bims-moremu 2024-05-12 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024–05–12
twenty-six papers selected by
Anna Vainshtein, Craft Science Inc.

Cyclo His-Pro Attenuates Muscle Degeneration in Murine Myopathy Models.
Reactive oxygen species promote endurance exercise-induced adaptations in skeletal muscles.
Late-Stage Skeletal Muscle Transcriptome in Duchenne muscular dystrophy shows a BMP4-Induced Molecular Signature.
High-intensity interval training impacts skeletal muscle core clock in overweight and obese men with insulin resistance.
Insights into post-translational regulation of skeletal muscle contractile function by the acetyltransferases, p300 and CBP.
Characteristics of nuclear architectural abnormalities of myotubes differentiated from LmnaH222P/H222P skeletal muscle cells.
AMPK and glucose deprivation exert an isoform-specific effect on the expression of Na+,K+-ATPase subunits in cultured myotubes.
Generation of allogenic and xenogeneic functional muscle stem cells for intramuscular transplantation.
Role of the gut-muscle axis in mitochondrial function of ageing muscle under different exercise modes.
Better maintenance of enzymatic capacity and higher levels of substrate transporter proteins in skeletal muscle of aging female mice.
Integrated multi-omics approach reveals the role of striated muscle preferentially expressed protein kinase in skeletal muscle including its relationship with myospryn complex.
Endurance Training Inhibits the JAK2/STAT3 Pathway to Alleviate Sarcopenia.
Pro-Brain-Derived Neurotrophic Factor (BDNF), but Not Mature BDNF, Is Expressed in Human Skeletal Muscle: Implications for Exercise-Induced Neuroplasticity.
Dynamics of pax7 expression during development, muscle regeneration, and in vitro differentiation of satellite cells in rainbow trout (Oncorhynchus mykiss).
Deubiquitinases in muscle physiology and disorders.
Effect of high-fat diet on isometric, concentric and eccentric contractile performance of skeletal muscle isolated from female CD-1 mice.
Accelerated, physics-inspired inference of skeletal muscle microstructure from diffusion-weighted MRI.
Potential limitations of micro-dystrophin gene therapy for Duchenne muscular dystrophy.
The effects of myosteatosis on skeletal muscle function in older adults.
Mechanism of static loading injury in human skeletal muscle cells.
Electrical Stimulation-Based Twitch Exercise Suppresses Progression of Immobilization-Induced Muscle Fibrosis via Downregulation of PGC-1?/VEGF Pathway.
Biomaterials-based Technologies in Skeletal Muscle Tissue Engineering.
Nature of epigenetic aging from a single-cell perspective.
Exercise ameliorates muscular excessive mitochondrial fission, insulin resistance and inflammation in diabetic rats via irisin/AMPK activation.
LPA-induced Expression of CCN2 in Muscular Fibro/adipogenic Progenitors (FAPs): Unraveling Cellular Communication Networks.
Transcriptome- and proteome-wide effects of a circular RNA encompassing four early exons of the spinal muscular atrophy genes.

Adv Sci (Weinh). 2024 May 10. e2305927

Cyclo His-Pro Attenuates Muscle Degeneration in Murine Myopathy Models.

Alessia De Masi, Nadège Zanou, Keno Strotjohann, Dohyun Lee, Tanes I Lima, Xiaoxu Li, Jongsu Jeon, Nicolas Place, Hoe-Yune Jung, Johan Auwerx.

  Among the inherited myopathies, a group of muscular disorders characterized by structural and metabolic impairments in skeletal muscle, Duchenne muscular dystrophy (DMD) stands out for its devastating progression. DMD pathogenesis is driven by the progressive degeneration of muscle fibers, resulting in inflammation and fibrosis that ultimately affect the overall muscle biomechanics. At the opposite end of the spectrum of muscle diseases, age-related sarcopenia is a common condition that affects an increasing proportion of the elderly. Although characterized by different pathological mechanisms, DMD and sarcopenia share the development of progressive muscle weakness and tissue inflammation. Here, the therapeutic effects of Cyclo Histidine-Proline (CHP) against DMD and sarcopenia are evaluated. In the mdx mouse model of DMD, it is shown that CHP restored muscle contractility and force production, accompanied by the reduction of fibrosis and inflammation in skeletal muscle. CHP furthermore prevented the development of cardiomyopathy and fibrosis in the diaphragm, the two leading causes of death for DMD patients. CHP also attenuated muscle atrophy and functional deterioration in a mouse model of age-related sarcopenia. These findings from two different models of muscle dysfunction hence warrant further investigation into the effects of CHP on muscle pathologies in animal models and eventually in patients.

Keywords:  Duchenne muscular dystrophy; cardiomyopathy; mitochondrial dysfunction; muscle fibrosis; sarcopenia

DOI:  https://doi.org/10.1002/advs.202305927
J Sport Health Sci. 2024 May 06. pii: S2095-2546(24)00062-0. [Epub ahead of print]

Reactive oxygen species promote endurance exercise-induced adaptations in skeletal muscles.

Scott K Powers, Zsolt Radak, Li Li Ji, Malcolm Jackson.

  The discovery that contracting skeletal muscle generates reactive oxygen species (ROS) was first reported over 40 years ago. The prevailing view in the 1980s was that exercise-induced ROS production promotes oxidation of proteins and lipids resulting in muscle damage. However, a paradigm shift occurred in the 1990s as growing research revealed that ROS are signaling molecules, capable of activating transcriptional activators/coactivators and promoting exercise-induced muscle adaptation. Growing evidence supports the notion that reduction-oxidation (redox) signaling pathways play an important role in the muscle remodeling that occurs in response to endurance exercise training. This review examines the specific role that redox signaling plays in this endurance exercise-induced skeletal muscle adaptation. We begin with a discussion of the primary sites of ROS production in contracting muscle fibers followed by a summary of the antioxidant enzymes involved in the regulation of ROS levels in the cell. We then discuss which redox-sensitive signaling pathways promote endurance exercise-induced muscle adaptation and debate the strength of the evidence supporting the notion that redox signaling plays an essential role in muscle adaptation to endurance exercise training. In hopes of stimulating future research, we highlight several important unanswered questions in this field.

Keywords:  Antioxidants; Mitochondrial biogenesis; Radicals; Redox signaling

DOI:  https://doi.org/10.1016/j.jshs.2024.05.001
bioRxiv. 2024 Apr 25. pii: 2024.04.19.590266. [Epub ahead of print]

Late-Stage Skeletal Muscle Transcriptome in Duchenne muscular dystrophy shows a BMP4-Induced Molecular Signature.

