Researchers in Europe, the US and Australia have identified 75 regions of the genome that are associated with Alzheimer's disease. Forty-two of these regions are novel, meaning that they have never before been implicated in the disease. The findings, published in Nature Genetics, bring new knowledge of the biological mechanisms at play and open up new avenues for treatment and diagnosis.
Alzheimer's disease is the most common form of dementia. This complex, multifactorial disease, which usually develops after the age of 65, has a strong genetic component. Most cases are thought to be caused by the interaction of different genetic predisposition factors with environmental factors. In order to better understand the origins of the disease, one of the major challenges of research is to better characterize its genetic risk factors by identifying the pathophysiological processes at play, and thereby propose novel therapeutic targets.
Largest Alzheimer’s patients’ group
Among others, researchers of Amsterdam Neuroscience were part of an international collaboration with researchers from Lille University Hospital and Université de Lile, to conduct a genome-wide study (GWAS) on the largest Alzheimer’s patient group set up until now. Here, the researchers were interested in the genetic data of 111,326 people who were diagnosed with Alzheimer's disease or had close relatives with the condition, and 677,663 healthy controls. These data are derived from several large European cohorts grouped within the European Alzheimer & Dementia BioBank (EADB) consortium.
Using this method, the scientists were able to identify 75regions (loci) of the genome associated with Alzheimer's, 42 of which had never previously been implicated in the disease. "Following this major discovery, we characterized these regions in order to give them meaning in relation to our clinical and biological knowledge, and thereby gain a better understanding of the cellular mechanisms and pathological processes at play", explains Inserm Research Director Jean-Charles Lambert.
Highlighting pathological phenomena
In Alzheimer's disease, two pathological brain phenomena are already well documented: namely, the accumulation of amyloid-beta peptides and the modification of the protein Tau, aggregates of which are found in the neurons. Here, the scientists confirmed the importance of these pathological processes. Their analyses of the various genome regions confirm that some are implicated in amyloid peptide production and Tau protein function.
Furthermore, these analyses also reveal that a dysfunction of innate immunity and of the action of the microglia is at play in Alzheimer's disease. Finally, this study shows for the first time that the tumor necrosis factor alpha (TNF-alpha)-dependent signaling pathway is involved in disease.
These findings confirm and add to our knowledge of the pathological processes involved in the disease and open up new avenues for therapeutic research. For example, they confirm the utility of the following: the conduct of clinical trials of therapies targeting the amyloid precursor protein, the continuation of microglial cell research that was initiated a few years ago, and the targeting of the TNF-alpha signaling pathway.
Based on their findings, the researchers also devised a genetic risk score in order to better evaluate which patients with cognitive impairment will, within three years of its clinical manifestation, go on to develop Alzheimer's disease. Although this tool is not intended for use in clinical practice at this moment, it could be very useful when setting up therapeutic trials in order to categorize participants according to their risk and improve the evaluation of the medications being tested.
In order to validate and expand their findings, the team would now like to continue its research in an even broader group. Beyond this exhaustive characterization of the genetic factors of Alzheimer's disease, the team is also developing numerous cellular and molecular biology approaches to determine their roles in its development.
Read the publication in Nature Genetics: New insights into the genetic etiology of Alzheimer’s disease and related Dementias