sc) was undetectable by conventional Western blotting and barely detectable after phosphotungstate precipitation, where it displayed an atypical pattern suggestive of noncanonical conformation. Therefore, we used a novel misfolded protein assay (MPA) that detects PrP aggregates independently of their protease resistance. The MPA revealed the presence of aggregated PrP in similar amounts as in typical sporadic Creutzfeldt-Jakob disease. These findings suggest that measurements of PrP aggregation with the MPA may be potentially more sensitive than protease-based methodologies.

[Prion disease--the characteristics and diagnostic points in Japan]

Prion disease develops when normal prion proteins change into transmissible abnormal prion proteins and the converted proteins accumulate in the brain. The Japanese Creutzfeldt-Jakob Disease (CJD) Surveillance Committee has identified 1320 patients with prion diseases in the 10 years since 1999 (classified into 3 types: sporadic, 77.2%; hereditary, 16.7%; and environmentally acquired, 6.1%). Compared with patients in other countries, a relatively larger number of Japanese patients characteristically have dura mater graft-associated CJD and hereditary prion diseases. All the environmentally acquired cases, except 1 case of variant CJD, were acquired from dura grafts. Although most patients were diagnosed with a classical subtype of sporadic CJD (sCJD), whose features include rapidly progressing dementia, myoclonus, hyperintensity in the cerebral cortex and basal ganglia in diffusion-weighted magnetic resonance imaging, and periodic synchronous discharge in electroencephalography, the number of cases with atypical symptoms, such as MM2 (0.8%), MV2 (0.2%), VV1 (0%), and VV2 (0.2%) subtypes of sCJD cases, was not negligible. Appropriate diagnosis should be made based on clinical features, neuroradiological findings, CSF findings (14-3-3 and total tau proteins), and genetic analysis of polymorphisms. Hereditary prion diseases are classified into 3 major phenotypes: familial CJD (fCJD); Gerstmann-Straeussler-Scheinker disease (GSS), which mainly presents as spinocerebellar ataxia; and fatal familial insomnia. Many mutations of the prion protein gene have been identified, but V180I (fCJD), P102L (GSS), and E200K (fCJD) mutations were the most common among the fCJD cases in Japan. Without a family history, genetic testing is necessary to distinguish even seemingly "sporadic" CJD from fCJD. Accurate diagnosis is important for clarification of the pathological process, prevention of secondary infection, and also psychological support.

The consequences of pathogenic mutations to the human prion protein

Prion diseases, in which the conformational transition of the native prion protein (PrP) to a misfolded form causes aggregation and subsequent neurodegeneration, have fascinated the scientific community as this transmissible disease appears to be purely protein-based. Disease can arise due to genetic factors only. At least 30 single point mutations have been indicated to cause disease in humans. Somehow, these mutations must influence the stability, processing and/or cellular interactions of PrP, such that aggregation can occur and disease develops. In this review, the current evidence for such effects of single point mutations is discussed, indicating that PrP can be affected in many different ways, although questions remain about the mechanism by which mutations cause disease.