Chitinase-3-like 1 protein (CHI3L1) locus influences cerebrospinal fluid levels of YKL-40

Background

Alzheimer’s disease (AD) pathology appears several years before clinical symptoms, so identifying ways to detect individuals in the preclinical stage is imperative. The cerebrospinal fluid (CSF) Tau/Aβ₄₂ ratio is currently the best known predictor of AD status and cognitive decline, and the ratio of CSF levels of chitinase-3-like 1 protein (CHI3L1, YKL-40) and amyloid beta (Aβ₄₂) were reported as predictive, but individual variability and group overlap inhibits their utility for individual diagnosis making it necessary to find ways to improve sensitivity of these biomarkers.

Methods

We used linear regression to identify genetic loci associated with CSF YKL-40 levels in 379 individuals (80 cognitively impaired and 299 cognitively normal) from the Charles F and Joanne Knight Alzheimer’s Disease Research Center. We tested correlations between YKL-40 and CSF Tau/Aβ₄₂ ratio, Aβ₄₂, tau, and phosphorylated tau (ptau₁₈₁). We used studentized residuals from a linear regression model of the log-transformed, standardized protein levels and the additive reference allele counts from the most significant locus to adjust YKL-40 values and tested the differences in correlations with CSF Tau/Aβ₄₂ ratio, Aβ₄₂, tau, and ptau₁₈₁.

Results

We found that genetic variants on the CH13L1 locus were significantly associated with CSF YKL-40 levels, but not AD risk, age at onset, or disease progression. The most significant variant is a reported expression quantitative trait locus for CHI3L1, the gene which encodes YKL-40, and explained 12.74 % of the variance in CSF YKL-40 in our study. YKL-40 was positively correlated with ptau₁₈₁ (r = 0.521) and the strength of the correlation significantly increased with the addition of genetic information (r = 0.573, p = 0.006).

Conclusions

CSF YKL-40 levels are likely a biomarker for AD, but we found no evidence that they are an AD endophenotype. YKL-40 levels are highly regulated by genetic variation, and by including genetic information the strength of the correlation between YKL-40 and ptau₁₈₁ levels is significantly improved. Our results suggest that studies of potential biomarkers may benefit from including genetic information.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-016-0742-9) contains supplementary material, which is available to authorized users.

The Role of Cardiovascular Risk Factors and Stroke in Familial Alzheimer Disease

IMPORTANCE

The contribution of cardiovascular disease (CV) and cerebrovascular disease to the risk for late-onset Alzheimer disease (LOAD) has been long debated. Investigations have shown that antecedent CV risk factors increase the risk for LOAD, although other investigations have failed to validate this association.

OBJECTIVE

To study the contribution of CV risk factors (type 2 diabetes, hypertension, and heart disease) and the history of stroke to LOAD in a data set of large families multiply affected by LOAD.

DESIGN, SETTING, AND PARTICIPANTS

The National Institute on Aging Late-Onset Alzheimer Disease/National Cell Repository for Alzheimer Disease family study (hereinafter referred to as NIA-LOAD study) is a longitudinal study of families with multiple members affected with LOAD. A multiethnic community-based longitudinal study (Washington Heights-Inwood Columbia Aging Project [WHICAP]) was used to replicate findings. The 6553 participants in the NIA-LOAD study were recruited from 23 US Alzheimer disease centers with ongoing data collection since 2003; the 5972 WHICAP participants were recruited at Columbia University with ongoing data collection since 1992. Data analysis was performed from 2003 to 2015.

MAIN OUTCOMES AND MEASURES

Generalized mixed logistic regression models tested the association of CV risk factors (primary association) with LOAD. History of stroke was used for the secondary association. A secondary model adjusted for the presence of an apolipoprotein E (APOE) ε4 allele. A genetic risk score, based on common variants associated with LOAD, was used to account for LOAD genetic risk beyond the APOE ε4 effect. Mediation analyses evaluated stroke as a mediating factor between the primary association and LOAD.

