Allelic variation of apolipoprotein E in Japanese sporadic Creutzfeldt-Jakob disease patients

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.

Genetic studies in human prion diseases

Human prion diseases are fatal neurodegenerative disorders that are characterized by spongiform changes, astrogliosis, and the accumulation of an abnormal prion protein (PrP(Sc)). Approximately 10%-15% of human prion diseases are familial variants that are caused by pathogenic mutations in the prion protein gene (PRNP). Point mutations or the insertions of one or more copies of a 24 bp repeat are associated with familial human prion diseases including familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome, and fatal familial insomnia. These mutations vary significantly in frequency between countries. Here, we compare the frequency of PRNP mutations between European countries and East Asians. Associations between single nucleotide polymorphisms (SNPs) of several candidate genes including PRNP and CJD have been reported. The SNP of PRNP at codon 129 has been shown to be associated with sporadic, iatrogenic, and variant CJD. The SNPs of several genes other than PRNP have been showed contradictory results. Case-control studies and genome-wide association studies have also been performed to identify candidate genes correlated with variant and/or sporadic CJD. This review provides a general overview of the genetic mutations and polymorphisms that have been analyzed in association with human prion diseases to date.

APOE gene polymorphisms and susceptibility to Creutzfeldt-Jakob disease

Associations between apolipoprotein E (APOE) gene polymorphisms and Creutzfeldt-Jakob disease (CJD) have been reported, but the results from many of these studies are conflicting. To investigate the association between APOE polymorphisms and CJD risk, we performed a meta-analysis. We used odds ratios (OR) with 95% confidence intervals (CI) to assess the strength of the association. The frequency of putative risk alleles in control subjects was estimated with the Mantel-Haenszel method. Cochran's Q statistic and the inconsistency index (I(2)) were used to test heterogeneity. Egger's test and an inverted funnel plot were used to assess bias. Our study included 11 published case-control studies with APOE genotyping, involving a total of 1001 CJD patients and 1211 controls. Overall, the APOE 34 (OR 1.37, 95% CI: 1.09-1.72), and APOE 44 (OR 3.16, 95% CI: 1.37-7.26) genotypes and the APOE 4 (OR 1.41, 95% CI: 1.08-1.85) allele were associated with an increased risk of CJD, and the APOE 33 (OR 0.81, 95% CI: 0.67-0.97) genotype tended to protect against CJD. However, we did not find significant evidence supporting associations of the APOE 22 (OR 1.15, 95% CI: 0.45-2.93), APOE 23 (OR 0.84, 95% CI: 0.64-1.09), or APOE 24 (OR 1.40, 95% CI: 0.70-2.77) genotypes, nor the APOE 2 (OR 1.02, 95% CI: 0.73-1.42) or APOE 3 (OR 0.82, 95% CI: 0.65-1.02) alleles with CJD using a fixed-effects model. Our results support a genetic association between APOE polymorphisms and CJD.

Expression analysis, single nucleotide polymorphisms and combined genotypes in candidate genes and their associations with growth and carcass traits in Qinchuan cattle

The apolipoprotein E (ApoE) gene is an important component of plasma lipoprotein, and Fas apoptosis inhibitory molecule (FAIM) is a novel anti-apoptotic gene. In this study, we researched and discussed seven genes in eight different tissues in Qinchuan cattle by quantitative Real-time PCR. The result of analysis showed that ApoE and FAIM 2 genes had a correlation with muscle and fat. PCR-RFLP was applied to analyze the genetic variations of the ApoE and FAIM 2 genes and verify the effect on growth and carcass traits in a total of 365 Qinchuan cattles. The result of haplotype analysis showed that nine different haplotypes were identified among the four SNPs in ApoE and FAIM 2 genes. The statistical analyses indicated that the four SNPs were significant association with growth and carcass traits (P < 0.05, N = 365); and the four SNPs were significant association between nine combined genotypes of candidate genes and growth and carcass traits. Taken together, our results provide the evidence that polymorphisms in candidate genes are associated with growth and carcass traits in Qinchuan cattle, and may be used as a possible candidate for marker-assisted selection and management in beef cattle breeding program.

APOE distribution in world populations with new data from India and the UK

BACKGROUND

The APOE gene and its protein product is associated with a number of plasma proteins like very-low density lipoprotein (VLDL), high density lipoprotein (HDL) chylomicrons, chylomicron remnants, and plays a crucial role in lipid metabolism. The APOE gene is polymorphic and common alleles (*E2, *E3 and *E4) have been associated with a number of common and complex diseases in different populations. Due to their crucial role in metabolism and clinical significance, it is imperative that allelic variation in different populations is analysed to evaluate the usage of APOE in an evolutionary and clinical context.

