A novel three extra-repeat insertion in the prion protein gene (PRNP) in a patient with Creutzfeldt-Jakob disease

Pooled analysis of patients with inherited prion disease caused by two- to twelve-octapeptide repeat insertions in the prion protein gene (PRNP)

Inherited prion diseases caused by two- to twelve-octapeptide repeat insertions (OPRIs) in the prion protein gene (PRNP) show significant clinical heterogeneity. This study describes a family with two new cases with a 4-OPRI mutation and two asymptomatic mutation carriers. The pooled analysis summarizes all cases reported in the literature to date and describes the relation between survival, age of onset, number of OPRI and codon 129 polymorphism. MEDLINE and Google Scholar were queried from database inception up to December 31, 2022. Age of onset was compared per number of OPRI and per codon 129 polymorphism using the Kruskal-Wallis and Wilcoxon-Mann-Whitney tests, respectively. Disease duration was modeled non-parametrically by a Kaplan-Meier model and semi-parametrically by a Cox model. This study comprised 164 patients. Lower number of OPRI and presence of valine (cis-V) versus methionine (cis-M) on codon 129 were associated with an older age of onset (P < 0.001 and P = 0.025, respectively) and shorter disease duration (P < 0.001 and P = 0.003, respectively). Within patients with 5- or more OPRI codon cis-V remained significantly associated with a shorter disease duration. Codon 129 homozygosity versus heterozygosity was not significantly associated with age of onset or disease duration (P = 0.076 and P = 0.409, respectively). This study summarized the largest cohort of patients with two- to twelve-OPRI to date. Lower number of OPRI and codon 129 cis-V is associated with an older age of onset and shorter disease duration, while homozygosity or heterozygosity on codon 129 was not.

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 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.

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.

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.

An overview of human prion diseases

Prion diseases are transmissible, progressive and invariably fatal neurodegenerative conditions associated with misfolding and aggregation of a host-encoded cellular prion protein, PrP^C. They have occurred in a wide range of mammalian species including human. Human prion diseases can arise sporadically, be hereditary or be acquired. Sporadic human prion diseases include Cruetzfeldt-Jacob disease (CJD), fatal insomnia and variably protease-sensitive prionopathy. Genetic or familial prion diseases are caused by autosomal dominantly inherited mutations in the gene encoding for PrP^C and include familial or genetic CJD, fatal familial insomnia and Gerstmann-Sträussler-Scheinker syndrome. Acquired human prion diseases account for only 5% of cases of human prion disease. They include kuru, iatrogenic CJD and a new variant form of CJD that was transmitted to humans from affected cattle via meat consumption especially brain. This review presents information on the epidemiology, etiology, clinical assessment, neuropathology and public health concerns of human prion diseases. The role of the PrP encoding gene (PRNP) in conferring susceptibility to human prion diseases is also discussed.

