The Alzheimer Disease Genetics Consortium (ADGC) performed a genome-wide association study (GWAS) of late-onset Alzheimer disease (LOAD) using a 3 stage design consisting of a discovery stage (Stage 1) and two replication stages (Stages 2 and 3). Both joint and meta-analysis analysis approaches were used. We obtained genome-wide significant results at MS4A4A [rs4938933; Stages 1+2, meta-analysis (PM) = 1.7 × 10−9, joint analysis (PJ) = 1.7 × 10−9; Stages 1–3, PM = 8.2 × 10−12], CD2AP (rs9349407; Stages 1–3, PM = 8.6 × 10−9), EPHA1 (rs11767557; Stages 1–3 PM = 6.0 × 10−10), and CD33 (rs3865444; Stages 1–3, PM = 1.6 × 10−9). We confirmed that CR1 (rs6701713; PM = 4.6×10−10, PJ = 5.2×10−11), CLU (rs1532278; PM = 8.3 × 10−8, PJ = 1.9×10−8), BIN1 (rs7561528; PM = 4.0×10−14; PJ = 5.2×10−14), and PICALM (rs561655; PM = 7.0 × 10−11, PJ = 1.0×10−10) but not EXOC3L2 are LOAD risk loci1–3.

Multifactorial mechanisms underlying late-onset Alzheimer's disease (LOAD) are poorly characterized from an integrative perspective. Here spatiotemporal alterations in brain amyloid-β deposition, metabolism, vascular, functional activity at rest, structural properties, cognitive integrity and peripheral proteins levels are characterized in relation to LOAD progression. We analyse over 7,700 brain images and tens of plasma and cerebrospinal fluid biomarkers from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Through a multifactorial data-driven analysis, we obtain dynamic LOAD–abnormality indices for all biomarkers, and a tentative temporal ordering of disease progression. Imaging results suggest that intra-brain vascular dysregulation is an early pathological event during disease development. Cognitive decline is noticeable from initial LOAD stages, suggesting early memory deficit associated with the primary disease factors. High abnormality levels are also observed for specific proteins associated with the vascular system's integrity. Although still subjected to the sensitivity of the algorithms and biomarkers employed, our results might contribute to the development of preventive therapeutic interventions.

The relationship between Alzheimer disease (AD) and aging is not currently known. In this study, postmortem frontal-and occipital-pole brain samples were obtained from 16 subjects with AD, 8 age-matched controls, and 5 young controls. These samples were analyzed both for protein oxidation products (carbonyl) and the activities of two enzymes vulnerable to mixed-function oxidation, glutamine synthetase and creatine kinase. Glutamine synthetase is more sensitive to mixed-function oxidation than creatine kinase. Carbonyl content rises exponentially with age, at double the rate in the frontal pole compared with the occipital pole. Compared with young controls, both aged groups (AD and age-matched controls) have increased carbonyl content and decreased glutamine synthetase and creatine kinase activities, which are more marked in the frontal than occipital pole in all instances. We conclude that protein oxidation products accumulate in the brain and that oxidation-vulnerable enzyme activities decrease with aging in the same regional pattern (frontal more affected than occipital). However, only glutamine synthetase activity distinguishes AD from age-matched controls: Because glutamine synthetase activity is differentially reduced in the frontal pole in AD, we suggest that AD may represent a specific brain vulnerability to age-related oxidation.Aging can be defined as the nonfunctional alteration of structure or homeostatic capability in an individual organism as it lives (1). A particular consequence of the aging process, at the cellular level, is the accumulation of proteins covalently modified by specific mechanisms-e.g., mixedfunction oxidation (MFO), deamidation, ubiquitin conjugation, and glycation (2-7). These steps have been reported to mark proteins for subsequent proteolysis.MFO is of particular interest because of the site-specific nature of the modifications (8-13), tending to occur near the metal-containing catalytic site of particular enzymes-e.g., glutamine synthetase. Free-radical-mediated forms of MFO could be one of the important mechanisms in normal aging (14)(15)(16), causing protein structural alterations, loss of enzymatic function, or interference with regulatory protein interactions.In this study, we provide evidence that the level of oxidatively modified protein is increased in the aging brain. We also demonstrate that in Alzheimer disease (AD), a disease strongly associated with aging, there is regional loss of glutamine synthetase activity. Glutamine synthetase is an enzyme particularly sensitive to MFO. We propose the hypothesis that AD is an alteration in the normal aging process in selectively vulnerable brain cells or brain areas that are challenged by increased oxidation with advancing age. MATERIALS AND METHODSBrain Tissue Samples. Brain specimens were obtained at autopsy from 16 patients with AD, 8 age-matched controls (AC), and 5 young controls (YC). Tissues were received from the Kentucky Medical Examiners Program and the University of Kentucky AD Research Center, under approv...