AIM

We report allelic variation at the APOE locus in three European and four Indian populations and evaluate global patterns of genetic variation at this locus. The large, intricate and unexpected heterogeneity of this locus in its global perspective may have insightful consequences, which we have explored in this paper.

SUBJECT AND METHODS

Apolipoprotein E genotypes were determined in four population groups (Punjabi Sikhs, Punjabi Hindus, Maria Gonds and Koch, total individuals = 497) of India and three regionally sub-divided British populations (Nottinghamshire, East Midlands and West Midlands, total individuals = 621). The extent and distribution of APOE allele frequencies were compared with 292 populations of the world using a variety of multivariate methods.

RESULTS

Three alleles, APOE*E2, APOE*E3 and APOE*E4, were observed with contrasting variation, although *E4 was absent in the tribal population of Koch. Higher heterozygosities (>43%) in British populations reflected their greater genetic diversity at this locus. The overall pattern of allelic diversity among these populations is comparable to many European and Indian populations. At a global level, higher frequencies of the *E2 allele were observed in Africa and Oceania (0.099 +/- 0.083 and 0.111 +/- 0.052, respectively). Similarly, *E4 allele averages were higher in Oceania (0.221 +/- 0.149) and Africa (0.209 +/- 0.090), while Indian and Asian populations showed the highest frequencies of *E3 allele. The coefficient of gene differentiation was found to be highest in South America (9.6%), although the highest genetic diversity was observed in Oceania (48.7%) and Africa (46.3%). APOE*E2 revealed a statistically significant decreasing cline towards the north in Asia (r = -0.407, d.f. = 70, p < 0.05), which is not compatible with the coronary heart disease statistics in this continent. APOE*E4 showed a significant increasing cline in North European populations. Spatial autocorrelation analysis shows that the variation at this locus is influenced by 'isolation by distance' with a strong positive correlation for lower distances up to 1313 km.

CONCLUSION

Overall APOE allelic variation in UK and Indian populations is comparable to previous studies but in tribal populations *E4 allele frequency was very low or absent. At a global level allelic variation shows that geography, isolation by distance, genetic drift and possibly pre-historical selection are responsible for shaping the spectrum of genetic variation at the APOE gene. Overall, APOE is a good anthropogenetic and clinical diagnostic marker.

Increased frequency of positive family history of dementia in sporadic CJD

OBJECTIVE

To analyze whether a positive family history of dementia (PFHD) is more common in sporadic CJD (sCJD) than in healthy/population controls and to study associated risk factors.

PATIENTS/METHODS

Six hundred and eighty-five sCJD patients and 659 sex-/age-matched controls were included. A PFHD in parents/grandparents/siblings was evaluated. The PRNP M129V polymorphism and ApoE genotype in sCJD with/without PFHD were determined by PCR.

RESULTS

PFHD was found in 12.1% of sCJD patients and 5.6% of controls (p<0.001). No significant difference in M129V polymorphism was found between sCJD with and without PFHD. Thirty-six percent of sCJD patients with PFHD, 26% without PFHD and 19% of healthy controls had at least one ApoE4 allele. Compared to controls, ApoE4 allele frequency (p=0.005) and proportion of ApoE4 allele carriers (p=0.019) were significantly higher in sCJD with PFHD.

INTERPRETATION

A higher frequency of the ApoE4 allele in sCJD with a PFHD could be indicative of an additional risk factor in CJD.

Phenotypic heterogeneity and genetic modification of P102L inherited prion disease in an international series

The largest kindred with inherited prion disease P102L, historically Gerstmann-Sträussler-Scheinker syndrome, originates from central England, with émigrés now resident in various parts of the English-speaking world. We have collected data from 84 patients in the large UK kindred and numerous small unrelated pedigrees to investigate phenotypic heterogeneity and modifying factors. This collection represents by far the largest series of P102L patients so far reported. Microsatellite and genealogical analyses of eight separate European kindreds support multiple distinct mutational events at a cytosine-phosphate diester-guanidine dinucleotide mutation hot spot. All of the smaller P102L kindreds were linked to polymorphic human prion protein gene codon 129M and were not connected by genealogy or microsatellite haplotype background to the large kindred or each other. While many present with classical Gerstmann-Sträussler-Scheinker syndrome, a slowly progressive cerebellar ataxia with later onset cognitive impairment, there is remarkable heterogeneity. A subset of patients present with prominent cognitive and psychiatric features and some have met diagnostic criteria for sporadic Creutzfeldt-Jakob disease. We show that polymorphic human prion protein gene codon 129 modifies age at onset: the earliest eight clinical onsets were all MM homozygotes and overall age at onset was 7 years earlier for MM compared with MV heterozygotes (P = 0.02). Unexpectedly, apolipoprotein E4 carriers have a delayed age of onset by 10 years (P = 0.02). We found a preponderance of female patients compared with males (54 females versus 30 males, P = 0.01), which probably relates to ascertainment bias. However, these modifiers had no impact on a semi-quantitative pathological phenotype in 10 autopsied patients. These data allow an appreciation of the range of clinical phenotype, modern imaging and molecular investigation and should inform genetic counselling of at-risk individuals, with the identification of two genetic modifiers.

