Genome wide association study meta-analysis of neuropathologic lesions of Alzheimer's disease and related dementias in a multi-site autopsy cohort.

Understanding the genetic foundations of dementia is critical to unraveling its complex molecular basis. Given that a clinical diagnosis of Alzheimer's disease (AD) dementia often results from interplay between multiple underlying neuropathologic co-morbidities, previous genome-wide association studies (GWAS) of clinically diagnosed AD are restricted in their ability to translate genetic associations to potential targeted therapeutics. The current study seeks to address these limitations by presenting the largest GWAS to date (n=12,509) of neuropathologic hallmarks of AD and AD related dementias (ADRDs). We further performed a candidate-variant analysis using loci previously identified in GWAS of clinically diagnosed AD dementia and Parkinson's disease (PD). Finally, we conducted heritability and genetic correlation analyses using linkage disequilibrium (LD) score regression. We found broad genome-wide significant associations with Author Summary: Clinically diagnosed Alzheimer's disease (AD) dementia is commonly associated with its hallmark pathologic changes plus neuropathologic features of prevalent co-morbid diseases such as cerebrovascular disease, Lewy body disease, and more recently discovered abnormalities in protein called TDP-43 (collectively, AD related dementias; ADRD). As a result, previous studies that associated clinical diagnosis of AD with specific genes may not tell us the whole story. For this study, we gathered autopsy and genetic data to identify relationships between genes and dementia-associated brain changes. We found some relationships between these diseases and genes that had been previously identified as contributing to clinical dementia, as well as some new relationships that had been previously unknown. We also found that some genes that had previously been identified in relation to AD were associated with different dementia-associated brain lesions. Finally, we found that the various brain lesions differ in the proportion that can be attributed to genetic vs. environmental differences. These results support that the pathway to a diagnosis of dementia can be caused by multiple factors and are an important step in beginning to identify individually based dementia treatments.