An integrated genome and phenome-wide association study approach to understanding Alzheimer's disease predisposition

Biomarker identification for Alzheimer's disease through integration of comprehensive Mendelian randomization and proteomics data

BACKGROUND

Alzheimer's disease (AD) is the main cause of dementia with few effective therapies. We aimed to identify potential plasma biomarkers or drug targets for AD by investigating the causal association between plasma proteins and AD by integrating comprehensive Mendelian randomization (MR) and multi-omics data.

METHODS

Using two-sample MR, cis protein quantitative trait loci (cis-pQTLs) for 1,916 plasma proteins were used as an exposure to infer their causal effect on AD liability in individuals of European ancestry, with two large-scale AD genome-wide association study (GWAS) datasets as the outcome for discovery and replication. Significant causal relationships were validated by sensitivity analyses, reverse MR analysis, and Bayesian colocalization analysis. Additionally, we investigated the causal associations at the transcriptional level with cis gene expression quantitative trait loci (cis-eQTLs) data across brain tissues and blood in European ancestry populations, as well as causal plasma proteins in African ancestry populations.

RESULTS

In those of European ancestry, the genetically predicted levels of five plasma proteins (BLNK, CD2AP, GRN, PILRA, and PILRB) were causally associated with AD. Among these five proteins, GRN was protective against AD, while the rest were risk factors. Consistent causal effects were found in the brain for cis-eQTLs of GRN, BLNK, and CD2AP, while the same was true for PILRA in the blood. None of the plasma proteins were significantly associated with AD in persons of African ancestry.

CONCLUSIONS

Comprehensive MR analyses with multi-omics data identified five plasma proteins that had causal effects on AD, highlighting potential biomarkers or drug targets for better diagnosis and treatment for AD.

Mendelian randomization provides a multi-omics perspective on the regulation of genes involved in ribosome biogenesis in relation to cardiac structure and function

BACKGROUND

Ribosome biogenesis (RiboSis) is a complex process for generating ribosomes, the cellular machinery responsible for protein synthesis. Dysfunctional RiboSis can disrupt cardiac structure and function, contributing to cardiovascular diseases. This study employed a Mendelian randomization (MR) approach, integrating multi-omics data, to investigate the relationship between RiboSis-related genes and standard cardiac structure and function.

METHODS

We utilized summary stats for methylation, RNA splicing, and gene expression, and UK Biobank cardiopulm MRI genetic associations (N = 41,135). MR evaluated RiboSis gene features against traits, complemented by hypothesis prioritization for multi-trait colocalization (HyPrColoc) and colocalization. Composite scores ranked RiboSis genes, and phenome-wide association study (PheWAS) with scQTLbase instrumental variables (IVs) confirmed results.

RESULTS

We identified 15 RiboSis-related genes: HEATR1, SENP3, ERI1, ERCC2, TSR1, UTP11, DDX17, SMARCB1, NIP7, ERAL1, NOP56, RPL10A, EIF6, EXOSC9, and NOP58. Notably, HEATR1 and SENP3 were ranked in the top quartile (Q1), scoring 25. In validation cohort, 12 genes associated with cardiac structures, functions, diseases. Only ERAL1, TSR1, and NIP7 lacked significant associations with cardiac traits.

CONCLUSION

Our multi-omics MR analysis identified 15 RiboSis-related genes associated with cardiac risk, with 12 further validated through gene set enrichment analysis. These findings suggest a link between RiboSis and cardiac health, enhancing understanding of cardiac disease mechanisms.

Advancing allergic rhinitis research through phenome-wide association studies: Insights from known genetic loci

Background

Allergic rhinitis (AR) is a common chronic respiratory disease that can lead to the development of various other conditions. Although genetic risk loci associated with AR have been reported, the connections between these loci and AR comorbidities or other diseases remain unclear.

Methods

This study conducted a phenome-wide association study (PheWAS) using known AR risk loci to explore the impact of known AR risk variants on a broad spectrum of phenotypes. Subsequently, linkage disequilibrium score regression (LDSC) and bidirectional two-sample mendelian randomization (TSMR) analyses were used to further analyze the genetic correlation and causal relationships between significant and potentially related phenotypes and AR.

