Search Results (136)

As so many drugs have failed in ALS a new approach is needed. The author proposes that recent human genetic variants may play major roles in the disease, changing metabolism. Evolution of hominins was accelerated 3–2.5 Mya, by cytidine monophospho-N-acetylneuraminic acid hydroxylase (CMAH) becoming a unitary pseudogene after a pathogenic infection, changing the sialome, and hence metabolism, brain development and neuromuscular junctions (NMJs). This was when hominins evolved to run in Africa and develop bigger brains. Deletion of CMAH in mice allows them to run for longer (~50%). The enzyme CMAH is critical for the sialome, particularly the neurotrophin GM1, a critical hub for viral infection and for NMJ stability, but which is lost from NMJs at the beginning of denervation, probably due a 10-fold increase in spinal cord glucosylceramidases (non-lysosomal GBA2). A GBA2 inhibitor, ambroxol, is currently in phase II for ALS. Human-specific GM1 may be critical for human evolution, lactate metabolism and ALS. Lipid/lactate metabolism changed to support these evolutionary changes and lactate is a major body/brain fuel, but compromised in ALS patients and a marker of disease progression. Recent progress in sports science involving lactate metabolism and human performance may also be relevant to ALS therapies, and incidence. Full article

We examined whether an increase in synaptic activity resulted in an increase in quantal size at the neuromuscular junction (NMJ) of third-instar Drosophila larvae. Spontaneous miniature excitatory postsynaptic currents (mEPSCs) or miniature excitatory postsynaptic potentials (mEPSPs) were recorded before and after nerve stimulation. We found that prolonged (60 s) or brief (1.25 s) nerve stimulation produced an increase in quantal size; this appears to be a general property of these synapses since it was seen at all four muscle fibers (MFs) used in this study. The effect was examined along Is and Ib terminals by expressing GCaMP in the MF membrane and examining postsynaptic Ca²⁺ signals produced by spontaneous transmitter release. The activity-dependent increase in quantal size occurred at both Is and Ib terminals, and the increase in frequency and amplitude of quantal events at individual synaptic boutons was correlated. Both the increase in quantal size and frequency were found to be dependent upon an increase in postsynaptic Ca²⁺, based on studies in which MFs were preinjected with the Ca²⁺ chelator BAPTA (1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid). To examine the effect of postsynaptic activity on glutamate sensitivity, we iontophoresed glutamate pulses at the NMJ and recorded the glutamate-evoked excitatory postsynaptic potentials (gEPSPs). Trains of glutamate pulses produced an increase in gEPSP amplitude; this potentiation was not seen when Ca²⁺ was eliminated from the bath or after inhibiting calmodulin or CaMKII. The activity-dependent increase in quantal size may result from an increase in postsynaptic sensitivity due to activation of CaMKII. Full article

Background/Objectives: Cerebral palsy (CP) is a leading cause of motor disability in children and is commonly associated with spasticity. Treatment with radial extracorporeal shock waves (rESWs) is an established non-invasive therapy for spasticity, although its underlying mechanisms remain poorly understood. Caenorhabditis elegans (C. elegans) represents a powerful model for neuromuscular research due to its fully mapped nervous system, conserved cholinergic pathways and suitability for high-throughput behavioral analysis. This study aimed to test whether rESWs modulate cholinergic signaling at the neuromuscular junction (NMJ) in C. elegans. Methods: Wild-type and acr-16 mutant C. elegans were exposed in liquid to varying doses of rESWs, nicotine and carbachol in different combinations. Locomotor behavior was recorded using high-resolution video tracking, and parameters including peristaltic speed, body wavelength, reversals and omega bends were quantified. Results: Exposure to rESWs transiently altered locomotion, most notably by reducing forward speed and increasing the frequency of reversals. However, rESWs did not consistently modify behavioral responses to nicotine or carbachol, and these effects were not clearly dependent on NMJ-associated nicotinic receptors. Conclusions: Exploring C. elegans as a model for rESW effects on spasticity proved informative but also revealed important limitations. Results indicate that rESWs act on the nervous system more broadly, extending beyond neuromuscular structures. This contrasts with the clinical situation, where rESWs primarily target muscles and connective tissues. While this precludes C. elegans as a direct model for CP-related spasticity, the observation that rESWs influence nervous-system function at a systemic level points to potential therapeutic avenues for neurological diseases. Full article