Hanna Sothers, Xianzhen Hu, David K Crossman, Ying Si, Matthew S Alexander, Merry-Lynn N McDonald, Peter H King, Michael A Lopez.

Duchenne muscular dystrophy (DMD) is a fatal X-linked recessive disease due to loss-of-function mutations in the DYSTROPHIN gene. DMD-related skeletal muscle wasting is typified by an aberrant immune response involving upregulation of TGFβ family of cytokines. We previously demonstrated that bone morphogenetic protein 4 (BMP4) is increased in DMD and BMP4 stimulation induces a 20-fold upregulation of Smad8 transcription. However, the role of BMP4 in severely affected DMD skeletal muscle is unknown. We hypothesized that transcriptomic signatures in severely affected human DMD skeletal muscle are driven by BMP4 signaling. Transcriptomes from skeletal muscle biopsies of late-stage DMD vs. non-DMD controls and C2C12 muscle cells with or without BMP4 stimulation were generated by RNA-Seq and analyzed for single transcript differential expression as well as by Ingenuity Pathway Analysis and weighted gene co-expression network analyses. A total of 2,328 and 5,291 transcripts in the human muscle and C2C12 muscle cells, respectively, were differentially expressed. We identified an overlapping molecular signature of 1,027 genes dysregulated in DMD muscle that were induced in BMP4-stimulated C2C12 muscle cells. Highly upregulated DMD transcripts that overlapped with BMP4-stimulated C2C12 muscle cells included ADAMTS3, HCAR2, SERPING1, SMAD8 , and UNC13C. The DMD transcriptome was characterized by dysregulation of pathways involving immune function, extracellular matrix remodeling, and metabolic/mitochondrial function. In summary, we define a late-stage DMD skeletal muscle transcriptome that substantially overlaps with the BMP4-induced molecular signature in C2C12 muscle cells. This supports BMP4 as a disease-driving regulator of transcriptomic changes in late-stage DMD skeletal muscle and expands our understanding of the evolution of dystrophic signaling pathways and their associated gene networks that could be explored for therapeutic development.

DOI: https://doi.org/10.1101/2024.04.19.590266
J Physiol. 2024 May 09.

High-intensity interval training impacts skeletal muscle core clock in overweight and obese men with insulin resistance.

Larissa Moreira Dias, Guilherme Correia Ferri Antonio.



Keywords:  chronic exercise; clock genes; metabolism; skeletal muscle

DOI:  https://doi.org/10.1113/JP286165
J Appl Physiol (1985). 2024 May 09.

Insights into post-translational regulation of skeletal muscle contractile function by the acetyltransferases, p300 and CBP.

Gretchen A Meyer, Jeremie L A Ferey, James A Sanford, Liam S Fitzgerald, Akiva E Greenberg, Kristoffer Svensson, Michael J Greenberg, Simon Schenk.

  Mice with skeletal muscle-specific and inducible double knockout of the lysine acetyltransferases, p300 (E1A binding protein p300) and CBP (cAMP-response element-binding protein binding protein), referred to as i-mPCKO, demonstrate a dramatic loss of contractile function in skeletal muscle and ultimately die within 7 days. Given that many proteins involved in ATP generation and cross-bridge cycling are acetylated, we investigated whether these processes are dysregulated in skeletal muscle from i-mPCKO mice and, thus, whether they could underlie the rapid loss of muscle contractile function. Just 4-5 days after inducing knockout of p300 and CBP in skeletal muscle from adult i-mPCKO mice, there was ~90% reduction in ex vivo contractile function in the extensor digitorum longus (EDL) and a ~65% reduction in in vivo ankle dorsiflexion torque, as compared to wildtype (WT; i.e. Cre negative) littermates. Despite this profound loss of contractile force in i-mPCKO mice, there were no genotype-driven differences in fatigability during repeated contractions, nor were there genotype differences in mitochondrial-specific pathway enrichment of the proteome, intermyofibrillar mitochondrial volume or mitochondrial respiratory function. As it relates to cross-bridge cycling, remarkably, the overt loss of contractile function in i-mPCKO muscle was reversed in permeabilized fibers supplied with exogenous Ca2+ and ATP, with active tension being similar between i-mPCKO and WT mice, regardless of Ca2+ concentration. Actin-myosin motility was also similar in skeletal muscle from i-mPCKO and WT mice. In conclusion, neither mitochondrial abundance/function, nor actomyosin cross-bridge cycling, are the underlying driver of contractile dysfunction in i-mPCKO mice.

Keywords:  actin; force; mitochondria; myosin; physiology

DOI:  https://doi.org/10.1152/japplphysiol.00156.2024
In Vitro Cell Dev Biol Anim. 2024 May 09.

Characteristics of nuclear architectural abnormalities of myotubes differentiated from LmnaH222P/H222P skeletal muscle cells.

Eiji Wada, Nao Susumu, Motoshi Kaya, Yukiko K Hayashi.

  The presence of nuclear architectural abnormalities is a hallmark of the nuclear envelopathies, which are a group of diseases caused by mutations in genes encoding nuclear envelope proteins. Mutations in the lamin A/C gene cause several diseases, named laminopathies, including muscular dystrophies, progeria syndromes, and lipodystrophy. A mouse model carrying with the LmnaH222P/H222P mutation (H222P) was shown to develop severe cardiomyopathy but only mild skeletal myopathy, although abnormal nuclei were observed in their striated muscle. In this report, we analyzed the abnormal-shaped nuclei in myoblasts and myotubes isolated from skeletal muscle of H222P mice, and evaluated the expression of nuclear envelope proteins in these abnormal myonuclei. Primary skeletal muscle cells from H222P mice proliferated and efficiently differentiated into myotubes in vitro, similarly to those from wild-type mice. During cell proliferation, few abnormal-shaped nuclei were detected; however, numerous markedly abnormal myonuclei were observed in myotubes from H222P mice on days 5 and 7 of differentiation. Time-lapse observation demonstrated that myonuclei with a normal shape maintained their normal shape, whereas abnormal-shaped myonuclei remained abnormal for at least 48 h during differentiation. Among the abnormal-shaped myonuclei, 65% had a bleb with a string structure, and 35% were severely deformed. The area and nuclear contents of the nuclear blebs were relatively stable, whereas the myocytes with nuclear blebs were actively fused within primary myotubes. Although myonuclei were markedly deformed, the deposition of DNA damage marker (γH2AX) or apoptotic marker staining was rarely observed. Localizations of lamin A/C and emerin were maintained within the blebs, strings, and severely deformed regions of myonuclei; however, lamin B1, nesprin-1, and a nuclear pore complex protein were absent in these abnormal regions. These results demonstrate that nuclear membranes from H222P skeletal muscle cells do not rupture and are resistant to DNA damage, despite these marked morphological changes.

