Differential serum microRNAs in premotor LRRK2 G2019S carriers from Parkinson’s disease. Differential serum microRNAs in premotor LRRK2 G2019S carriers from Parkinson’s disease

The LRRK2 G2019S pathogenic mutation causes LRRK2-associated Parkinson’s disease (L2PD) with incomplete penetrance. LRRK2 non-manifesting carriers (L2NMC) are at PD high risk but predicting pheno-conversion is challenging given the lack of progression biomarkers. To investigate novel biomarkers for PD premotor stages, we performed a longitudinal microRNA (miRNA) assessment of serum samples from G2019S L2NMC followed-up over 8 years. Our cohort consisted of G2019S L2NMC stratified by dopamine transporter single-photon emission computed tomography (DaT-SPECT) into DaT-negative (n=20) and DaT-positive L2NMC (n=20), pheno-converted G2019S L2PD patients (n=20), idiopathic PD (iPD) (n=19), and controls (n=40). We also screened a second cohort of L2PD patients (n=19) and controls (n=20) (Total n=158). Compared to healthy controls, we identified 8 deregulated miRNAs in DaT-negative L2NMC, 6 in DaT-positive L2NMC, and one in L2PD. Between groups, the highest miRNA differences, 24 candidate miRNAs, occurred between DaT-positive L2NMC and L2PD. Longitudinally, we found 11 common miRNAs with sustained variation in DaT-negative and DaT-positive L2NMCs compared to their baselines. Our study identifies novel miRNA alterations in premotor stages of PD co-occurring with progressive DaT-SPECT decline before motor manifestation, whose deregulation seems to attenuate after the diagnosis of L2PD. Moreover, we identified 4 miRNAs with relatively high discriminative ability (AUC=0.82) between non-pheno-converted DaT-positive G2019S carriers and pheno-converted L2PD patients (miR-4505, miR-8069, miR-6125, and miR-451a), which hold potential as early progression biomarkers for PD. Overall design: No replicates. For differential miRNA expression analysis (4 groups), we used the global normalization method adjusting by gender, age, and hybridization date.