Identification of Blood-based Biomarkers for Early Stage Parkinson's Disease

Parkinsons disease (PD) affects millions of people worldwide and causes symptoms such as bradykinesia and disrupted speech. Parkinsons disease is known to be characterized by the mass death of dopaminergic neurons in the substantia nigra region. In the status quo, PD is often diagnosed at late stages because obvious motor symptoms appear after the disease has progressed far. It is advantageous to diagnose PD before the onset of motor symptoms because treatments are often more effective at early stages. While motor symptoms usually manifest when over 50% of dopaminergic neurons in the substantia nigra are already lost, molecular signatures of PD may be present at early stages in patient blood. This study aimed to analyze several gene expression studies data for commonly differentially expressed genes (DEGs) in the blood of early stage PD patients. 147 DEGs were identified in at least two out of three datasets and passed cut-off criteria. A protein interaction network for the DEGs was constructed and various tools were used to identify network characteristics and hub genes. PANTHER analysis revealed that the biological process "cellular response to glucagon stimulus" was overrepresented by almost 21 times among the DEGs and "lymphocyte differentiation" by 5.98 times. Protein catabolic processes and protein kinase functions were also overrepresented. ESR1, CD19, SMAD3, FOS, CXCR5, and PRKACA may be potential biomarkers and warrant further study. Overall, the findings of the present study provide insights on molecular mechanisms of PD and provide greater confidence on which genes are differentially expressed in PD. The results also are additional evidence for the role of the immune system in PD, a topic that is gaining interest in the PD research community.