Keywords:  DNA damage; Emery-Dreifuss muscular dystrophy; Lamin a/c; Nuclear deformation; Skeletal muscle

DOI:  https://doi.org/10.1007/s11626-024-00915-1
J Muscle Res Cell Motil. 2024 May 06.

AMPK and glucose deprivation exert an isoform-specific effect on the expression of Na+,K+-ATPase subunits in cultured myotubes.

Anja Vidović, Klemen Dolinar, Alexander V Chibalin, Sergej Pirkmajer.

  In skeletal muscle, Na+,K+-ATPase (NKA), a heterodimeric (α/β) P-type ATPase, has an essential role in maintenance of Na+ and K+ homeostasis, excitability, and contractility. AMP-activated protein kinase (AMPK), an energy sensor, increases the membrane abundance and activity of NKA in L6 myotubes, but its potential role in regulation of NKA content in skeletal muscle, which determines maximum capacity for Na+ and K+ transport, has not been clearly delineated. We examined whether energy stress and/or AMPK affect expression of NKA subunits in rat L6 and primary human myotubes. Energy stress, induced by glucose deprivation, increased protein content of NKAα1 and NKAα2 in L6 myotubes, while decreasing the content of NKAα1 in human myotubes. Pharmacological AMPK activators (AICAR, A-769662, and diflunisal) modulated expression of NKA subunits, but their effects only partially mimicked those that occurred in response to glucose deprivation, indicating that AMPK does not mediate all effects of energy stress on NKA expression. Gene silencing of AMPKα1/α2 increased protein levels of NKAα1 in L6 myotubes and NKAα1 mRNA levels in human myotubes, while decreasing NKAα2 protein levels in L6 myotubes. Collectively, our results suggest a role for energy stress and AMPK in modulation of NKA expression in skeletal muscle. However, their modulatory effects were not conserved between L6 myotubes and primary human myotubes, which suggests that coupling between energy stress, AMPK, and regulation of NKA expression in vitro depends on skeletal muscle cell model.

Keywords:  AMPK; Energy stress; Glucose; Myotubes; Na+,K+-ATPase; Skeletal muscle

DOI:  https://doi.org/10.1007/s10974-024-09673-9
J Clin Invest. 2024 May 07. pii: e166998. [Epub ahead of print]

Generation of allogenic and xenogeneic functional muscle stem cells for intramuscular transplantation.

Ajda Lenardič, Seraina A Domenig, Joel Zvick, Nicola Bundschuh, Monika Tarnowska-Sengül, Regula Furrer, Falko J Noé, Christine Ling Li Trautmann, Adhideb Ghosh, Giada Bacchin, Pjeter Gjonlleshaj, Xhem Qabrati, Evi Masschelein, Katrien De Bock, Christoph Handschin, Ori Bar-Nur.

  Satellite cells, the stem cells of skeletal muscle tissue, hold a remarkable regeneration capacity and therapeutic potential in regenerative medicine. However, low satellite cell yield from autologous or donor-derived muscles hinders the adoption of satellite cell transplantation for the treatment of muscle diseases, including Duchenne muscular dystrophy (DMD). To address this limitation, here we investigated whether satellite cells can be derived in allogeneic or xenogeneic animal hosts. First, injection of CRISPR/Cas9-corrected mouse DMD-induced pluripotent stem cells (iPSCs) into mouse blastocysts carrying an ablation system of host satellite cells gave rise to intraspecies chimeras exclusively carrying iPSC-derived satellite cells. Furthermore, injection of genetically corrected DMD-iPSCs into rat blastocysts resulted in the formation of interspecies rat-mouse chimeras harboring mouse satellite cells. Remarkably, iPSC-derived satellite cells or derivative myoblasts produced in intraspecies or interspecies chimeras restored dystrophin expression in DMD mice following intramuscular transplantation, and contributed to the satellite cell pool. Collectively, this study demonstrates the feasibility of producing therapeutically competent stem cells across divergent animal species, raising the possibility of generating human muscle stem cells in large animals for regenerative medicine purposes.

Keywords:  Movement disorders; Muscle biology; Skeletal muscle; Stem cells; iPS cells

DOI:  https://doi.org/10.1172/JCI166998
Ageing Res Rev. 2024 May 03. pii: S1568-1637(24)00134-X. [Epub ahead of print]98 102316

Role of the gut-muscle axis in mitochondrial function of ageing muscle under different exercise modes.

Xiaoting Xie, Cong Huang.

  The fundamental role of the gut microbiota through the gut-muscle axis in skeletal muscle ageing is increasingly recognised. Metabolites derived from the intestinal microbiota are essential in maintaining skeletal muscle function and metabolism. The energy produced by mitochondria and moderate levels of reactive oxygen species can contribute to this process. Metabolites can effectively target the mitochondria, slowing the progression of muscle ageing and potentially representing a marker of ageing-related skeletal muscle loss. Moreover, mitochondria can contribute to the immune response, gut microbiota biodiversity, and maintenance of the intestinal barrier function. However, the causal relationship between mitochondrial function and gut microbiota crosstalk remains poorly understood. In addition to elucidating the regulatory pathways of the gut-muscle axis during the ageing process, we focused on the potential role of the "exercise-gut-muscle axis", which represents a pathway under stimulation from different exercise modes to induce mitochondrial adaptations, skeletal muscle metabolism and maintain intestinal barrier function and biodiversity stability. Meanwhile, different exercise modes can induce mitochondrial adaptations and skeletal muscle metabolism and maintain intestinal barrier function and biodiversity. Resistance exercise may promote mitochondrial adaptation, increase the cross-sectional area of skeletal muscle and muscle hypertrophy, and promote muscle fibre and motor unit recruitment. Whereas endurance exercise promotes mitochondrial biogenesis, aerobic capacity, and energy utilisation, activating oxidative metabolism-related pathways to improve skeletal muscle metabolism and function. This review describes the effects of different exercise modes through the gut-muscle axis and how they act through mitochondria in ageing to define the current state of the field and issues requiring resolution.

Keywords:  Ageing; Exercise; Gut microbiota; Gut-muscle axis; Metabolism; Mitochondria

DOI:  https://doi.org/10.1016/j.arr.2024.102316
Appl Physiol Nutr Metab. 2024 May 06.

