Genetic architecture of subcortical brain structures in 38,851 individuals

Subcortical brain structures are integral to motion, consciousness, emotions and learning. We identified common genetic variation related to the volumes of the nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen and thalamus, using genome-wide association analyses in almost 40,000 individuals from CHARGE, ENIGMA and UK Biobank. We show that variability in subcortical volumes is heritable, and identify 48 significantly associated loci (40 novel at the time of analysis). Annotation of these loci by utilizing gene expression, methylation and neuropathological data identified 199 genes putatively implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, inflammation/infection and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease

Common variants in P2RY11 are associated with narcolepsy.

l e t t e r s Growing evidence supports the hypothesis that narcolepsy with cataplexy is an autoimmune disease. We here report genomewide association analyses for narcolepsy with replication and fine mapping across three ethnic groups (3,406 individuals of European ancestry, 2,414 Asians and 302 African Americans). We identify a SNP in the 3′ untranslated region of P2RY11, the purinergic receptor subtype P2Y 11 gene, which is associated with narcolepsy (rs2305795, combined P = 6.1 × 10 −10 , odds ratio = 1.28, 95% CI 1.19-1.39, n = 5689). The diseaseassociated allele is correlated with reduced expression of P2RY11 in CD8 + T lymphocytes (339% reduced, P = 0.003) and natural killer (NK) cells (P = 0.031), but not in other peripheral blood mononuclear cell types. The low expression variant is also associated with reduced P2RY11-mediated resistance to ATP-induced cell death in T lymphocytes (P = 0.0007) and natural killer cells (P = 0.001). These results identify P2RY11 as an important regulator of immune-cell survival, with possible implications in narcolepsy and other autoimmune diseases

Rare coding variants in PLCG2, ABI3, and TREM2 implicate microglial-mediated innate immunity in Alzheimer's disease

We identified rare coding variants associated with Alzheimer’s disease (AD) in a 3-stage case-control study of 85,133 subjects. In stage 1, 34,174 samples were genotyped using a whole-exome microarray. In stage 2, we tested associated variants (P<1×10-4) in 35,962 independent samples using de novo genotyping and imputed genotypes. In stage 3, an additional 14,997 samples were used to test the most significant stage 2 associations (P<5×10-8) using imputed genotypes. We observed 3 novel genome-wide significant (GWS) AD associated non-synonymous variants; a protective variant in PLCG2 (rs72824905/p.P522R, P=5.38×10-10, OR=0.68, MAFcases=0.0059, MAFcontrols=0.0093), a risk variant in ABI3 (rs616338/p.S209F, P=4.56×10-10, OR=1.43, MAFcases=0.011, MAFcontrols=0.008), and a novel GWS variant in TREM2 (rs143332484/p.R62H, P=1.55×10-14, OR=1.67, MAFcases=0.0143, MAFcontrols=0.0089), a known AD susceptibility gene. These protein-coding changes are in genes highly expressed in microglia and highlight an immune-related protein-protein interaction network enriched for previously identified AD risk genes. These genetic findings provide additional evidence that the microglia-mediated innate immune response contributes directly to AD development

Cerebral small vessel disease genomics and its implications across the lifespan

White matter hyperintensities (WMH) are the most common brain-imaging feature of cerebral small vessel disease (SVD), hypertension being the main known risk factor. Here, we identify 27 genome-wide loci for WMH-volume in a cohort of 50,970 older individuals, accounting for modification/confounding by hypertension. Aggregated WMH risk variants were associated with altered white matter integrity (p = 2.5×10-7) in brain images from 1,738 young healthy adults, providing insight into the lifetime impact of SVD genetic risk. Mendelian randomization suggested causal association of increasing WMH-volume with stroke, Alzheimer-type dementia, and of increasing blood pressure (BP) with larger WMH-volume, notably also in persons without clinical hypertension. Transcriptome-wide colocalization analyses showed association of WMH-volume with expression of 39 genes, of which four encode known drug targets. Finally, we provide insight into BP-independent biological pathways underlying SVD and suggest potential for genetic stratification of high-risk individuals and for genetically-informed prioritization of drug targets for prevention trials.</p

