Functional regulatory variants implicate distinct transcriptional networks in dementia

Abstract Predicting functionality of noncoding variation is one of the major challenges in modern genetics. We employed massively parallel reporter assays to screen 5,706 variants from genome-wide association studies for both Alzheimer’s disease (AD) and Progressive Supranuclear Palsy (PSP). We identified 320 functional regulatory polymorphisms (SigVars) comprising 27 of 34 unique tested loci, including multiple independent signals across the complex 17q21.31 region. We identify novel risk genes including PLEKHM1 in PSP and APOC1 in AD, and perform gene-editing to validate four distinct causal loci, confirming complement 4 (C4A) as a novel genetic risk factor for AD. Moreover, functional variants preferentially disrupt transcription factor binding sites that converge on enhancers with differential cell-type specific activity in PSP and AD, implicating a neuronal SP1-driven regulatory network in PSP pathogenesis. These analyses support a novel mechanism underlying noncoding genetic risk, whereby common genetic variants drive disease risk via their aggregate activity on specific transcriptional programs. One Sentence Summary High-throughput functional analysis of GWAS loci reveals cell-type specific regulatory networks that mediate genetic risk for dementia.