Divergent clinical and neuropathological phenotype in a Gerstmann-Sträussler-Scheinker P102L family

A family with mental disorder as the first symptom finally confirmed with Gerstmann-Sträussler-Scheinker disease with P102L mutation in PRNP gene - case report

Gerstmann-Sträussler-Scheinker (GSS) disease is an autosomal dominant neurodegenerative disease, and it is characterized by progressive cerebellar ataxia. Up to now, GSS cases with the p.P102L mutation have mainly been reported in Caucasian, but rarely in Asian populations. A 54-year-old female patient presented with an unstable gait in the hospital. Last year, she was unable to walk steadily and occasionally choked, could not even walk independently gradually. After taking her medical history, we found that she was misdiagnosed with schizophrenia before the gait problems. The patient's father showed similar symptoms and was diagnosed with brain atrophy at the age of 56, but her daughter showed no similar symptoms at present. On arrival at the Neurology Department, the patient's vital signs and laboratory examinations showed no abnormality. As the proband presented with cerebellar ataxia and had an obvious family history, we were sure that she had hereditary cerebellar ataxia. Then, patient's brain MRI showed an abnormal signal in the right parietal cortex and bilateral small ischaemic lesions in the frontal lobe. A gene panel (including 142 ataxia-related genes) was performed, and a heterozygous mutation PRNP Exon2 c.305C>T p. (Pro102Leu) was identified. Her daughter had the same heterozygous mutation. The patient was diagnosed with GSS with mental disorders as initial symptoms. After 2 months of TCM treatment, the patient's walking instability decreased, and her emotional fluctuations were less than before. In conclusion, we have reported a rare case of GSS in Sichuan, China, and the family with mental disorder as the first symptom was finally confirmed with GSS PRNP P102L mutation.

Evolutionarily Conserved Proline Residues Impede the Misfolding of the Mouse Prion Protein by Destabilizing an Aggregation-competent Partially Unfolded Form

The misfolding of the prion protein has been linked to several neurodegenerative diseases. Despite extensive studies, the mechanism of the misfolding process remains poorly understood. The present study structurally delineates the role of the conserved proline residues present in the structured C-terminal domain of the mouse prion protein (moPrP) in the misfolding process. It is shown that mutation of these Pro residues to Ala leads to destabilization of the native (N) state, and also to rapid misfolding. Using hydrogen-deuterium exchange (HDX) studies coupled with mass spectrometry (MS), it has been shown that the N state of moPrP is in rapid equilibrium with a partially unfolded form (PUF2*) at pH 4. It has been shown that the Pro to Ala mutations make PUF2* energetically more accessible from the N state by stabilizing it relative to the unfolded (U) state. The apparent rate constant of misfolding is found to be linearly proportional to the extent to which PUF2* is populated in equilibrium with the N state, strongly indicating that misfolding commences from PUF2*. It has also been shown that the Pro residues restrict the boundary of the structural core of the misfolded oligomers. Overall, this study highlights how the conserved proline residues control misfolding of the prion protein by modulating the stability of the partially unfolded form from which misfolding commences.

Description of the first Spanish case of Gerstmann-Sträussler-Scheinker disease with A117V variant: clinical, histopathological and biochemical characterization

Gerstmann–Sträussler–Scheinker disease (GSS) is a rare neurodegenerative illness that belongs to the group of hereditary or familial Transmissible Spongiform Encephalopathies (TSE). Due to the presence of different pathogenic alterations in the prion protein (PrP) coding gene, it shows an enhanced proneness to misfolding into its pathogenic isoform, leading to prion formation and propagation. This aberrantly folded protein is able to induce its conformation to the native counterparts forming amyloid fibrils and plaques partially resistant to protease degradation and showing neurotoxic properties. PrP with A117V pathogenic variant is the second most common genetic alteration leading to GSS and despite common phenotypic and neuropathological traits can be defined for each specific variant, strikingly heterogeneous manifestations have been reported for inter-familial cases bearing the same pathogenic variant or even within the same family. Given the scarcity of cases and their clinical, neuropathological, and biochemical variability, it is important to characterize thoroughly each reported case to establish potential correlations between clinical, neuropathological and biochemical hallmarks that could help to define disease subtypes. With that purpose in mind, this manuscript aims to provide a detailed report of the first Spanish GSS case associated with A117V variant including clinical, genetic, neuropathological and biochemical data, which could help define in the future potential disease subtypes and thus, explain the high heterogeneity observed in patients suffering from these maladies.

