Aims: Parkinson's disease (PD) is a progressive and age‐dependent neurodegenerative disease characterised clinically by a variety of motor symptoms and cognitive impairment. PD was initially considered to be a grey matter disease; however, recently, evidence has emerged that white matter changes in PD precede the neuronal loss seen in the grey matter. The cause of these initial white matter changes is yet to be elucidated. Here, we explored whether dysregulated miRNAs and their target mRNA could provide insight into the underlying mechanisms of early white matter changes in PD.Methods: We analysed the expression of miRNAs in three different stages of PD through RNA‐sequencing and validated the differential expression of miRNAs through quantitative reverse transcription polymerase chain reaction. With bioinformatic analyses, we predicted target genes of dysregulated miRNAs and investigated their biomarker potential. Finally, in vitro, we confirmed the targetting of the gene SIRT1 by miR‐543.Results: We identified 12 dysregulated miRNAs in PD and found that miR‐543 holds potential as a biomarker for late‐stage PD with dementia. We report upregulation of miR‐543 in early PD white matter tissue and downregulation of SIRT1. In vitro experiments showed that the upregulation of miR‐543 results in the downregulation of SIRT1 in the white matter, but not in the grey matter.Conclusions: We validated SIRT1 as a target of miR‐543 in the brain and showed its function as a potential biomarker. Our results highlight the idea that dysregulation of miR‐543 in early PD white matter, resulting in the dysregulation of SIRT1, potentially influencing the early white matter changes observed in PD.

GABAergic interneurons play a critical role in maintaining neural circuit balance, excitation–inhibition regulation, and cognitive function modulation. In tuberous sclerosis complex (TSC), GABAergic neuron dysfunction contributes to disrupted network activity and associated neurological symptoms, assumingly in a cell type-specific manner. This GABAergic centric study focuses on identifying specific interneuron subpopulations within TSC, emphasizing the unique characteristics of medial ganglionic eminence (MGE)- and caudal ganglionic eminence (CGE)-derived interneurons. Using single-nuclei RNA sequencing in TSC patient material, we identify somatostatin-expressing (SST+) interneurons as a unique and immature subpopulation in TSC. The disrupted maturation of SST+ interneurons may undergo an incomplete switch from excitatory to inhibitory GABAergic signaling during development, resulting in reduced inhibitory properties. Notably, this study reveals markers of immaturity specifically in SST+ interneurons, including an abnormal NKCC1/KCC2 ratio, indicating an imbalance in chloride homeostasis crucial for the postsynaptic consequences of GABAergic signaling as well as the downregulation of GABA_A receptor subunits, GABRA1, and upregulation of GABRA2. Further exploration of SST+ interneurons revealed altered localization patterns of SST+ interneurons in TSC brain tissue, concentrated in deeper cortical layers, possibly linked to cortical dyslamination. In the epilepsy context, our research underscores the diverse cell type-specific roles of GABAergic interneurons in shaping seizures, advocating for precise therapeutic considerations. Moreover, this study illuminates the potential contribution of SST+ interneurons to TSC pathophysiology, offering insights for targeted therapeutic interventions.

Tuberous sclerosis complex (TSC) is a rare multi-system genetic disorder characterized by a high incidence of epilepsy and neuropsychiatric manifestations known as tuberous-sclerosis-associated neuropsychiatric disorders (TANDs), including autism spectrum disorder (ASD) and intellectual disability (ID). MicroRNAs (miRNAs) are small regulatory non-coding RNAs that regulate the expression of more than 60% of all protein-coding genes in humans and have been reported to be dysregulated in several diseases, including TSC. In the current study, RNA sequencing analysis was performed to define the miRNA and isoform (isomiR) expression patterns in serum. A Receiver Operating Characteristic (ROC) curve analysis was used to identify circulating molecular biomarkers, miRNAs, and isomiRs, able to discriminate the development of neuropsychiatric comorbidity, either ASD, ID, or ASD + ID, in patients with TSC. Part of our bioinformatics predictions was verified with RT-qPCR performed on RNA isolated from patients’ serum. Our results support the notion that circulating miRNAs and isomiRs have the potential to aid standard clinical testing in the early risk assessment of ASD and ID development in TSC patients.

Objective: Structural epilepsies can manifest months or years after the occurrence of an initial epileptogenic insult, making them amenable for secondary prevention. However, development of preventive treatments has been challenged by a lack of biomarkers for identifying the subset of individuals with the highest risk of epilepsy after the epileptogenic insult.Methods: Four different rat models of epileptogenesis were investigated to identify differentially expressed circulating microRNA (miRNA) and isomiR profiles as biomarkers for epileptogenesis. Plasma samples were collected on day 2 and day 9 during the latency period from animals that did or did not develop epilepsy during long‐term video‐electroencephalographic monitoring. miRNAs and isomiRs were identified and measured in an unsupervised manner, using a genome‐wide small RNA sequencing platform. Receiver operating characteristic analysis was performed to determine the performance of putative biomarkers.Results: Two days after an epileptogenic insult, alterations in the levels of several plasma miRNAs and isomiRs predicted epileptogenesis in a model‐specific manner. One miRNA, miR‐3085, showed good sensitivity (but low specificity) as a prognostic biomarker for epileptogenesis in all four models (area under the curve = .729, sensitivity = 83%, specificity = 64%, p < .05).Significance: Identified plasma miRNAs and isomiRs are mostly etiology‐specific rather than common prognostic biomarkers of epileptogenesis. These data imply that in preclinical and clinical studies, it may be necessary to identify specific biomarkers for different epilepsy etiologies. Importantly, circulating miRNAs like miR‐3085 with high negative predictive value for epileptogenesis in different etiologies could be useful candidates for initial screening purposes of epileptogenesis risk.

Malformations of cortical development are manifestations of mTORopathies, including tubers in context of Tuberous Sclerosis Complex (TSC) cortical tubers and Focal Cortical Dysplasia (FCD), and are associated with epilepsy, often accompanied by comorbidities such as autism spectrum disorder (ASD). This study aims to investigate the cell-type-specific transcriptional alterations and disrupted intercellular communication networks in mTORopathies, focusing on their implications for cortical network dysfunction. Using single-cell RNA sequencing, we identified 33 transcriptionally distinct cell clusters across control and pathological samples, including neuronal, glial, and endothelial populations. Our analysis revealed disease-specific changes, such as the loss of certain glutamatergic and microglial clusters in cortical tubers (TSC), MTOR_FCD and DEPDC5_FCD, and the presence of a unique endothelial cluster in pathological samples. Pathway enrichment analysis highlighted the critical role of synaptic signaling, axonogenesis, and neuroimmune regulation in these disorders. Additionally, cell–cell communication network analysis demonstrated disrupted interactions between neuron-astrocyte, astrocyte-OPC, and microglia-neuron across mTORopathies. We found that the neurexins-neuroligins (NRXN-NLGN) signaling pathway, crucial for synapse formation and stability, was altered in both glutamatergic and GABAergic neurons, reflecting dysregulated synaptic plasticity and impaired neuron-glia communication. These findings provide novel insights into the molecular underpinnings of mTORopathies and suggest potential therapeutic targets to restore cellular communication and synaptic function in these disorders.