Better maintenance of enzymatic capacity and higher levels of substrate transporter proteins in skeletal muscle of aging female mice.

Kenya Takahashi, Yu Kitaoka, Hideo Hatta.

This study investigated sex-specific differences in high-energy phosphate, glycolytic, and mitochondrial enzyme activities and also metabolite transporter protein levels in the skeletal muscles of adult (5 months old), middle-aged (12 months old), and advanced-aged (24 months old) mice. While gastrocnemius glycogen content increased with age regardless of sex, gastrocnemius triglyceride levels increased only in advanced-aged female mice. Aging decreased creatine kinase and adenylate kinase activities in the plantaris muscle of both sexes and in the soleus muscle of male mice but not in female mice. Irrespective of sex, phosphofructokinase and lactate dehydrogenase (LDH) activities decreased in the plantaris and soleus muscles. Additionally, hexokinase activity in the plantaris muscle and LDH activity in the soleus muscle decreased to a greater extent in aged female mice compared with those in aged male mice. Mitochondrial enzyme activities increased in the plantaris muscle of aged female mice but did not change in male mice. The protein content of the glucose transporter 4 in the aged plantaris muscle and fatty acid translocase/cluster of differentiation 36 increased in the aged plantaris and soleus muscles of both sexes, with a significantly higher content in female mice. These findings suggest that females possess a better ability to maintain metabolic enzyme activity and higher levels of metabolite transport proteins in skeletal muscle during aging, despite alterations in lipid metabolism. Our data provide a basis for studying muscle metabolism in the context of age-dependent metabolic perturbations and diseases that affect females and males differently.

DOI: https://doi.org/10.1139/apnm-2024-0016
J Cachexia Sarcopenia Muscle. 2024 May 09.

Integrated multi-omics approach reveals the role of striated muscle preferentially expressed protein kinase in skeletal muscle including its relationship with myospryn complex.

Qifei Li, Jasmine Lin, Shiyu Luo, Klaus Schmitz-Abe, Rohan Agrawal, Melissa Meng, Behzad Moghadaszadeh, Alan H Beggs, Xiaoli Liu, Mark A Perrella, Pankaj B Agrawal.

   BACKGROUND: Autosomal-recessive mutations in SPEG (striated muscle preferentially expressed protein kinase) have been linked to centronuclear myopathy with or without dilated cardiomyopathy (CNM5). Loss of SPEG is associated with defective triad formation, abnormal excitation-contraction coupling, calcium mishandling and disruption of the focal adhesion complex in skeletal muscles. To elucidate the underlying molecular pathways, we have utilized multi-omics tools and analysis to obtain a comprehensive view of the complex biological processes and molecular functions.
METHODS: Skeletal muscles from 2-month-old SPEG-deficient (Speg-CKO) and wild-type (WT) mice were used for RNA sequencing (n = 4 per genotype) to profile transcriptomics and mass spectrometry (n = 4 for WT; n = 3 for Speg-CKO mice) to profile proteomics and phosphoproteomics. In addition, interactomics was performed using the SPEG antibody on pooled muscle lysates (quadriceps, gastrocnemius and triceps) from WT and Speg-CKO mice. Based on the multi-omics results, we performed quantitative real-time PCR, co-immunoprecipitation and immunoblot to verify the findings.
RESULTS: We identified that SPEG interacts with myospryn complex proteins CMYA5, FSD2 and RyR1, which are critical for triad formation, and that SPEG deficiency results in myospryn complex abnormalities (protein levels decreased to 22 ± 3% for CMYA5 [P < 0.05] and 18 ± 3% for FSD2 [P < 0.01]). Furthermore, SPEG phosphorylates RyR1 at S2902 (phosphorylation level decreased to 55 ± 15% at S2902 in Speg-CKO mice; P < 0.05), and its loss affects JPH2 phosphorylation at multiple sites (increased phosphorylation at T161 [1.90 ± 0.24-fold], S162 [1.61 ± 0.37-fold] and S165 [1.66 ± 0.13-fold]; decreased phosphorylation at S228 and S231 [39 ± 6%], S234 [50 ± 12%], S593 [48 ± 3%] and S613 [66 ± 10%]; P < 0.05 for S162 and P < 0.01 for other sites). On analysing the transcriptome, the most dysregulated pathways affected by SPEG deficiency included extracellular matrix-receptor interaction (P < 1e-15) and peroxisome proliferator-activated receptor signalling (P < 9e-14).
CONCLUSIONS: We have elucidated the critical role of SPEG in the triad as it works closely with myospryn complex proteins (CMYA5, FSD2 and RyR1), it regulates phosphorylation levels of various residues in JPH2 and S2902 in RyR1, and its deficiency is associated with dysregulation of several pathways. The study identifies unique SPEG-interacting proteins and their phosphorylation functions and emphasizes the importance of using a multi-omics approach to comprehensively evaluate the molecular function of proteins involved in various genetic disorders.

Keywords:  congenital myopathy; multi‐omics; myospryn complex; skeletal muscle; striated muscle preferentially expressed protein kinase

DOI:  https://doi.org/10.1002/jcsm.13470
Physiol Res. 2024 Apr 30. 73(2): 295-304

Endurance Training Inhibits the JAK2/STAT3 Pathway to Alleviate Sarcopenia.

B Yao, L Li, X Guan, J Zhu, Q Liu, B Qu, H Ding.

Aging leads to a decrease in muscle function, mass, and strength in skeletal muscle of animals and humans. The transcriptome identified activation of the JAK/STAT pathway, a pathway that is associated with skeletal muscle atrophy, and endurance training has a significant effect on improving sarcopenia; however, the exact mechanism still requires further study. We investigated the effect of endurance training on sarcopenia. Six-month-old male SAMR1 mice were used as a young control group (group C), and the same month-old male SAMP8 mice were divided into an exercise group (group E) and a model group (group M). A 3-month running exercise intervention was performed on group E, and the other two groups were kept normally. Aging caused significant signs of sarcopenia in the SAMP8 mice, and endurance training effectively improved muscle function, muscle mass, and muscle strength in the SAMP8 mice. The expression of JAK2/STAT3 pathway factor was decreased in group E compared with group M, and the expression of SOCS3, the target gene of STAT3, and NR1D1, an atrophy-related factor, was significantly increased. Endurance training significantly improved the phenotypes associated with sarcopenia, and the JAK2/STAT3 pathway is a possible mechanism for the improvement of sarcopenia by endurance training, while NR1D1 may be its potential target. Keywords: Sarcopenia, Endurance training, Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3), Nuclear receptor subfamily 1, group D member 1 (Nr1d1).
Function (Oxf). 2024 ;5(3): zqae005

Pro-Brain-Derived Neurotrophic Factor (BDNF), but Not Mature BDNF, Is Expressed in Human Skeletal Muscle: Implications for Exercise-Induced Neuroplasticity.

