Polymorphism at codon 129 of the prion protein gene is not associated with sporadic AD

A clinicopathological study of selected cognitive impairment cases in Lothian, Scotland: enhanced CJD surveillance in the 65 + population group

BACKGROUND

Variant Creutzfeldt-Jakob Disease (vCJD) is primarily associated with dietary exposure to bovine-spongiform-encephalopathy. Cases may be missed in the elderly population where dementia is common with less frequent referral to specialist neurological services. This study's twin aims were to determine the feasibility of a method to detect possible missed cases in the elderly population and to identify any such cases.

METHODS

A multi-site study was set-up in Lothian in 2016, to determine the feasibility of enhanced CJD-surveillance in the 65 + population-group, and undertake a clinicopathological investigation of patients with features of 'atypical' dementia.

RESULTS

Thirty patients are included; 63% male, 37% female. They were referred because of at least one neurological feature regarded as 'atypical' (for the common dementing illnesses): cerebellar ataxia, rapid progression, or somato-sensory features. Mean-age at symptom-onset (66 years, range 53-82 years), the time between onset-of-symptoms and referral to the study (7 years, range 1-13 years), and duration-of-illness from onset-of-symptoms until death or the censor-date (9.5 years, range 1.1-17.4 years) were determined. By the censor-date, 9 cases were alive and 21 had died. Neuropathological investigations were performed on 10 cases, confirming: Alzheimer's disease only (2 cases), mixed Alzheimer's disease with Lewy bodies (2 cases), mixed Alzheimer's disease with amyloid angiopathy (1 case), moderate non-amyloid small vessel angiopathy (1 case), a non-specific neurodegenerative disorder (1 case), Parkinson's disease with Lewy body dementia (1 case), and Lewy body dementia (2 cases). No prion disease cases of any type were detected.

CONCLUSION

The surveillance approach used was well received by the local clinicians and patients, though there were challenges in recruiting sufficient cases; far fewer than expected were identified, referred, and recruited. Further research is required to determine how such difficulties might be overcome. No missed cases of vCJD were found. However, there remains uncertainty whether this is because missed cases are very uncommon or because the study had insufficient power to detect them.

The characterization of AD/PART co-pathology in CJD suggests independent pathogenic mechanisms and no cross-seeding between misfolded Aβ and prion proteins

Current evidence indicating a role of the human prion protein (PrP) in amyloid-beta (Aβ) formation or a synergistic effect between Aβ and prion pathology remains controversial. Conflicting results also concern the frequency of the association between the two protein misfolding disorders and the issue of whether the apolipoprotein E gene (APOE) and the prion protein gene (PRNP), the major modifiers of Aβ- and PrP-related pathologies, also have a pathogenic role in other proteinopathies, including tau neurofibrillary degeneration. Here, we thoroughly characterized the Alzheimer's disease/primary age-related tauopathy (AD/PART) spectrum in a series of 450 cases with definite sporadic or genetic Creutzfeldt-Jakob disease (CJD). Moreover, we analyzed: (i) the effect of variables known to affect CJD pathogenesis and the co-occurring Aβ- and tau-related pathologies; (II) the influence of APOE genotype on CJD pathology, and (III) the effect of AD/PART co-pathology on the clinical CJD phenotype. AD/PART characterized 74% of CJD brains, with 53.3% and 8.2% showing low or intermediate-high levels of AD pathology, and 12.4 and 11.8% definite or possible PART. There was no significant correlation between variables affecting CJD (i.e., disease subtype, prion strain, PRNP genotype) and those defining the AD/PART spectrum (i.e., ABC score, Thal phase, prevalence of CAA and Braak stage), and no difference in the distribution of APOE ε4 and ε2 genotypes among CJD subtypes. Moreover, AD/PART co-pathology did not significantly affect the clinical presentation of typical CJD, except for a tendency to increase the frequency of cognitive symptoms. Altogether, the present results seem to exclude an increased prevalence AD/PART co-pathology in sporadic and genetic CJD, and indicate that largely independent pathogenic mechanisms drive AD/PART and CJD pathology even when they coexist in the same brain.

Prion Protein PRNP: A New Player in Innate Immunity? The Aβ Connection

The prion protein PRNP has been centrally implicated in the transmissible spongiform encephalopathies (TSEs), but its normal physiological role remains obscure. We highlight emerging evidence that PRNP displays antimicrobial activity, inhibiting the replication of multiple viruses, and also interacts directly with Alzheimer's disease (AD) amyloid-β (Aβ) peptide whose own antimicrobial role is now increasingly secure. PRNP and Aβ share share membrane-penetrating, nucleic acid binding, and antiviral properties with classical antimicrobial peptides such as LL-37. We discuss findings that binding of abnormal nucleic acids to PRNP leads to oligomerization of the protein, and suggest that this may be an entrapment and sequestration process that contributes to its antimicrobial activity. Some antimicrobial peptides are known to be exploited by infectious agents, and we cover evidence that PRNP is usurped by herpes simplex virus (HSV-1) that has evolved a virus-encoded 'anti-PRNP'.unction. These findings suggest that PRNP, like LL-37 and Aβ, is likely to be a component of the innate immune system, with implications for the pathoetiology of both AD and TSE.

