Genetics of Alzheimer disease in the pre- and post-GWAS era.

Since the 1990s, the genetics of Alzheimer disease (AD) has been an active area of research. The identification of deterministic mutations in the APP, PSEN1, and PSEN2 genes responsible for early-onset autosomal dominant familial forms of AD led to a better understanding of the pathophysiology of this disease. In the past decade, the plethora of candidate genes and regions emerging from genetic linkage and smaller-scale association studies yielded intriguing 'hits' that have often proven difficult to replicate consistently. In the last two years, 11 published genome-wide association studies (GWASs) in AD confirmed the universally accepted role of APOE as a genetic risk factor for late-onset AD as well as generating additional candidate genes that require confirmation. It is unclear whether GWASs, though a promising novel approach in the genetics of complex diseases, can help explain most of the underlying genetic risk for AD. This review provides a brief summary of the genetic studies in AD preceding the GWAS era, with the main focus on the findings from recent GWASs. Potential approaches that could provide further insight into the genetics of AD in the post-GWAS era are also discussed.