RESULTS

A total of 6553 NIA-LOAD participants were included in the analyses (4044 women [61.7%]; 2509 men [38.3%]; mean [SD] age, 77.0 [9] years), with 5972 individuals from the WHICAP study included in the replication sample (4072 women [68.2%]; 1900 men [31.8%]; mean [SD] age, 76.5 [7.0] years). Hypertension was associated with decreased LOAD risk (odds ratio [OR], 0.63; 95% CI, 0.55-0.72); type 2 diabetes and heart disease were not. History of stroke conferred greater than 2-fold increased risk for LOAD (OR, 2.23; 95% CI, 1.75-2.83). Adjustment for APOE ε4 did not alter results. The genetic risk score was associated with LOAD (OR, 2.85; 95% CI, 2.05-3.97) but did not change the independent association of LOAD with hypertension or stroke. In the WHICAP sample, hypertension was not associated with LOAD (OR, 0.99; 95% CI, 0.88-1.11), whereas history of stroke increased the risk for LOAD (OR, 1.96; 95% CI, 1.56-2.46). The effect of hypertension on LOAD risk was also mediated by stroke in the NIA-LOAD and the WHICAP samples.

CONCLUSIONS AND RELEVANCE

In familial and sporadic LOAD, a history of stroke was significantly associated with increased disease risk and mediated the association between selected CV risk factors and LOAD, which appears to be independent of the LOAD-related genetic background.

Phenotypic Similarities Between Late-Onset Autosomal Dominant and Sporadic Alzheimer Disease: A Single-Family Case-Control Study

IMPORTANCE

The amyloid hypothesis posits that disrupted β-amyloid homeostasis initiates the pathological process resulting in Alzheimer disease (AD). Autosomal dominant AD (ADAD) has an early symptomatic onset and is caused by single-gene mutations that result in overproduction of β-amyloid 42. To the extent that sporadic late-onset AD (LOAD) also results from dysregulated β-amyloid 42, the clinical phenotypes of ADAD and LOAD should be similar when controlling for the effects of age.

OBJECTIVE

To use a family with late-onset ADAD caused by a presenilin 1 (PSEN1) gene mutation to mitigate the potential confound of age when comparing ADAD and LOAD.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study was conducted at the Knight Alzheimer Disease Research Center at Washington University, St Louis, Missouri, and other National Institutes of Aging-funded AD centers in the United States. Ten PSEN1 A79V mutation carriers from multiple generations of a family with late-onset ADAD and 12 noncarrier family members were followed up at the Knight Alzheimer Disease Research Center (1985-2015) and 1115 individuals with neuropathologically confirmed LOAD were included from the National Alzheimer Coordinating Center database (September 2005-December 2014). Data analysis was completed in January 2016, including Knight Alzheimer Disease Research Center patient data collected up until the end of 2015.

MAIN OUTCOMES AND MEASURES

Planned comparison of clinical characteristics between cohorts, including age at symptom onset, associated symptoms and signs, rates of progression, and disease duration.

RESULTS

Of the PSEN1 A79V carriers in the family with late-onset ADAD, 4 were female (57%); among those with LOAD, 529 were female (47%). Seven mutation carriers (70%) developed AD dementia, while 3 were yet asymptomatic in their seventh and eighth decades of life. No differences were observed between mutation carriers and individuals with LOAD concerning age at symptom onset (mutation carriers: mean, 75 years [range, 63-77 years] vs those with LOAD: mean, 74 years [range, 60-101 years]; P = .29), presenting symptoms (memory loss in 7 of 7 mutation carriers [100%] vs 958 of 1063 individuals with LOAD [90.1%]; P ≥ .99) and duration (mutation carriers: mean, 9.9 years [range, 2.3-12.8 years] vs those with LOAD: 9 years [range, 1-27 years]; P = .73), and rate of progression of dementia (median annualized change in Clinical Dementia Rating-Sum of Boxes score, mutation carriers: 1.2 [range, 0.1-3.3] vs those with LOAD: 1.9 [range, -3.5 to 11.9]; P = .73). Early emergence of comorbid hallucinations and delusions were observed in 57% of individuals with ADAD (4 of 7) vs 19% of individuals with LOAD (137 of 706) (P = .03). Three of 12 noncarriers (25%) from the PSEN1 A79V family are potential phenocopies as they also developed AD dementia (median age at onset, 76.0 years).