Frequency distribution of PRNP polymorphisms in the Pakistani population

Prion diseases are neurodegenerative conditions caused by misfolding of a normal host-encoded prion protein (PrPC) into pathogenic scrapie prion protein (PrPSc). In human prion diseases, the M129V prion protein polymorphism is known to confer susceptibility to the disease, determines PrPSc conformation and alters clinicopathological phenotypes. To date, all clinicopathologically confirmed cases of a variant form of Cruetzfeldt-Jacob disease (vCJD) have been 129MM homozygotes. There is also predominance of 129MM homozygotes in sporadic CJD (sCJD). No information regarding prion disorders is available from Pakistan. Although only invasive procedures like brain biopsy can confirm the diagnosis of prion disorders, testing a corresponding human population for variation in the prion protein gene (PRNP) may provide some insights into the presence of these disorders in a locality. The current study therefore aimed at exploring the genetic susceptibility of Pakistani population to CJD. A total of 909 unrelated individuals including 221 hemophiliacs representing all 4 major provinces of Pakistan were screened for M129V polymorphism and insertions or deletions of octapeptide repeats (OPRIs/OPRDs) using Polymerase Chain Reaction coupled with Restriction Fragment Length Polymorphism (PCR-RFLP). Concordance of the results of some PCR-RFLP reactions was also confirmed by dideoxy automated Sanger sequencing. The frequencies of M129V alleles (129M and 129V) and genotypes (129MM, 129MV and 129VV) were found in all 909 individuals to be 0.7101, 0.2899, 0.5270, 0.3663 and 0.1067, respectively. Deletion of 1 octapeptide repeat (1-OPRD) was detected in heterozygous state in PRNP of 10 individuals and in homozygous state in 1 individual. An insertion of 3 octapeptide repeats (3-OPRI) was found in 1 individual and an insertion of 1 octapeptide repeat (1-OPRI) in two individuals. Both 3-OPRI and 1-OPRI were present in heterozygous state and were linked to 129M allele. There were no significant χ2 differences between M129V allelic and genotypic frequencies of healthy individuals and hemophiliacs. However, M129V allelic and genotypic frequencies differed significantly between Pakistani population and East Asian and Western populations. Non-significant χ2 differences between M129V frequencies of healthy individuals and hemophiliacs suggest that individuals manifesting single gene disorders may provide naturally randomized samples for studies aiming at surveying the genetic variation. The combined excess of 129MM and 129VV homozygosity and the presence of 3-OPRI in 1 individual imply that Pakistani population is susceptible to prion disorders. Cases of prion disorders may exist in Pakistan, albeit at lower annual prevalence than other countries where life expectancy is greater than 65 years.

Macromolecular crowding converts the human recombinant PrPC to the soluble neurotoxic beta-oligomers

Prion diseases are fatal neurodegenerative disorders and are linked with the conversion of the cellular isoform of the prion protein (PrP(C)) into the abnormal beta-sheet-rich isoform. It is widely accepted that the soluble oligomers of beta-PrP are neurotoxic and that they are more pathologically significant. To unravel the molecular mechanism under the conversion process, it is critical to identify the factors that can promote the conversion from PrP(C) to the beta-oligomers. By recording circular dichroism spectra and performing a size-exclusion HPLC assay, we found that the conformation of the recombinant human prion protein (rPrP(C)) was converted from an alpha-helical conformation into beta-sheet oligomers under a macromolecular crowding condition. The soluble beta-oligomers of rPrP were resistant to proteinase K digestion and could bind to the dyes thioflavin T and 8-anilino-1-naphthalene sulfonate. Furthermore, by the 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, we showed that the soluble beta-oligomers were neurotoxic. These results suggest that macromolecular crowding, which has not been considered before, is a key intracellular factor in the formation of soluble neurotoxic beta-oligomers in prion diseases.

Early onset prion disease from octarepeat expansion correlates with copper binding properties

Insertional mutations leading to expansion of the octarepeat domain of the prion protein (PrP) are directly linked to prion disease. While normal PrP has four PHGGGWGQ octapeptide segments in its flexible N-terminal domain, expanded forms may have up to nine additional octapeptide inserts. The type of prion disease segregates with the degree of expansion. With up to four extra octarepeats, the average onset age is above 60 years, whereas five to nine extra octarepeats results in an average onset age between 30 and 40 years, a difference of almost three decades. In wild-type PrP, the octarepeat domain takes up copper (Cu²⁺) and is considered essential for in vivo function. Work from our lab demonstrates that the copper coordination mode depends on the precise ratio of Cu²⁺ to protein. At low Cu²⁺ levels, coordination involves histidine side chains from adjacent octarepeats, whereas at high levels each repeat takes up a single copper ion through interactions with the histidine side chain and neighboring backbone amides. Here we use both octarepeat constructs and recombinant PrP to examine how copper coordination modes are influenced by octarepeat expansion. We find that there is little change in affinity or coordination mode populations for octarepeat domains with up to seven segments (three inserts). However, domains with eight or nine total repeats (four or five inserts) become energetically arrested in the multi-histidine coordination mode, as dictated by higher copper uptake capacity and also by increased binding affinity. We next pooled all published cases of human prion disease resulting from octarepeat expansion and find remarkable agreement between the sudden length-dependent change in copper coordination and onset age. Together, these findings suggest that either loss of PrP copper-dependent function or loss of copper-mediated protection against PrP polymerization makes a significant contribution to early onset prion disease.