ApoE distribution and family history in genetic prion diseases in Germany

We analyzed the ApoE genotype in patients with genetic prion diseases (gPD) with respect to family history (FH) of dementia/prion disease (PD) compared to non-demented controls. Fifty-nine gPD patients and 51 sex-/age-matched controls were included. A positive FH of dementia and PD (PFH) were evaluated. The prion protein gene (PRNP) codon 129 and ApoE genotype were determined by polymerase chain reaction (PCR). The frequency of FH of neurodegenerative disorder/prion disease/dementia varied in different PRNP mutations. PFH was found in 87% of D178N patients, but was rarer in others. Although the ApoE genotype distribution was not significantly different between gPD patients and controls, the protective E2 alleles were more frequent in controls than in patients without a PFH and even less frequent in those with a PFH (18, 16, and 11%). E4 alleles as a risk factor of Alzheimer's disease were more common in controls and patients with a PFH than in those without PFH (25, 21, and 13%). No effect of the codon 129 genotype was detected. Only about two-thirds of gPD patients had PFH of PD, while in one-third, PFH of slowly progressive dementia was reported. Underreporting of PFH of gPD may play a role; however, the varying PFH frequency across various mutations is not explained by this factor only.

Recombinant neural protein PrP can bind with both recombinant and native apolipoprotein E in vitro

The most essential and crucial step during the pathogenesis of transmissible spongiform encephalopathy is the conformational change of cellular prion protein (PrP(C)) to pathologic isoform (PrP(Sc)). A lot of data revealed that caveolae-like domains (CLDs) in the cell surface were the probable place where the conversion of PrP proteins happened. Apolipoprotein E (ApoE) is an apolipoprotein which is considered to play an important role in the development of Alzheimer's disease and other neurodegenerative diseases by forming protein complex through binding to the receptor located in the clathrin-coated pits of the cell surface. In this study, a 914-bp cDNA sequence encoding human ApoE3 was amplified from neuroblastoma cell line SH-SY5Y. Three human ApoE isomers were expressed and purified from Escherichia coli. ApoE-specific antiserum was prepared by immunizing rabbits with the purified ApoE3. GST/His pull-down assay, immunoprecipitation and ELISA revealed that three full-length ApoE isomers interact with the recombinant full-length PrP protein in vitro. The regions corresponding to protein binding were mapped in the N-terminal segment of ApoE (amino acid 1-194) and the N-terminal of PrP (amino acid 23-90). Moreover, the recombinant PrP showed the ability to form a complex with the native ApoE from liver tissues. Our data provided direct evidence of molecular interaction between ApoE and PrP. It also supplied scientific clues for assessing the significance of CLDs on the surface of cellular membrane in the process of conformational conversion from PrP(C) to PrP(Sc) and probing into the pathogenesis of transmissible spongiform encephalopathy.

Meat‐Adaptive Genes and the Evolution of Slower Aging in Humans

The chimpanzee life span is shorter than that of humans, which is consistent with a faster schedule of aging. We consider aspects of diet that may have selected for genes that allowed the evolution of longer human life spans with slower aging. Diet has changed remarkably during human evolution. All direct human ancestors are believed to have been largely herbivorous. Chimpanzees eat more meat than other great apes, but in captivity are sensitive to hypercholesterolemia and vascular disease. We argue that this dietary shift to increased regular consumption of fatty animal tissues in the course of hominid evolution was mediated by selection for "meat-adaptive" genes. This selection conferred resistance to disease risks associated with meat eating also increased life expectancy. One candidate gene is apolipoprotein E (apoE), with the E3 allele evolved in the genus Homo that reduces the risks for Alzheimer's and vascular disease, as well as influencing inflammation, infection, and neuronal growth. Other evolved genes mediate lipid metabolism and host defense. The timing of the evolution of apoE and other candidates for meat-adaptive genes is discussed in relation to key events in human evolution.

Influence of the prion protein and the apolipoprotein E genotype on the Creutzfeldt-Jakob Disease phenotype

We investigated the risk associated with the codon 129 polymorphism in the prion protein gene (PRNP) and apolipoprotein E gene (APOE) isoforms for development of Creutzfeldt-Jakob disease (CJD) (n=126) and the possible influences on the disease pathology and its most important clinical characteristics. The PRNP M129V (PRNP129) polymorphism was determined using both DNA extracted from formalin fixed and paraffin embedded brain tissue (n=59) and leukocyte extracted DNA (n=67). In the latter group also the PRNP open reading frame and the APOE genotype were analysed and compared to a neurologically unaffected, age and sex matched control group (n=79). We found that methionine homozygosity of the PRNP129 increases the risk for developing CJD. PRNP129 also influenced the prion accumulation patterns in brain. The APOE 4 allele was an independent risk factor for developing CJD. We further observed a significant dose dependent APOE 4 effect on the number and type of amyloid-beta plaques in the brain of CJD patients.

