VALIDATION OF BLOOD PRKN mRNA EXPRESSION AS A BIOMARKER FOR PRKN-RELATED PARKINSON’S DISEASE

Abstract

Background: Mutations in the PRKN gene, encoding the E3 ubiquitin ligase Parkin, are a major cause of early–onset, autosomal recessive Parkinson’s disease (PD). Identifying carriers currently requires complex genetic testing. Prior work suggested that PRKN mRNA levels in peripheral blood mononuclear cells (PBMCs) may discriminate PRKN-related PD from idiopathic PD (iPD) and controls.

Objective: To validate and expand previous findings using a partially independent cohort and a novel RT-PCR primer set, assessing the diagnostic potential of PRKN mRNA qualification as a screening tool for PRKN-related PD.

Methods: PBMCs were isolated from 7 PRKN-related PD patients (3 biallelic, 4 heterozygous), 8 iPD patients and 7 matched healthy controls. PRKN mRNA expression was quantified using RT-PCR with newly designed primes. Genetic characterization employed Mulpiplex Ligation-dependent Probe Amplification (MLPA) and Whole Exome Sequencing (WES). Statistical comparisons were performed using ANOVA with post hoc tests and diagnostic accuracy was assessed by ROC analysis.

Results: PRKN mRNA levels were significantly reduced in PRKN-related PD compared to controls (181-fold or 99,45% lower, p=0,0041) and iPD (74-fold or 98,7% lower, p=0,021). Expression levels were uniformly low in both biallelic and heterozygous carriers. ROC analysis showed 100% sensitivity and specificity for distinguishing PRKN mutation carriers from non-carriers (PPV=100%, 95% CI: 72,3-100%).

Conclusion: Peripheral PRKN mRNA quantification is a highly sensitive and specific marker for PRKN mutation carrier status in PD, including in the heterozygous state. This non-invasive assay holds promise as a rapid screening tool, but warrants larger, multicenter validation.