Epidemiological genetics and meta-analysis of a polymorphism at codon 129 of the PRNP gene in Alzheimer's disease in Brazil

The polymorphism at codon 129 of the prion protein gene (PRNP) is a major risk factor for Creutzfeldt-Jakob disease (CJD). Several authors reported neuropathological and clinical overlapping between CJD and Alzheimer's disease (AD), with a few association studies generating conflicting results. To investigate the distribution of this polymorphism in AD, we selected 58 patients with probable AD and 73 controls from a Brazilian population. There was no association between the PRNP polymorphism at codon 129 and AD. Our meta-analysis (performed using Alzgene; http://www.alzgene.org) along with previous studies conducted in Brazil demonstrated a negative association.

Prnp gene and cerebellum volume in patients with refractory mesial temporal lobe epilepsy

The cellular prion protein, encoded by Prnp gene, is involved in neuroprotection, neuroplasticity and neurodevelopment. The variant allele Valine at codon 129 of the Prnp was associated with decreased brain volume in healthy volunteers and schizophrenic patients. We investigate the association between the cerebellum volume and the presence of variant allele Valine at codon 129 of the Prnp gene in patients with mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS). The Prnp coding sequence was determined in 41 refractory MTLE-HS patients. The cerebellum volume corrected by the intracranial volume of patients with the normal Prnp genotypes was compared with that of patients presenting the variant alleles at codon 129. Twenty patients showed the Met129Met genotype, 16 showed Met129Val, and 5 had Val129Val. There were no association among clinical, demographic, electrophysiological, antiepileptic drugs used, and the presence of the Prnp variant alleles. The presence of Prnp variant allele at codon 129 was not associated with the analyzed cerebellum volume. Prnp variant alleles at codon 129 are not associated with cerebellum volume in patients with refractory MTLE-HS.

Codon 129 polymorphism of prion protein gene in is not a risk factor for Alzheimer's disease

Interaction of prion protein and amyloid-b oligomers has been demonstrated recently. Homozygosity at prion protein gene (PRNP) codon 129 is associated with higher risk for Creutzfeldt-Jakob disease. This polymorphism has been addressed as a possible risk factor in Alzheimer disease (AD).ObjectiveTo describe the association between codon 129 polymorphisms and AD.MethodsWe investigated the association of codon 129 polymorphism of PRNP in 99 AD patients and 111 controls, and the association between this polymorphism and cognitive performance. Other polymorphisms of PRNP and additive effect of apolipoprotein E gene (ApoE) were evaluated.ResultsCodon 129 genotype distribution in AD 45.5% methionine (MM), 42.2% methionine valine (MV), 12.1% valine (VV); and 39.6% MM, 50.5% MV, 9.9% VV among controls (p>0.05). There were no differences of cognitive performance concerning codon 129. Stratification according to ApoE genotype did not reveal difference between groups.ConclusionCodon 129 polymorphism is not a risk factor for AD in Brazilian patients.

The association between the methionine/valine (M/V) polymorphism (rs1799990) in the PRNP gene and the risk of Alzheimer disease: an update by meta-analysis

BACKGROUND

The M/V polymorphism in the PRNP gene has been extensively examined for the association to the risk of Alzheimer disease (AD); however, results from different studies have been inconsistent. The aim of this study is to evaluate the association between the M/V polymorphism in the PRNP gene and the risk of AD.

METHODS

A meta-analysis was carried out to analyze the association between the M/V polymorphism in the PRNP gene and the risk of AD.

RESULTS

A total of 4228 cases and 4324 controls in 16 case-control studies were included in the meta-analysis. The results indicated that the variant V allele carriers (VV+MV) had a 13% decreased risk of AD, when compared with the homozygote MM (VV+MV vs. MM: OR=0.87, 95% CI=0.79-0.96, P=0.004). In the subgroup analysis by ethnicity, significant decreased risks of AD were found in the Caucasian V allele carriers (OR=0.85, 95% CI=0.77-0.94, P=0.002), but not in Asian V allele carriers (OR=1.11, 95% CI=0.78-1.57, P=0.57). In the subgroup analysis by age of onset, significant decreased risks of AD were associated with V allele carriers in late-onset Alzheimer disease (OR=0.76, 95% CI=0.62-0.93, P=0.007) but not in early-onset Alzheimer disease (OR=0.86, 95% CI=0.70-1.06, P=0.17).

CONCLUSIONS

Our results suggest that the M/V polymorphism in the PRNP gene contributes to the susceptibility of Alzheimer disease.

Can infections cause Alzheimer's disease?

