Epistasis between intracellular cholesterol trafficking-related genes (NPC1 and ABCA1) and Alzheimer's disease risk

Aberrant cholesterol metabolism has been implicated in Alzheimer´s disease (AD). Recent findings have suggested an interaction of Niemann-Pick C1 (NPC1) and ATP-binding cassette transporter A1 (ABCA1) proteins in intracellular cholesterol transport and in maintaining cell cholesterol balance. Underexpression of NPC1 in concert with underexpression of ABCA1 would result in increased cholesterol accumulation and increased AD risk. We examined a functional polymorphism in the ABCA1 promoter region (−477, rs2422493), and four NPC1 polymorphisms in exon 6 (rs18050810), intron 20 (rs4800488), intron 22 (rs2236707), and intron 24 (rs2510344) capturing 85% of genetic variability in Hap Map CEU population, in a group of 631 Spanish AD patients and 731 controls. Subjects carrying both the ABCA1 (−477) TT genotype and the NPC1 (exon 6) GG genotype (OR = 1.89; 95% CI 1.04-3.41), NPC1 (intron 20) AA genotype (OR = 2.05; 95% CI 1.26-3.33), NPC1 (intron 22) AA genotype (OR = 2.05; 95% CI 1.18-3.58), or NPC1 (intron 24) GG genotype (OR = 1.89; 95% CI 1.16-3.07) had a higher risk of developing AD than subjects without these risk genotypes. Testing for epistatic interaction between genes in the pathway of cholesterol metabolism might be useful for predicting AD risk

Genetic risk score predicting accelerated progression from mild cognitive impairment to Alzheimer's disease

Aside from APOE, the genetic factors that influence in the progression from mild cognitive impairment (MCI) to Alzheimer´s disease (AD) remain largely unknown. We assessed whether a genetic risk score (GRS), based on 8 non-APOE genetic variants previously associated with AD risk in genome-wide association studies, is associated with either risk of conversion or with rapid progression from MCI to AD. Among 288 subjects with MCI, follow-up (mean 26.3 months) identified 118 MCI-converters to AD and 170 MCI-nonconverters. We genotyped ABCA7 rs3764650, BIN1 rs744373, CD2AP rs9296559, CLU rs1113600, CR1 rs1408077, MS4A4E rs670139, MS4A6A rs610932, and PICALM rs3851179. For each subject we calculated a cumulative GRS, defined as the number of risk alleles (range 0-16) with each allele weighted by the AD risk odds ratio. GRS was not associated with risk of conversion from MCI to AD. However, MCI-converters to AD harboring 6 or more risk alleles (second and third GRS tertiles) progressed 2-fold more rapidly to AD when compared with those with less than 6 risk alleles (first GRS tertile). Our GRS is a first step toward development of prediction models for conversion from MCI to AD that incorporate aggregate genetic factors

Genetic variation in the tau kinases pathway may contribute to the risk of Alzheimer´s disease

Tau abnormal hyperphosphorylation and the formation of neurofibrillary tangles in Alzheimer´s disease (AD) brain is the result of upregulation of tau kinases. In a group of 729 Spanish late-onset AD patients and 670 healthy controls, we examined variations into a set of 20 candidate genes of kinases involved in tau phosphorylation at AD-related sites (PRKACB; CAMK2A; MARK1, 2, 3 and 4; CSNK1D; CDC2; RPS6KB1 and 2; p38α and β; IB1; JNK1, 2 and 3; MEK1 and 2; ERK1 and 2), to address hypotheses of genetic variation that might influence AD risk. There was an increased frequency of RPS6KB2 (intron 2, rs917570) minor allele in patients (50%) versus controls (39%) (OR = 1.52; 95% CI 1.30-1.77; p = 1.24×10−5 Bonferroni corrected), and the CDC2 AGC haplotype derived from SNPs in introns 3 (rs2448347), 5 (rs2456772), and 7 (rs1871447) showed a protective effect against AD in APOE ε4 allele noncarriers (permutation p = 1.0×10-4) with a frequency of 9% in cases and 15% in controls. Common genetic variation in the tau kinases pathway does underlie individual differences in susceptibility to AD