MicroRNAs (miRNAs) have emerged as important biomarkers for complex neurological conditions. Modifications in synaptic morphology characterize several of these disease states, indicating a possible role of miRNA in modulating synaptic formation and plasticity. Within the third-instar larvae of Drosophila melanogaster, we uncovered a functional role for highly human-conserved miR-92 in synaptogenesis of the glutamatergic peripheral nervous system. Loss of miR-92 results in underdeveloped synaptic architecture, coinciding with significantly reduced physiological activity. We demonstrate a novel role for miR-92 glial-specific expression to support synaptic growth function and plasticity. Modifications of miR-92 within glial tissue result in aberrant glial barrier properties, including an increased uptake of external dyes. Within the glia, miR-92 regulates a V-ATPase subunit (Vha55), impairing the glial cells from forming appropriate insulating layers around the nervous system. These modifications may impact how the nervous system adapts to its environment, increasing immature ‘ghost bouton’ budding and impairing responses to changes in environmental conditions. Our work highlights the importance of glial-specific miR-92 on synaptic development, affecting glial health and function through its downstream target Vha55, and demonstrates a novel mechanism for glia in synaptogenesis and homeostatic plasticity. Full article

Background/Objectives: The neuromuscular junction (NMJ) is the area where peripheral nerves communicate with muscle tissue. Muscle injury can occur as part of an acute degenerative process at the NMJ. This study aims to investigate the remodeling of the NMJ after a muscle injury in an experimental model. Methods: We used sixty male Wistar rats divided into five groups: a control group (C) and four muscle injury groups (MI) at different time points: 0 h, 24 h, 48 h, and 7 d after injury. We subjected the right hind limb to muscle injury and dissected the gastrocnemius muscles for analysis. We employed light microscopy to examine cell nuclei and the connective tissue, immunostaining to identify and measure the pre- and postsynaptic regions as well as calcium channels (P/Q), and real-time PCR to assess the gene expression of NRG1 and Agrin. Results: Our findings revealed an accumulation of nuclei and connective tissue in the acute injury groups (0 to 48 h). The morpho-quantitative analyses showed that the presynaptic structures and calcium channels underwent similar remodeling due to their morpho-functional relationship. Meanwhile, the postsynaptic receptors were significantly affected by the degenerative and inflammatory processes. These results can be linked to increased expression of NRG1 and Agrin in the acute injury groups. Conclusions: In conclusion, the synaptic regions displayed substantial adaptations within the first 48 h, with the presynaptic region recovering rapidly and the postsynaptic region recovering slowly. This relationship suggests that significant increases in Agrin and NRG1 play a crucial role in maintaining the integrity of these structures. Full article

This study investigated the associations among age, physical activity level, knee muscle function, and neuromuscular junction (NMJ) biomarkers in a cohort of 80 middle-aged and young men residing in the Republic of Korea. Despite comparable levels of physical activity between the groups, the middle-aged participants exhibited significantly higher body fat percentage, elevated levels of the neurodegeneration marker neurofilament light chain (NfL), and a marked decline in lower-extremity muscle function compared to their younger counterparts. Advancing age was negatively associated with knee extensor peak torque, body weight–normalized torque (BW/PT), and the rate of torque development at 0.18 s (RTD@0.18s). In contrast, higher physical activity levels were positively correlated with certain indicators of muscle function and were associated with lower circulating concentrations of the NMJ degeneration marker, C-terminal agrin fragment (CAF). These findings suggest that neuromuscular decline and muscle function deterioration may begin as early as middle age. The results underscore the importance of implementing tailored exercise regimens and lifestyle interventions to preserve neuromuscular health and prevent early-onset muscle loss. Full article