CONCLUSIONS AND RELEVANCE

In this family, the amyloidogenic PSEN1 A79V mutation recapitulates the clinical attributes of LOAD. Previously reported clinical phenotypic differences between individuals with ADAD and LOAD may reflect age- or mutation-dependent effects.

Variants in ACPP are associated with cerebrospinal fluid Prostatic Acid Phosphatase levels

BACKGROUND

Prostatic Acid Phosphatase (PAP) is an enzyme that is produced primarily in the prostate and functions as a cell growth regulator and potential tumor suppressor. Understanding the genetic regulation of this enzyme is important because PAP plays an important role in prostate cancer and is expressed in other tissues such as the brain.

METHODS

We tested association between 5.8 M SNPs and PAP levels in cerebrospinal fluid across 543 individuals in two datasets using linear regression. We then performed meta-analyses using METAL =with a significance threshold of p < 5 × 10(-8) and removed SNPs where the direction of the effect was different between the two datasets, identifying 289 candidate SNPs that affect PAP cerebrospinal fluid levels. We analyzed each of these SNPs individually and prioritized SNPs that had biologically meaningful functional annotations in wANNOVAR (e.g. non-synonymous, stop gain, 3' UTR, etc.) or had a RegulomeDB score less than 3.

RESULTS

Thirteen SNPs met our criteria, suggesting they are candidate causal alleles that underlie ACPP regulation and expression.

CONCLUSIONS

Given PAP's expression in the brain and its role as a cell-growth regulator and tumor suppressor, our results have important implications in brain health such as cancer and other brain diseases including neurodegenerative diseases (e.g., Alzheimer's disease and Parkinson's disease) and mental health (e.g., anxiety, depression, and schizophrenia).

Variants in CCL16 are associated with blood plasma and cerebrospinal fluid CCL16 protein levels

Background

CCL16 is a chemokine predominantly expressed in the liver, but is also found in the blood and brain, and is known to play important roles in immune response and angiogenesis. Little is known about the gene’s regulation.

Methods

Here, we test for potential causal SNPs that affect CCL16 protein levels in both blood plasma and cerebrospinal fluid in a genome-wide association study across two datasets. We then use METAL to performed meta-analyses with a significance threshold of p < 5x10⁻⁸. We removed SNPs where the direction of the effect was different between the two datasets.

Results

We identify 10 SNPs associated with increased CCL16 protein levels in both biological fluids.

Conclusions

Our results will help understand CCL16’s regulation, allowing researchers to better understand the gene’s effects on human health.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2788-x) contains supplementary material, which is available to authorized users.

Influence of Coding Variability in APP-Aβ Metabolism Genes in Sporadic Alzheimer's Disease

The cerebral deposition of Aβ42, a neurotoxic proteolytic derivate of amyloid precursor protein (APP), is a central event in Alzheimer's disease (AD)(Amyloid hypothesis). Given the key role of APP-Aβ metabolism in AD pathogenesis, we selected 29 genes involved in APP processing, Aβ degradation and clearance. We then used exome and genome sequencing to investigate the single independent (single-variant association test) and cumulative (gene-based association test) effect of coding variants in these genes as potential susceptibility factors for AD, in a cohort composed of 332 sporadic and mainly late-onset AD cases and 676 elderly controls from North America and the UK. Our study shows that common coding variability in these genes does not play a major role for the disease development. In the single-variant association analysis, the main hits, none of which statistically significant after multiple testing correction (1.9e-4 Collapse

