Acute mitochondrial damage and the energy crisis following axonal injury highlight mitochondrial transport as an important target for axonal regeneration. Syntaphilin (Snph), known for its potent mitochondrial anchoring action, has emerged as a significant inhibitor of both mitochondrial transport and axonal regeneration. Therefore, investigating the molecular mechanisms that influence the expression levels of the snph gene can provide a viable strategy to regulate mitochondrial trafficking and enhance axonal regeneration. Here, we reveal the inhibitory effect of microRNA-146b (miR-146b) on the expression of the homologous zebrafish gene syntaphilin b (snphb). Through CRISPR/Cas9 and single-cell electroporation, we elucidated the positive regulatory effect of the miR-146b-snphb axis on Mauthner cell (M-cell) axon regeneration at the global and single-cell levels. Through escape response tests, we show that miR-146b-snphb signaling positively regulates functional recovery after M-cell axon injury. In addition, continuous dynamic imaging in vivo showed that reprogramming miR-146b significantly promotes axonal mitochondrial trafficking in the pre-injury and early stages of regeneration. Our study reveals an intrinsic axonal regeneration regulatory axis that promotes axonal regeneration by reprogramming mitochondrial transport and anchoring. This regulation involves noncoding RNA, and mitochondria-associated genes may provide a potential opportunity for the repair of central nervous system injury.
Animals ; Zebrafish ; MicroRNAs/genetics* ; Nerve Regeneration/physiology* ; Mitochondria/metabolism* ; Zebrafish Proteins/genetics* ; Axons/metabolism* ; Signal Transduction/physiology* ; Axonal Transport/physiology* ; Nerve Tissue Proteins/genetics*

Effective axon regeneration is essential for the successful restoration of nerve functions in patients suffering from axon injury-associated neurological diseases. Certain self-regeneration occurs in injured peripheral axonal branches of dorsal root ganglion (DRG) neurons but does not occur in their central axonal branches. By performing rat sciatic nerve or dorsal root axotomy, we determined the expression of the dysbindin domain containing 2 (DBNDD2) in the DRGs after the regenerative peripheral axon injury or the non-regenerative central axon injury, respectively, and found that DBNDD2 is down-regulated in the DRGs after peripheral axon injury but up-regulated after central axon injury. Furthermore, we found that DBNDD2 expression differs in neonatal and adult rat DRGs and is gradually increased during development. Functional analysis through DBNDD2 knockdown revealed that silencing DBNDD2 promotes the outgrowth of neurites in both neonatal and adult rat DRG neurons and stimulates robust axon regeneration in adult rats after sciatic nerve crush injury. Bioinformatic analysis data showed that transcription factor estrogen receptor 1 (ESR1) interacts with DBNDD2, exhibits a similar expression trend as DBNDD2 after axon injury, and may targets DBDNN2. These studies indicate that reduced level of DBNDD2 after peripheral axon injury and low abundance of DBNDD2 in neonates contribute to axon regeneration and thus suggest the manipulation of DBNDD2 expression as a promising therapeutic approach for improving recovery after axon damage.
Animals ; Ganglia, Spinal/metabolism* ; Nerve Regeneration/genetics* ; Rats ; Axons/metabolism* ; Sciatic Nerve/injuries* ; Rats, Sprague-Dawley ; Male

Amyotrophic Lateral Sclerosis (ALS) is a complex neurodegenerative disorder characterized by progressive axonopathy, jointly leading to the dying back of the motor neuron, disrupting both nerve signaling and motor control. In this review, we highlight the roles of axonopathy in ALS progression, driven by the interplay of multiple factors including defective trafficking machinery, protein aggregation, and mitochondrial dysfunction. Dysfunctional intracellular transport, caused by disruptions in microtubules, molecular motors, and adaptors, has been identified as a key contributor to disease progression. Aberrant protein aggregation involving TDP-43, FUS, SOD1, and dipeptide repeat proteins further amplifies neuronal toxicity. Mitochondrial defects lead to ATP depletion, oxidative stress, and Ca²⁺ imbalance, which are regarded as key factors underlying the loss of neuromuscular junctions and axonopathy. Mitigating these defects through interventions including neurotrophic treatments offers therapeutic potential. Collaborative research efforts aim to unravel ALS complexities, opening avenues for holistic interventions that target diverse pathological mechanisms.
Humans ; Amyotrophic Lateral Sclerosis/therapy* ; Animals ; Axons/metabolism* ; Mitochondria/metabolism* ; Motor Neurons/pathology*

