Creutzfeldt-Jakob disease associated with an R148H mutation of the prion protein gene

Phenotypic diversity of genetic Creutzfeldt-Jakob disease: a histo-molecular-based classification

The current classification of sporadic Creutzfeldt–Jakob disease (sCJD) includes six major clinicopathological subtypes defined by the physicochemical properties of the protease-resistant core of the pathologic prion protein (PrP^Sc), defining two major PrP^Sc types (i.e., 1 and 2), and the methionine (M)/valine (V) polymorphic codon 129 of the prion protein gene (PRNP). How these sCJD subtypes relate to the well-documented phenotypic heterogeneity of genetic CJD (gCJD) is not fully understood. We analyzed molecular and phenotypic features in 208 individuals affected by gCJD, carrying 17 different mutations, and compared them with those of a large series of sCJD cases. We identified six major groups of gCJD based on the combination PrP^Sc type and codon 129 genotype on PRNP mutated allele, each showing distinctive histopathological characteristics, irrespectively of the PRNP associated mutation. Five gCJD groups, named M1, M2C, M2T, V1, and V2, largely reproduced those previously described in sCJD subtypes. The sixth group shared phenotypic traits with the V2 group and was only detected in patients carrying the E200K-129M haplotype in association with a PrP^Sc type of intermediate size (“i”) between type 1 and type 2. Additional mutation-specific effects involved the pattern of PrP deposition (e.g., a “thickened” synaptic pattern in E200K carriers, cerebellar “stripe-like linear granular deposits” in those with insertion mutations, and intraneuronal globular dots in E200K-V2 or -M”i”). A few isolated cases linked to rare PRNP haplotypes (e.g., T183A-129M), showed atypical phenotypic features, which prevented their classification into the six major groups. The phenotypic variability of gCJD is mostly consistent with that previously found in sCJD. As in sCJD, the codon 129 genotype and physicochemical properties of PrP^Sc significantly correlated with the phenotypic variability of gCJD. The most common mutations linked to CJD appear to have a variable and overall less significant effect on the disease phenotype, but they significantly influence disease susceptibility often in a strain-specific manner. The criteria currently used for sCJD subtypes can be expanded and adapted to gCJD to provide an updated classification of the disease with a molecular basis.

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 Creutzfeldt-Jakob disease

Genetic Creutzfeldt-Jakob disease (CJD) is associated with mutations in the human PrP gene (PRNP) on chromosome 20p12-pter. Pathogenic mutations have been identified in 10-15% of all CJD patients, who often have a family history of autosomal-dominant pattern of inheritance and variable penetrance. However, the use of genetic tests implemented by surveillance networks all over the world increasingly identifies unexpectedly PRNP mutations in persons apparently presenting with a sporadic form of CJD. A high phenotypic variability was reported in genetic prion diseases, which partly overlap with the features of sporadic CJD. Here we review recent advances on the epidemiologic, clinical, and neuropathologic features of cases that phenotypically resemble CJD linked to point and insert mutations of the PRNP gene. Multidisciplinary studies are still required to understand the phenotypic spectrum, penetrance, and significance of PRNP mutations.

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.

Genetic Creutzfeldt-Jakob disease and fatal familial insomnia: insights into phenotypic variability and disease pathogenesis