Prion diseases are neurodegenerative disorders involving the prion protein, a normal component of the central nervous system. An unusual class of inherited mutations giving rise to prion disease involves elongation of the so-called octarepeat domain, near the protein's N-terminus. Research from our lab and others shows that this domain binds the micronutrient copper, an essential element for proper neurological function. We investigated how octarepeat elongation influences copper binding by examining both the molecular features and the binding equilibrium. We find that elongation beyond a specific threshold, which confers profound early onset disease, gives rise to concomitant changes in copper uptake. The remarkable agreement between onset age and altered copper binding points to loss of copper protein function as significant in prion neurodegeneration.

PRNP 1368 polymorphism is not associated with sporadic Creutzfeldt-Jakob disease in the Korean population

BACKGROUND

Human prion protein gene (PRNP) is considered a critical and fundamental gene in determining the incidence of human prion diseases. Codons 129 and 219 play an important role in the susceptibility to sporadic Creutzfeldt-Jakob disease (CJD). An association between sporadic CJD and the polymorphism (PRNP 1368) in an upstream of PRNP exon 1 has been reported in the British and German populations, but study in the Dutch population has failed to confirm an association.

PURPOSE

To investigate whether the PRNP 1368 polymorphism is associated with sporadic CJD in the Korean population.

METHODS

We compared the genotype and allele frequencies of PRNP 1368 polymorphism in 171 sporadic CJD patients with those in 212 healthy Koreans.

RESULT AND CONCLUSION

A significant difference of genotype and allele frequencies at PRNP 1368 was found between the normal Korean population and various European populations. In contrast to the results in the British and German populations, our study does not show a significant difference in genotype (P = 0.2763) and allele (P = 0.3750) frequencies of PRNP 1368 between sporadic CJD and normal controls.

Prion proteins with insertion mutations have altered N-terminal conformation and increased ligand binding activity and are more susceptible to oxidative attack

We compared the biochemical properties of a wild type recombinant normal human cellular prion protein, rPrP(c), with a recombinant mutant human prion protein that has three additional octapeptide repeats, rPrP(8OR). Monoclonal antibodies that are specific for the N terminus of rPrP(c) react much better with rPrP(8OR) than rPrP(c), suggesting that the N terminus of rPrP(8OR) is more exposed and hence more available for antibody binding. The N terminus of PrP(c) contains a glycosaminoglycan binding motif. Accordingly, rPrP(8OR) also binds more glycosaminoglycan than rPrP(c). In addition, the divalent cation copper modulates the conformations of rPrP(c) and rPrP(8OR) differently. When compared with rPrP(c), rPrP(8OR) is also more susceptible to oxidative damage. Furthermore, the abnormalities associated with rPrP(8OR) are recapitulated, but even more profoundly, in another insertion mutant, which has five extra octapeptide repeats, rPrP(10OR). Therefore, insertion mutants appear to share common features, and the degree of abnormality is proportional to the number of insertions. Any of these anomalies may contribute to the pathogenesis of inherited human prion disease.

Association of sporadic Creutzfeldt-Jakob disease with homozygous genotypes at PRNP codons 129 and 219 in the Korean population

Human prion protein gene (PRNP) is considered an important gene in determining the incidence of human transmissible spongiform encephalopathies or prion diseases. Polymorphisms of PRNP at codon 129 in Europeans and codon 219 in Japanese may play an important role in the susceptibility to sporadic Creutzfeldt-Jakob disease (CJD); data regarding codon 129 in the Japanese population have led to divergent interpretations. In order to determine which, if any, of the PRNP genotypes in Korean people are associated with sporadic CJD, we examined the genotype and allelic distributions of human PRNP polymorphisms in 150 patients with sporadic CJD. All Korean sporadic CJD patients were Met/Met at codon 129, Glu/Glu at codon 219 and undeleted at the octarepeat region of PRNP. Our study showed significant differences in genotype frequency of PRNP at codon 129 (chi 2=8.8998, P=0.0117) or 219 (chi 2=12.6945, P=0.0004) between sporadic CJD and normal controls. Furthermore, the genotype frequency of the heterozygotes for codons 129 and/or 219 showed a significant difference between the normal population and sporadic CJD patients (chi 2=21.0780, P<0.0001).