Sebastian Edman, Oscar Horwath, Thibaux Van der Stede, Sarah Joan Blackwood, Isabel Moberg, Henrik Strömlind, Fabian Nordström, Maria Ekblom, Abram Katz, William Apró, Marcus Moberg.

  Exercise promotes brain plasticity partly by stimulating increases in mature brain-derived neurotrophic factor (mBDNF), but the role of the pro-BDNF isoform in the regulation of BDNF metabolism in humans is unknown. We quantified the expression of pro-BDNF and mBDNF in human skeletal muscle and plasma at rest, after acute exercise (+/- lactate infusion), and after fasting. Pro-BDNF and mBDNF were analyzed with immunoblotting, enzyme-linked immunosorbent assay, immunohistochemistry, and quantitative polymerase chain reaction. Pro-BDNF was consistently and clearly detected in skeletal muscle (40-250 pg mg-1 dry muscle), whereas mBDNF was not. All methods showed a 4-fold greater pro-BDNF expression in type I muscle fibers compared to type II fibers. Exercise resulted in elevated plasma levels of mBDNF (55%) and pro-BDNF (20%), as well as muscle levels of pro-BDNF (∼10%, all P < 0.05). Lactate infusion during exercise induced a significantly greater increase in plasma mBDNF (115%, P < 0.05) compared to control (saline infusion), with no effect on pro-BDNF levels in plasma or muscle. A 3-day fast resulted in a small increase in plasma pro-BDNF (∼10%, P < 0.05), with no effect on mBDNF. Pro-BDNF is highly expressed in human skeletal muscle, particularly in type I fibers, and is increased after exercise. While exercising with higher lactate augmented levels of plasma mBDNF, exercise-mediated increases in circulating mBDNF likely derive partly from release and cleavage of pro-BDNF from skeletal muscle, and partly from neural and other tissues. These findings have implications for preclinical and clinical work related to a wide range of neurological disorders such as Alzheimer's, clinical depression, and amyotrophic lateral sclerosis.

Keywords:  exercise; fasting; lactate; muscle fiber type; neurotrophins; β-hydroxybutyrate

DOI:  https://doi.org/10.1093/function/zqae005
PLoS One. 2024 ;19(5): e0300850

Dynamics of pax7 expression during development, muscle regeneration, and in vitro differentiation of satellite cells in rainbow trout (Oncorhynchus mykiss).

Cécile Rallière, Sabrina Jagot, Nathalie Sabin, Jean-Charles Gabillard.

Essential for muscle fiber formation and hypertrophy, muscle stem cells, also called satellite cells, reside beneath the basal lamina of the muscle fiber. Satellite cells have been commonly identified by the expression of the Paired box 7 (Pax7) due to its specificity and the availability of antibodies in tetrapods. In fish, the identification of satellite cells remains difficult due to the lack of specific antibodies in most species. Based on the development of a highly sensitive in situ hybridization (RNAScope®) for pax7, we showed that pax7+ cells were detected in the undifferentiated myogenic epithelium corresponding to the dermomyotome at day 14 post-fertilization in rainbow trout. Then, from day 24, pax7+ cells gradually migrated into the deep myotome and were localized along the muscle fibers and reach their niche in satellite position of the fibres after hatching. Our results showed that 18 days after muscle injury, a large number of pax7+ cells accumulated at the wound site compared to the uninjured area. During the in vitro differentiation of satellite cells, the percentage of pax7+ cells decreased from 44% to 18% on day 7, and some differentiated cells still expressed pax7. Taken together, these results show the dynamic expression of pax7 genes and the follow-up of these muscle stem cells during the different situations of muscle fiber formation in trout.

DOI: https://doi.org/10.1371/journal.pone.0300850
Biochem Soc Trans. 2024 May 08. pii: BST20230562. [Epub ahead of print]

Deubiquitinases in muscle physiology and disorders.

Cyriel S Olie, Darragh P O'Brien, Hannah B L Jones, Zhu Liang, Andreas Damianou, Ilknur Sur-Erdem, Adán Pinto-Fernández, Vered Raz, Benedikt M Kessler.

  In vivo, muscle and neuronal cells are post-mitotic, and their function is predominantly regulated by proteostasis, a multilayer molecular process that maintains a delicate balance of protein homeostasis. The ubiquitin-proteasome system (UPS) is a key regulator of proteostasis. A dysfunctional UPS is a hallmark of muscle ageing and is often impacted in neuromuscular disorders (NMDs). Malfunction of the UPS often results in aberrant protein accumulation which can lead to protein aggregation and/or mis-localization affecting its function. Deubiquitinating enzymes (DUBs) are key players in the UPS, controlling protein turnover and maintaining the free ubiquitin pool. Several mutations in DUB encoding genes are linked to human NMDs, such as ATXN3, OTUD7A, UCHL1 and USP14, whilst other NMDs are associated with dysregulation of DUB expression. USP5, USP9X and USP14 are implicated in synaptic transmission and remodeling at the neuromuscular junction. Mice lacking USP19 show increased maintenance of lean muscle mass. In this review, we highlight the involvement of DUBs in muscle physiology and NMDs, particularly in processes affecting muscle regeneration, degeneration and inflammation following muscle injury. DUBs have recently garnered much respect as promising drug targets, and their roles in muscle maturation, regeneration and degeneration may provide the framework for novel therapeutics to treat muscular disorders including NMDs, sarcopenia and cachexia.

Keywords:  deubiquitinase; muscle atrophy; muscle regeneration; myopathies; neuromuscular disorders; ubiquitin

DOI:  https://doi.org/10.1042/BST20230562
Exp Physiol. 2024 May 09.

Effect of high-fat diet on isometric, concentric and eccentric contractile performance of skeletal muscle isolated from female CD-1 mice.

Jason Tallis, Rob S James, Emma L J Eyre, Sharn P Shelley, Cameron Hill, Derek Renshaw, Josh Hurst.

