Genetic mutations, altered RNA regulation, and protein aggregation are the main hallmarks of Parkinson’s disease (PD), a neurodegenerative disorder. Investigation into the molecular basis of the disease revealed that post-transcriptional regulation, specifically RNA processing, contributes to neuronal vulnerability in PD. Alterations in alternative splicing affecting genes involved in neuronal function and cellular homeostasis have been reported in PD, including SNCA, LRRK2, MAPT, PRKN, and BIN1. These alterations impact central neuronal pathways, including cytoskeletal maintenance, mitochondrial function, synaptic activity, oxidative stress, and intracellular trafficking. This review aims to provide an overview of alternative splicing in key PD gene transcripts, with a focus on their roles in pathogenesis and disease progression. Emerging data suggest that dysregulation of RNA binding proteins (RBPs) may influence RNA processing in PD. We will examine current evidence on the RNA regulatory networks in PD, highlighting the role of transcript isoforms and RBPs in neuronal dysfunction. Finally, we will discuss emerging experimental models such as 3D-brain organoids that offer new opportunities to investigate splicing regulation.

Tau is a protein associated with microtubules principally expressed in neuronal cells, where it plays a fundamental role in cytoskeleton stabilization and axonal transport. Several diseases collectively named tauopathies, such as Alzheimer’s disease, have been associated with an imbalance in the expression of alternative spliced Tau transcripts and the accumulation of hyperphosphorylated Tau, causing dysfunction and death of neuronal cells. Therefore, understanding the Tau exon splicing mechanisms may contribute to elucidating molecular factors that could underlie the development of neurodegenerative disorders. The aim of this study was to define the role of selected splicing factors in regulating Tau exon expression in cell lines and neuronal organoids. We demonstrated the role of the RNA-binding motif protein 20 (RBM20) splicing factor in regulating Tau exon 6 and exon 10, applying RNA-binding assay and qPCR analyses. Furthermore, we demonstrated that Tau expression was regulated during cerebral organoid differentiation, recapitulating in vivo Tau expression. These results suggest the feasibility of using brain organoid technology to study Tau alternative splicing during neural development, confirming that 3D cellular models could be used to study and characterize pathological processes taking place in Tau-related pathologies.

Background/Objectives: Non-coding microRNA-34a (miR-34a) regulates the expression of key factors involved in several cellular processes, such as differentiation, apoptosis, proliferation, cell cycle, and senescence. Deregulation of the expression of these factors is implicated in the onset and progression of several human diseases, including cancer, neurodegenerative disorders, and pathologies associated with viral infections and inflammation. Despite numerous studies, the molecular mechanisms regulated by miR-34a remain to be fully understood. The present study aimed to generate miR-34a knockout cell lines to identify novel genes potentially regulated by its expression. Methods: We employed the CRISPR-Cas9 gene editing system to knock out the hsa-miR-34a gene in HeLa and 293T cell lines, two widely used models for studying molecular and cellular mechanisms. We compared proliferation rates and gene expression profiles via RNA-seq and qPCR analyses between the wild-type and miR-34a KO cell lines. Results: Knockout of miR-34a resulted in a decreased proliferation rate in both cell lines. Noteworthy, the ablation of miR-34a resulted in increased expression of the long non-coding RNA MALAT1. Additionally, miR-34a-5p silencing in the A375 melanoma cell line led to MALAT1 overexpression. Conclusions: Our findings support the role of the miR-34a/MALAT1 axis in regulating proliferation processes.