Abstract
BACKGROUND: Synaptic dysfunction and synapse loss occur in Alzheimer's disease (AD). The current study aimed to identify synaptic-related genes with diagnostic potential for AD. METHODS: Differentially expressed genes (DEGs) were overlapped with phenotype-associated module selected through weighted gene co-expression network analysis (WGCNA), and synaptic-related genes. The overlapped hub genes were further processed using machine learning algorithms, intersected with module gene from protein-protein interaction (PPI) network constructed with DEGs, to yield co-hub genes. The diagnostic potentials of the co-hub genes were examined by receiver operating characteristic (ROC) analysis. Correlation between co-hub genes with clinical features and immune cell infiltration was analyzed. Finally, the expression of co-hub genes was analyzed in several datasets and validated in AD transgenic mice. RESULTS: A total of three co-hub genes were identified, including MAP1B, L1CAM, and GABBR2. GABBR2 showed area under the curve (AUC) values of 0.98, 0.81, and 0.88 in the training and two external validation datasets. GABBR2 was negatively correlate with beta- and gamma-secretase activities, and infiltration of natural killer T cells and effector memory CD8 T cells. Finally, GABBR2 was validated to be downregulated in AD transgenic mice, aligning with bioinformatic findings. GABBR2 overexpression in N2a/APP cells increased ADAM10 while decreased of BACE1, leading to upregulation of sAPPα while downregulation of sAPPβ. CONCLUSION: In conclusion, GABBR2 acts as a novel biomarker for the diagnosis of AD and negatively correlated with Aβ in AD.