Diabetic neuropathic pain (DNP) is the most common disabling complication of diabetes. Emerging evidence has linked the pathogenesis of DNP to the aberrant sprouting of sensory axons into the epidermal area; however, the underlying molecular events remain poorly understood. Here we found that an axon guidance molecule, Netrin-3 (Ntn-3), was expressed in the sensory neurons of mouse dorsal root ganglia (DRGs), and downregulation of Ntn-3 expression was highly correlated with the severity of DNP in a diabetic mouse model. Genetic ablation of Ntn-3 increased the intra-epidermal sprouting of sensory axons and worsened the DNP in diabetic mice. In contrast, the elevation of Ntn-3 levels in DRGs significantly inhibited the intra-epidermal axon sprouting and alleviated DNP in diabetic mice. In conclusion, our studies identified Ntn-3 as an important regulator of DNP pathogenesis by gating the aberrant sprouting of sensory axons, indicating that Ntn-3 is a potential druggable target for DNP treatment.
Mice ; Animals ; Diabetes Mellitus, Experimental/metabolism* ; Axons/physiology* ; Diabetic Neuropathies ; Sensory Receptor Cells/metabolism* ; Neuralgia/metabolism*

Neurons migrate from their birthplaces to the destinations, and extending axons navigate to their synaptic targets by sensing various extracellular cues in spatiotemporally controlled manners. These evolutionally conserved guidance cues and their receptors regulate multiple aspects of neural development to establish the highly complex nervous system by mediating both short- and long-range cell-cell communications. Neuronal guidance genes (encoding cues, receptors, or downstream signal transducers) are critical not only for development of the nervous system but also for synaptic maintenance, remodeling, and function in the adult brain. One emerging theme is the combinatorial and complementary functions of relatively limited classes of neuronal guidance genes in multiple processes, including neuronal migration, axonal guidance, synaptogenesis, and circuit formation. Importantly, neuronal guidance genes also regulate cell migration and cell-cell communications outside the nervous system. We are just beginning to understand how cells integrate multiple guidance and adhesion signaling inputs to determine overall cellular/subcellular behavior and how aberrant guidance signaling in various cell types contributes to diverse human diseases, ranging from developmental, neuropsychiatric, and neurodegenerative disorders to cancer metastasis. We review classic studies and recent advances in understanding signaling mechanisms of the guidance genes as well as their roles in human diseases. Furthermore, we discuss the remaining challenges and therapeutic potentials of modulating neuronal guidance pathways in neural repair.
Humans ; Axon Guidance/genetics* ; Neurons ; Axons/metabolism* ; Signal Transduction/genetics* ; Cell Communication

Enhancing remyelination after injury is of utmost importance for optimizing the recovery of nerve function. While the formation of myelin by Schwann cells (SCs) is critical for the function of the peripheral nervous system, the temporal dynamics and regulatory mechanisms that control the progress of the SC lineage through myelination require further elucidation. Here, using in vitro co-culture models, gene expression profiling of laser capture-microdissected SCs at various stages of myelination, and multilevel bioinformatic analysis, we demonstrated that SCs exhibit three distinct transcriptional characteristics during myelination: the immature, promyelinating, and myelinating states. We showed that suppressor interacting 3a (Sin3A) and 16 other transcription factors and chromatin regulators play important roles in the progress of myelination. Sin3A knockdown in the sciatic nerve or specifically in SCs reduced or delayed the myelination of regenerating axons in a rat crushed sciatic nerve model, while overexpression of Sin3A greatly promoted the remyelination of axons. Further, in vitro experiments revealed that Sin3A silencing inhibited SC migration and differentiation at the promyelination stage and promoted SC proliferation at the immature stage. In addition, SC differentiation and maturation may be regulated by the Sin3A/histone deacetylase2 (HDAC2) complex functionally cooperating with Sox10, as demonstrated by rescue assays. Together, these results complement the recent genome and proteome analyses of SCs during peripheral nerve myelin formation. The results also reveal a key role of Sin3A-dependent chromatin organization in promoting myelinogenic programs and SC differentiation to control peripheral myelination and repair. These findings may inform new treatments for enhancing remyelination and nerve regeneration.
Animals ; Axons ; Chromatin/metabolism* ; Gene Expression Profiling ; Myelin Sheath/metabolism* ; Nerve Regeneration/physiology* ; Rats ; Schwann Cells/metabolism* ; Sciatic Nerve/injuries*

Spinal cord injury is a severe central nervous system disease, which will cause a series of complex pathophysiological changes and activate a variety of signaling pathways including Notch signaling. Studies have evidenced that activation of the Notch signaling pathway is not conducive to nerve repair and symptom improvement after spinal cord injury. Its mechanisms include inhibiting neuronal differentiation and axon regeneration, promoting reactive astrocyte proliferation, promoting M1 macrophage polarization and the release of proinflammatory factors, and inhibiting angiogenesis. Therefore, it has become a promising therapeutic strategy to inhibit Notch signal as a target in the treatment of spinal cord injury. In recent years, some researchers have used drugs, cell transplantation or genetic modification to regulate Notch signaling, which can promote the recovery of nerve function after spinal cord injury, thereby providing new treatment strategies for the treatment of spinal cord injury. This article will summarize the mechanism of Notch signaling pathway in spinal cord injury, and at the same time review the research progress in the treatment of spinal cord injury by modulating Notch signaling pathway in recent years, so as to provide new research ideas for further exploring new strategies for spinal cord injury.
Axons/metabolism* ; Cell Transplantation ; Humans ; Nerve Regeneration ; Signal Transduction/genetics* ; Spinal Cord/metabolism* ; Spinal Cord Injuries/metabolism*