Late-onset Alzheimer's disease (AD) is the most prevalent cause of dementia among older adults, yet more than a century of research has not determined why this disease develops. One prevailing hypothesis is that late-onset AD is caused by infectious pathogens, an idea widely studied in both humans and experimental animal models. This review examines the infectious AD etiology hypothesis and summarizes existing evidence associating infectious agents with AD in humans. The various mechanisms through which different clinical and subclinical infections could cause or promote the progression of AD are considered, as is the concordance between putative infectious agents and the epidemiology of AD. We searched the PubMed, Web of Science, and EBSCO databases for research articles pertaining to infections and AD and systematically reviewed the evidence linking specific infectious pathogens to AD. The evidence compiled from the literature linking AD to an infectious cause is inconclusive, but the amount of evidence suggestive of an association is too substantial to ignore. Epidemiologic, clinical, and basic science studies that could improve on current understanding of the associations between AD and infections and possibly uncover ways to control this highly prevalent and debilitating disease are suggested.

Genetic cross-interaction between APOE and PRNP in sporadic Alzheimer's and Creutzfeldt-Jakob diseases

Alzheimer's disease (AD) and Creutzfeldt-Jakob disease (CJD) represent two distinct clinical entities belonging to a wider group, generically named as conformational disorders that share common pathophysiologic mechanisms. It is well-established that the APOE ε4 allele and homozygosity at polymorphic codon 129 in the PRNP gene are the major genetic risk factors for AD and human prion diseases, respectively. However, the roles of PRNP in AD, and APOE in CJD are controversial. In this work, we investigated for the first time, APOE and PRNP genotypes simultaneously in 474 AD and 175 sporadic CJD (sCJD) patients compared to a common control population of 335 subjects. Differences in genotype distribution between patients and control subjects were studied by logistic regression analysis using age and gender as covariates. The effect size of risk association and synergy factors were calculated using the logistic odds ratio estimates. Our data confirmed that the presence of APOE ε4 allele is associated with a higher risk of developing AD, while homozygosity at PRNP gene constitutes a risk for sCJD. Opposite, we found no association for PRNP with AD, nor for APOE with sCJD. Interestingly, when AD and sCJD patients were stratified according to their respective main risk genes (APOE for AD, and PRNP for sCJD), we found statistically significant associations for the other gene in those strata at higher previous risk. Synergy factor analysis showed a synergistic age-dependent interaction between APOE and PRNP in both AD (SF = 3.59, p = 0.027), and sCJD (SF = 7.26, p = 0.005). We propose that this statistical epistasis can partially explain divergent data from different association studies. Moreover, these results suggest that the genetic interaction between APOE and PRNP may have a biological correlate that is indicative of shared neurodegenerative pathways involved in AD and sCJD.

Worldwide distribution of PSEN1 Met146Leu mutation: a large variability for a founder mutation

OBJECTIVE

Large kindreds segregating familial Alzheimer disease (FAD) offer the opportunity of studying clinical variability as observed for presenilin 1 (PSEN1) mutations. Two early-onset FAD (EOFAD) Calabrian families with PSEN1 Met146Leu (ATG/CTG) mutation constitute a unique population descending from a remote common ancestor. Recently, several other EOFAD families with the same mutation have been described worldwide.

METHODS

We searched for a common founder of the PSEN1 Met146Leu mutation in families with different geographic origins by genealogic and molecular analyses. We also investigated the phenotypic variability at onset in a group of 50 patients (mean age at onset 40.0 +/- 4.8 years) by clinical, neuropsychological, and molecular methodologies.

RESULTS

EOFAD Met146Leu families from around the world resulted to be related and constitute a single kindred originating from Southern Italy before the 17th century. Phenotypic variability at onset is broad: 4 different clinical presentations may be recognized, 2 classic for AD (memory deficits and spatial and temporal disorientation), whereas the others are expressions of frontal impairment. The apathetic and dysexecutive subgroups could be related to orbital-medial prefrontal cortex and dorsolateral prefrontal cortex dysfunction.

CONCLUSIONS

Genealogic and molecular findings provided evidence that the PSEN1 Met146Leu families from around the world analyzed in this study are related and represent a single kindred originating from Southern Italy. The marked phenotypic variability might reflect early involvement by the pathologic process of different cortical areas. Although the clinical phenotype is quite variable, the neuropathologic and biochemical characteristics of the lesions account for neurodegenerative processes unmistakably of Alzheimer nature.

[Acquired human prion diseases--past and present issues]

Transmissible spongiform encephalopathies, or prion diseases, are fatal neurodegenerative disorders. In aetiological viewpoint, human prion diseases are classified into 1) sporadic Creutzfeldt-Jakob disease (CJD) which comprises 80-90% of the total population of human prion disaeses, 2) inherited forms, and 3) acquired types by prion-contaminated surgical instruments, biopharmaceuticals or foodstuffs. The diseases cause an accumulation of the disease-associated form(s) of prion protein (PrP(Sc)) in the central nervous system. PrP(Sc) is regarded as the entity of prion agents and generally exerts infectivity, irrespective of its origin being from the sporadic cases or the inherited cases. Variant CJD (vCJD), first identified in the United Kingdom (UK) in 1996, is an acquired type of human CJD by oral intake of BSE prion. Cumulative numbers of 215 patients in the world have been reported for definite or probable vCJD cases according to the UK National Creutzfeldt-Jakob Disease Surveillance Unit by September, 2009. Different from sporadic CJD cases, vCJD patients show an accumulation of PrP(Sc) in spleen and tonsils. Such distribution of PrP(Sc) in lymphoid tissues raised clinical concern about the potential infectivity in the blood or blood components used for blood transfusion. To date, five instances of probable transfusion-mediated transmission of vCJD prion have been found in UK. Here we review the past and the present issues about the acquired human prion diseases.