  Despite evidence inferring muscle and contractile mode-specific effects of high-fat diet (HFD), no study has yet considered the impact of HFD directly on eccentric muscle function. The present work uniquely examined the effect of 20-week HFD on the isometric, concentric and eccentric muscle function of isolated mouse soleus (SOL) and extensor digitorum longus (EDL) muscles. CD-1 female mice were randomly split into a control (n = 16) or HFD (n = 17) group and for 20 weeks consumed standard lab chow or HFD. Following this period, SOL and EDL muscles were isolated and assessments of maximal isometric force and concentric work loop (WL) power were performed. Each muscle was then subjected to either multiple concentric or eccentric WL activations. Post-fatigue recovery, as an indicator of incurred damage, was measured via assessment of concentric WL power. In the EDL, absolute concentric power and concentric power normalised to muscle mass were reduced in the HFD group (P < 0.038). HFD resulted in faster concentric fatigue and reduced eccentric activity-induced muscle damage (P < 0.05). For the SOL, maximal isometric force was increased, and maximal eccentric power normalised to muscle mass and concentric fatigue were reduced in the HFD group (P < 0.05). HFD effects on eccentric muscle function are muscle-specific and have little relationship with changes in isometric or concentric function. HFD has the potential to negatively affect the intrinsic concentric and eccentric power-producing capacity of skeletal muscle, but a lack of a within-muscle uniform response indicates disparate mechanisms of action which require further investigation.

Keywords:  isolated skeletal muscle; muscle lengthening; obesity; work‐loop

DOI:  https://doi.org/10.1113/EP091832
IEEE Trans Med Imaging. 2024 May 06. PP

Accelerated, physics-inspired inference of skeletal muscle microstructure from diffusion-weighted MRI.

Noel Naughton, Stacey Cahoon, Brad Sutton, John G Georgiadis.

Muscle health is a critical component of overall health and quality of life. However, current measures of skeletal muscle health take limited account of microstructural variations within muscle, which play a crucial role in mediating muscle function. To address this, we present a physics-inspired, machine learning-based framework for the non-invasive estimation of microstructural organization in skeletal muscle from diffusion-weighted MRI (dMRI) in an uncertainty-aware manner. To reduce the computational expense associated with direct numerical simulations of dMRI physics, a polynomial meta-model is developed that accurately represents the input/output relationships of a high-fidelity numerical model. This meta-model is used to develop a Gaussian process (GP) model that provides voxel-wise estimates and confidence intervals of microstructure organization in skeletal muscle. Given noise-free data, the GP model accurately estimates microstructural parameters. In the presence of noise, the diameter, intracellular diffusion coefficient, and membrane permeability are accurately estimated with narrow confidence intervals, while volume fraction and extracellular diffusion coefficient are poorly estimated and exhibit wide confidence intervals. A reduced-acquisition GP model, consisting of one-third the diffusion-encoding measurements, is shown to predict parameters with similar accuracy to the original model. The fiber diameter and volume fraction estimated by the reduced GP model is validated via histology, with both parameters accurately estimated, demonstrating the capability of the proposed framework as a promising non-invasive tool for assessing skeletal muscle health and function.

DOI: https://doi.org/10.1109/TMI.2024.3397790
JCI Insight. 2024 May 07. pii: e165869. [Epub ahead of print]

Potential limitations of micro-dystrophin gene therapy for Duchenne muscular dystrophy.

Cora C Hart, Young Il Lee, Jun Xie, Guangping Gao, Brian L Lin, David W Hammers, H Lee Sweeney.

  Clinical trials delivering high doses of adeno-associated viruses (AAVs) expressing truncated dystrophin molecules (micro-dystrophins) are underway for individuals with Duchenne muscular dystrophy (DMD). We examined the efficiency and efficacy of this strategy with four micro-dystrophin constructs (three in clinical trials and a variant of the largest clinical construct), in a severe mouse model of DMD, using doses of AAV comparable to those used in the clinical trials. We achieved high levels of micro-dystrophin expression in striated muscle with cardiac expression ~10 fold higher than that observed in skeletal muscle. Significant, albeit incomplete, correction of the skeletal muscle disease was observed. Surprisingly, a lethal acceleration of cardiac disease progression occurred with two of the micro-dystrophins. The detrimental impact on the heart appears to be caused by the high levels of micro-dystrophin resulting in variable competition (dependent on the design of the micro-dystrophin) between micro-dystrophin and utrophin at the cardiomyocyte membrane. There may also be a contribution from an overloading of protein degradation. The significance of these observations for patients currently being treated with AAV-micro-dystrophin therapies is unclear since the levels of expression being achieved in the DMD hearts are unknown. However, it suggests that micro-dystrophin treatments need to avoid excessively high levels of expression in the heart and cardiac function should be carefully monitored in these patients.

Keywords:  Gene therapy; Muscle biology; Therapeutics

DOI:  https://doi.org/10.1172/jci.insight.165869
Physiol Rep. 2024 May;12(9): e16042

The effects of myosteatosis on skeletal muscle function in older adults.

Kathleen Dondero, Ben Friedman, Julie Rekant, Rian Landers-Ramos, Odessa Addison.

  Myosteatosis, or the infiltration of fatty deposits into skeletal muscle, occurs with advancing age and contributes to the health and functional decline of older adults. Myosteatosis and its inflammatory milieu play a larger role in adipose tissue dysfunction, muscle tissue dysfunction, and increased passive muscle stiffness. Combined with the age-related decline of sex hormones and development of anabolic resistance, myosteatosis also contributes to insulin resistance, impaired muscle mechanics, loss of force production from the muscle, and increased risk of chronic disease. Due to its highly inflammatory secretome and the downstream negative effects on muscle metabolism and mechanics, myosteatosis has become an area of interest for aging researchers and clinicians. Thus far, myosteatosis treatments have had limited success, as many lack the potency to completely rescue the metabolic and physical consequences of myosteatosis. Future research is encouraged for the development of reliable assessment methods for myosteatosis, as well as the continued exploration of pharmacological, nutritional, and exercise-related interventions that may lead to the success in attenuating myosteatosis and its clinical consequences within the aging population.

Keywords:  aging; muscle function; muscle stiffness; myosteatosis

DOI:  https://doi.org/10.14814/phy2.16042
Am J Transl Res. 2024 ;16(4): 1135-1144

Mechanism of static loading injury in human skeletal muscle cells.

Yuan Yuan, Hui Zhang, Ya-Fang Li, Xin-Na Xue, Guo-Hui Zhang, Hong Zhang.