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MESH Headings

• Alzheimer Disease/genetics
• Alzheimer Disease/metabolism
• Amyloid beta-Peptides/genetics
• Amyloid beta-Peptides/metabolism
• Amyloid beta-Protein Precursor/genetics
• Amyloid beta-Protein Precursor/metabolism
• Computational Biology
• Exome
• Humans

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Grants

• U24 AG021886 NIA NIH HHS
• P50 AG016574 NIA NIH HHS
• U01 AG052411 NIA NIH HHS
• MR/L016397/1 Medical Research Council
• P01 AG026276 NIA NIH HHS
• Z01 AG000950 Intramural NIH HHS
• G1100695 Medical Research Council
• RF1 AG044546 NIA NIH HHS
• Wellcome Trust
• R01 AG018023 NIA NIH HHS
• U01 AG006786 NIA NIH HHS
• P01 AG003991 NIA NIH HHS
• P50 AG005681 NIA NIH HHS
• Alzheimer’s Research UK
• Wellcome Trust/MRC Joint Call in Neurodegeneration Award
• National Institute for Health Research Biomedical Research Unit in Dementia at University College London Hospitals
• the Big Lottery
• Alzheimer's Research UK
• Intramural Research Programs of the National Institute on Aging and the National Institute of Neurological Disease and Stroke

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ABCA7 p.G215S as potential protective factor for Alzheimer's disease

Genome-wide association studies (GWASs) have been effective approaches to dissect common genetic variability underlying complex diseases in a systematic and unbiased way. Recently, GWASs have led to the discovery of over 20 susceptibility loci for Alzheimer's disease (AD). Despite the evidence showing the contribution of these loci to AD pathogenesis, their genetic architecture has not been extensively investigated, leaving the possibility that low frequency and rare coding variants may also occur and contribute to the risk of disease. We have used exome and genome sequencing data to analyze the single independent and joint effect of rare and low-frequency protein coding variants in 9 AD GWAS loci with the strongest effect sizes after APOE (BIN1, CLU, CR1, PICALM, MS4A6A, ABCA7, EPHA1, CD33, and CD2AP) in a cohort of 332 sporadic AD cases and 676 elderly controls of British and North-American ancestry. We identified coding variability in ABCA7 as contributing to AD risk. This locus harbors a low-frequency coding variant (p.G215S, rs72973581, minor allele frequency = 4.3%) conferring a modest but statistically significant protection against AD (p-value = 0.024, odds ratio = 0.57, 95% confidence interval = 0.41–0.80). Notably, our results are not driven by an enrichment of loss of function variants in ABCA7, recently reported as main pathogenic factor underlying AD risk at this locus. In summary, our study confirms the role of ABCA7 in AD and provides new insights that should address functional studies.

Genome-wide polygenic scores for age at onset of alcohol dependence and association with alcohol-related measures

Age at onset of alcohol dependence (AO-AD) is a defining feature of multiple drinking typologies. AO-AD is heritable and likely shares genetic liability with other aspects of alcohol consumption. We examine whether polygenic variation in AO-AD, based on a genome-wide association study (GWAS), was associated with AO-AD and other aspects of alcohol consumption in two independent samples. Genetic risk scores (GRS) were created based on AO-AD GWAS results from a discovery sample of 1788 regular drinkers from extended pedigrees from the Collaborative Study of the Genetics of Alcoholism (COGA). GRS were used to predict AO-AD, AD and Alcohol dependence symptom count (AD-SX), age at onset of intoxication (AO-I), as well as maxdrinks in regular drinking participants from two independent samples-the Study of Addictions: Genes and Environment (SAGE; n=2336) and an Australian sample (OZ-ALC; n=5816). GRS for AO-AD from COGA explained a modest but significant proportion of the variance in all alcohol-related phenotypes in SAGE. Despite including effect sizes associated with large numbers of single nucleotide polymorphisms (SNPs; >110 000), GRS explained, at most, 0.7% of the variance in these alcohol measures in this independent sample. In OZ-ALC, significant but even more modest associations were noted with variance estimates ranging from 0.03 to 0.16%. In conclusion, there is modest evidence that genetic variation in AO-AD is associated with liability to other aspects of alcohol involvement.