Autism spectrum disorder (ASD) encompasses a range of conditions, primarily marked by deficits in social behaviors, along with several comorbidities such as sleep abnormalities and motor dysfunction. Recent studies have identified genetic risk factors associated with ASD, including the CAMK4 (calcium/calmodulin-dependent protein kinase 4). However, the molecular mechanisms linking CAMK4 dysregulation and ASD-associated phenotypes remain poorly understood. Here, we used Drosophila melanogaster as a model system to investigate ASD-associated phenotypes in flies with dysregulated CaMKI, the fly homolog of mammalian CAMK4. We show that CaMKI manipulations affect sleep, circadian rhythmicity, and social behavior. Consistent with the higher prevalence of dementia observed in autistic patients, we also observed a significantly enhanced behavioral decline in motor performance and dendritic degeneration in flies expressing RNAi-based CaMKI knockdown in flight motoneurons, suggesting a link between developmental and degenerative processes. As aberrant synaptic pruning is hypothesized to underlie the synaptic phenotypes observed in brains of autistic patients, we examined synaptic phenotypes following CaMKI manipulations using the larval neuromuscular junction (NMJ) and observed miswiring phenotypes suggesting aberrant synaptic refinement. We performed shotgun mass-spectrometry proteomics and identified various molecular candidates, particularly molecules involved in cytoskeleton regulation and chemorepulsion, likely to regulate the phenotypes described here. Thus, our results suggest that CaMKI plays a role in developmental processes and influences aging-dependent degenerative processes, possibly providing mechanistic insight into the genetic basis of ASD etiology and the development of effective treatments. Full article

As an indigenous goat breed unique to southern China, Leizhou Black Goats (LZBGs) are highly valued for their rapid growth, high reproductive performance, and superior meat quality. However, their offspring frequently exhibit symptoms of muscle atrophy and malnutrition, suggesting potential genetic defects underlying these adverse phenotypes. As a unique extracellular matrix component, collagen Q (COLQ) is specifically enriched within the synaptic basal lamina at vertebrate neuromuscular junctions (NMJs), where it anchors acetylcholinesterase (AChE) to facilitate efficient acetylcholine hydrolysis, ensuring precise neuromuscular signaling. The current investigation sought to characterize the spectrum of genetic polymorphisms within the COLQ gene and assess their correlation with key production traits, including growth performance and meat quality parameters, in the LZBG population. Previously, through whole-genome sequencing and transcriptome sequencing analyses of an LZBG population, we identified four SNPs in the COLQ gene, namely, two missense mutations (SNP1: p.238A/S and SNP3: p.47G/S), one intronic variant (SNP2), and one synonymous mutation (SNP4: p.101P/P). Population genetic analysis revealed strong linkage disequilibrium between SNP1 and SNP2. Computational modeling of protein structures predicted that the identified missense mutations may lead to alterations in protein conformation. Association analyses demonstrated significant correlations of SNP1 and SNP3 with growth and meat quality traits (p < 0.05), where SNP3 reduced COLQ expression by 0.64-fold in homozygotes. Association analysis revealed that both SNP1 and SNP3 showed significant correlations with growth and meat quality traits in LZBGs (p < 0.05). Notably, SNP3 (p.47G/S) was found to regulate COLQ gene expression, reducing its levels by 0.64-fold in homozygous individuals, suggesting its potential as a genetic marker for selecting goats with superior growth performance and muscular development characteristics. The identified genetic variants establish a foundation for marker-assisted selection in LZBG breeding programs with particular relevance to growth performance enhancement, while also advancing the understanding of COLQ’s functional mechanisms in muscle development. Full article

SLC35A2-CDG is a congenital disorder of glycosylation caused by mutations in the SLC35A2 gene encoding a Golgi-localized UDP-galactose transporter. This transporter plays an essential role in glycan synthesis by transporting UDP-galactose from the cytoplasm into the Golgi lumen. Its dysfunction leads to impaired galactose-containing glycans and various neurological symptoms, although the underlying mechanisms remain largely unknown. We identified a novel SLC35A2-CDG patient carrying a pathogenic variant (c.617_620del, p.(Gln206ArgfsTer45)) who exhibited neurological abnormalities including bilateral ventriculomegaly. To investigate the disease mechanism, we established the first Drosophila model of SLC35A2-CDG. Knockout of Ugalt, the fly ortholog of SLC35A2, resulted in embryonic lethality, indicating its essential role. Knockdown of Ugalt reduced mucin-type O-glycans on muscles and neuromuscular junctions (NMJs), without affecting N-glycans. Ugalt knockdown larvae exhibited mislocalized NMJ boutons accompanied by a deficiency in basement membrane components on muscles. This phenotype resembles that of mutants of dC1GalT1 and dGlcAT-P, both involved in mucin-type O-glycosylation. Genetic interaction between Ugalt and dC1GalT1 was confirmed through double knockdown and double heterozygous analyses. Given that Drosophila NMJs are widely used as a model for mammalian central synapses, our findings suggest that Ugalt regulates NMJ architecture via mucin-type O-glycosylation and provide insights into the molecular basis of neurological abnormalities in SLC35A2-CDG. Full article