Lack of association between PRNP 1368 polymorphism and Alzheimer's disease or vascular dementia

BACKGROUND

Polymorphisms of the prion protein gene (PRNP) at codons 129 and 219 play an important role in the susceptibility to Creutzfeldt-Jakob disease (CJD), and might be associated with other neurodegenerative disorders. Several recent reports indicate that polymorphisms outside the coding region of PRNP modulate the expression of prion protein and are associated with sporadic CJD, although other studies failed to show an association. These reports involved the polymorphism PRNP 1368 which is located upstream from PRNP exon 1. In a case-controlled protocol, we assessed the possible association between the PRNP 1368 polymorphism and either Alzheimer's disease (AD) or vascular dementia (VaD).

METHODS

To investigate whether the PRNP 1368 polymorphism is associated with the occurrence of AD or VaD in the Korean population, we compared the genotype, allele, and haplotype frequencies of the PRNP 1368 polymorphism in 152 AD patients and 192 VaD patients with frequencies in 268 healthy Koreans.

RESULTS AND CONCLUSION

Significant differences in genotype, allele and haplotype frequencies of PRNP 1368 polymorphism were not observed between AD and normal controls. There were no significant differences in the genotype and allele frequencies of the PRNP 1368 polymorphism between Korean VaD patients and normal controls. However, in the haplotype analysis, haplotype Ht5 was significantly over-represented in Korean VaD patients. This was the first genetic association study of a polymorphism outside the coding region of PRNP in relation to AD and VaD.

Molecular pathology of human prion diseases

Prion diseases are fatal neurodegenerative conditions in humans and animals. In this review, we summarize the molecular background of phenotypic variability, relation of prion protein (PrP) to other proteins associated with neurodegenerative diseases, and pathogenesis of neuronal vulnerability. PrP exists in different forms that may be present in both diseased and non-diseased brain, however, abundant disease-associated PrP together with tissue pathology characterizes prion diseases and associates with transmissibility. Prion diseases have different etiological background with distinct pathogenesis and phenotype. Mutations of the prion protein gene are associated with genetic forms. The codon 129 polymorphism in combination with the Western blot pattern of PrP after proteinase K digestion serves as a basis for molecular subtyping of sporadic Creutzfeldt-Jakob disease. Tissue damage may result from several parallel, interacting or subsequent pathways that involve cellular systems associated with synapses, protein processing, oxidative stress, autophagy, and apoptosis.

Physiology of the prion protein

Prion diseases are transmissible spongiform encephalopathies (TSEs), attributed to conformational conversion of the cellular prion protein (PrP(C)) into an abnormal conformer that accumulates in the brain. Understanding the pathogenesis of TSEs requires the identification of functional properties of PrP(C). Here we examine the physiological functions of PrP(C) at the systemic, cellular, and molecular level. Current data show that both the expression and the engagement of PrP(C) with a variety of ligands modulate the following: 1) functions of the nervous and immune systems, including memory and inflammatory reactions; 2) cell proliferation, differentiation, and sensitivity to programmed cell death both in the nervous and immune systems, as well as in various cell lines; 3) the activity of numerous signal transduction pathways, including cAMP/protein kinase A, mitogen-activated protein kinase, phosphatidylinositol 3-kinase/Akt pathways, as well as soluble non-receptor tyrosine kinases; and 4) trafficking of PrP(C) both laterally among distinct plasma membrane domains, and along endocytic pathways, on top of continuous, rapid recycling. A unified view of these functional properties indicates that the prion protein is a dynamic cell surface platform for the assembly of signaling modules, based on which selective interactions with many ligands and transmembrane signaling pathways translate into wide-range consequences upon both physiology and behavior.

The normal distribution of PRNP codon 129 polymorphism in the Moroccan population (Arabs and Casablanca residents)

The common prion protein gene (PRNP) codon 129 polymorphism is a strong susceptibility factor for human prion diseases. In this study, we examined the allelic variation of methionine and valine at codon 129 in 147 subjects representing the normal Moroccan population. The sharing of the genotype was 57.1% for Methionine-Methionine (MM), 36% for Methionine-Valine (MV), and 6, 8% for Valine-Valine (VV). These results are indeed intermediate between those discovered at the European and Asian populations. However, and for a better assessment of the risk to develop prion diseases in the Moroccan population, the survey of the frequency of the codon 219 polymorphism is required.

