Trans-pQTL study identifies immune crosstalk between Parkinson and Alzheimer loci
NEUROLOGY-GENETICS
Authors: Chan, Gail; White, Charles C.; Winn, Phoebe A.; Cimpean, Maria; Replogle, Joseph M.; Glick, Laura R.; Cuerdon, Nicole E.; Ryan, Katie J.; Johnson, Keith A.; Schneider, Julie A.; Bennett, David A.; Chibnik, Lon B.; Sperling, Reisa A.; De Jager, Philip L.; Bradshaw, Elizabeth M.
Abstract
Objective: Given evidence from genetic studies, we hypothesized that there may be a shared component to the role of myeloid function in Parkinson and Alzheimer disease (PD and AD) and assessed whether PD susceptibility variants influenced protein expression of well-established AD-associated myeloid genes in human monocytes. Methods: We repurposed data in which AD-related myeloid proteins CD33, TREM1, TREM2, TREML2, TYROBP, and PTK2B were measured by flow cytometry in monocytes from 176 participants of the PhenoGenetic Project (PGP) and Harvard Aging Brain Study. Linear regression was used to identify associations between 24 PD risk variants and protein expression. The 2 cohorts were meta-analyzed in a discovery analysis, and the 4 most strongly suggestive results were validated in an independent cohort of 50 PGP participants. Results: We discovered and validated an association between the PD risk allele rs12456492(G) in the RIT2 locus and increased CD33 expression (P-joint = 3.50 x 10(-5) and found strongly suggestive evidence that rs11060180(A) in the CCDC62/HIP1R locus decreased PTK2B expression (p(joint) = 1.12 x 10(-4)). Furthermore, in older individuals, increased CD33 expression on peripheral monocytes was associated with a greater burden of parkinsonism (p = 0.047), particularly bradykinesia (p = 6.64 x 10(-3)). Conclusions: We find that the rs12456492 PD risk variant affects expression of AD-associated protein CD33 in peripheral monocytes, which suggests that genetic factors for these 2 diseases may converge to influence overlapping innate immune-mediated mechanisms that contribute to neurodegeneration. Furthermore, the effect of the rs12456492(G) PD risk allele on increased CD33 suggests that the inhibition of certain myeloid functions may contribute to PD susceptibility, as is the case for AD.
CFH Variants Affect Structural and Functional Brain Changes and Genetic Risk of Alzheimer's Disease
NEUROPSYCHOPHARMACOLOGY
Authors: Zhang, Deng-Feng; Li, Jin; Wu, Huan; Cui, Yue; Bi, Rui; Zhou, He-Jiang; Wang, Hui-Zhen; Zhang, Chen; Wang, Dong; Kong, Qing-Peng; Li, Tao; Fang, Yiru; Jiang, Tianzi; Yao, Yong-Gang
Abstract
The immune response is highly active in Alzheimer's disease (AD). Identification of genetic risk contributed by immune genes to AD may provide essential insight for the prognosis, diagnosis, and treatment of this neurodegenerative disease. In this study, we performed a genetic screening for AD-related top immune genes identified in Europeans in a Chinese cohort, followed by a multiple-stage study focusing on Complement Factor H (CFH) gene. Effects of the risk SNPs on AD-related neuroimaging endophenotypes were evaluated through magnetic resonance imaging scan, and the effects on AD cerebrospinal fluid biomarkers (CSF) and CFH expression changes were measured in aged and AD brain tissues and AD cellular models. Our results showed that the AD-associated top immune genes reported in Europeans (CR1, CD33, CLU, and TREML2) have weak effects in Chinese, whereas CFH showed strong effects. In particular, rs1061170 (P-meta = 5.0 x 10(-4)) and rs800292 (P-meta = 1.3 x 10(-5)) showed robust associations with AD, which were confirmed in multiple world-wide sample sets (4317 cases and 16 795 controls). Rs1061170 (P = 2.5 x 10(-3)) and rs800292 (P = 4.7 x 10(-4)) risk-allele carriers have an increased entorhinal thickness in their young age and a higher atrophy rate as the disease progresses. Rs800292 risk-allele carriers have higher CSF tau and A beta levels and severe cognitive decline. CFH expression level, which was affected by the risk-alleles, was increased in AD brains and cellular models. These comprehensive analyses suggested that CFH is an important immune factor in AD and affects multiple pathological changes in early life and during disease progress.