Osteosarcopenia is a widespread geriatric condition resulting from the coexistence of osteoporosis and sarcopenia, where the connection between bone and muscle is, in part, driven by bone–muscle crosstalk. Given the close, reciprocal influence of muscle on nerve, and vice versa, it is not surprising that there are corresponding aging changes in the biochemistry and morphology of the neuromuscular junction (NMJ). Indeed, degeneration of motor neurons and progressive disruption of the neuromuscular connectivity were observed in old age. Extracellular vesicles (EVs) derived from human amniotic fluid stem cells (hAFSC), exhibiting antioxidant properties, which can also explain their anti-aging and cytoprotective effects, can be considered as potential treatment for age-related diseases. To study cell interactions under both healthy and pathological conditions occurring in musculo–skeletal apparatus, we developed a three-culture system exploiting the use of well-known transwell supports. This system allows both myotubes and neurons, eventually treated with EVs, and osteoblasts, induced to osteoporosis, to interact physically and biochemically. Collectively, this method allowed us to understand how the modifications induced in osteoblasts during bone disorders trigger a cascade of detrimental effects in the muscle and neuron parts. Moreover, we demonstrated the efficacy of hAFSC-EVs in preventing NMJ dysfunction, muscle atrophy, and osteoblast impairment. Full article

Voltage-gated Ca²⁺ channels (VGCCs) are regulated by four CaVβ subunits (CaVβ1–CaVβ4), each showing specific expression patterns in excitable cells. While primarily known for regulating VGCC function, CaVβ proteins also have channel-independent roles, including gene expression modulation. Among these, CaVβ1 is expressed in skeletal muscle as multiple isoforms. The adult isoform, CaVβ1D, localizes at the triad and modulates CaV1 activity during Excitation–Contraction Coupling (ECC). In this study, we investigated the lesser-known embryonic/perinatal CaVβ1 isoforms and their roles in neuromuscular junction (NMJ) formation, maturation, and maintenance. We found that CaVβ1 isoform expression is developmentally regulated through differential promoter activation. Specifically, CaVβ1A is expressed in embryonic muscle and reactivated in denervated adult muscle, alongside the known CaVβ1E isoform. Nerve injury in adult muscle triggers a shift in promoter usage, resulting in re-expression of embryonic/perinatal Cacnb1A and Cacnb1E transcripts. Functional analyses using aneural agrin-induced AChR clustering on primary myotubes demonstrated that these isoforms contribute to NMJ formation. Additionally, their expression during early post-natal development is essential for NMJ maturation and long-term maintenance. These findings reveal previously unrecognized roles of CaVβ1 isoforms beyond VGCC regulation, highlighting their significance in neuromuscular system development and homeostasis. Full article

The neuronal progenitor NG108-15 neuroblastoma x glioma cell line proliferates indefinitely in vitro and is capable of directed differentiation into cholinergic neurons. The cell line is a robust model for investigating neuronal differentiation and function in vitro. The lineage-specific transcription factor-mediated differentiation of pluripotent stem cell lines (PSCs) leads to more rapid, efficient, and functional neurons. In this study, we tested the hypothesis that transcription factors could also drive the fate of an immortalised cell line. We first established a stable NG108-15 cell line, by piggyBac (pBac) transposition, that conditionally expresses neurogenin-2 (Ngn2), a common transcription factor for specifying neuronal fate. Following doxycycline-induction of Ngn2, we observed more rapid and efficient differentiation, and improved neurite outgrowth and viability compared with the WT cell line. Moreover, when co-cultured with C2C12 mouse myotubes, the modified NG108-15 cells resulted in significantly larger acetylcholine receptor (AChR) aggregates, suggesting enhanced neuromuscular junction (NMJ) formation. These findings describe a novel methodology for differentiating NG108-15 cells more efficiently, to enhance the usefulness of the cell line as a motor neuron model. Full article

