Unravelling Synaptic and Metabolic Mechanisms of Cognitive Resilience in Asymptomatic Alzheimer’s Disease Across Two Alzheimer’s Disease Cohorts

Asymptomatic Alzheimer's Disease (AsymAD) is a preclinical stage of Alzheimer's Disease (AD) identified by amyloid plaques and neurofibrillary tangles in cognitively normal individuals and offers essential understanding for early diagnosis and treatment of AD. To uncover molecular insights into AsymAD, RNA sequencing (RNA-seq) datasets from two different consortia, ROSMAP (Religious Orders Study and Memory and Aging Project) and MSBB (Mount Sinai Brain Bank), were investigated. The individuals in the datasets were grouped into AD and AsymAD based on clinical and neuropathological criteria. Differentially expressed genes (DEGs), differentially expressed transcripts (DETs), and differentially used transcripts (DUTs) were identified between AD and AsymAD samples. The results were interpreted through functional enrichment analysis and compared with the predefined lists of AD-related and learning-memory-cognition-related genes, and genes from an independent mouse dataset. The genes from the list of DEGs, DETs and DUTs were mapped onto a human protein-protein interaction network, revealing subnetworks associated with AsymAD. This led to the discovery of biomarker candidate genes: NRXN3, DGKB, ADAMTS2, GNG4, ENPP5, PCOLCE, COL25A1, COL26A1, MRPL1, and MRPL30. This study introduces an innovative approach by including DETs and DUTs in the analyses, beyond the standard focus on DEGs, pointing out comprehensive insights into the molecular mechanisms of AsymAD. In addition, combining the results of the subnetwork analysis from DEGs, DETs, and DUTs provided a new perspective to AsymAD and resulted in the discovery of further important genes, which can pave the way for early detection and intervention of AD.