Caspase-1 genetic variation is not associated with Alzheimer's disease risk

BACKGROUND: Interleukin (IL)-1beta is a potent proinflammatory cytokine markedly overexpressed in the brains of patients with Alzheimer's disease (AD), and also involved in development of atherosclerosis and coronary artery disease. Caspase-1 (CASP1), formerly called IL-1beta converting enzyme (ICE), mediates the cleavage of the inactive precursor of IL-1beta into the biologically active form. CASP1 genetic variation (G+7/in6A, rs501192) has been associated with susceptibility to myocardial infarction and cardiovascular death risk. We examined the contribution of this gene to the susceptibility for AD. METHODS: We examined genetic variations of CASP1 by genotyping haplotype tagging SNPs (htSNPs) (rs501192, rs556205 and rs530537) in a group of 628 Spanish AD cases and 722 controls. RESULTS: There were no differences in the genotypic, allelic or haplotypic distributions between cases and controls in the overall analysis or after stratification by age, gender or APOE epsilon4 allele. CONCLUSION: Our negative findings in the Spanish population argue against the hypothesis that CASP1 genetic variations are causally related to AD risk

No association of CDK5 genetic variants with Alzheimer's disease risk

<p>Abstract</p> <p>Background</p> <p>As cyclin-dependent kinase 5 (CDK5) has been implicated in the abnormal hyperphosphorylation of tau in Alzheimer's disease (AD) brain, and the development of neurofibrillary tangles, we examined the contribution of this gene to the susceptibility for AD.</p> <p>Methods</p> <p>We examined genetic variations of CDK5 by genotyping haplotype tagging SNPs (htSNPs) (rs9278, rs2069459, rs891507, rs2069454, rs1549759 and rs2069442) in a group of 408 Spanish AD cases and 444 controls.</p> <p>Results</p> <p>There were no differences in the genotypic, allelic or haplotypic distributions between cases and controls in the overall analysis or after stratification by APOE ε4 allele.</p> <p>Conclusion</p> <p>Our negative findings in the Spanish population argue against the hypothesis that CDK5 genetic variations are causally related to AD risk. Still, additional studies using different sets of patients and control subjects deserve further attention, since supporting evidence for association between CDK5 gene and AD risk in the Dutch population exists.</p

DYRK1A genetic variants are not linked to Alzheimer's disease in a Spanish case-control cohort

<p>Abstract</p> <p>Background</p> <p>As dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) has been implicated in the abnormal hyperphosphorylation of tau in Alzheimer's disease (AD) brain, and the development of neurofibrillary tangles, we examined the contribution of this gene to the susceptibility for AD.</p> <p>Methods</p> <p>We examined genetic variations of DYRK1A by genotyping haplotype tagging SNPs (htSNPs) (rs11701483, rs2835740, rs1137600, rs2835761, rs2835762, rs2154545 and rs8132976) in a group of 634 Spanish AD cases and 733 controls.</p> <p>Results</p> <p>There were no differences in the genotypic, allelic or haplotypic distributions between cases and controls in the overall analysis or after stratification by APOE ε4 allele.</p> <p>Conclusion</p> <p>Our negative findings in the Spanish population argue against the hypothesis that DYRK1A genetic variations are causally related to AD risk. Still, additional studies using different sets of patients and control subjects deserve further attention, since supporting evidence for association between DYRK1A gene and AD risk in the Japanese population exists.</p

Detection of early Alzheimer's disease in MCI patients by the combination of MMSE and an episodic memory test