Association of Long Runs of Homozygosity With Alzheimer Disease Among African American Individuals

IMPORTANCE

Mutations in known causal Alzheimer disease (AD) genes account for only 1% to 3% of patients and almost all are dominantly inherited. Recessive inheritance of complex phenotypes can be linked to long (>1-megabase [Mb]) runs of homozygosity (ROHs) detectable by single-nucleotide polymorphism (SNP) arrays.

OBJECTIVE

To evaluate the association between ROHs and AD in an African American population known to have a risk for AD up to 3 times higher than white individuals.

DESIGN, SETTING, AND PARTICIPANTS

Case-control study of a large African American data set previously genotyped on different genome-wide SNP arrays conducted from December 2013 to January 2015. Global and locus-based ROH measurements were analyzed using raw or imputed genotype data. We studied the raw genotypes from 2 case-control subsets grouped based on SNP array: Alzheimer's Disease Genetics Consortium data set (871 cases and 1620 control individuals) and Chicago Health and Aging Project-Indianapolis Ibadan Dementia Study data set (279 cases and 1367 control individuals). We then examined the entire data set using imputed genotypes from 1917 cases and 3858 control individuals.

MAIN OUTCOMES AND MEASURES

The ROHs larger than 1 Mb, 2 Mb, or 3 Mb were investigated separately for global burden evaluation, consensus regions, and gene-based analyses.

RESULTS

The African American cohort had a low degree of inbreeding (F ~ 0.006). In the Alzheimer's Disease Genetics Consortium data set, we detected a significantly higher proportion of cases with ROHs greater than 2 Mb (P = .004) or greater than 3 Mb (P = .02), as well as a significant 114-kilobase consensus region on chr4q31.3 (empirical P value 2 = .04; ROHs >2 Mb). In the Chicago Health and Aging Project-Indianapolis Ibadan Dementia Study data set, we identified a significant 202-kilobase consensus region on Chr15q24.1 (empirical P value 2 = .02; ROHs >1 Mb) and a cluster of 13 significant genes on Chr3p21.31 (empirical P value 2 = .03; ROHs >3 Mb). A total of 43 of 49 nominally significant genes common for both data sets also mapped to Chr3p21.31. Analyses of imputed SNP data from the entire data set confirmed the association of AD with global ROH measurements (12.38 ROHs >1 Mb in cases vs 12.11 in controls; 2.986 Mb average size of ROHs >2 Mb in cases vs 2.889 Mb in controls; and 22% of cases with ROHs >3 Mb vs 19% of controls) and a gene-cluster on Chr3p21.31 (empirical P value 2 = .006-.04; ROHs >3 Mb). Also, we detected a significant association between AD and CLDN17 (empirical P value 2 = .01; ROHs >1 Mb), encoding a protein from the Claudin family, members of which were previously suggested as AD biomarkers.

CONCLUSIONS AND RELEVANCE

To our knowledge, we discovered the first evidence of increased burden of ROHs among patients with AD from an outbred African American population, which could reflect either the cumulative effect of multiple ROHs to AD or the contribution of specific loci harboring recessive mutations and risk haplotypes in a subset of patients. Sequencing is required to uncover AD variants in these individuals.

Global and local ancestry in African-Americans: Implications for Alzheimer's disease risk

INTRODUCTION

African-American (AA) individuals have a higher risk for late-onset Alzheimer's disease (LOAD) than Americans of primarily European ancestry (EA). Recently, the largest genome-wide association study in AAs to date confirmed that six of the Alzheimer's disease (AD)-related genetic variants originally discovered in EA cohorts are also risk variants in AA; however, the risk attributable to many of the loci (e.g., APOE, ABCA7) differed substantially from previous studies in EA. There likely are risk variants of higher frequency in AAs that have not been discovered.