M129V variation in the prion protein gene and psychotic disorders: relationship to neuropsychological and psychopathological measures

The methionine/valine polymorphism at position 129 in the prion protein gene, PRNP M129V, is a known risk factor for Creutzfeldt-Jakob disease (CJD). Psychiatric manifestations including psychosis are common in the early phase of CJD and it has therefore been hypothesized that the prion protein could be involved in psychotic disorders. Moreover, among the various hypothesized functions of the prion protein, a role in synaptic activity has been described. We have studied the PRNP M129V variant with regard to psychotic disorders from two perspectives: first as a genetic risk factor and second as a genetic factor influencing phenotypic variation. A case-control study of 482 psychotic patients and 502 controls indicated that differences between patients and controls were not present in genotype distributions or allele frequencies. We also studied the influence of this variant in psychopathological symptomatology and neuropsychological performance in a subgroup of 159 psychotic patients. In our sample, patients homozygous for valine at this position presented less severe scores in the general psychopathological subscale (p=0.003) and in the sum of the total items (p=0.007) of the Positive and Negative Syndrome Scale (PANSS). Also, homozygote VV patients presented better scores in most neuropsychological tests, the most significant result of which was for delayed visual memory (p=0.021). In summary, our results do not support the hypothesis that M129V is a susceptibility factor for psychotic disorders. However, it could influence their phenotypic variation at the psychopathological and neuropsychological level. Independent replications are needed to confirm that being homozygotic for valine at PRNP M129V position is associated with better psychopathological and neuropsychological scores in psychotic disorders.

Absence of association between codon 129 and 219 polymorphisms of the prion protein gene and vascular dementia

BACKGROUND

Polymorphisms of the prion protein gene (PRNP) are known to cause a strong susceptibility to the occurrence of prion diseases, such as Creutzfeldt-Jakob disease, and might be associated with other neurodegenerative disorders. However, an association between PRNP polymorphisms and vascular dementia (VaD) has not been reported thus far.

OBJECTIVE

To investigate whether the PRNP polymorphisms are associated with an increased risk for developing VaD in the Korean population.

METHODS

We compared the genotype, allele and haplotype frequencies of PRNP polymorphisms in 160 VaD patients with those in 236 healthy Koreans.

RESULTS AND CONCLUSION

Codon 129 (M129V) and 219 (Q219K) polymorphisms in Korean VaD patients were found in the open reading frame of PRNP. Our study shows that there is no significant difference in the genotype, allele and haplotype frequencies of PRNP codon 129 and 219 polymorphisms between Korean VaD patients and normal controls. This was the first genetic association study of the polymorphisms of PRNP with VaD.

Polymorphisms at codons 129 and 219 of the prion protein gene (PRNP) are not associated with sporadic Alzheimer's disease in the Korean population

Polymorphisms of prion protein gene (PRNP) at codons 129 and 219 play an important role in the susceptibility to Creutzfeldt-Jakob disease (CJD). Alzheimer's disease (AD) and prion diseases, such as CJD, are both characterized by the accumulation of abnormally folded proteins in the brain. An association between sporadic AD and the PRNP polymorphism at codon 129 has been reported in several studies, but other studies have failed to confirm an association. To investigate whether PRNP polymorphisms are associated with an increased risk for developing sporadic AD in the Korean population, we compared the genotype, allele, and haplotype frequencies of PRNP polymorphisms in 271 sporadic AD patients with those in 236 healthy Koreans. Our study does not show a significant difference in PRNP genotype, allele, and haplotype frequency at codons 129 and 219 between sporadic AD and normal controls. Analyses stratifying by age at disease onset, and gender also failed to reveal any association between these polymorphisms and sporadic AD. These results indicate that these PRNP polymorphisms have no direct influence on the susceptibility to sporadic AD in the Korean population.

Analysis of PRNP gene codon 129 polymorphism in the Greek population

Creutzfeldt-Jakob disease (CJD) is a fatal transmissible neurodegenerative prion disease with a rapid progression comprising familial, sporadic, iatrogenic and variant forms. A polymorphism at codon 129 of PRNP gene has been implicated in the development of variant CJD. We examined Met/Val allele frequencies and the genotype distribution, with respect to the polymorphic codon 129 of PRNP gene in 348 healthy individuals from the region of Athens, Greece. The following genotype frequencies were observed in the Greek population: Met/Met 50%, Met/Val 39% and Val/Val 11%. The presence of the Methionine allele frequencies in various European populations, according to the published data, increases gradually from northwestern to southeastern countries, implying the presence of a cline. The distribution of genotypes of Met homozygotes displays random declination across the 10 compared populations. The observed higher frequency of Met homozygotes at codon 129 does not necessarily suggest that these populations are at increased risk of developing CJD.