Clinical Variability in P102L Gerstmann-Sträussler-Scheinker Syndrome

Gerstmann-Sträussler-Scheinker syndrome (GSS) with the P102L mutation is a rare genetic prion disease caused by a pathogenic mutation at codon 102 in the prion protein gene. Cluster analysis encompassing data from 7 Czech patients and 87 published cases suggests the existence of 4 clinical phenotypes (typical GSS, GSS with areflexia and paresthesia, pure dementia GSS, and Creutzfeldt-Jakob disease-like GSS); GSS may be more common than previously estimated. In making a clinical diagnosis or progression estimates of GSS, magnetic resonance imaging and real-time quaking-induced conversion may be helpful, but the results should be evaluated with respect to the overall clinical context. ANN NEUROL 2019;86:643-652.

An autopsy report of three kindred in a Gerstmann-Sträussler-Scheinker disease P105L family with a special reference to prion protein, tau, and beta-amyloid

INTRODUCTION

Gerstmann-Sträussler-Scheinker disease P105L (GSS105) is a rare variant of GSS caused by a point mutation of the prion protein (PrP) gene at codon 105 (proline to leucine substitution). It is clinically characterized by spastic paraparesis and dementia and histopathologically defined by PrP-plaques in the brain. This report describes a clinicopathological analysis of three autopsied kindred from a Japanese GSS105 family, plus a topological analysis of PrP, hyperphosphorylated tau (p-tau), and beta-amyloid (Aβ).

METHODS

Using paraffin-embedded sections, we applied histology and single- and multiple-labeling immunohistochemistry for PrP, p-tau, and Aβ to the three cases. Comparative semi-quantitative analyses of tissue injuries and PrP-plaques were also employed.

RESULTS

Case 1 (45 years old (yo)) and Case 2 (56 yo) are sisters, and Case 3 (49 yo) is the son of Case 2. Case 1 and Case 2 presented with spastic paraparesis followed by dementia, whereas Case 3 presented, not with spastic paraparesis, but with psychiatric symptoms. In Case 1 and Case 2, the brain showed tissue injuries with many PrP-plaques in the cerebral cortices, and the pyramidal tract showed myelin loss/pallor. In Case 3, the brain was least degenerated with a number of PrP-plaques; however, the pyramidal tract remained intact. In addition, p-tau was deposited in all cases, where p-tau was present in or around PrP-plaques. By double-labeling immunohistochemistry, the colocalization of p-tau with PrP-plaques was confirmed. Moreover in Case 2, Aβ was deposited in the cerebral cortices. Interestingly, not only p-tau but also Aβ was colocalized with PrP-plaques. In all cases, both three repeat tau and four repeat tau were associated with PrP-plaques.

CONCLUSIONS

The clinicopathological diversity of GSS105, which is possible even in the same family, was ascertained. Not only p-tau but also Aβ could be induced by PrP ("secondary degeneration"), facilitating the kaleidoscopic symptoms of GSS.

Clinical features of Chinese patients with Gerstmann-Sträussler-Scheinker identified by targeted next-generation sequencing