   OBJECTIVE: To establish a cellular-level mechanical injury model for human skeletal muscle cells and investigate changes in the mechanical effect mechanism after such injuries.
METHODS: The FX-5000™ Compression System was used to apply constant static mechanical pressure to human skeletal muscle cells. A factorial design analysis was conducted to discover the optimal injury model by evaluating the correlation between the amount of pressure, the duration of mechanical stimulation, and the number of days of observation. Skeletal muscle cell injury was evaluated by measuring cell metabolism, morphology, and calcium homeostasis.
RESULTS: Mechanical injury was modeled as continuous pressure of 1 MPa for 2 hours with observation for 3 days. The results show that mechanical injury increased creatine kinase, intracellular Ca2+ concentration, and malondialdehyde content, decreased superoxide dismutase, and caused cell swelling and severe cytoplasmic vacuolization (all P < 0.05).
CONCLUSION: This model of mechanically-injured human skeletal muscle cells provides an experimental model for the clinically common skeletal muscle injury caused by static loading pressure. It may be used to study the mechanism of action of treatment methods for mechanically injured skeletal muscle.

Keywords:  FX-5000™; Mechanical injury; factorial design; mechanical effects; mechanism study

DOI:  https://doi.org/10.62347/HCXU6226
Physiol Res. 2024 Apr 30. 73(2): 285-294

Electrical Stimulation-Based Twitch Exercise Suppresses Progression of Immobilization-Induced Muscle Fibrosis via Downregulation of PGC-1?/VEGF Pathway.

Y Honda, A Takahashi, N Tanaka, Y Kajiwara, R Sasaki, H Kataoka, J Sakamoto, M Okita.

This study aimed to determine whether electrical stimulation-based twitch exercise is effective in inhibiting the progression of immobilization-induced muscle fibrosis. 19 Wistar rats were randomly divided into a control group (n=6), an immobilization group (n=6; with immobilization only), and a Belt group (n=7; with immobilization and twitch exercise through the belt electrode device, beginning 2 weeks after immobilization). The bilateral soleus muscles were harvested after the experimental period. The right soleus muscles were used for histological analysis, and the left soleus muscles were used for biochemical and molecular biological analysis. As a result, in the picrosirius red images, the perimysium and endomysium were thicker in both the immobilization and Belt groups compared to the control group. However, the perimysium and endomysium thickening were suppressed in the Belt group. The hydroxyproline content and alpha-SMA, TGF-beta1, and HIF-1alpha mRNA expressions were significantly higher in the immobilization and belt groups than in the control group. These expressions were significantly lower in the Belt group than in the immobilization group. The capillary-to-myofiber ratio and the mRNA expressions of VEGF and PGC-1alpha were significantly lower in the immobilization and belt groups than in the control group, these were significantly higher in the Belt group than in the immobilization group. From these results, Electrical stimulation-based twitch exercise using the belt electrode device may prevent the progression of immobilization-induced muscle fibrosis caused by downregulating PGC-1alpha/VEGF pathway, we surmised that this intervention strategy might be effective against the progression of muscle contracture. Keywords: Immobilization, Skeletal muscle, Fibrosis, Electrical stimulation-based twitch exercise, PGC-1alpha/VEGF pathway.
Adv Healthc Mater. 2024 May 07. e2304196

Biomaterials-based Technologies in Skeletal Muscle Tissue Engineering.

Wei Luo, Hanli Zhang, Renwen Wan, Yuxi Cai, Yinuo Liu, Yang Wu, Yimeng Yang, Jiani Chen, Deju Zhang, Zhiwen Luo, Xiliang Shang.

  For many clinically prevalent severe injuries, the inherent regenerative capacity of skeletal muscle remains inadequate. Skeletal muscle tissue engineering (SMTE) seeks to meet this clinical demand. With continuous progress in biomedicine and related technologies including micro/nanotechnology and 3D printing, numerous studies have uncovered various intrinsic mechanisms regulating skeletal muscle regeneration and developed tailored biomaterial systems based on these understandings. Here, we discussed the skeletal muscle structure and regeneration process and explored in detail the diverse biomaterial systems derived from various technologies. Biomaterials serve not merely as local niches for cell growth, but also as scaffolds endowed with structural or physicochemical properties that provide tissue regenerative cues such as topographical, electrical, and mechanical signals. They can also act as delivery systems for stem cells and bioactive molecules that have been shown as key participants in endogenous repair cascades. To achieve bench-to-bedside translation, we have also summarized the typical effect enabled by biomaterial systems and the potential underlying molecular mechanisms. We hope to provide insights into the roles of biomaterials in SMTE from cellular and molecular perspectives. Finally, we provided perspectives on the advancement of SMTE, for which gene therapy, exosomes, and hybrid biomaterials may hold promise to make important contributions. This article is protected by copyright. All rights reserved.

Keywords:  3D bioprinting; biomaterials; exosomes; micro/nanotechnologies; ncRNA; skeletal muscle; tissue engineering

DOI:  https://doi.org/10.1002/adhm.202304196
Nat Aging. 2024 May 09.

Nature of epigenetic aging from a single-cell perspective.

Andrei E Tarkhov, Thomas Lindstrom-Vautrin, Sirui Zhang, Kejun Ying, Mahdi Moqri, Bohan Zhang, Alexander Tyshkovskiy, Orr Levy, Vadim N Gladyshev.

Age-related changes in DNA methylation (DNAm) form the basis of the most robust predictors of age-epigenetic clocks-but a clear mechanistic understanding of exactly which aspects of aging are quantified by these clocks is lacking. Here, to clarify the nature of epigenetic aging, we juxtapose the dynamics of tissue and single-cell DNAm in mice. We compare these changes during early development with those observed during adult aging in mice, and corroborate our analyses with a single-cell RNA sequencing analysis within the same multiomics dataset. We show that epigenetic aging involves co-regulated changes as well as a major stochastic component, and this is consistent with transcriptional patterns. We further support the finding of stochastic epigenetic aging by direct tissue and single-cell DNAm analyses and modeling of aging DNAm trajectories with a stochastic process akin to radiocarbon decay. Finally, we describe a single-cell algorithm for the identification of co-regulated and stochastic CpG clusters showing consistent transcriptomic coordination patterns. Together, our analyses increase our understanding of the basis of epigenetic clocks and highlight potential opportunities for targeting aging and evaluating longevity interventions.

DOI: https://doi.org/10.1038/s43587-024-00616-0
Sci Rep. 2024 05 09. 14(1): 10658

Exercise ameliorates muscular excessive mitochondrial fission, insulin resistance and inflammation in diabetic rats via irisin/AMPK activation.