Prion protein gene M129 allele is a risk factor for Alzheimer's disease

Prion protein gene polymorphism M129V represents a known risk factor for Creutzfeldt-Jakob disease. Recently, the meta-analysis revealed that homozygosity at codon 129 is connected with increased risk of Alzheimer's disease (AD). To determine whether M129V polymorphism is a risk factor for AD we analyzed a group of early-onset, and late-onset Polish AD patients. We observed that in LOAD patients there is a statistically significant increase of MM (p=0.0028) and decrease of MV (p=0.0006) genotype frequency, as compared to controls. When both groups were stratified according to APOE4 status, increase of MM and decrease of MV genotype frequency were significant in the LOAD subgroup with no APOE4 (p=0.017, and p=0.018, respectively). In the subgroup with APOE4 allele, only MV genotype frequency was significantly lower, as compared to controls (p=0.035). However, no interaction was found between APOE4 status and M129V polymorphism. We conclude that MM genotype increases LOAD risk in Polish population independently from the APOE4 status.

Genotype frequencies at codon 129 of the prion protein gene in Brazil: Implications in susceptibility to variant Creutzfeldt-Jakob disease compared to European and Asian populations

A polymorphism at codon 129 of the prion protein gene has been shown to confer genetic susceptibility to prion diseases, and to influence the epidemic course of variant Creutzfeldt-Jakob disease. We employed a PCR-endonuclease digestion-based assay to investigate this genetic trait in Brazil, and then compared our results to previously published data from several European and Asian countries.

Polymorphism of PRNP codons in the normal Icelandic population

OBJECTIVES

Polymorphisms in the prion protein gene in humans influence susceptibility to, and phenotype of, prion diseases. Methionine-methionine (MM) homozygosity at codon 129 is a risk factor for sporadic Creutzfeldt-Jakob disease (CJD). Polymorphism at codon 117 and changes in the octapeptide repeat region have been associated with genetic CJD. Knowledge of genetic background in normal populations may contribute to better understanding of prion diseases.

MATERIALS AND METHODS

Polymorphism at codon 129, codon 117 and deletions of octapetide repeats were studied in 208 healthy blood donors of both genders and of different age.

RESULTS

Polymorphism at codon 129 was: MM 46.6%, methionine-valine 44.7%, valine-valine 8.7%. Polymorphism at codon 117 was observed in 4.8%. Deletions of octapeptide repeats were not detected. There were no gender or age differences in the distribution of codon 129 polymorphism. The frequency of codon 129 polymorphisms was, with one exception, not significantly different from that observed elsewhere in Europe.

Is M129V of PRNP gene associated with Alzheimer's disease? A case-control study and a meta-analysis

The methionine/valine (M/V) polymorphism at codon 129 within the prion protein gene (PRNP) represents a known risk factor for Creutzfeldt-Jakob disease (CJD). Few authors reported also the effects of this polymorphism on the risk of Alzheimer's disease (AD), although with controversial results. To better clarify this issue, we performed a novel case-control study and a meta-analysis of published association studies between PRNP and AD. Our findings argue against PRNP as a susceptibility gene for developing AD in the Italian population but support the hypothesis that the V allele influences cognitive performances. The meta-analysis, revealed that Caucasian subjects homozygous at codon 129 had a 1.3-fold increased risk [95% CI: 1.0-1.6, p = 0.05] of developing AD compared to heterozygous individuals. We also observed that MM genotype and M allele represent a risk factor for AD, independently from the ethnic background, providing a significant but modest association between this polymorphism and AD.

Cognitive performance of patients with mesial temporal lobe epilepsy is not associated with human prion protein gene variant allele at codons 129 and 171

Cognitive impairment has long been recognized in people with medically refractory epilepsies. Mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS), the most common surgically remediable epileptic syndrome, has been associated with a cellular prion protein (PrPc) gene (Prnp) variant allele at codon 171. The polymorphism consisting of a methionine-for-valine substitution at codon 129 has been associated with early cognitive deterioration in elderly people and patients with Down syndrome. The same variant allele in homozygosis (V129V) has been associated to a lower long-term memory in healthy humans. PrPc mediates several processes related to neuroplasticity, and its role in cognitive processes remains unknown. In this study, we evaluated the genetic contribution of Prnp alleles to cognitive performance in patients with MTLE-HS. Cognitive performance, measured with 19 neuropsychological tests, of patients with refractory MTLE-HS with the normal Prnp genotypes was compared with that of patients with the variant alleles at codons 129 and 171. With the effects of clinical, demographic, electrophysiological, and neuroimaging variable interactions controlled by multiple linear regression analysis and adjustment for multiple test comparisons, the presence of Prnp variant alleles was found not to be significantly associated to cognitive performance of patients with MTLE-HS. The presence of variant alleles at codons 129 and 171 is not associated to cognitive performance of patients with refractory MTLE-HS.

