Identification of a PRNP gene mutation in Jakob's original Creutzfeldt-Jakob disease family

Clarence J. Gibbs Effect and the "Creutzfeldt-Jakob Disease" Eponym

In 2014, American neurologist and Nobel laureate Stanley Prusiner reported that microbiologist Clarence Joseph Gibbs at the US NIH had intentionally, systematically, and mischievously used the eponym Creutzfeldt-Jakob disease, rather than Jakob-Creutzfeldt disease, because of the correspondence with Gibbs' own initials, to imply "Clarence Joseph disease." The present study examines temporal trends in the use of "Creutzfeldt-Jakob" and "Jakob-Creutzfeldt" in scientific articles and monographs from 1946 to 2019 to assess whether there was a "Clarence J. Gibbs effect" that influenced the general use of a specific eponym by the scientific community. During Gibbs' period of publication on Creutzfeldt-Jakob disease (CJD), there was an abrupt, dramatic, and steady increase in use of the CJD eponym while use of the Jakob-Creutzfeldt disease (JCD) eponym remained at a low level. In the period after Gibbs ceased to publish, there was a corresponding marked fall-off in use of the CJD eponym. Surviving collaborators thought Gibbs may have been joking, but in 1991 Gibbs had admitted what Prusiner reported. Regardless of motive, Gibbs strongly influenced the preferred eponym for this human prion disease by (1) publishing a seminal and highly referenced initial article in a high-profile journal; (2) sustained output of further important studies published in high-quality journals over more than 30 years; (3) professional affiliation with an esteemed national laboratory where he worked with a large number of high-profile colleagues; and (4) extensive collaborations with a large number of colleagues, who published multiple further articles using the eponym Gibbs preferred.

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.

Exosomes and their role in the intercellular trafficking of normal and disease associated prion proteins

Over the past decade, small extracellular vesicles called exosomes have been observed to harbour protein and genetic cargo that can assist in health and also cause disease. Many groups are extensively investigating the mechanisms involved that regulate the trafficking and packaging of exosomal contents and how these processes may be deregulated in disease. Prion diseases are transmissible neurodegenerative disorders and are characterized by the presence of detectable misfolded prion proteins. The disease associated form of the prion protein can be found in exosomes and its transmissible properties have provided a reliable experimental read out that can be used to understand how exosomes and their cargo are involved in cell-cell communication and in the spread of prion diseases. This review reports on the current understanding of how exosomes are involved in the intercellular spread of infectious prions. Furthermore, we discuss how these principles are leading future investigations in developing new exosome based diagnostic tools and therapeutic drugs that could be applied to other neurodegenerative diseases.

Comprehensive neuropathologic analysis of genetic prion disease associated with the E196K mutation in PRNP reveals phenotypic heterogeneity

The genetic forms of human transmissible spongiform encephalopathies (TSEs) are linked to mutations in the gene encoding the prion protein (PRNP) and account for 10% to 15% of human TSE cases. Some are distinct with respect to clinical signs, disease onset/duration, and diagnostic findings, whereas others closely resemble sporadic Creutzfeldt-Jakob disease (sCJD). We report a comprehensive analysis of 4 patients carrying the rare E196K (GAG→AAG) mutation who presented with clinical features of CJD. To date, information on this PRNP mutation is limited to clinical and genetic data. Consequently, the E196K mutation could not be unequivocally assigned to human prion disease. We report histopathologic and biochemical findings in addition to clinical observations, thus providing a more comprehensive analysis of this presumably genetic prion disease. Our data indicate that (i) the E196K mutation is causally linked to human prion disease, (ii) there is a complex phenotypic spectrum of this mutation that includes nonspecific symptoms at onset and features typical of sCJD during disease progression, and (iii) the corresponding histologic picture comprises both cases with atypical neuropathology and cases that closely resemble subtypes of sCJD corresponding to the classification of Parchi et al, with subtle modifications in hippocampal regions CA1-4.

