Integrative systems and functional analyses reveal a role of dopaminergic signaling in myelin pathogenesis

Developmental dopaminergic signaling modulates neural circuit formation and contributes to autism spectrum disorder (ASD)-related phenotypes

Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder with a complex etiology. Recent evidence suggests that dopamine plays a crucial role in neural development. However, it remains unclear whether and how disrupted dopaminergic signaling during development contributes to ASD. In this study, human brain RNA-seq transcriptome analysis revealed a significant correlation between changes in dopaminergic signaling pathways and neural developmental signaling in ASD patients. In the zebrafish model, disrupted developmental dopaminergic signaling led to neural circuit abnormalities and behavior reminiscent of autism. Dopaminergic signaling may impact neuronal specification by potentially modulating integrins. These findings shed light on the mechanisms underlying the link between disrupted developmental dopamine signaling and ASD, and they point to the possibility of targeting dopaminergic signaling in early development for ASD treatment.

Exploring the Role of Neurotransmitters in Multiple Sclerosis: An Expanded Review

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system (CNS). Although emerging evidence has shown that changes in neurotransmitter levels in the synaptic gap may contribute to the pathophysiology of MS, their specific role has not been elucidated yet. In this review, we aim to analyze preclinical and clinical evidence on the structural and functional changes in neurotransmitters in MS and critically discuss their potential role in MS pathophysiology. Preclinical studies have demonstrated that alterations in glutamate metabolism may contribute to MS pathophysiology, by causing excitotoxic neuronal damage. Dysregulated interaction between glutamate and GABA results in synaptic loss. The GABAergic system also plays an important role, by regulating the activity and plasticity of neural networks. Targeting GABAergic/glutamatergic transmission may be effective in fatigue and cognitive impairment in MS. Acetylcholine (ACh) and dopamine can also affect the T-mediated inflammatory responses, thereby being implicated in MS-related neuroinflammation. Also, melatonin might affect the frequency of relapses in MS, by regulating the sleep-wake cycle. Increased levels of nitric oxide in inflammatory lesions of MS patients may be also associated with axonal neuronal degeneration. Therefore, neurotransmitter imbalance may be critically implicated in MS pathophysiology, and future studies are needed for our deeper understanding of their role in MS.

Expression of myelin transcription factor 1 and lamin B receptor mediate neural progenitor fate transition in the zebrafish spinal cord pMN domain

The pMN domain is a restricted domain in the ventral spinal cord, defined by the expression of the olig2 gene. Though it is known that the pMN progenitor cells can sequentially generate motor neurons and oligodendrocytes, the lineages of these progenitors are controversial and how their progeny are generated is not well understood. Using single-cell RNA sequencing, here, we identified a previously unknown heterogeneity among pMN progenitors with distinct fates and molecular signatures in zebrafish. Notably, we characterized two distinct motor neuron lineages using bioinformatic analysis. We then went on to investigate specific molecular programs that regulate neural progenitor fate transition. We validated experimentally that expression of the transcription factor myt1 (myelin transcription factor 1) and inner nuclear membrane integral proteins lbr (lamin B receptor) were critical for the development of motor neurons and neural progenitor maintenance, respectively. We anticipate that the transcriptome features and molecular programs identified in zebrafish pMN progenitors will not only provide an in-depth understanding of previous findings regarding the lineage analysis of oligodendrocyte progenitor cells and motor neurons but will also help in further understanding of the molecular programming involved in neural progenitor fate transition.

Neurotoxicity induced by toluene: In silico and in vivo evidences of mitochondrial dysfunction and dopaminergic neurodegeneration

Toluene is an air pollutant widely used as an organic solvent in industrial production and emitted by fossil fuel combustion, in addition to being used as a drug of abuse. Its toxic effects in the central nervous system have not been well established, and how and which neurons are affected remains unknown. Hence, this study aimed to fill this gap by investigating three central questions: 1) How does toluene induce neurotoxicity? 2) Which neurons are affected? And 3) What are the long-term effects induced by airborne exposure to toluene? To this end, a Caenorhabditis elegans model was employed, in which worms at the fourth larval stage were exposed to toluene in the air for 24 h in a vapor chamber to simulate four exposure scenarios. After the concentration-response curve analysis, we chose scenarios 3 (E3: 792 ppm) and 4 (E4: 1094 ppm) for the following experiments. The assays were performed 1, 48, or 96 h after removal from the exposure environments, and an irreversible reduction in neuron fluorescence and morphologic alterations were observed in different neurons of exposed worms, particularly in the dopaminergic neurons. Moreover, a significant impairment in a dopaminergic-dependent behavior was also associated with negative effects in healthspan endpoints, and we also noted that mitochondria may be involved in toluene-induced neurotoxicity since lower adenosine 5'-triphosphate (ATP) levels and mitochondrial viability were observed. In addition, a reduction of electron transport chain activity was evidenced using ex vivo protocols, which were reinforced by in silico and in vitro analysis, demonstrating toluene action in the mitochondrial complexes. Based on these findings model, it is plausible that toluene neurotoxicity can be initiated by complex I inhibition, triggering a mitochondrial dysfunction that may lead to irreversible dopaminergic neuronal death, thus impairing neurobehavioral signaling.