Prion protein codon 129 genotype prevalence is altered in primary progressive aphasia

The prion protein (PrP) is central to the prion diseases, although a role in other neurodegenerative diseases has been postulated. A common polymorphism (Met or Val) at codon 129 of the PrP gene (PRNP) features prominently in the risk and phenotype, of prion disease, and an abnormality in its distribution frequency may signal a role for PrP in other diseases. We conducted a case-control study to compare the PRNP codon 129 genotype distribution in Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and primary progressive aphasia (PPA), including 281 AD, 256 ALS, 39 PPA, and 415 healthy control subjects. Statistical analysis was applied to determine the presence or absence of disease-specific genotype associations. The distribution of codon 129 genotypes was similar among healthy control, AD, and ALS subjects, although the heterozygous state was significantly overrepresented (age-adjusted odds ratio, 8.47) in PPA, a rare condition of unknown cause. Although these findings do not entirely exclude a role for PrP in AD or ALS, they do not support the codon 129 genotype as a risk factor for either disease. However, the strong association between heterozygosity and PPA raises new questions about its cause and the role of PrP in other neurodegenerative diseases.

Creutzfeldt-Jakob disease risk and PRNP codon 129 polymorphism: necessity to revalue current data

The polymorphism at codon 129 (M129V) of the prion protein gene (PRNP) is a recognized genetic marker for susceptibility to Creutzfeldt-Jakob disease (CJD) in the Caucasians. The distribution of this polymorphism in healthy individuals provides an important starting point for the evaluation of CJD risk in the general population. Early studies of reference population cohorts demonstrated that methionine/valine heterozygosity was the most frequent genotype. These studies were performed in relatively small numbers of control subjects and do not correspond with the findings of more recent investigations. In this study, we present an analysis of the codon M129V distribution in 613 corneal donors, representing one of the largest control groups examined to date. Methionine homozygotes represented 48.1%, valine homozygotes 8.7% and methionine/valine heterozygotes 43.2%. While age-related difference was not significant, differentiation according to the gender showed significant difference. The observed highest proportion of methionine homozygotes and statistically significant difference between genders as well as comparison with results obtained in other countries underline the need to re-evaluate the generally used reference data on M129V, including consideration of the gender, age and geographical distribution.

Absence of mutations in the prion-protein gene in a large cohort of HMSN patients

Cellular prion-protein is expressed in axons and Schwann cells of peripheral nerves. Some patients with prion diseases show peripheral nerve involvement and prion-protein deficient mice develop age dependent demyelination of peripheral nerves. Therefore we tested the hypothesis that mutations in the prion-protein gene might also cause hereditary motor and sensory neuropathies. We screened 108 patients with a diagnosis of hereditary motor and sensory neuropathies in whom the common genetic defects causing hereditary motor and sensory neuropathies had previously been excluded for mutations in the protein-coding region of the PRNP gene. Mutations in the coding region of the prion-protein gene were not found. We conclude that mutations in the protein coding region of the prion-protein gene are not a common cause of HMSN (95% CI 0-0.034).

The population distribution of the Met allele at the PRNP129 polymorphism (a high risk factor for Creutzfeldt-Jakob disease) in various regions of France and in West Europe

The present study has been conducted to ascertain the level of allelic variation at codon 129 of the prion protein gene in France. Six French populations have been studied (Paris, Lille, Rennes, Chambéry, Grasse and Perpignan), totalling 1374 normal subjects. Mean heterozygosity in France is 46.5%, and the mean Met 129 allele (a high risk susceptibility factor for Creutzfeldt-Jakob disease) is 0.674. There is a genetic heterogeneity (chi(2)=38.44, p<0.001) between the six populations compared, and Met allele frequencies are inversely correlated with latitude (r=-0.93, p<0.01). Such an inverse correlation with latitude (r=-0.78, p=0.01) is also found when Met allele frequencies in France are compared to those already published in five other European countries and in Turkey. We hypothesise that high Met 129 frequencies populations may be at higher risk for Creutzfeldt-Jakob disease.

The normal population distribution of PRNP codon 129 polymorphism

OBJECTIVES

The common prion protein gene (PRNP) codon 129 polymorphism modifies the susceptibility to and the phenotype of prion diseases. However, no truly representative normal population-based data, or data stratified according to age or gender are available on the distribution of this polymorphism.

MATERIAL AND METHODS

Allelic variation of codon 129 in three Finnish populations representing different age groups, and among Finnish, British and Irish blood donors were examined.

RESULTS

The PRNP codon 129 genotype distribution in the total Finnish sample was 49% for methionine-methionine (MM), 42% for methionine-valine (MV) and 9% for valine-valine (VV), for the UK blood donors 42% for MM, 47% for MV and 11% for VV, and for the Irish blood donors 34% for MM, 56% for MV, and 10% for VV.

CONCLUSIONS

The genotype frequencies were almost identical in all three Finnish populations of different ages, with no gender differences, and did not differ from corresponding figures for the Finnish blood donors. However, the PRNP codon 129 genotype distribution in Finland differed significantly from that of the British and the Irish blood donors and the previously published blood donor data on other Western Europeans and Americans.