Risk of dementia in parents of probands with and without the apolipoprotein E4 allele. The EVA study

STUDY OBJECTIVE

Age, family history of dementia and the epsilon 4 allele of the apolipoprotein E gene have been associated with Alzheimer's disease (AD). Considering the strength of APOE-epsilon 4 as a genetic risk factor for AD, this factor might explain a large part of the association between AD and a family history of dementia. Therefore, in the general population, a higher frequency of dementia should be observed among parents of probands with at least one epsilon 4 allele than in parents of probands without this allele.

DESIGN, SETTING, AND PARTICIPANTS

The study investigated a sample of 1153 volunteers between 59 and 71 years old, genotyped for the APOE gene, all participating in the EVA study. Dementia in their parents was determined using a self reported questionnaire.

MAIN RESULTS

The frequency of dementia in 2164 parents was examined and it was found that 245 were demented. The percentage of demented parents was 13.0% in the subgroup of parents of subjects having one or two epsilon 4 alleles and 10.8% in the other subgroup. The relative risk of dementia among parents according to the APOE-epsilon 4 status of probands, was calculated using a Cox model adjusted for the educational level of parents and their history of stroke: RR = 1.21 (95% CI 0.90, 1.63).

CONCLUSION

This lack of association supports the observation that in the general population, APOE-epsilon 4 cannot explain a large part of family history of dementia.

Apolipoprotein E epsilon 4 allele and Japanese late-onset depressive disorders

BACKGROUND

Several studies have suggested that late-onset depressive disorder (LOD) and the apolipoprotein E (Apo E) epsilon 4 allele are associated with dementia, respectively. The Apo E polymorphism is significantly heterogeneous among races. We hypothesized that the Apo E epsilon 4 allele frequency is elevated in Japanese LOD.

METHODS

The Apo E genotype was studied in 134 patients (male, 53; female, 81) with early-/late-onset depressive disorder and 105 healthy normal controls (male, 41; female, 64). The patients were subdivided into those with early onset and late onset using 45 and 50 years as the cutoff ages. All the subjects were Japanese.

RESULTS

There was statistically no difference between normal control subjects and patients with depressive disorders in Apo E genotype or allele frequency. There was statistically no difference in the age of onset of depressive disorders according to the Apo E genotype. There was no relation between the age of onset of depressive disorder and the number of epsilon 4 alleles the patient had. There was also no association between early-/late-onset depressive disorder and the Apo E genotype or allele frequency.

CONCLUSIONS

Our results suggest that there is no association between the Apo E epsilon 4 allele and Japanese LOD.

Evaluation of risk factors for Alzheimer's disease in elderly east Africans

A number of biological risk factors have been implicated for Alzheimer's disease (AD). The investigation of prevalence rates of AD in crosscultural populations has much potential in validating these factors. We previously assessed brain amyloid beta (A beta) protein deposition and other lesions associated with AD as possible markers for preclinical AD in elderly nondemented East Africans. In further analysis, we demonstrate that 17-19% of elderly East African subjects without clinical neurological disease exhibited neocortical A beta deposits and minimal neurofibrillary changes at necropsy that was qualitatively and quantitatively similar to that in an age-matched elderly control sample from Cleveland, OH. A beta deposits varied from numerous diffuse to highly localized neuritic plaques and were predominantly reactive for the longer A beta 42 species. In parallel studies, we evaluated another recently implicated factor in AD, the apolipoprotein E genotype. We found relatively high frequencies of the apolipoprotein E-epsilon 4 allele in elderly nondemented East Africans. The frequencies were comparable to those in other African populations but higher than in subjects from developed countries. Our limited study suggests that elderly East Africans acquire cerebral lesions found in AD subjects but the apolipoprotein E-epsilon 4 allele may not be a highly specific factor for the disease among East Africans.

Apolipoprotein E in sporadic and familial Creutzfeldt-Jakob disease

We assessed the apolipoprotein E (ApoE) genotype in 49 sporadic and ten familial Creutzfeldt-Jakob disease (CJD) patients, in seven healthy siblings with a PRNP mutation and in 84 controls. In sporadic CJD, ApoE genotypes and allelic frequencies do not significantly differ from that of controls. No influence of ApoE genotypes on age at onset was found. In familial cases, the disease appeared in mutated subjects showing the same ApoE genotype as members who have not yet developed CJD. Our results provide further evidence that ApoE is not a risk factor for CJD.