Junjie Lin, Xin Zhang, Yu Sun, Haocheng Xu, Nan Li, Yuanxin Wang, Xin Tian, Chen Zhao, Bin Wang, Baishu Zhu, Renqing Zhao.

  This study aimed to investigate the effects of exercise on excessive mitochondrial fission, insulin resistance, and inflammation in the muscles of diabetic rats. The role of the irisin/AMPK pathway in regulating exercise effects was also determined. Thirty-two 8-week-old male Wistar rats were randomly divided into four groups (n = 8 per group): one control group (Con) and three experimental groups. Type 2 diabetes mellitus (T2DM) was induced in the experimental groups via a high-fat diet followed by a single intraperitoneal injection of streptozotocin (STZ) at a dosage of 30 mg/kg body weight. After T2DM induction, groups were assigned as sedentary (DM), subjected to 8 weeks of treadmill exercise training (Ex), or exercise training combined with 8-week cycloRGDyk treatment (ExRg). Upon completion of the last training session, all rats were euthanized and samples of fasting blood and soleus muscle were collected for analysis using ELISA, immunofluorescence, RT-qPCR, and Western blotting. Statistical differences between groups were analyzed using one-way ANOVA, and differences between two groups were assessed using t-tests. Our findings demonstrate that exercise training markedly ameliorated hyperglycaemia, hyperlipidaemia, and insulin resistance in diabetic rats (p < 0.05). It also mitigated the disarranged morphology and inflammation of skeletal muscle associated with T2DM (p < 0.05). Crucially, exercise training suppressed muscular excessive mitochondrial fission in the soleus muscle of diabetic rats (p < 0.05), and enhanced irisin and p-AMPK levels significantly (p < 0.05). However, exercise-induced irisin and p-AMPK expression were inhibited by cycloRGDyk treatment (p < 0.05). Furthermore, the administration of CycloRGDyk blocked the effects of exercise training in reducing excessive mitochondrial fission and inflammation in the soleus muscle of diabetic rats, as well as the positive effects of exercise training on improving hyperlipidemia and insulin sensitivity in diabetic rats (p < 0.05). These results indicate that regular exercise training effectively ameliorates insulin resistance and glucolipid metabolic dysfunction, and reduces inflammation in skeletal muscle. These benefits are partially mediated by reductions in mitochondrial fission through the irisin/AMPK signalling pathway.

Keywords:  Diabetes; Exercise training; Inflammation; Irisin; Mitochondrial fission

DOI:  https://doi.org/10.1038/s41598-024-61415-6
Matrix Biol. 2024 May 07. pii: S0945-053X(24)00062-3. [Epub ahead of print]

LPA-induced Expression of CCN2 in Muscular Fibro/adipogenic Progenitors (FAPs): Unraveling Cellular Communication Networks.

Adriana Córdova-Casanova, Meilyn Cruz-Soca, Felipe S Gallardo, Jennifer Faundez-Contreras, Alexia Bock-Pereda, Jerold Chun, Carlos P Vio, Juan Carlos Casar, Enrique Brandan.

  Cellular Communication Network Factor 2, CCN2, is a profibrotic cytokine implicated in physiological and pathological processes in mammals. The expression of CCN2 is markedly increased in dystrophic muscles. Interestingly, diminishing CCN2 genetically or inhibiting its function improves the phenotypes of chronic muscular fibrosis in rodent models. Elucidating the cell-specific mechanisms behind the induction of CCN2 is a fundamental step in understanding its relevance in muscular dystrophies. Here, we show that the small lipids LPA and 2S-OMPT induce CCN2 expression in fibro/adipogenic progenitors (FAPs) through the activation of the LPA1 receptor and, to a lower extent, by also the LPA6 receptor. These cells show a stronger induction than myoblasts or myotubes. We show that the LPA/LPARs axis requires ROCK kinase activity and organized actin cytoskeleton upstream of YAP/TAZ signaling effectors to upregulate CCN2 levels, suggesting that mechanical signals are part of the mechanism behind this process. In conclusion, we explored the role of the LPA/LPAR axis on CCN2 expression, showing a strong cytoskeletal-dependent response in muscular FAPs.

Keywords:  CCN2; FAPs; LPA; muscular fibrosis; stiffness

DOI:  https://doi.org/10.1016/j.matbio.2024.05.001
Sci Rep. 2024 05 07. 14(1): 10442

Transcriptome- and proteome-wide effects of a circular RNA encompassing four early exons of the spinal muscular atrophy genes.

Diou Luo, Eric W Ottesen, Ji Heon Lee, Ravindra N Singh.

  Spinal muscular atrophy (SMA) genes, SMN1 and SMN2 (hereinafter referred to as SMN1/2), produce multiple circular RNAs (circRNAs), including C2A-2B-3-4 that encompasses early exons 2A, 2B, 3 and 4. C2A-2B-3-4 is a universally and abundantly expressed circRNA of SMN1/2. Here we report the transcriptome- and proteome-wide effects of overexpression of C2A-2B-3-4 in inducible HEK293 cells. Our RNA-Seq analysis revealed altered expression of ~ 15% genes (4172 genes) by C2A-2B-3-4. About half of the affected genes by C2A-2B-3-4 remained unaffected by L2A-2B-3-4, a linear transcript encompassing exons 2A, 2B, 3 and 4 of SMN1/2. These findings underscore the unique role of the structural context of C2A-2B-3-4 in gene regulation. A surprisingly high number of upregulated genes by C2A-2B-3-4 were located on chromosomes 4 and 7, whereas many of the downregulated genes were located on chromosomes 10 and X. Supporting a cross-regulation of SMN1/2 transcripts, C2A-2B-3-4 and L2A-2B-3-4 upregulated and downregulated SMN1/2 mRNAs, respectively. Proteome analysis revealed 61 upregulated and 57 downregulated proteins by C2A-2B-3-4 with very limited overlap with those affected by L2A-2B-3-4. Independent validations confirmed the effect of C2A-2B-3-4 on expression of genes associated with chromatin remodeling, transcription, spliceosome function, ribosome biogenesis, lipid metabolism, cytoskeletal formation, cell proliferation and neuromuscular junction formation. Our findings reveal a broad role of C2A-2B-3-4, and expands our understanding of functions of SMN1/2 genes.

Keywords:  Circular RNA, circRNA; Proteome; Spinal muscular atrophy, SMA; Survival Motor Neuron, SMN; Transcriptome

DOI:  https://doi.org/10.1038/s41598-024-60593-7