BACKGROUND: Mild cognitive impairment (MCI) is a heterogeneous clinical entity that comprises the prodromal phase of Alzheimer's disease (Pr-AD). New biomarkers are useful in detecting Pr-AD, but they are not universally available. We aimed to investigate baseline clinical and neuropsychological variables that might predict progression from MCI to AD dementia. METHODS: All patients underwent a complete clinical and neuropsychological evaluation at baseline and every 6 months during a two-year follow-up period, with 54 out of 109 MCI patients progressing to dementia (50 of them progressed to AD dementia), and 55 remaining as stable MCI (S-MCI). RESULTS: A combination of MMSE and California Verbal Learning Test Long Delayed Total Recall (CVLT-LDTR) constituted the best predictive model: subjects scoring above 26/30 on MMSE and 4/16 on CVLT-LDTR had a negative predictive value of 93.93% at 2 years, whereas those subjects scoring below both of these cut-off scores had a positive predictive value of 80.95%. CONCLUSIONS: Pr-AD might be distinguished from S-MCI at baseline using the combination of MMSE and CVLT-LDTR. These two neuropsychological predictors are relatively brief and may be readily completed in non-specialist clinical settings

Replication by the Epistasis Project of the interaction between the genes for IL-6 and IL-10 in the risk of Alzheimer's disease

Background: Chronic inflammation is a characteristic of Alzheimer's disease (AD). An interaction associated with the risk of AD has been reported between polymorphisms in the regulatory regions of the genes for the pro-inflammatory cytokine, interleukin-6 (IL-6, gene: IL6), and the anti-inflammatory cytokine, interleukin-10 (IL-10, gene: IL10).Methods: We examined this interaction in the Epistasis Project, a collaboration of 7 AD research groups, contributing DNA samples from 1,757 cases of AD and 6,295 controls.Results: We replicated the interaction. For IL6 rs2069837 AA x IL10 rs1800871 CC, the synergy factor (SF) was 1.63 (95% confidence interval: 1.10-2.41, p = 0.01), controlling for centre, age, gender and apolipoprotein E epsilon 4 (APOE epsilon 4) genotype. Our results are consistent between North Europe (SF = 1.7, p = 0.03) and North Spain (SF = 2.0, p = 0.09). Further replication may require a meta-analysis. However, association due to linkage disequilibrium with other polymorphisms in the regulatory regions of these genes cannot be excluded.Conclusion: We suggest that dysregulation of both IL-6 and IL-10 in some elderly people, due in part to genetic variations in the two genes, contributes to the development of AD. Thus, inflammation facilitates the onset of sporadic AD

Assessing the role of the TREM2 p.R47H variant as a risk factor for Alzheimer's disease and frontotemporal dementia

4 páginas, 1 figura, a tabla. Los autores pertenecen a The dementia genetic Spanish consortium (DEGESCO).A non-synonymous genetic rare variant, rs75932628-T (p.R47H), in the TREM2 gene has recently been reported to be a strong genetic risk factor for Alzheimer's disease (AD). Also, rare recessive mutations have been associated with frontotemporal dementia (FTD). We aimed to investigate the role of p.R47H variant in AD and FTD through a multi-center study comprising 3,172 AD and 682 FTD patients and 2,169 healthy controls from Spain. We found that 0.6% of AD cases carried this variant compared to 0.1% of controls (odds ratio [OR]=4.12, 95% confidence interval [CI]: 1.21-14.00, P=0.014). A meta-analysis comprising 32,598 subjects from four previous studies demonstrated the large effect of the p.R47H variant in AD risk (OR=4.11, 95% CI: 2.99-5.68, P=5.27x10-18). We did not find an association between p.R47H and age of onset of AD or family history of dementia. Finally, none of the FTD patients harbored this genetic variant. These data strongly support the important role of p.R47H in AD risk and suggest that this rare genetic variant is not related to FTD.This study was supported by grants from Instituto de Salud Carlos III (PI12/01311 and 12/00013), grants from the Ministry of Science (SAF2010-15558, SAF2009-10434), Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED, Spain), Consolider (CSD2010-00045), and the Department of Health of the Government of Navarra (refs. 13085 and 3/2008). CR held during the period 2009-2013 a “Torres Quevedo” fellowship from the Spanish Ministry of Science and Technology, co-financed by the European Social Fund. Fundació ACE researchers are indebted to Trinitat Port-Carbó and her family who are supporting Fundació ACE scientific programs.Peer reviewe