A Mendelian Randomization-Based Causal Investigation on Bacterial Infection-Related Genes and Neurodegenerative Diseases.

Neurodegenerative diseases remain the most prevalent and unsolved health problems in human society, especially Alzheimer's disease (AD) and Parkinson's disease (PD). The pathogenesis, pathology, and potential clinical treatments of neurodegenerative diseases still require in-depth research. In the wake of the association between pandemics and a growing number of neurodegeneration patients, there has been growing speculation that infections are linked to AD and PD. The Aβ peptide is an important causal-related biomarker of AD and is reported to share structural and functional similarities with certain antimicrobial peptides, suggesting that it has a role in eliciting an immune response against microbes. But how neurodegeneration is related to bacterial chronic infection has not been thoroughly investigated. Using the data from genome-wide association studies (GWAS), we performed Mendelian Randomization (MR) and map 7 genes in multiple bacterial infection pathways as exposure, which show a significant association with the outcome of AD or PD. As co-verification, we perform Gene Set Enrichment Analysis (GSEA) on selected genetic variants incorporating their perturb-seq gene list (combining single-cell RNA-seq and CRISPR-based perturbations). We observed clustering of the differentially expressed genes (DEGs) in the upstream and downstream of AD and PD-related KEGG pathways, hence confirming their causal association with AD and PD and providing new perspectives on the true cause of neurodegeneration.