Objective-To determine the frequency and possible cognitive effect of histological Alzheimer's disease (AD) in autopsied older nondemented individuals.Design-Senile plaques (SPs) and neurofibrillary tangles (NFTs) were assessed quantitatively in 97 cases from 7 Alzheimer's Disease Centers (ADCs). Neuropathological diagnoses of AD (npAD) were also made with four sets of criteria. Adjusted linear mixed models tested differences between participants with and without npAD on the quantitative neuropathology measures and psychometric test scores prior to death. Spearman rank-order correlations between AD lesions and psychometric scores at last assessment were calculated for cases with pathology in particular regions. Setting-Washington University Alzheimer's Disease Research Center.Participants-Ninety-seven nondemented participants who were age 60 years or older at death (mean = 84 years).Results-About 40% of nondemented individuals met at least some level of criteria for npAD; when strict criteria were used, about 20% of cases had npAD. Substantial overlap of Braak neurofibrillary stages occurred between npAD and no-npAD cases. Although there was no measurable cognitive impairment prior to death for either the no-npAD or npAD groups, cognitive function in nondemented aging appears to be degraded by the presence of NFTs and SPs.Conclusions-Neuropathological processes related to AD in persons without dementia appear to be associated with subtle cognitive dysfunction and may represent a preclinical stage of the illness. By age 80-85 years, many nondemented older adults have substantial AD pathology.

Genome-wide association studies (GWAS) have identified several risk variants for late-onset Alzheimer's disease (LOAD)1,2. These common variants have replicable but small effects on LOAD risk and generally do not have obvious functional effects. Low-frequency coding variants, not detected by GWAS, are predicted to include functional variants with larger effects on risk. To identify low frequency coding variants with large effects on LOAD risk, we performed whole exome-sequencing (WES) in 14 large LOAD families and follow-up analyses of the candidate variants in several large case-control datasets. A rare variant in PLD3 (phospholipase-D family, member 3, rs145999145; V232M) segregated with disease status in two independent families and doubled risk for AD in seven independent case-control series (V232M meta-analysis; OR= 2.10, CI=1.47-2.99; p= 2.93×10-5, 11,354 cases and controls of European-descent). Gene-based burden analyses in 4,387 cases and controls of European-descent and 302 African American cases and controls, with complete sequence data for PLD3, indicate that several variants in this gene increase risk for AD in both populations (EA: OR= 2.75, CI=2.05-3.68; p=1.44×10-11, AA: OR= 5.48, CI=1.77-16.92; p=1.40×10-3). PLD3 is highly expressed in brain regions vulnerable to AD pathology, including hippocampus and cortex, and is expressed at lower levels in neurons from AD brains compared to control brains (p=8.10×10-10). Over-expression of PLD3 leads to a significant decrease in intracellular APP and extracellular Aβ42 and Aβ40, while knock-down of PLD3 leads to a significant increase in extracellular Aβ42 and Aβ40. Together, our genetic and functional data indicate that carriers of PLD3 coding variants have a two-fold increased risk for LOAD and that PLD3 influences APP processing. This study provides an example of how densely affected families may be used to identify rare variants with large effects on risk for disease or other complex traits.