Description
Background: Genomic studies of Alzheimer’s disease (AD) have primarily focused on non-Hispanic White (NHW) participants affected by the late-onset form of the disease (LOAD; onset age: >65), or the study of early onset AD (EOAD; onset age <=65) cases from families showing Mendelian inheritance patterns associated with mutations in the APP, PSEN1 and PSEN2 genes. However, mutations in these three genes explain ~10% of EOAD cases. There are no large-scale efforts to collect and study EOAD cases not explained by these genes, even though this unexplained EOAD category accounts for ~90% of cases. The few smaller studies that have been conducted suggest that the genetic architecture of EOAD overlaps with the late-onset form only partially. Thus, studying EOAD in subjects without APP, PSEN1 and PSEN2 mutations is a critical gap that provides a unique opportunity for discovering novel therapeutic targets and molecular pathways. To address this issue we aim to identify additional EOAD-associated variants through a large-scale whole-genome sequencing (WGS) study of unexplained EOAD. We will include cases from several well-established AD cohorts including the Resource for Early-onset Alzheimer Disease Research (READR), the Knight-ADRC at Washington University, the Alzheimer’s Disease Genetics Consortium (ADGC), and others.
Inclusion/Populations: Inclusion criteria include AD cases with early onset (<65) and near-early (<70) onset, as well as cognitive controls. If APP, PSEN1, PSEN2 mutations have been typed the individual must be negative. Samples are not excluded by race/ethnicity, so the total sample set includes non-Hispanic whites, Hispanic, and (limited) African American. Samples are derived from ascertainment at Washington University, Columbia University, University of Miami, the ADCs/NCRAD, as well as collaborating institutions.
Disease Type: Primary phenotypes are AD, MCI, and cognitive controls. Phenotypes related to neurodegeneration and dementia may also be considered (neuropsychiatric phenotypes especially)
Autopsy: Autopsy may be available for a limited number of individuals but will not be a primary phenotype in this study.
Dataset Description: The overall dataset consists of whole genome sequence derived from early-onset Alzheimer disease, MCI, and cognitive controls. Most “case” samples have onset 65 and under, though some up to 70 were included. All participants (AD, MCI, and cognitively intact) have standard neurocognitive/psychiatric exams and are evaluated under standard AD criteria. While the majority of participants are of non-Hispanic white ancestry, we also include Hispanic and African American samples as available. The overall dataset will consist of approximately 4,000 EOAD plus cognitive controls; additional EOAD (~1,000) and cognitive controls will be utilized from the ADSP/ADSP-FUS datasets.
Samples originate from four primary sources:
Alzheimer Disease Research Centers: The majority of samples were derived from the ADRCs, a nation-wide, NIH-funded program working to advance AD research, diagnosis, and clinical care. These samples and data are available through a collaboration between the ADGC, the National Centralized Repository for Alzheimer Disease (NCRAD, Foroud PI), and the National Alzheimer’s Coordinating Center (NACC, Kukull PI). The majority of the samples (>80%) have detailed phenotyping using the NACC Uniform Dataset (UDS).
University of Miami: Samples from the University of Miami, Hussman Institute for Human Genomics (HIHG) were provided through two efforts: READR (Beecham, PI) and the Collaborative Alzheimer Project (Pericak-Vance, PI). Samples have detailed cognitive phenotyping and often include strong family-history of AD/EOAD.
Columbia University: Dr. Reitz contributed additional EOAD samples from Columbia University. These include samples belonging to the READR collection as well as additional cases and controls. Additional data will be included from EFIGA and the NIA-LOAD study (Mayeux).
Knight ADRC: Through the Knight ADRC we will have access to approximately 400 additional EOAD with matched cognitive controls. Many of these also present with family history of AD. Additional samples came from collaborators at Cardiff University (Williams, Simms): these include 400 samples, approximately 270 EOAD cases and 130 cognitive controls.