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Browsing by Author "Bu, Guojun"
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Item Genome-wide association study of brain biochemical phenotypes reveals distinct genetic architecture of Alzheimer's disease related proteins(BMC, 2023-01-07) Oatman, Stephanie R.; Reddy, Joseph S.; Quicksall, Zachary; Carrasquillo, Minerva M.; Wang, Xue; Liu, Chia‑Chen; Yamazaki, Yu; Nguyen, Thuy T.; Malphrus, Kimberly; Heckman, Michael; Biswas, Kristi; Nho, Kwangsik; Baker, Matthew; Martens, Yuka A.; Zhao, Na; Kim, Jun Pyo; Risacher, Shannon L.; Rademakers, Rosa; Saykin, Andrew J.; DeTure, Michael; Murray, Melissa E.; Kanekiyo, Takahisa; Alzheimer’s Disease Neuroimaging Initiative; Dickson, Dennis W.; Bu, Guojun; Allen, Mariet; Ertekin‑Taner, Nilüfer; Radiology and Imaging Sciences, School of MedicineBackground: Alzheimer's disease (AD) is neuropathologically characterized by amyloid-beta (Aβ) plaques and neurofibrillary tangles. The main protein components of these hallmarks include Aβ40, Aβ42, tau, phosphor-tau, and APOE. We hypothesize that genetic variants influence the levels and solubility of these AD-related proteins in the brain; identifying these may provide key insights into disease pathogenesis. Methods: Genome-wide genotypes were collected from 441 AD cases, imputed to the haplotype reference consortium (HRC) panel, and filtered for quality and frequency. Temporal cortex levels of five AD-related proteins from three fractions, buffer-soluble (TBS), detergent-soluble (Triton-X = TX), and insoluble (Formic acid = FA), were available for these same individuals. Variants were tested for association with each quantitative biochemical measure using linear regression, and GSA-SNP2 was used to identify enriched Gene Ontology (GO) terms. Implicated variants and genes were further assessed for association with other relevant variables. Results: We identified genome-wide significant associations at seven novel loci and the APOE locus. Genes and variants at these loci also associate with multiple AD-related measures, regulate gene expression, have cell-type specific enrichment, and roles in brain health and other neuropsychiatric diseases. Pathway analysis identified significant enrichment of shared and distinct biological pathways. Conclusions: Although all biochemical measures tested reflect proteins core to AD pathology, our results strongly suggest that each have unique genetic architecture and biological pathways that influence their specific biochemical states in the brain. Our novel approach of deep brain biochemical endophenotype GWAS has implications for pathophysiology of proteostasis in AD that can guide therapeutic discovery efforts focused on these proteins.Item Performance of plasma phosphorylated tau 181 and 217 in the community(Springer Nature, 2022) Mielke, Michelle M.; Dage, Jeffrey L.; Frank, Ryan D.; Algeciras-Schimnich, Alicia; Knopman, David S.; Lowe, Val J.; Bu, Guojun; Vemuri, Prashanthi; Graff-Radford, Jonathan; Jack, Clifford R., Jr.; Petersen, Ronald C.; Neurology, School of MedicinePlasma phosphorylated tau 181 (P-tau181) and 217 (P-tau217) are indicators of both amyloid and tau pathology in clinical settings, but their performance in heterogeneous community-based populations is unclear. We examined P-tau181 and P-tau217 (n = 1,329, aged 30-98 years), in the population-based Mayo Clinic Study of Aging. Continuous, unadjusted plasma P-tau181 and P-tau217 predicted abnormal amyloid positron-emission tomography (PET) (area under the receiver operating characteristic curve (AUROC) = 0.81-0.86) and tau PET entorhinal cortex (AUROC > 0.80), but was less predictive of a tau PET temporal region of interest (AUROC < 0.70). Multiple comorbidities were associated with higher plasma P-tau181 and P-tau217 levels; the difference between participants with and without chronic kidney disease (CKD) was similar to the difference between participants with and without elevated brain amyloid. The exclusion of participants with CKD and other comorbidities affected the establishment of a normal reference range and cutpoints. Understanding the effect of comorbidities on P-tau181 and P-tau217 levels is important for their future interpretation in the context of clinical screening, diagnosis or prognosis at the population level.