sTREM2 Mediates the Correlation Between <i>BIN1</i> Gene Polymorphism and Tau Pathology in Alzheimer’s Disease

Background: Bridging integrator 1 ( BIN1) gene polymorphism has been reported to play a role in the pathological processes of Alzheimer’s disease (AD). Objective: To explore the association of BIN1 loci with neuroinflammation and AD pathology. Methods: Alzheimer’s Disease Neuroimaging Initiative (ADNI, N = 495) was the discovery cohort, and Chinese Alzheimer’s Biomarker and LifestylE (CABLE, N = 619) study was used to replicate the results. Two BIN1 gene polymorphism (rs7561528 and rs744373) were included in the analysis. Multiple linear regression model and causal mediation analysis conducted through 10,000 bootstrapped iterations were used to examine the BIN1 loci relationship with cerebrospinal fluid (CSF) AD biomarkers and alternative biomarker of microglial activation microglia-soluble triggering receptor expressed on myeloid cells 2 (sTREM2). Results: In ADNI database, we found a significant association between BIN1 loci (rs7561528 and rs744373) and levels of CSF phosphorylated-tau (P-tau) (p c = 0.017; 0.010, respectively) and total-tau (T-tau) (p c = 0.011; 0.013, respectively). The BIN1 loci were also correlated with CSF sTREM2 levels (p c = 0.010; 0.008, respectively). Mediation analysis demonstrated that CSF sTREM2 partially mediated the association of BIN1 loci with P-tau (Proportion of rs7561528 : 20.8%; Proportion of rs744373 : 24.8%) and T-tau (Proportion of rs7561528 : 36.5%; Proportion of rs744373 : 43.9%). The analysis in CABLE study replicated the mediation role of rs7561528. Conclusions: This study demonstrated the correlation between BIN1 loci and CSF AD biomarkers as well as microglia biomarkers. Additionally, the link between BIN1 loci and tau pathology was partially mediated by CSF sTREM2.