Results

The PheWAS analysis indicated significant associations between asthma, eczema, nasal polyps, hypothyroidism, and AR risk variants. Additionally, potential associations were observed with ulcerative colitis, psoriasis, chalazion, pernicious anemia, glaucoma, multiple sclerosis, arthritis, prostate cancer, varicose veins of lower extremities, and heart attack. LDSC analysis showed that only asthma, eczema, and nasal polyps have significant positive genetic correlations with AR. Furthermore, TSMR analysis revealed causal relationships between AR and asthma, eczema, and nasal polyps.

Conclusion

This study highlights the impact of AR risk loci on a variety of diseases. By revealing new associations and shared genetic pathways, our findings provide valuable insights into the pathophysiology of AR and pave the way for more effective targeted interventions to manage AR and its related diseases.

Causal association between pregnancy disorders and neonatal jaundice: a two-sample Mendelian randomization study

Background

Some studies have suggested that complications during pregnancy, such as preeclampsia, leiomyoma during pregnancy, oxytocin induction, and mode of delivery, may be risk factors for neonatal jaundice. Herein, we applied Mendelian randomization (MR) analysis to investigate a causal association between pregnancy disorders and neonatal jaundice.

Methods

Data related to neonatal jaundice and pregnancy disorders (including pre-eclampsia or eclampsia, gestational diabetes, and gestational edema) were sourced from the FinnGen Consortium and Integrated Epidemiology Unit (IEU) databases. Inverse-variance weighted (IVW) was used as a main approach for data analysis, while MR-Egger, weighted median (WM), and weighted mode methods were used to validate the robustness of the results. MR-Egger regression method was applied to explore the presence of horizontal pleiotropy. MR pleiotropy residual sum and outlier (MR-PRESSO) method was used to detect potential outliers. Cochran's Q test was used to assess heterogeneity among instrumental variables (IVs); leave-one-out (LOO) analyses were used to evaluate the presence of predominant IVs.

Results

The IVW approach showed that pre-eclampsia or eclampsia {odds ratio (OR) [95% confidence interval (CI)]: 0.86 (0.36-2.07), P=0.73}, gestational edema and proteinuria [OR (95% CI): 1.04 (0.62-1.74), P=0.87], and gestational diabetes mellitus [OR (95% CI): 0.95 (0.60-1.49), P=0.81] were not associated with neonatal jaundice. The MR-Egger regression results showed that horizontal pleiotropy did not affect the relationship between exposure factors and outcomes. Also, no heterogeneity was observed. The MR-PRESSO analysis showed no outliers, confirming that these data were robust.

Conclusions

Our data suggested no genetic causal association between pre-eclampsia or eclampsia, gestational edema, proteinuria, gestational diabetes mellitus, and neonatal jaundice. However, further research is needed to determine if these results apply to other races.

CD2AP is Co-Expressed with Tropomyosin-Related Kinase A and Ras-Related Protein Rab-5A in Cholinergic Neurons of the Murine Basal Forebrain

Basal forebrain cholinergic neurons project to the hippocampus and cortex, are critical for learning and memory, and are central to the pathogenesis of Alzheimer's disease (AD). GWAS have consistently shown that genomic variants at the CD2AP gene locus are associated with significant increased risk of AD. GWAS studies have also shown that genetic variants in endocytosis genes, including RAB5A , significantly increase susceptibility to AD. Previous work in our lab has shown that CD2AP functions as a docking-scaffold/adaptor protein as a coordinator of nerve growth factor (NGF) and trophic signaling in neurons. We have also demonstrated that CD2AP positively regulates Rab5-mediated mechanisms of endocytosis in primary sensory neurons. The purpose of this study was to perform an in vivo characterization of CD2AP expression in cholinergic neurons of the brain regions most relevant to AD pathogenesis and to investigate the colocalization of CD2AP and Rab5 in cholinergic neurons of the murine basal forebrain. Brain tissue was perfused, harvested from ChAT BAC -eGFP transgenic mice (N=4 male, N=4 female; aged 10 mo), where cholinergic neurons (co-) express green fluorescence protein (GFP) in central and peripheral neurons that express choline acetyltransferase (ChAT). Frozen tissue sections were used to assess the specificity of the reporter in mouse brain along with localization of both CD2AP and Rab5 (co-) expression using immunofluorescence (IF) analysis of ChAT-GFP+ neurons and primary antibodies against ChAT, CD2AP and Rab5. Image J software was used to develop and optimize a colocalization assay for CD2AP and Rab5 puncta. Experiments were repeated in a follow-up cohort of aged-adult mice (N=2 male, N=2 female; aged 18 mo). IF expression of CD2AP was quantified in the basal forebrain, diagonal band of Broca (vDB), and striatal regions and compared to results from the cortical regions of the adult mouse brain. Colocalization of CD2AP was observed in the cell bodies of ChAT-GFP+ neurons of the striatum, vDB and basal forebrain regions, where CD2AP expression intensity as well as the number of cell bodies with positive signal increased incrementally. Colocalization analyses revealed near-complete overlap of CD2AP and Rab5 expression in ChAT-GFP+ cholinergic neurons of the basal forebrain region. We conclude that cholinergic neurons express CD2AP in healthy adult and aged-adult mouse brains. These data provide the first evidence of quantifiable CD2AP protein expression of cholinergic neurons specific to the diagonal band of Broca (vDB) and basal forebrain. Together with previous research from our lab, these data support a role for CD2AP in the pathogenesis of AD through orchestration of endocytosis and retrograde signaling. Ongoing studies are underway to verify these findings in a novel AD mouse model that incorporates the humanized variant of CD2AP , created by MODEL-AD, where we aim to further investigate how CD2AP variants may affect mechanistic components of Rab5 endocytosis as well as subsequent survival of cholinergic neurons in the context of known amyloid beta and Tau pathologies.