Retrospective sequence analysis of the human PRNP gene from the formaldehyde-fixed paraffin-embedded tissues: report of two cases of Creutzfeldt-Jakob disease

The definitive diagnosis of the CJD (Creutzfeldt-Jakob disease; very rare neurodegenerative disorder) can be established only on the basis of post-mortem examination of the central nervous system tissue. Formaldehyde-fixed paraffin-embedded (FFPE) tissue samples may thus constitute the only material available for molecular pathology analyses. We performed post-mortem analysis of the coding region of the prion-protein gene (PRNP)-sequence variations in two definite CJD cases suggestive of genetic form. Only FFPE tissues were available for molecular analyses. The PRNP gene open reading frame was amplified from the genomic DNA (FFPE isolated) in four overlapping, two round semi-nested PCR products that were directly sequenced. We found known pathogenic sequence variation g.532 G>A (Asp178Asn) in patient 1 but we did not find any pathogenic sequence variation in patient 2 despite her origin from the Slovak Orava region. Based on these results, we were able to discriminate between genetic and sporadic form of CJD in patient 1 and 2, respectively. The established method was found to be efficient for the sequence-variation analysis of the entire PRNP gene coding region using the genomic DNA isolated from the FFPE tissues; it can be employed in other retrospective molecular studies.

Prion disease genetics

Prion diseases have stimulated intense scientific scrutiny since it was proposed that the infectious agent was devoid of nucleic acid. Despite this finding, genetics has played a key role in understanding the pathobiology and clinical aspects of prion disease through the effects of a series of polymorphisms and mutations in the prion protein gene (PRNP). The advent of variant Creutzfeldt-Jakob disease has confirmed one of the most powerful human genetic susceptibility factors, as all tested patients have an identical genotype at polymorphic codon 129 of PRNP. This review will also consider the accrued reports of inherited prion disease and attempt a genotype-phenotype correlation. The prospects for detection of novel genetic susceptibility factors using mouse models and human genetic association studies will be explored.

Hereditary Creutzfeldt-Jakob disease and fatal familial insomnia

Studies on hereditary CJD and FFI have contributed greatly to the understanding of all forms of prion disease. Most importantly, they have provided strong support for the prion hypothesis [2]. The linkage of pathogenic PRNP mutations to human prion disease strengthens the notion that a change in PrP conformation is a key event that triggers the development of the disease. Although hereditary CJD and FFI account for only 10% of all cases of human prion disease, they provide a unique opportunity for studying disease pathogenesis initiated by perturbation in the PrP structure. An understanding of the events that accompany a change in PrP conformation has far-reaching implications for sCJD (the most common form of the disease) and for sporadic fatal insomnia. A wealth of available evidence indicates that a common pathway in disease pathogenesis may be shared by both the sporadic and the hereditary forms of prion disease, except that the initiating events are stochastic in the former, rather than predetermined by the presence of a germ-line mutation. In addition, investigations of hereditary CJD and FFI have provided plausible mechanisms of phenotypic heterogeneity in prion disease, a phenomenon analogous to the "prion strain" diversity in animal prion disease. Although many other neurodegenerative diseases such as Alzheimer's disease, amyotrophic lateral sclerosis, and Huntington's chorea are fairly homogeneous in disease phenotype, prion disease includes many clinically and pathologically distinct disease entities. In hereditary prion disease, the disease phenotype is likely to be determined by the combined effect of pathogenic mutations, codon 129 polymorphism, and the type of PrPSc. The pathogenic mutations include point mutations that are located mostly in the central and C-terminal region of PrP, and deletion and insertion mutations that are located in the N-terminal region. It is conceivable that these distinct types of mutations may result in differential changes in conformation or stability of PrP. The codon 129 polymorphism plays a twofold role in modulating the disease outcome. On the mutant allele, it determines the basic features of the disease phenotype--as in the case of FFI and CJD178--that result respectively from the coupling of M or V at codon 129 with the D178N mutation. On the normal allele, it may modulate the severity of the phenotype. A PrPSc subtype is encoded by the PRNP haplotype, and subsequently is generated by a conformational conversion process that transforms the cellular isoform to the pathogenic protein. The site for the formation of a specific PrPSc conformer and its accumulation in different brain regions are likely to contribute to the clinical features and pathologic lesions. The phenotypic homogeneity in other neurologic diseases, including Alzheimer's disease, may be due, in part, to the lack of a powerful genetic modifier such as the codon 129 polymorphism in the PrP gene, and the lack of the ability of affected gene products such as PrP to assume multiple protein conformations. Clearly, the remaining issue in the understanding of pathogenesis of prion disease is a detailed and accurate knowledge of the in vivo processes and conditions for the formation of PrPSc that inevitably lead to the development and expression of the disease. This knowledge will enable the development of a rational and effective strategy for therapeutic intervention.