METHODS

We performed a comprehensive analysis of genetically determined local and global ancestry in AAs with regard to LOAD status.

RESULTS

Compared to controls, LOAD cases showed higher levels of African ancestry, both globally and at several LOAD relevant loci, which explained risk for AD beyond global differences.

DISCUSSION

Exploratory post hoc analyses highlight regions with greatest differences in ancestry as potential candidate regions for future genetic analyses.

Alzheimer's Disease Risk Polymorphisms Regulate Gene Expression in the ZCWPW1 and the CELF1 Loci

Late onset Alzheimer’s disease (LOAD) is a genetically complex and clinically heterogeneous disease. Recent large-scale genome wide association studies (GWAS) have identified more than twenty loci that modify risk for AD. Despite the identification of these loci, little progress has been made in identifying the functional variants that explain the association with AD risk. Thus, we sought to determine whether the novel LOAD GWAS single nucleotide polymorphisms (SNPs) alter expression of LOAD GWAS genes and whether expression of these genes is altered in AD brains. The majority of LOAD GWAS SNPs occur in gene dense regions under large linkage disequilibrium (LD) blocks, making it unclear which gene(s) are modified by the SNP. Thus, we tested for brain expression quantitative trait loci (eQTLs) between LOAD GWAS SNPs and SNPs in high LD with the LOAD GWAS SNPs in all of the genes within the GWAS loci. We found a significant eQTL between rs1476679 and PILRB and GATS, which occurs within the ZCWPW1 locus. PILRB and GATS expression levels, within the ZCWPW1 locus, were also associated with AD status. Rs7120548 was associated with MTCH2 expression, which occurs within the CELF1 locus. Additionally, expression of several genes within the CELF1 locus, including MTCH2, were highly correlated with one another and were associated with AD status. We further demonstrate that PILRB, as well as other genes within the GWAS loci, are most highly expressed in microglia. These findings together with the function of PILRB as a DAP12 receptor supports the critical role of microglia and neuroinflammation in AD risk.

Genome-wide linkage analyses of non-Hispanic white families identify novel loci for familial late-onset Alzheimer's disease

INTRODUCTION

Few high penetrance variants that explain risk in late-onset Alzheimer's disease (LOAD) families have been found.

METHODS

We performed genome-wide linkage and identity-by-descent (IBD) analyses on 41 non-Hispanic white families exhibiting likely dominant inheritance of LOAD, and having no mutations at known familial Alzheimer's disease (AD) loci, and a low burden of APOE ε4 alleles.

RESULTS

Two-point parametric linkage analysis identified 14 significantly linked regions, including three novel linkage regions for LOAD (5q32, 11q12.2-11q14.1, and 14q13.3), one of which replicates a genome-wide association LOAD locus, the MS4A6A-MS4A4E gene cluster at 11q12.2. Five of the 14 regions (3q25.31, 4q34.1, 8q22.3, 11q12.2-14.1, and 19q13.41) are supported by strong multipoint results (logarithm of odds [LOD*] ≥1.5). Nonparametric multipoint analyses produced an additional significant locus at 14q32.2 (LOD* = 4.18). The 1-LOD confidence interval for this region contains one gene, C14orf177, and the microRNA Mir_320, whereas IBD analyses implicates an additional gene BCL11B, a regulator of brain-derived neurotrophic signaling, a pathway associated with pathogenesis of several neurodegenerative diseases.

DISCUSSION

Examination of these regions after whole-genome sequencing may identify highly penetrant variants for familial LOAD.