A novel Alzheimer disease locus located near the gene encoding tau protein

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordAPOE ε4, the most significant genetic risk factor for Alzheimer disease (AD), may mask effects of other loci. We re-analyzed genome-wide association study (GWAS) data from the International Genomics of Alzheimer's Project (IGAP) Consortium in APOE ε4+ (10 352 cases and 9207 controls) and APOE ε4- (7184 cases and 26 968 controls) subgroups as well as in the total sample testing for interaction between a single-nucleotide polymorphism (SNP) and APOE ε4 status. Suggestive associations (P<1 × 10-4) in stage 1 were evaluated in an independent sample (stage 2) containing 4203 subjects (APOE ε4+: 1250 cases and 536 controls; APOE ε4-: 718 cases and 1699 controls). Among APOE ε4- subjects, novel genome-wide significant (GWS) association was observed with 17 SNPs (all between KANSL1 and LRRC37A on chromosome 17 near MAPT) in a meta-analysis of the stage 1 and stage 2 data sets (best SNP, rs2732703, P=5·8 × 10-9). Conditional analysis revealed that rs2732703 accounted for association signals in the entire 100-kilobase region that includes MAPT. Except for previously identified AD loci showing stronger association in APOE ε4+ subjects (CR1 and CLU) or APOE ε4- subjects (MS4A6A/MS4A4A/MS4A6E), no other SNPs were significantly associated with AD in a specific APOE genotype subgroup. In addition, the finding in the stage 1 sample that AD risk is significantly influenced by the interaction of APOE with rs1595014 in TMEM106B (P=1·6 × 10-7) is noteworthy, because TMEM106B variants have previously been associated with risk of frontotemporal dementia. Expression quantitative trait locus analysis revealed that rs113986870, one of the GWS SNPs near rs2732703, is significantly associated with four KANSL1 probes that target transcription of the first translated exon and an untranslated exon in hippocampus (P≤1.3 × 10-8), frontal cortex (P≤1.3 × 10-9) and temporal cortex (P≤1.2 × 10-11). Rs113986870 is also strongly associated with a MAPT probe that targets transcription of alternatively spliced exon 3 in frontal cortex (P=9.2 × 10-6) and temporal cortex (P=2.6 × 10-6). Our APOE-stratified GWAS is the first to show GWS association for AD with SNPs in the chromosome 17q21.31 region. Replication of this finding in independent samples is needed to verify that SNPs in this region have significantly stronger effects on AD risk in persons lacking APOE ε4 compared with persons carrying this allele, and if this is found to hold, further examination of this region and studies aimed at deciphering the mechanism(s) are warranted

Factors Associated With Ischemic Stroke Survival and Recovery in Older Adults

Little is known about factors that predispose older adults to poor recovery after a stroke. In this study, we sought to evaluate prestroke measures of frailty and related factors as markers of vulnerability to poor outcomes after ischemic stroke. In participants aged 65 to 99 years with incident ischemic strokes from the Cardiovascular Health Study, we evaluated the association of several risk factors (frailty, frailty components, C-reactive protein, interleukin-6, and cystatin C) assessed before stroke with stroke outcomes of survival, cognitive decline (≥5 points on Modified Mini-Mental State Examination), and activities of daily living decline (increase in limitations). Among 717 participants with incident ischemic stroke with survival data, slow walking speed, low grip strength, and cystatin C were independently associated with shorter survival. Among participants <80 years of age, frailty and interleukin-6 were also associated with shorter survival. Among 509 participants with recovery data, slow walking speed, and low grip strength were associated with both cognitive and activities of daily living decline poststroke. C-reactive protein and interleukin-6 were associated with poststroke cognitive decline among men only. Frailty status was associated with activities of daily living decline among women only. Markers of physical function-walking speed and grip strength-were consistently associated with survival and recovery after ischemic stroke. Inflammation, kidney function, and frailty also seemed to be determinants of survival and recovery after an ischemic stroke. These markers of vulnerability may identify targets for differing pre and poststroke medical management and rehabilitation among older adults at risk of poor stroke outcomes

Risk Factors for Incident Carotid Artery Revascularization among Older Adults: The Cardiovascular Health Study