Gerstmann-Sträussler-Scheinker (GSS) is an autosomal dominant neurodegenerative disease due to mutations within prion protein (PRNP) gene. Clinically, it is not easy to distinguish GSS from spinocerebellar ataxia (SCA), especially in the early stage of disease. We aimed to identify genetic mutations in 8 Chinese pedigrees with dominant ataxia but excluded dynamic mutations of SCA genes. Targeted next-generation sequencing was performed in the 8 probands. A customized panel was designed to capture 24 known causative genes, including 15 autosomal dominant SCA genes and 9 dementia-related genes. A 2-year follow-up was performed in these patients who harbored mutation. Of the 8 probands, 5 were identified to harbor the p.P102L mutation within PRNP. All these 5 cases had progressive ataxia with age at onset ranging from 48 to 52 years (49.5 ± 4.51). Remarkable phenotypic heterogeneity was observed in them. Cognitive decline was found in 4/5 probands. The average duration from initial symptoms to cognitive decline is 32.5 months, ranging from 22 to 48 months. In this study, we presented the detailed clinical features of 5 GSS pedigrees with PRNP p.P102L mutation. The variable phenotypes among these GSS patients indicated other genetic or environmental factors might be involved in the phenotypic heterogeneity of GSS. Our findings also support the proposal that screening of PRNP mutations should be performed for the patients with dominant ataxia if dynamic mutations of SCA genes were excluded.

Prion protein scrapie and the normal cellular prion protein

Prions are infectious proteins and over the past few decades, some prions have become renowned for their causative role in several neurodegenerative diseases in animals and humans. Since their discovery, the mechanisms and mode of transmission and molecular structure of prions have begun to be established. There is, however, still much to be elucidated about prion diseases, including the development of potential therapeutic strategies for treatment. The significance of prion disease is discussed here, including the categories of human and animal prion diseases, disease transmission, disease progression and the development of symptoms and potential future strategies for treatment. Furthermore, the structure and function of the normal cellular prion protein (PrP(C)) and its importance in not only in prion disease development, but also in diseases such as cancer and Alzheimer's disease will also be discussed.

Transmission Properties of Human PrP 102L Prions Challenge the Relevance of Mouse Models of GSS

Inherited prion disease (IPD) is caused by autosomal-dominant pathogenic mutations in the human prion protein (PrP) gene (PRNP). A proline to leucine substitution at PrP residue 102 (P102L) is classically associated with Gerstmann-Sträussler-Scheinker (GSS) disease but shows marked clinical and neuropathological variability within kindreds that may be caused by variable propagation of distinct prion strains generated from either PrP 102L or wild type PrP. To-date the transmission properties of prions propagated in P102L patients remain ill-defined. Multiple mouse models of GSS have focused on mutating the corresponding residue of murine PrP (P101L), however murine PrP 101L, a novel PrP primary structure, may not have the repertoire of pathogenic prion conformations necessary to accurately model the human disease. Here we describe the transmission properties of prions generated in human PrP 102L expressing transgenic mice that were generated after primary challenge with ex vivo human GSS P102L or classical CJD prions. We show that distinct strains of prions were generated in these mice dependent upon source of the inoculum (either GSS P102L or CJD brain) and have designated these GSS-102L and CJD-102L prions, respectively. GSS-102L prions have transmission properties distinct from all prion strains seen in sporadic and acquired human prion disease. Significantly, GSS-102L prions appear incapable of transmitting disease to conventional mice expressing wild type mouse PrP, which contrasts strikingly with the reported transmission properties of prions generated in GSS P102L-challenged mice expressing mouse PrP 101L. We conclude that future transgenic modeling of IPDs should focus exclusively on expression of mutant human PrP, as other approaches may generate novel experimental prion strains that are unrelated to human disease.

Inherited prion disease (IPD) is caused by pathogenic mutations in the human prion protein (PrP) gene leading to the formation of lethal prions in the brain. To-date the properties of prions causing IPD and their similarities to prions causing other forms of human prion disease remain ill-defined. In the present study we have investigated the properties of prions seen in patients with Gerstmann-Sträussler-Scheinker (GSS) disease associated with the substitution of leucine for proline at amino acid position 102 (GSS P102L). We examined the ability of these prions to infect transgenic mice expressing human mutant 102L PrP, human wild-type PrP or wild-type mice. We found that GSS-102L prions have properties distinct from other types of human prions by showing that they can only infect transgenic mice expressing human PrP carrying the same mutation. Mice expressing wild-type human PrP or wild-type mouse PrP were entirely resistant to infection with GSS-102L prions. We conclude that accurate modeling of inherited prion disease requires the expression of authentic mutant human PrP in transgenic models, as other approaches may generate results that do not mirror the human disease.