Linkage analyses in Caribbean Hispanic families identify novel loci associated with familial late-onset Alzheimer's disease

INTRODUCTION

We performed linkage analyses in Caribbean Hispanic families with multiple late-onset Alzheimer's disease (LOAD) cases to identify regions that may contain disease causative variants.

METHODS

We selected 67 LOAD families to perform genome-wide linkage scan. Analysis of the linked regions was repeated using the entire sample of 282 families. Validated chromosomal regions were analyzed using joint linkage and association.

RESULTS

We identified 26 regions linked to LOAD (HLOD ≥3.6). We validated 13 of the regions (HLOD ≥2.5) using the entire family sample. The strongest signal was at 11q12.3 (rs2232932: HLODmax = 4.7, Pjoint = 6.6 × 10(-6)), a locus located ∼2 Mb upstream of the membrane-spanning 4A gene cluster. We additionally identified a locus at 7p14.3 (rs10255835: HLODmax = 4.9, Pjoint = 1.2 × 10(-5)), a region harboring genes associated with the nervous system (GARS, GHRHR, and NEUROD6).

DISCUSSION

Future sequencing efforts should focus on these regions because they may harbor familial LOAD causative mutations.

Genetic variants associated with susceptibility to psychosis in late-onset Alzheimer's disease families

Psychotic symptoms are frequent in late-onset Alzheimer's disease (LOAD) patients. Although the risk for psychosis in LOAD is genetically mediated, no genes have been identified. To identify loci potentially containing genetic variants associated with risk of psychosis in LOAD, a total of 263 families from the National Institute of Aging-LOAD cohort were classified into psychotic (LOAD+P, n = 215) and nonpsychotic (LOAD-P, n = 48) families based on the presence/absence of psychosis during the course of LOAD. The LOAD+P families yielded strong evidence of linkage on chromosome 19q13 (two-point [2-pt] ​logarithm of odds [LOD] = 3.8, rs2285513 and multipoint LOD = 2.7, rs541169). Joint linkage and association in 19q13 region detected strong association with rs2945988 (p = 8.7 × 10(-7)). Linkage results for the LOAD-P families yielded nonsignificant 19q13 LOD scores. Several 19q13 single-nucleotide polymorphisms generalized the association of LOAD+P in a Caribbean Hispanic (CH) cohort, and the strongest signal was rs10410711 (pmeta = 5.1 × 10(-5)). A variant located 24 kb upstream of rs10410711 and rs10421862 was strongly associated with LOAD+P (pmeta = 1.0 × 10(-5)) in a meta-analysis of the CH cohort and an additional non-Hispanic Caucasian dataset. Identified variants rs2945988 and rs10421862 affect brain gene expression levels. Our results suggest that genetic variants in genes on 19q13, some of which are involved in brain development and neurodegeneration, may influence the susceptibility to psychosis in LOAD patients.

A Genetic Variant (COMT) Coding Dopaminergic Activity Predicts Personality Traits in Healthy Elderly

Association studies between the NEO five factor personality inventory and COMT rs4680 have focused on young adults and the results have been inconsistent. However, personality and cortical changes with age may put older adults in a more sensitive range for detecting a relationship. The present study examined associations of COMT rs4680 and personality in older adults. Genetic association analyses were carried out between the NEO and the targeted COMT rs4680 in a large, well-characterized sample of healthy, cognitively normal older adults (N = 616, mean age = 69.26 years). Three significant associations were found: participants with GG genotype showed lower mean scores on Neuroticism (p = 0.039) and higher scores on Agreeableness (p = 0.020) and Conscientiousness (p = 0.006) than participants with AA or AG genotypes. These results suggest that older adults with higher COMT enzymatic activity (GG), therefore lower dopamine level, have lower Neuroticism scores, and higher Agreeableness and Conscientiousness scores. This is consistent with a recent model of phasic and tonic dopamine release suggesting that even though GG genotype is associated with lower tonic dopamine release, the phasic release of dopamine might be optimal for a more adaptive personality profile.