Variable phenotype in a P102L Gerstmann-Sträussler-Scheinker Italian family

Case report: A Chinese patient with spinocerebellar ataxia finally confirmed as Gerstmann-Sträussler-Scheinker syndrome with P102L mutation

Gerstmann-Sträussler-Scheinker syndrome (GSS) is a rare genetic prion disease caused by a mutation in the prion protein (PRNP) gene. It is typically characterized by progressive cerebellar ataxia and slowly progressive dementia. We present a case study of the GSS from China in which a 45-year-old male with a progressive gait and balance disorder developed cerebellar ataxia onset but was misdiagnosed as spinocerebellar ataxia (SCA) for 2 years. The patient's clinical, electrophysiological, and radiological data were retrospectively analyzed. Examination revealed ataxia, dysarthria, muscle weakness, areflexia in lower limbs, including a pyramidal sign, whereas cognitive decline was insignificant. His late mother had a similar unsteady gait. An electroencephalogram (EEG) showed normal findings, and 14-3-3 protein was negative. A brain MRI was performed for global brain atrophy and ventricular enlargement. Positron emission tomography-computed tomography (PET-CT) (18F-fluoro-2-deoxy-d-glucose, FDG) images showed mild to moderate decreased glucose metabolism in the left superior parietal lobe and left middle temporal lobe. According to genetic testing, his younger brother also had the P102L variant in the PRNP gene. This single case adds to the clinical and genetic phenotypes of GSS.

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.

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.

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.

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.

The structure of human prions: from biology to structural models-considerations and pitfalls

Prion diseases are a family of transmissible, progressive, and uniformly fatal neurodegenerative disorders that affect humans and animals. Although cross-species transmissions of prions are usually limited by an apparent “species barrier”, the spread ofa prion disease to humans by ingestion of contaminated food, or via other routes of exposure, indicates that animal prions can pose a significant public health risk. The infectious agent responsible for the transmission of prion diseases is a misfolded conformer of the prion protein, PrPSc, a pathogenic isoform of the host-encoded, cellular prion protein,PrPC. The detailed mechanisms of prion conversion and replication, as well as the high-resolution structure of PrPSc, are unknown. This review will discuss the general background related to prion biology and assess the structural models proposed to date,while highlighting the experimental challenges of elucidating the structure of PrPSc.

Clinical neurogenetics: behavioral management of inherited neurodegenerative disease

Psychiatric symptoms often manifest years before overt neurologic signs in patients with inherited neurodegenerative disease. The most frequently cited example of this phenomenon is the early onset of personality changes in "presymptomatic" Huntington patients. In some cases the changes in mood and cognition are even more debilitating than their neurologic symptoms. The goal of this article is to provide the neurologist with a concise primer that can be applied in a busy clinic or private practice.

Physicochemical characteristics of soluble oligomeric Aβand their pathologic role in Alzheimer's disease

Extracellular fibrillar amyloid deposits are prominent and universal Alzheimer's disease (AD) features, but senile plaque abundance does not always correlate directly with the degree of dementia exhibited by AD patients. The mechanism(s) and dynamics of Abeta fibril genesis and deposition remain obscure. Enhanced Abeta synthesis rates coupled with decreased degradative enzyme production and accumulating physical modifications that dampen proteolysis may all enhance amyloid deposit formation. Amyloid accumulation may indirectly exert the greatest pathologic effect on the brain vasculature by destroying smooth muscle cells and creating a cascade of negative impacts on cerebral blood flow. The most visible manifestation of amyloid dis-equilibrium could actually be a defense mechanism employed to avoid serious vascular wall degradation while the major toxic effects to the gray and white matter neurons are mediated by soluble oligomeric Abeta peptides with high beta-sheet content. The recognition that dynamic soluble oligomeric Abeta pools exist in AD and are correlated to disease severity led to neurotoxicity and physical conformation studies. It is now recognized that the most basic soluble Abeta peptides are stable dimers with hydrophobic regions sequestered from the aqueous environment and are capable of higher order aggregations. Time course experiments employing a modified ELISA method able to detect Abeta oligomers revealed dynamic intermolecular interactions and additional experiments physically confirmed the presence of stable amyloid multimers. Amyloid peptides that are rich in beta-sheet structure are capable of creating toxic membrane ion channels and a capacity to self-assemble as annular structures was confirmed in vitro using atomic force microscopy. Biochemical studies have established that soluble Abeta peptides perturb metabolic processes, provoke release of deleterious reactive compounds, reduce blood flow, induce mitochondrial apoptotic toxicity and inhibit angiogenesis. While there is no question that gross amyloid deposition does contribute to AD pathology, the destructive potential now associated with soluble Abeta suggests that treatment strategies that target these molecules may be efficacious in preventing some of the devastating effects of AD.

Gerstmann-Sträussler-Scheinker syndrome with the P102L pathogenic mutation presenting as familial Creutzfeldt-Jakob disease: a case report and review of the literature

Gerstmann-Sträussler-Scheinker syndrome is a rare autosomal dominant disease caused by a mutation in the prion gene, usually manifesting as progressive ataxia with late cognitive decline. A 44-year-old woman with a positive family history developed early personality and behavior changes, followed by paresthesias and ataxia, later associated with memory problems, pyramidal signs, anosognosia and very late myoclonus, spasticity, and severe dysexecutive impairment. Magnetic resonance showed caudate, mesio-frontal, and insular hyper-intensities, electroencephalography revealed generalized triphasic periodic complexes. A pathogenic P102L mutation in the prion gene was detected. Our case differed from classical Gerstmann-Sträussler-Scheinker syndrome by rapid progression, severe dementia, abnormal electroencephalography and magnetic resonance findings, which were highly suggestive of familial Creutzfeldt-Jakob disease.