Background: Population-based risk factors for carotid artery revascularization are not known. We investigated the association between demographic and clinical characteristics and incident carotid artery revascularization in a cohort of older adults. Methods: Among Cardiovascular Health Study participants, a population-based cohort of 5,888 adults aged 65 years or older enrolled in two waves (1989-1990 and 1992-1993), 5,107 participants without a prior history of carotid endarterectomy (CEA) or cerebrovascular disease had a carotid ultrasound at baseline and were included in these analyses. Cox proportional hazards multivariable analysis was used to determine independent risk factors for incident carotid artery revascularization. Results: Over a mean follow-up of 13.5 years, 141 participants underwent carotid artery revascularization, 97% were CEA. Baseline degree of stenosis and incident ischemic cerebral events occurring during follow-up were the strongest predictors of incident revascularization. After adjustment for these, factors independently associated with an increased risk of incident revascularization were: hypertension (HR 1.53; 95% CI: 1.05-2.23), peripheral arterial disease (HR 2.57; 95% CI: 1.34-4.93), and low-density lipoprotein cholesterol (HR 1.23 per standard deviation [SD] increment [35.4 mg/dL]; 95% CI: 1.04-1.46). Factors independently associated with a lower risk of incident revascularization were: female gender (HR 0.51; 95% CI: 0.34-0.77) and older age (HR 0.69 per SD increment [5.5 years]; 95% CI: 0.56-0.86). Conclusions: Even after accounting for carotid stenosis and incident cerebral ischemic events, carotid revascularization is related to age, gender, and cardiovascular risk factors. Further study of these demographic disparities and the role of risk factor control is warranted

Risk Factors for Incident Carotid Artery Revascularization among Older Adults: The Cardiovascular Health Study

Background: Population-based risk factors for carotid artery revascularization are not known. We investigated the association between demographic and clinical characteristics and incident carotid artery revascularization in a cohort of older adults. Methods: Among Cardiovascular Health Study participants, a population-based cohort of 5,888 adults aged 65 years or older enrolled in two waves (1989-1990 and 1992-1993), 5,107 participants without a prior history of carotid endarterectomy (CEA) or cerebrovascular disease had a carotid ultrasound at baseline and were included in these analyses. Cox proportional hazards multivariable analysis was used to determine independent risk factors for incident carotid artery revascularization. Results: Over a mean follow-up of 13.5 years, 141 participants underwent carotid artery revascularization, 97% were CEA. Baseline degree of stenosis and incident ischemic cerebral events occurring during follow-up were the strongest predictors of incident revascularization. After adjustment for these, factors independently associated with an increased risk of incident revascularization were: hypertension (HR 1.53; 95% CI: 1.05-2.23), peripheral arterial disease (HR 2.57; 95% CI: 1.34-4.93), and low-density lipoprotein cholesterol (HR 1.23 per standard deviation [SD] increment [35.4 mg/dL]; 95% CI: 1.04-1.46). Factors independently associated with a lower risk of incident revascularization were: female gender (HR 0.51; 95% CI: 0.34-0.77) and older age (HR 0.69 per SD increment [5.5 years]; 95% CI: 0.56-0.86). Conclusions: Even after accounting for carotid stenosis and incident cerebral ischemic events, carotid revascularization is related to age, gender, and cardiovascular risk factors. Further study of these demographic disparities and the role of risk factor control is warranted

A prospective cohort study of stroke characteristics, care, and mortality in a hospital stroke registry in Vietnam

<p>Abstract</p> <p>Background</p> <p>As low and middle-income countries such as Vietnam experience the health transition from infectious to chronic diseases, the morbidity and mortality from stroke will rise. In line with the recommendation of the Institute of Medicine’s report on “Promoting Cardiovascular Health in the Developing World” to “improve local data”, we sought to investigate patient characteristics and clinical predictors of mortality among stroke inpatients at Da Nang Hospital in Vietnam.</p> <p>Methods</p> <p>A stroke registry was developed and implemented at Da Nang Hospital utilizing the World Health Organization’s Stroke STEPS instrument for data collection.</p> <p>Results</p> <p>754 patients were hospitalized for stroke from March 2010 through February 2011 and admitted to either the intensive care unit or cardiology ward. Mean age was 65 years, and 39% were female. Nearly 50% of strokes were hemorrhagic. At 28-day follow-up, 51.0% of patients with hemorrhagic stroke died whereas 20.3% of patients with ischemic stroke died. A number of factors were independently associated with 28-day mortality; the two strongest independent predictors were depressed level of consciousness on presentation and hemorrhagic stroke type. While virtually all patients completed a CT during the admission, evidence-based processes of care such as anti-thrombotic therapy and carotid ultrasound for ischemic stroke patients were underutilized.</p> <p>Conclusions</p> <p>This cohort study highlights the high mortality due in part to the large proportion of hemorrhagic strokes in Vietnam. Lack of hypertension awareness and standards of care exacerbated clinical outcomes. Numerous opportunities for simple, inexpensive interventions to improve outcomes or reduce recurrent stroke have been identified.</p