Cognitive improvement effect of nervonic acid and essential fatty acids on rats ingesting Acer truncatum Bunge seed oil revealed by lipidomics approach

Acer truncatum Bunge seed oil (ASO) is rich in ω-9 (53.93%) and ω-6 (30.7%) fatty acids (FAs) and characterized by 3-7% nervonic acid (NA, C24:1ω-9). Evidence suggests that ω-9 FAs such as NA participate in processes of cognitive improvement; however, their mechanism remains ambiguous. In this study, we investigated the effect of ASO on rat memory and the change in lipid profiling and underlying metabolism. After ASO was administrated to rats for one, three and seven days, their capacity for learning and memory significantly increased via the MWM test. Lipid profiling showed alterations in a wide range of metabolic features after ASO was administrated to the rats, in which sphingolipids (SP) in the serum and glycerophospholipids (GP) in the brain were regulated significantly. The changes in the fatty acids in the serum and brain showed the synergetic effects of NA, EA, OA and DHA, where NA, EA and OA exhibited similar change trends. The enrichment analysis based on KEGG indicated that ASO supplementation evoked the pathways of neurotrophin signaling, glycerophospholipid metabolism and sphingolipid metabolism, which are related to memory and cognition improvement. Among the metabolites with different molecular forms, the biomarkers with C24:1ω-9 chains exhibited a positive correlation with others both in the serum SP and brain GP. These results suggest the synergistic effects of ω-9 FAs and that their conversion into each other may result in enhanced cognition in rats ingesting Acer truncatum Bunge seed oil.

Striatal dopaminergic neurons as a potential target for GDNF based ischemic stroke therapy

BACKGROUND

Glial cell-line-derived neurotrophic factor (GDNF) is a well-known regulatory neurotrophic factor on dopaminergic neurons. Several pathologies have been documented so far in case of any impairment in the dopaminergic system. This study aimed to investigate the potential protective role of lentiviral GNDF delivery on the small population of tyrosine hydroxylase (TH) positive dopamine producing striatal neurons after ischemic stroke.

METHODS

Fourteen C57BL/6J male mice (8-10 weeks) were intracerebrally treated with lentiviral GDNF (Lv-GDNF) or vehicle. Ten days after injections, cerebral ischemia was induced by blockage of the middle cerebral artery. Animals were terminated 72 h after ischemia, and their brains were taken for histological and molecular investigations. Following confirmation of GDNF overexpression, TH immunostaining and immunoblotting were used to evaluate the role of GDNF on dopaminergic neurons. Next, Fluro Jade C staining was implemented to examine the degree of neuronal degeneration at the damaged parenchyma.

RESULTS

Neither the amount of TH positive dopaminergic neurons nor the expression of TH changed in the Lv-GDNF treated animals comparing to the vehicle group. On the other hand, GDNF exposure caused a significant increase in the expression of Nurr1, an essential transcription factor for dopaminergic neurons and Gap43, growth and plasticity promoting protein, in the ischemic striatum. Treatment with Lv-GDNF gave rise to a significant reduction in the number of degenerated neurons. Finally, enhanced GDNF expression also induced expression of an important stress-related transcription factor NF-κB as well as the nitric oxide synthase enzymes iNOS and nNOS in the contralesional hemisphere.

Alternative splicing transitions associate with emerging atrophy phenotype during denervation-induced skeletal muscle atrophy

Alternative splicing (AS) presents a key posttranscriptional regulatory mechanism associated with numerous physiological processes. However, little is known about its role in skeletal muscle atrophy. In this study, we used a rat model of denervated skeletal muscle atrophy and performed RNA-sequencing to analyze transcriptome profiling of tibialis anterior muscle at multiple time points following denervation. We found that AS is a novel mechanism involving muscle atrophy, which is independent changes at the transcript level. Bioinformatics analysis further revealed that AS transitions are associated with the appearance of the atrophic phenotype. Moreover, we found that the inclusion of multiple highly conserved exons of Obscn markedly increased at 3 days after denervation. In addition, we confirmed that this newly transcript inhibited C2C12 cell proliferation and exacerbated myotube atrophy. Finally, our study revealed that a large number of RNA-binding proteins were upregulated when the atrophy phenotype appeared. Our data emphasize the importance of AS in this process.

Epitranscriptomic m6A regulation following spinal cord injury

RNA methylation is involved in multiple physiological and pathological processes. However, the role of RNA methylation in spinal cord regeneration has not been reported. In this study, we find an altered m6A (N6-methyladenosine) RNA methylation profiling following zebrafish spinal cord injury (SCI), in line with an altered transcription level of the m6A methylase Mettl3. Interestingly, many of the differential m6A-tagged genes associated with neural regeneration are hypomethylated, but their transcription levels are upregulated in SCI. Moreover, we find that METTL3 may be important for spinal cord regeneration. We also show a conserved feature of METTL3 changes in mouse SCI model, in which the expression of METTL3 is increased in both astrocytes and neural stem cells. Together, our results indicate that m6A RNA methylation is dynamic and conserved following SCI and may contribute to spinal cord regeneration.