Characterization of the genetic landscape of Alzheimer’s disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/‘proxy’ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele.

Background Coronary artery calcification (CAC) is a noninvasive measure of coronary atherosclerosis, the proximal pathophysiology underlying most cases of myocardial infarction (MI). We sought to identify expression signatures of early MI and subclinical atherosclerosis in the Framingham Heart Study (FHS). In this study, we conducted paired-end RNA sequencing on whole blood collected from 198 FHS participants (55 with a history of early MI, 72 with high CAC without prior MI, and 71 controls free of elevated CAC levels or history of MI). We applied DESeq2 to identify coding-genes and long intergenic noncoding RNAs (lincRNAs) differentially expressed in MI and high CAC, respectively, compared with the control. Results On average, 150 million paired-end reads were obtained for each sample. At the false discovery rate (FDR) < 0.1, we found 68 coding genes and 2 lincRNAs that were differentially expressed in early MI versus controls. Among them, 60 coding genes were detectable and thus tested in an independent RNA-Seq data of 807 individuals from the Rotterdam Study, and 8 genes were supported by p value and direction of the effect. Immune response, lipid metabolic process, and interferon regulatory factor were enriched in these 68 genes. By contrast, only 3 coding genes and 1 lincRNA were differentially expressed in high CAC versus controls. APOD, encoding a component of high-density lipoprotein, was significantly downregulated in both early MI (FDR = 0.007) and high CAC (FDR = 0.01) compared with controls. Conclusions We identified transcriptomic signatures of early MI that include differentially expressed protein-coding genes and lincRNAs, suggesting important roles for protein-coding genes and lincRNAs in the pathogenesis of MI.

Apolipoprotein ε4 (APOE ε4) is the most significant genetic risk factor for late-onset Alzheimer’s disease (AD). Elevated blood C-reactive protein (CRP) further increases the risk of AD for people carrying the APOE ε4 allele. We hypothesized that CRP, as a key inflammatory element, could modulate the impact of other genetic variants on AD risk. We selected ten single nucleotide polymorphisms (SNPs) in reported AD risk loci encoding proteins related to inflammation. We then tested the interaction effects between these SNPs and blood CRP levels on AD incidence using the Cox proportional hazards model in UK Biobank (n = 279,176 white participants with 803 incident AD cases). The five top SNPs were tested for their interaction with different CRP cutoffs for AD incidence in the Framingham Heart Study (FHS) Generation 2 cohort (n = 3009, incident AD = 156). We found that for higher concentrations of serum CRP, the AD risk increased for SNP genotypes in 3 AD-associated genes (SPI1, CD33, and CLU). Using the Cox model in stratified genotype analysis, the hazard ratios (HRs) for the association between a higher CRP level (≥10 vs. <10 mg/L) and the risk of incident AD were 1.94 (95% CI: 1.33–2.84, p < 0.001) for the SPI1 rs1057233-AA genotype, 1.75 (95% CI: 1.20–2.55, p = 0.004) for the CD33 rs3865444-CC genotype, and 1.76 (95% CI: 1.25–2.48, p = 0.001) for the CLU rs9331896-C genotype. In contrast, these associations were not observed in the other genotypes of these genes. Finally, two SNPs were validated in 321 Alzheimer’s Disease Neuroimaging (ADNI) Mild Cognitive Impairment (MCI) patients. We observed that the SPI1 and CD33 genotype effects were enhanced by elevated CRP levels for the risk of MCI to AD conversion. Furthermore, the SPI1 genotype was associated with CSF AD biomarkers, including t-Tau and p-Tau, in the ADNI cohort when the blood CRP level was increased (p < 0.01). Our findings suggest that elevated blood CRP, as a peripheral inflammatory biomarker, is an important moderator of the genetic effects of SPI1 and CD33 in addition to APOE ε4 on AD risk. Monitoring peripheral CRP levels may be helpful for precise intervention and prevention of AD for these genotype carriers.

We conducted a circular-transcriptome-wide analysis and examined circRNA expression patterns associated with AD and clinical and neuropathological AD severity measures in the human hippocampus and cortex brain regions. We validated prior studies of circRNA in the AD cortex, and demonstrate novel patterns of expression in the AD hippocampus. We also examined circRNA expression across multiple types of dementia and show that circRNA expression differs by dementia subtype. We demonstrate robust circRNA expression in human neuronal precursor cells (NPCs). Then, using NPCs to study qPCR validated circRNA, we show that exposure to oligomeric tau elicits downregulation of circRNA similar to that observed in AD brain. These data identify circRNA that are changed with AD, and suggest that treating neuronal cells with oligomeric tau can recapitulate some of these changes.

Background Previously, we found that elevated blood C‐reactive protein (CRP) increased the impact of the apolipoprotein ε4 allele (APOE ε4) on the risk of Alzheimer’s disease (AD).1 In this study, we hypothesized that interactions between CRP and other AD‐associated genes also increase AD risk. Method SNPs in 10 AD risk loci, which also encode proteins related to inflammation, were used to test interaction with CRP on AD risk using additive model or dominant model with Cox proportional hazards regression and survival analysis. Result There were 279,176 UKBB white participants with average age (mean±SD) 60.1 ± 5.5 years including 53.9% females and 803 (0.3%) incident AD cases among 8.3 ± 0.9 years follow‐up on average. We found that for higher concentrations of serum CRP, the AD risk increased for SNP genotypes in 3 AD associated genes (SPI1, CD33 and CLU). Using Cox proportional hazards model in stratified genotype analysis, the hazard ratios (HR) for the association between higher CRP level (≥ 10 vs < 10 mg/L) and the risk of incident AD were 1.94 (95% CI: 1.33‐2.84, p<0.001) among SPI1 rs1057233‐AA genotype, 1.75 (95% CI: 1.20‐2.55, p = 0.004) for CD33 rs3865444‐CC genotype, and 1.76 (95% CI: 1.25‐2.48, p = 0.001) for CLU rs9331896‐CC+CT genotype, respectively. All models adjusted for age at baseline, sex, years of education, APOE ε4 and population principal components. In contrast, these associations were not observed in the other genotypes of these genes. Similar results for SPI1 and CD33 genotypes impacted by elevated CRP levels were observed for MCI to AD conversion and CSF AD biomarkers including t‐Tau and p‐Tau in the ADNI cohort (p<0.01). Conclusion Elevated blood CRP released in peripheral inflammation may be an important mediator in the association of genetic variants in SPI1, CD33 and CLU in addition to APOE ε4 for AD risk. Monitoring of CRP levels may be useful for more precise intervention and prevention of AD for these genotype carriers. 1. Tao Q, Ang TFA, DeCarli C, et al. Association of Chronic Low‐grade Inflammation With Risk of Alzheimer Disease in ApoE4 Carriers. JAMA Netw Open. Oct 5 2018;1(6):e183597. https://doi.org/10.1001/jamanetworkopen.2018.3597