Relationships between clinicopathological features and cerebrospinal fluid biomarkers in Japanese patients with genetic prion diseases

A national system for surveillance of prion diseases (PrDs) was established in Japan in April 1999. Here, we analyzed the relationships among prion protein gene (PRNP) mutations and the clinical features, cerebrospinal fluid (CSF) markers, and pathological characteristics of the major genotypes of genetic PrDs (gPrDs). We retrospectively analyzed age at onset and disease duration; the concentrations and incidences of 14-3-3 protein, tau protein, and abnormal prion protein (PrP(Sc)) in the CSF of 309 gPrD patients with P102L, P105L, E200K, V180I, or M232R mutations; and brain pathology in 32 autopsied patients. Three clinical phenotypes were seen: rapidly progressive Creutzfeldt-Jakob disease (CJD), which included 100% of E200K cases, 70% of M232R, and 21% of P102L; slowly progressive CJD, which included 100% of V180I and 30% of M232R; and Gerstmann-Sträussler-Scheinker disease, which included 100% of P105L and 79% of P102L. PrP(Sc) was detected in the CSF of more than 80% of patients with E200K, M232R, or P102L mutations but in only 39% of patients with V180I. V180I was accompanied by weak PrP immunoreactivity in the brain. Patients negative for PrP(Sc) in the CSF were older at disease onset than positive patients. Patients with mutations associated with high 14-3-3 protein levels in the CSF typically had synaptic deposition of PrP in the brain and a rapid course of disease. The presence of small PrP protein fragments in brain homogenates was not correlated with other clinicopathological features. Positivity for PrP(Sc) in the CSF may reflect the pathological process before or at disease onset, or abnormality in the secretion or metabolism of PrP(Sc). The amount of 14-3-3 protein in the CSF likely indicates the severity of the pathological process and accompanying neuronal damage. These characteristic features of the CSF in cases of gPrD will likely facilitate accurate diagnosis and clinicopathological study of the various disease subtypes.

Early detection of abnormal prion protein in genetic human prion diseases now possible using real-time QUIC assay

Introduction

The definitive diagnosis of genetic prion diseases (gPrD) requires pathological confirmation. To date, diagnosis has relied upon the finding of the biomarkers 14-3-3 protein and total tau (t-tau) protein in the cerebrospinal fluid (CSF), but many researchers have reported that these markers are not sufficiently elevated in gPrD, especially in Gerstmann-Sträussler-Scheinker syndrome (GSS). We recently developed a new in vitro amplification technology, designated “real-time quaking-induced conversion (RT-QUIC)”, to detect the abnormal form of prion protein in CSF from sporadic Creutzfeldt-Jakob disease (sCJD) patients. In the present study, we aimed to investigate the presence of biomarkers and evaluate RT-QUIC assay in patients with gPrD, as the utility of RT-QUIC as a diagnostic tool in gPrD has yet to be determined.

Method/Principal Findings

56 CSF samples were obtained from gPrD patients, including 20 cases of GSS with P102L mutation, 12 cases of fatal familial insomnia (FFI; D178N), and 24 cases of genetic CJD (gCJD), comprising 22 cases with E200K mutation and 2 with V203I mutation. We subjected all CSF samples to RT-QUIC assay, analyzed 14-3-3 protein by Western blotting, and measured t-tau protein using an ELISA kit. The detection sensitivities of RT-QUIC were as follows: GSS (78%), FFI (100%), gCJD E200K (87%), and gCJD V203I (100%). On the other hand the detection sensitivities of biomarkers were considerably lower: GSS (11%), FFI (0%), gCJD E200K (73%), and gCJD V203I (67%). Thus, RT-QUIC had a much higher detection sensitivity compared with testing for biomarkers, especially in patients with GSS and FFI.

Conclusion/Significance

RT-QUIC assay is more sensitive than testing for biomarkers in gPrD patients. RT-QUIC method would thus be useful as a diagnostic tool when the patient or the patient's family does not agree to genetic testing, or to confirm the diagnosis in the presence of a positive result for genetic testing.