Impact of NDUFAF6 on breast cancer prognosis: linking mitochondrial regulation to immune response and PD-L1 expression

BACKGROUND

Breast cancer is a major global health concern, and there is a continuous search for novel biomarkers to predict its prognosis. The mitochondrial protein NDUFAF6, previously studied in liver cancer, is now being investigated for its role in breast cancer. This study aims to explore the expression and functional significance of NDUFAF6 in breast cancer using various databases and experimental models.

METHODS

We analyzed breast cancer samples from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Human Protein Atlas (HPA) databases, supplemented with immunohistochemistry (IHC) staining to assess NDUFAF6 expression. A breast cancer cell xenograft mouse model was used to evaluate tumor growth, apoptosis, and NDUFAF6 expression. Survival probabilities were estimated through Kaplan-Meier plots and Cox regression analysis. A Protein-Protein Interaction (PPI) network was constructed, and differentially expressed genes related to NDUFAF6 were analyzed using GO, KEGG, and GSEA. The relationship between NDUFAF6 expression, immune checkpoints, and immune infiltration was also evaluated.

RESULTS

NDUFAF6 was found to be overexpressed in breast cancer patients and in the xenograft mouse model. Its expression correlated with worse clinical features and prognosis. NDUFAF6 expression was an independent predictor of breast cancer outcomes in both univariate and multivariate analyses. Functionally, NDUFAF6 is implicated in several immune-related pathways. Crucially, NDUFAF6 expression correlated with various immune infiltrating cells and checkpoints, particularly promoting PD-L1 expression by inhibiting the NRF2 signaling pathway.

CONCLUSION

The study establishes NDUFAF6 as a potential prognostic biomarker in breast cancer. Its mechanism of action, involving the inhibition of NRF2 to upregulate PD-L1, highlights its significance in the disease's progression and potential as a target for immunotherapy.

Functional genomics identify causal variant underlying the protective CTSH locus for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent age-related neurodegenerative disease, which has a high heritability of up to 79%. Exploring the genetic basis is essential for understanding the pathogenic mechanisms underlying AD development. Recent genome-wide association studies (GWASs) reported an AD-associated signal in the Cathepsin H (CTSH) gene in European populations. However, the exact functional/causal variant(s), and the genetic regulating mechanism of CTSH in AD remain to be determined. In this study, we carried out a comprehensive study to characterize the role of CTSH variants in the pathogenesis of AD. We identified rs2289702 in CTSH as the most significant functional variant that is associated with a protective effect against AD. The genetic association between rs2289702 and AD was validated in independent cohorts of the Han Chinese population. The CTSH mRNA expression level was significantly increased in AD patients and AD animal models, and the protective allele T of rs2289702 was associated with a decreased expression level of CTSH through the disruption of the binding affinity of transcription factors. Human microglia cells with CTSH knockout showed a significantly increased phagocytosis of Aβ peptides. Our study identified CTSH as being involved in AD genetic susceptibility and uncovered the genetic regulating mechanism of CTSH in pathogenesis of AD.