Comprehensive miRNome-Wide Profiling in a Neuronal Cell Model of Synucleinopathy Implies Involvement of Cell Cycle Genes

Abstract

Growing evidence suggests that epigenetic mechanisms like microRNA-mediated transcriptional regulation contribute to the pathogenesis of parkinsonism. In order to study the influence of microRNAs (miRNAs), we analyzed the miRNome 2 days prior to major cell death in α-synuclein-overexpressing Lund human mesencephalic neurons, a well-established cell model of Parkinson’s disease (PD), by next-generation sequencing. The expression levels of 23 miRNAs were significantly altered in α-synuclein-overexpressing cells, 11 were down- and 12 upregulated (P < 0.01; non-adjusted). The in silico analysis of known target genes of these miRNAs was complemented by the inclusion of a transcriptome dataset (BeadChip) of the same cellular system, revealing the G0/G1 cell cycle transition to be markedly enriched. Out of 124 KEGG-annotated cell cycle genes, 15 were present in the miRNA target gene dataset and six G0/G1 cell cycle genes were found to be significantly altered upon α-synuclein overexpression, with five genes up- (CCND1, CCND2, and CDK4 at P < 0.01; E2F3, MYC at P < 0.05) and one gene downregulated (CDKN1C at P < 0.001). Additionally, several of these altered genes are targeted by miRNAs hsa-miR-34a-5p and hsa-miR-34c-5p, which also modulate α-synuclein expression levels. Functional intervention by siRNA-mediated knockdown of the cell cycle gene cyclin D1 (CCND1) confirmed that silencing of cell cycle initiation is able to substantially reduce α-synuclein-mediated cytotoxicity. The present findings suggest that α-synuclein accumulation induces microRNA-mediated aberrant cell cycle activation in post-mitotic dopaminergic neurons. Thus, the mitotic cell cycle pathway at the level of miRNAs might offer interesting novel therapeutic targets for PD.

Regulatory miRNA–mRNA Networks in Parkinson’s Disease

“…Recently, some cell cycle genes were found enriched in a cell model of PD, and CCND1 was reported as upregulated and involved in alpha-synuclein cell death. It was shown that the knockdown of CCND1 reduces cell death [43], reinforcing our results of upregulation of miRNAs that regulate CCND1 in the brain.…”

Alpha-Synuclein Pathology Coincides With Increased Number of Early Stage Neural Progenitors in the Adult Hippocampus

“…As documented for epileptic seizures, such alterations of neuronal activity may promote adult neurogenesis ( Jessberger and Parent, 2015 ). Finally, α-syn pathology through gain or loss of function may directly impact mechanisms of cell cycle regulation along the process of neurogenesis, leading to NPCs stuck or shifting in proliferation or maturation processes ( Lee et al, 2003 ; Winner et al, 2012 ; Rodríguez-Losada et al, 2020 ; Findeiss et al, 2021 ). If α-syn pathology spreads across synapses ( Chu and Kordower, 2015 ; Melki, 2018 ), none of the above mechanisms require a direct intracellular toxicity in DG neurons, which could be argued against given the relatively low expression level of α-syn in this region, physiologically and in Thy1-aSyn mice as discussed above.…”

MicroRNA-sequencing Analysis of Plasma-derived Exosomes Provides Novel Insights into the Disease Mechanism of Childhood Atopic Dermatitis

“…Hsa-miR-34a-5p was the most signi cantly upregulated miRNA in our study. Hsa-miR-34a-5p has been reported to be expressed in blood mononuclear cells [40], neurons [41], T cells [42], and several cancer cell lines [43]. It has been shown to regulate T-cell differentiation and plasticity by targeting histone gene expression and histone modi cation [42] to play a critical role as a tumor suppressor via regulation of the p53 signaling pathway to mediate cell proliferation, invasion, and apoptosis [44] and to be implicated in large B-cell lymphoma [44] and lung broblasts [45].…”