Local genetic correlations exist among neurodegenerative and neuropsychiatric diseases

Genetic correlation (rg) between traits can offer valuable insight into underlying shared biological mechanisms. Neurodegenerative diseases overlap neuropathologically and often manifest comorbid neuropsychiatric symptoms. However, global rg analyses show minimal rg among neurodegenerative and neuropsychiatric diseases. Importantly, local rgs can exist in the absence of global relationships. To investigate this possibility, we applied LAVA, a tool for local rg analysis, to genome-wide association studies of 3 neurodegenerative diseases (Alzheimers disease, Lewy body dementia and Parkinsons disease) and 3 neuropsychiatric disorders (bipolar disorder, major depressive disorder and schizophrenia). We identified several local rgs missed in global analyses, including between (i) all 3 neurodegenerative diseases and schizophrenia and (ii) Alzheimers and Parkinsons disease. For those local rgs identified in genomic regions containing disease-implicated genes, such as SNCA, CLU and APOE, incorporation of expression quantitative trait loci identified genes that may drive genetic overlaps between diseases. Collectively, we demonstrate that complex genetic relationships exist among neurodegenerative and neuropsychiatric diseases, highlighting putative pleiotropic genomic regions and genes. These findings imply sharing of pathogenic processes and the potential existence of common therapeutic targets.