Sporadic and familial CJD: classification and characterisation

Prion diseases are unique transmissible neurodegenerative diseases that have diverse phenotypes and can be familial, sporadic, or acquired by infection. Recent findings indicate that the PrP genotype and the PrP(Sc) type have a major influence on the disease phenotype in both sporadic and familial human prion diseases. This review attempts to classify and characterise sporadic and familial Creutzfeldt-Jakob disease (CJD) as a function of these two disease determinants. Based on the genotype at codon 129 on both PRNP alleles, the size of protease resistant PrP(Sc) fragments and disease phenotype, we divide sporadic CJD into six subtypes: sCJDMM1/sCJDMV1, sCJDVV2, sCJDMV2, sCJDMM2, sCJDVV1, and sporadic fatal insomnia (sFI). Familial CJD is classified into many haplotypes based on the PRNP mutation and codon 129 (and other polymorphic codons) on the mutant allele. The clinical and pathological features are summarised for each sporadic CJD subtype and familial CJD haplotype.

Prion diseases in man

Prion diseases are uncommon fatal neurodegenerative disorders which have gained scientific and public importance as a result of major advances in the understanding of the nature of the causative agent, and the emergence of new forms of these diseases in both animals and man. The transmissible agent in prion diseases is unique and is closely associated with an abnormal isoform of a widely distributed cell-surface glycoprotein, prion protein. The precise mechanisms of conversion to the abnormal isoform are unknown; changes in protein folding are of major importance. The abnormal isoform of the protein accumulates in the central nervous system in all prion diseases, but the processes involved in protein accumulation and the pathogenesis of neuronal dysfunction and cell death are poorly understood. Human prion diseases occur as sporadic, familial, and acquired disorders, the most recently identified of which is new variant Creutzfeldt-Jakob disease, which has been aetiologically linked to exposure to the bovine spongiform encephalopathy agent through the food chain. Surveillance of human prion diseases will be crucial in the assessment of the impact of this new disease in the United Kingdom and elsewhere. Effective surveillance depends on accurate diagnosis, which in turn places a high priority on autopsy in suspected cases; neuropathology is essential for the diagnosis of human prion diseases. Phenotypic variation is prominent in all forms of human prion disease; future classifications of these disorders are likely to incorporate genetic and biochemical data in addition to clinical and pathological parameters.

Human prion diseases

The classical prion diseases in man comprise Creutzfeldt-Jakob disease (CJD), Kuru and Gerstmann-Sträussler-Scheinker syndrome (GSS). Recent advances in the biochemistry and the molecular biology of the transmissible agents responsible for these human spongiform encephalopathies have prompted renewed interest in their clinical and pathological features. A broadening spectrum of human prion diseases has now been identified including novel entities such as Fatal Familial Insomnia and variants of CJD and GSS characterised by specific abnormalities in the human prion protein (PrP) gene on chromosome 20. Accumulation of PrP in the central nervous system is a characteristic feature of all these disorders, although the relationship between PrP localisation, classical neuropathology, clinical features and genotype still requires clarification. A national surveillance project for CJD was established in 1990 in the United Kingdom in order to assess the possible implications of bovine spongiform encephalopathy for human health. The identification of an apparently new variant of CJD in young patients in UK raises the possibility of such a link; further studies are required to assess the significance of this observation.

The nosology of Creutzfeldt-Jakob disease and conditions related to the accumulation of PrPCJD in the nervous system

Although typical cases of Creutzfeldt-Jakob disease are readily recognized pathologically and clinically, variant forms often pose a diagnostic challenge. From the 1920's, when this disease was first characterized, until quite recently diagnosis relied heavily on morphologic changes. New advances in immunoassays and PrP gene analysis now provide important adjuncts in recognizing the spectrum of disorders of PrP metabolism associated with these transmissible encephalopathies.