The inhibitory environment that surrounds the lesion site and the lack of intrinsic regenerative capacity of the adult mammalian central nervous system (CNS) impede the regrowth of injured axons and thereby the reestablishment of neural circuits required for functional recovery after spinal cord injuries (SCI). To circumvent these barriers, biomaterial scaffolds are applied to bridge the lesion gaps for the regrowing axons to follow, and, often by combining stem cell transplantation, to enable the local environment in the growth-supportive direction. Manipulations, such as the modulation of PTEN/mTOR pathways, can also enhance intrinsic CNS axon regrowth after injury. Given the complex pathophysiology of SCI, combining biomaterial scaffolds and genetic manipulation may provide synergistic effects and promote maximal axonal regrowth. Future directions will primarily focus on the translatability of these approaches and promote therapeutic avenues toward the functional rehabilitation of patients with SCIs.
Animals ; Axons ; physiology ; Biocompatible Materials ; Genetic Enhancement ; methods ; Humans ; Nerve Regeneration ; PTEN Phosphohydrolase ; metabolism ; Recovery of Function ; Spinal Cord Injuries ; physiopathology ; Tissue Engineering ; methods ; Tissue Scaffolds

Axon regeneration is crucial for recovery from neurological diseases. Numerous studies have identified several genes, microRNAs (miRNAs), and transcription factors (TFs) that influence axon regeneration. However, the regulatory networks involved have not been fully elucidated. In the present study, we analyzed a regulatory network of 51 miRNAs, 27 TFs, and 59 target genes, which is involved in axon regeneration. We identified 359 pairs of feed-forward loops (FFLs), seven important genes (Nap1l1, Arhgef12, Sema6d, Akt3, Trim2, Rab11fip2, and Rps6ka3), six important miRNAs (hsa-miR-204-5p, hsa-miR-124-3p, hsa-miR-26a-5p, hsa-miR-16-5p, hsa-miR-17-5p, and hsa-miR-15b-5p), and eight important TFs (Smada2, Fli1, Wt1, Sp6, Sp3, Smad4, Smad5, and Creb1), which appear to play an important role in axon regeneration. Functional enrichment analysis revealed that axon-associated genes are involved mainly in the regulation of cellular component organization, axonogenesis, and cell morphogenesis during neuronal differentiation. However, these findings need to be validated by further studies.
Axons/physiology* ; Cell Differentiation ; Cluster Analysis ; Embryonic Stem Cells/cytology* ; Gene Expression Profiling ; Gene Expression Regulation ; Gene Regulatory Networks ; Humans ; MicroRNAs/metabolism* ; Nerve Regeneration ; Neurons/metabolism* ; Software ; Transcription Factors/metabolism*

The GABAergic neurons in the parafacial zone (PZ) play an important role in sleep-wake regulation and have been identified as part of a sleep-promoting center in the brainstem, but the long-range connections mediating this function remain poorly characterized. Here, we performed whole-brain mapping of both the inputs and outputs of the GABAergic neurons in the PZ of the mouse brain. We used the modified rabies virus EnvA-ΔG-DsRed combined with a Cre/loxP gene-expression strategy to map the direct monosynaptic inputs to the GABAergic neurons in the PZ, and found that they receive inputs mainly from the hypothalamic area, zona incerta, and parasubthalamic nucleus in the hypothalamus; the substantia nigra, pars reticulata and deep mesencephalic nucleus in the midbrain; and the intermediate reticular nucleus and medial vestibular nucleus (parvocellular part) in the pons and medulla. We also mapped the axonal projections of the PZ GABAergic neurons with adeno-associated virus, and defined the reciprocal connections of the PZ GABAergic neurons with their input and output nuclei. The newly-found inputs and outputs of the PZ were also listed compared with the literature. This cell-type-specific neuronal whole-brain mapping of the PZ GABAergic neurons may reveal the circuits underlying various functions such as sleep-wake regulation.
Animals ; Axons ; physiology ; Brain ; anatomy & histology ; Brain Mapping ; Brain Stem ; cytology ; GABAergic Neurons ; physiology ; Green Fluorescent Proteins ; genetics ; metabolism ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Neural Pathways ; physiology ; Peptide Elongation Factor 1 ; genetics ; metabolism ; Rabies virus ; genetics ; metabolism ; Transduction, Genetic ; Vesicular Inhibitory Amino Acid Transport Proteins ; genetics ; metabolism