Polymorphism of the codon 129 of the prion protein (PrP) gene and neuropathology of cerebral ageing

We studied whether codon 129 polymorphism of the PrP gene modulates the presence of tau- and Abeta-associated lesions among 188 patients over 70 years of age without evidence of dementia. Val allele carriers, either heterozygotes or homozygotes, were more frequently affected by Abeta-associated lesions than non Val allele carriers, whereas there were no differences for tau-positive neurones. Val allele carriers also had more focal and diffuse Abeta deposits. This association was most significant in the highest Braak's stages for neurofibrillary tangles (>/=III). In this group, cases with at least one Val allele had nearly twice as many Abeta-associated lesions. The most affected areas were the entorhinal cortex, TF-TH and the superior temporal cortex, where odds ratios for focal Abeta deposits ranged from 3.5 to 4.6.

Balancing selection at the prion protein gene consistent with prehistoric kurulike epidemics

Kuru is an acquired prion disease largely restricted to the Fore linguistic group of the Papua New Guinea Highlands, which was transmitted during endocannibalistic feasts. Heterozygosity for a common polymorphism in the human prion protein gene (PRNP) confers relative resistance to prion diseases. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are, in marked contrast to younger unexposed Fore, predominantly PRNP 129 heterozygotes. Kuru imposed strong balancing selection on the Fore, essentially eliminating PRNP 129 homozygotes. Worldwide PRNP haplotype diversity and coding allele frequencies suggest that strong balancing selection at this locus occurred during the evolution of modern humans.

PRNP Val129 homozygosity increases risk for early-onset Alzheimer's disease

We analyzed the PRNP M129V polymorphism in a Dutch population-based early-onset Alzheimer's disease sample. We observed a significant association between early-onset Alzheimer's disease and homozygosity of M129V (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.1-3.3; p = 0.02) with the highest risk for V homozygotes (OR, 3.2; 95% CI, 1.4-7.1; p < 0.01). In patients with a positive family history, these risks increased to 2.6 (95% CI, 1.3-5.3; p < 0.01) and 3.5 (95% CI, 1.3-9.3; p = 0.01), respectively.

Does the prion protein gene 129 codon polymorphism influence sleep? Evidence from a fatal familial insomnia kindred

OBJECTIVE

Experimental and clinical evidence in prion diseases suggests that the prion protein gene (PRNP) plays a role in regulating sleep.

METHODS

Seventeen healthy individuals belonging to a single fatal familial insomnia pedigree, 8 carriers and 9 non-carriers of the PRNP codon 178 mutation, underwent polysomnography and spectral electroencephalographic (EEG) analysis. All were also characterized with regard to the codon 129 polymorphism on both PRNP alleles.

RESULTS

PRNP codon 129 polymorphism exhibited influences on sleep-EEG activities. In particular, spindle frequency band power and balance between delta and spindle activity were found to correlate with the genotype of PRNP codon 129, irrespective of the mutation at codon 178.

CONCLUSIONS

Our data suggest that PRNP codon 129 polymorphism may also affect sleep in the healthy population and warrant further studies in the general population and other sleep disorders.

Polymorphism at codon 174 of the prion-like protein gene is not associated with sporadic Alzheimer's disease

Alzheimer's disease (AD) and prion diseases are associated with the occurrence of protein aggregates called amyloid fibrils, containing the amyloid-beta peptide in AD, and a modified form (PrP(Sc)) of the normal cellular prion protein (PrP(c)) in prion diseases. PrP(c) is encoded by the prion protein gene, and a common polymorphism at codon 129 of this gene is a determinant of susceptibility to acquired and sporadic prion diseases but not for sporadic AD. A recently identified novel protein, named Doppel, shares biochemical and structural homology with PrP(c). Preliminary evidence in a German population indicates that a polymorphism at codon 174 of the prion-like protein (PRND) gene encoding for Doppel protein is a predisposing factor for both prion diseases and sporadic AD. A case-control study utilizing a clinically well-defined group of 283 sporadic AD patients and 288 control subjects was performed to test this association. The current study does not demonstrate any significant difference in T174M PRND genotype or allele frequencies between AD patients and controls. Our study in the Spanish population argues against the hypothesis that the PRND gene is causally related to AD.

Distribution of the M129V polymorphism of the prion protein gene in a Turkish population suggests a high risk for Creutzfeldt-Jakob disease

A polymorphism (M129V) at codon 129 of the prion protein gene (PRNP) results in either a methionine residue (Met) or a valine residue (Val) and is known to determine susceptibility for the development of sporadic or acquired Creutzfeldt-Jakob disease (CJD). The distributions of M129V genotypes and alleles in various general populations have been reported and there are clear differences between Western Europeans and East Asians. We analysed the coding sequence of the PRNP gene in 100 healthy Turkish subjects to determine whether the distributions of the M129V genotypes and alleles or other PRNP gene variants in the Turkish population differ from those in other normal populations. Three known polymorphisms but no other gene variants were detected in the PRNP coding sequence of the Turkish individuals. Genotype frequencies at codon 129 were 57% Met/Met, 34% Met/Val and 9% Val/Val, with an allele frequency of 0.740:0.260 Met:Val. These distributions are considerably different from those reported for other normal populations residing in Western Europe and East Asia, except in Crete. The higher frequency of 129 Met-homozygotes in Turkey than in Western Europe suggests that the Turkish are at greater risk of developing CJD.