Human prion diseases are a group of rare neurodegenerative disorders characterized by the conversion of the constitutively expressed prion protein, PrP(C), into an abnormally aggregated isoform, called PrP(Sc). While most people who develop a prion disease have no identifiable cause and a few acquire the disease through an identified source of infection, about 10-15% of patients are affected by a genetic form and carry either a point mutation or an insertion of octapeptide repeats in the prion protein gene. Prion diseases show the highest extent of phenotypic heterogeneity among neurodegenerative disorders and comprise three major disease entities with variable though overlapping phenotypic features: Creutzfeldt-Jakob disease (CJD), fatal insomnia and the Gerstmann-Sträussler-Scheinker syndrome. Both CJD and fatal insomnia are fully transmissible diseases, a feature that led to the isolation and characterization of different strains of the agent or prion showing distinctive clinical and neuropathological features after transmission to syngenic animals. Here, we review the current knowledge of the effects of the pathogenic mutations linked to genetic CJD and fatal familial insomnia on the prion protein metabolism and physicochemical properties, the disease phenotype and the strain characteristics. The data derived from studies in vitro and from those using cell and animal models are compared with those obtained from the analyses of the naturally occurring disease. The extent of phenotypic variation in genetic prion disease is analyzed in comparison to that of the sporadic disease, which has recently been the topic of a systematic and detailed characterization.

Cerebrospinal fluid biomarkers in human genetic transmissible spongiform encephalopathies

The 14-3-3 protein test has been shown to support the clinical diagnosis of sporadic Creutzfeldt-Jakob disease (CJD) when associated with an adequate clinical context, and a high differential potential for the diagnosis of sporadic CJD has been attributed to other cerebrospinal fluid (CSF) proteins such as tau protein, S100b and neuron specific enolase (NSE). So far there has been only limited information available about biochemical markers in genetic transmissible spongiform encephalopathies (gTSE), although they represent 10–15% of human TSEs. In this study, we analyzed CSF of 174 patients with gTSEs for 14-3-3 (n = 166), tau protein (n = 78), S100b (n = 46) and NSE (n = 50). Levels of brain-derived proteins in CSF varied in different forms of gTSE. Biomarkers were found positive in the majority of gCJD (81%) and insert gTSE (69%), while they were negative in most cases of fatal familial insomnia (13%) and Gerstmann-Sträussler-Scheinker syndrome (10%). Disease duration and codon 129 genotype influence the findings in a different way than in sporadic CJD.

A novel subtype of Creutzfeldt-Jakob disease characterized by a small 6 kDa PrP fragment

We report on a novel subtype of Creutzfeldt-Jakob disease with a single proteinase K-resistant prion protein fragment of about 6 kDa in Western blots of brain homogenates. Clinically this patient showed a progressive spastic disorder and dementia over 3 years. No mutation of the prion protein gene was found. Since this patient had received a blood transfusion, an iatrogenic cause, albeit unlikely, cannot be ruled out. Future studies will have to be attentive to small prion protein fragments, which may cause or be associated with unusual clinical disease that might possibly only be diagnosed by immunoblotting of brain homogenates.

Creutzfeldt-Jakob disease (CJD) with a mutation at codon 148 of prion protein gene: relationship with sporadic CJD

Creutzfeldt-Jakob disease (CJD), the most common human prion disease, includes sporadic (s) and familial (f) forms. Regardless of etiology, both forms are thought to share the pathogenic mechanism whereby the cellular prion protein (PrP(C)) converts into its pathogenic isoform (PrP(Sc)). While PrP(C) conversion is thought to be random in sCJD, conversion in fCJD is facilitated by the congenital presence of mutated PrP. Differences in PrP genotype (PRNP) and in conversion circumstances lead to PrP(Sc) with distinct characteristics that elicit different disease phenotypes. Here, we describe a case of fCJD with a substitution of histidine (H) for arginine (R) at codon 148 (R148H) and heterozygosity of the methionine/valine (M/V) polymorphic codon 129, with the 129M allele coupled with the mutation. The disease phenotype and all major characteristics of PrP(Sc) of fCJD(R148H) were virtually indistinguishable from those of sCJDMV2, which has features different from those of any other sCJD. Therefore, despite the differences in etiology, PRNP, and conversion process, the two forms of PrP(Sc) had similar characteristics. Furthermore, comparison of fCJD(R148H) with a recently reported case carrying R148H and homozygosity at codon 129 suggests that codon 129 coupled with the mutation as well as that located on the normal allele can modify major phenotypic and PrP(Sc) features of fCJD(R148H).