Gerstmann-Sträussler-Scheinker disease

Gerstmann-Sträussler-Scheinker (GSS) is a slowly progressive hereditary autosomal dominant disease (OMIM: 137440) and the first human transmissible spongiform encephalopathy (TSE) in which a mutation in a gene encoding for prion protein (PrP) was discovered. The first "H" family had been known by the Viennese neuropsychiatrists since the XXth century and was reported by Gerstmann, Sträussler and Scheinker in 1936. In this chapter we present the clinical, neuropathological and molecular data on GSS with the mutations in the PRNP gene: at codons 102, 105, 117, 131, 145, 187, 198, 202, 212, 217 and 232. In several families with GSS the responsible mutations are unknown.

Human prion diseases: from Kuru to variant Creutzfeldt-Jakob disease

Transmissible spongiform encephalopathies (TSEs) or prion diseases are the names given to the group of fatal neurodegenerative disorders that includes kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), fatal and sporadic familial insomnia and the novel prion disease variable protease-sensitive prionopathy (PSPr) in humans. Kuru was restricted to natives of the Foré linguistic group in Papua New Guinea and spread by ritualistic endocannibalism. CJD appears as sporadic, familial (genetic or hereditary) and infectious (iatrogenic) forms. Variant CJD is a zoonotic CJD type and of major public health importance, which resulted from transmission from bovine spongiform encephalopathy (BSE) through ingestion of contaminated meat products. GSS is a slowly progressive hereditary autosomal dominant disease and the first human TSE in which a mutation in a gene encoding for prion protein (PrP) was discovered. The rarest human prion disease is fatal insomnia, which may occur, in genetic and sporadic form. More recently a novel prion disease variable protease-sensitive prionopathy (PSPr) was described in humans.TSEs are caused by a still incompletely defined infectious agent known as a "prion" which is widely regarded to be an aggregate of a misfolded isoform (PrP(Sc)) of a normal cellular glycoprotein (PrP(c)). The conversion mechanism of PrP(c) into PrP(Sc) is still not certain.

Report on the first Chinese family with Gerstmann-Sträussler-Scheinker disease manifesting the codon 102 mutation in the prion protein gene

The authors found a female patient aged 33-years with dementia and cerebellar ataxia rapidly progressing for a year. EEG tracings were abnormal but without features of typical CJD. The patient died 13 months after the onset of illness. Biopsy of her cerebral cortex showed moderate spongiform changes, neuronal loss and gliosis. Numerous deposits of eosinophilic substance amorphous or in the shape of Kuru plaques were disclosed in the cerebral cortex. All deposits stained strongly with monoclonal 3F4 antibody to human prion protein. Genetic studies disclosed the Pro to Leu point mutation at codon 102 with a 102 Leu-129 Met in the PrP gene. Codon 129 was heterozygous for Met/Val, and codon 219 was homozygous for Glu/Glu. It was established; moreover, that the patient's grandfather had a similar disease and died at age 48 and the patient's brother died after a 10-year long neurological disease diagnosed as hereditary cerebellar ataxia. On the basis of clinical, neuropathological and genetic findings, the authors diagnosed the Gerstmann-Sträussler-Scheinker disease, a familial prion disease with an autosomal dominant character. This is the first report on this disease in China.

Treadmill Training Effects in Different Age Groups following Middle Cerebral Artery Occlusion in Rats

BACKGROUND

Despite the increased understanding of treadmill training on stroke patients, its effects on different age groups are not clearly known. The present study presents such effects through a model of cerebral ischemia on young and old groups of rats.

OBJECTIVES

To investigate the effect of treadmill training on young and old rats after cerebral ischemia caused by middle cerebral artery occlusion (MCAO).

METHODS

Forty old (22-24 months of age) and 32 young (3-4 months of age) rats underwent the MCAO procedure for 60 min. Rats that survived the procedure were randomly assigned to a 1- or a 2-week treadmill training group, or a time-matched control group (n=6-8 for each group). The infarct volume was compared between the treadmill training and the control groups for both the young and old rats at 1 or 2 weeks.

RESULTS

After treadmill training for 1 week, the mean infarct volume was 7.26+/-0.49 and 9.51+/-0.84% for the young and old rats, respectively. The 1-week treadmill training effect was significant in the young rats (p=0.0207) but not in the old rats (p=0.0840). The mean infarct volume was 6.84+/-0.51 and 7.63+/-0.52% for the young and old rats, respectively, after the 2-week treadmill training. Both the young and old rat groups demonstrated a significant reduction in the infarct volume compared with that of the control group (p=0.021 for the young group and p=0.039 for the old group) after 2 weeks of treadmill training.

CONCLUSION

The present findings clearly demonstrate the different training effects of locomotor activity in reducing ischemic infarction in young and old rats. The delayed reduction in ischemic infarction in old rats was notable and may be attributable to the slow response of angiogenic and neurogenic mechanisms in the old rats.

Characterization of ataxias with magnetic resonance imaging and spectroscopy

A wide variety of autosomal transmitted ataxias exist and their ultimate characterization requires genetic testing. Common clinical characteristics among different ataxia types complicate the choice of the appropriate genetic test. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) generally show cerebellar or cerebral atrophy and perturbed metabolite levels which differ between ataxias. In order to help the clinician accurately identify the ataxia type, reported MRI and MRS data in different brain regions are summarized for more than 60 different types of autosomal inherited and sporadic ataxias.