Autophagy impairments have been implicated in various aging conditions. Previous studies in cervical motor neurons show an age-dependent increase in the key autophagy proteins LC3 and p62, reflecting autophagy impairment and autophagosome accumulation. Chloroquine is commonly used to inhibit autophagy by preventing autophagosome–lysosome fusion and may thus emulate the effects of aging on the neuromuscular system. Indeed, acute chloroquine administration in old mice decreases maximal transdiaphragmatic pressure generation, consistent with aging effects. We hypothesized that chloroquine alters diaphragm muscle neuromuscular junction (NMJ) morphology and increases denervation. Adult male and female C57BL/6 × 129J mice between 5 and 8 months of age were used to examine diaphragm muscle NMJ morphology and denervation following daily intraperitoneal injections of chloroquine (10 mg/kg/d) or vehicle for 7 days. The motor end-plates and pre-synaptic terminals were fluorescently labeled with α-bungarotoxin and anti-synaptophysin, respectively. Confocal microscopy was used to assess pre- and post-synaptic morphology and denervation. At diaphragm NMJs, chloroquine treatment decreased pre-synaptic volume by 12% compared to the vehicle (p < 0.05), with no change in post-synaptic volume. Chloroquine treatment increased the proportion of partially denervated NMJs by 2.7-fold compared to vehicle treatment (p < 0.05). The morphological changes observed were similar to those previously reported in the diaphragm muscles of 18-month-old mice. These findings highlight the importance of autophagy in the maintenance of the structural properties at adult NMJs in vivo. Full article

In this review paper, we will evaluate LRP4, a low-density lipoprotein receptor-related protein, and its many roles involving myasthenia gravis (MG), Wnt signaling, bone formation and craniofacial development. In MG, LRP4 is critical to the formation of the neuromuscular junction (NMJ) and the key function is to allow for controlled muscle contraction. LRP4 works in combination with agrin and MuSK to form the functional complex. In Wnt signaling, LRP4 was recently identified as a critical player in the pathway for both bone and tooth development and function. Its ability to act as an inhibitor sheds new light on bone formation and resorption. LRP4 binds sclerostin to LRP5 and LRP6, facilitating inhibitory effects important for bone homeostasis and remodeling. In this review paper, we will summarize the known roles of LRP4 as well as explore future directions for research surrounding LRP4 functionality. Full article

Burn injuries cause severe muscle wasting and weakness. However, the relative contribution of neuromuscular junction (NMJ) degradation remains elusive. We investigated the associations of plasma c-terminal agrin fragment-22 (CAF22), a marker of NMJ degradation, with muscle decline in burn patients. We recruited male patients with burns (n = 32, age = 32.3 ± 4.5 years, percent burn area = 15.2 ± 2.3) and age-matched controls to evaluate handgrip strength (HGS), skeletal muscle mass index (SMI), phase angle, and creatine kinase and plasma levels of CAF22, c-reactive protein, and 8-isoprostanes. We used an unpaired t-test and regression analysis for statistics. The burn patients had lower HGS, SMI, and phase angle than the controls (all p < 0.05). These patients also exhibited higher plasma CAF22, CRP, 8-isoprostanes, and creatine kinase than the controls (all p < 0.05), suggesting NMJ degradation and heightened inflammation and oxidative stress. Correlation analysis revealed significant correlations of plasma CAF22 with HGS and phase angle in the burn patients, suggesting the potential contributions of NMJ degradation to muscle weakness and atrophy (both p < 0.05). We also found correlations of plasma CRP with HGS and phase angle in these patients (both p < 0.05). Altogether, NMJ degradation appears to play a significant role in burn-induced muscle injury and may warrant further investigation for potential therapeutic interventions. Full article