bims-musmir 2025-02-09 papers

bioRxiv. 2025 Jan 20. pii: 2025.01.17.633623. [Epub ahead of print]

The liver clock tunes transcriptional rhythms in skeletal muscle to regulate mitochondrial function.

Valentina Sica, Tomoki Sato, Ioannis Tsialtas, Sophia Hernandez, Siwei Chen, Pierre Baldi, Pura Muñoz Cánoves, Paolo Sassone-Corsi, Kevin B Koronowski, Jacob G Smith.

Circadian clocks present throughout the brain and body coordinate diverse physiological processes to support daily homeostasis and respond to changing environmental conditions. The local dependencies within the mammalian clock network are not well defined. We previously demonstrated that the skeletal muscle clock controls transcript oscillations of genes involved in fatty acid metabolism in the liver, yet whether the liver clock also regulates the muscle was unknown. Here, we use hepatocyte-specific Bmal1 KO mice (Bmal1 hep-/- ) and reveal that approximately one third of transcriptional rhythms in skeletal muscle are regulated by the liver clock vivo. Treatment of myotubes with serum harvested from Bmal1 hep-/- mice inhibited expression of genes involved in metabolic pathways, including oxidative phosphorylation. Overall, the transcriptional changes induced by liver clock-driven endocrine-communication revealed from our in vitro system were small in magnitude, leading us to surmise that the liver clock acts to fine-tune metabolic gene expression in muscle. Strikingly, treatment of myotubes with serum from Bmal1 hep-/- mice inhibited mitochondrial ATP production compared to WT and this effect was only observed with serum harvested during the active phase. Overall, our results reveal communication between the liver clock and skeletal muscle-uncovering a bidirectional endocrine communication pathway dependent on clocks in these two key metabolic tissues. Targeting liver and muscle circadian clocks may represent a potential avenue for exploration for diseases associated with dysregulation of metabolism in these tissues.

DOI: https://doi.org/10.1101/2025.01.17.633623

Front Neurosci. 2025 ;19 1527181

Muscle-specific Bet1L knockdown induces neuromuscular denervation, motor neuron degeneration, and motor dysfunction in a rat model of familial ALS.

Adam Eckardt, Charles Marble, Bradley Fern, Henry Moritz, Charles Kotula, Jiayi Ke, Clarisse Rebancos, Samantha Robertson, Hiroshi Nishimune, Masatoshi Suzuki.

Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by specific loss of motor neurons in the spinal cord and brain stem. Although ALS has historically been characterized as a motor neuron disease, there is evidence that motor neurons degenerate in a retrograde manner, beginning in the periphery at the neuromuscular junctions (NMJs) and skeletal muscle. We recently reported a vesicle trafficking protein Bet1L (Bet1 Golgi Vesicular Membrane Trafficking Protein Like) as a new molecule possibly linked to NMJ degeneration in ALS. In this study, we tested the hypothesis that Bet1L gene silencing in skeletal muscle could influence NMJ integrity, motor neuron function, and survival in a rat model of familial ALS (SOD1G93A transgenic). Small interfering RNA (siRNA) targeting the Bet1L gene was injected on a weekly basis into the hindlimb muscle of pre-symptomatic ALS and wild-type (WT) rats. After 3 weeks, intramuscular Bet1L siRNA injection significantly increased the number of denervated NMJs in the injected muscle. Bet1L knockdown decreased motor neuron size in the lumbar spinal cord, which innervated the siRNA-injected hindlimb. Impaired motor function was identified in the hindlimbs of Bet1L siRNA-injected rats. Notably, the effects of Bet1L knockdown on NMJ and motor neuron degeneration were more significant in ALS rats when compared to WT rats. Together, Bet1L knockdown induces denervation of NMJs, but also this knockdown accelerates the disease progression in ALS. Our results provide new evidence to support the potential roles of Bet1L as a key molecule in NMJ maintenance and ALS pathogenesis.

Keywords: Bet1L; SOD1G93A rats; amyotrophic lateral sclerosis (ALS); distal axonopathy; motor neuron; neuromuscular junction; skeletal muscle; small interfering RNA (siRNA)

DOI: https://doi.org/10.3389/fnins.2025.1527181

Inflamm Res. 2025 Jan 31. 74(1): 31

A window into intracellular events in myositis through subcellular proteomics.

Jennifer M Peterson, Valérie Leclair, Olumide E Oyebode, Dema M Herzallah, Andrea L Nestor-Kalinoski, Jose Morais, René P Zahedi, Mazen Alamr, John A Di Battista, Marie Hudson.

OBJECTIVE AND DESIGN: Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of inflammatory muscle disorders of unknown etiology. It is postulated that mitochondrial dysfunction and protein aggregation in skeletal muscle contribute to myofiber degeneration. However, molecular pathways that lead to protein aggregation in skeletal muscle are not well defined.
SUBJECTS: Here we have isolated membrane-bound organelles (e.g., nuclei, mitochondria, sarcoplasmic/endoplasmic reticulum, Golgi apparatus, and plasma membrane) from muscle biopsies of normal (n = 3) and muscle disease patients (n = 11). Of the myopathy group, 10 patients displayed mitochondrial abnormalities (IIM (n = 9); mitochondrial myopathy (n = 1)), and one IIM patient did not show mitochondrial abnormalities (polymyositis).
METHODS: Global proteomic analysis was performed using an Orbitrap Fusion mass spectrometer. Upon unsupervised clustering, normal and mitochondrial myopathy muscle samples clustered separately from IIM samples.
RESULTS: We have confirmed previously known protein alterations in IIM and identified several new ones. For example, we found differential expression of (i) nuclear proteins that control cell division, transcription, RNA regulation, and stability, (ii) ER and Golgi proteins involved in protein folding, degradation, and protein trafficking in the cytosol, and (iii) mitochondrial proteins involved in energy production/metabolism and alterations in cytoskeletal and contractile machinery of the muscle.
CONCLUSIONS: Our data demonstrates that molecular alterations are not limited to protein aggregations in the cytosol (inclusions) and occur in nuclear, mitochondrial, and membrane compartments of IIM skeletal muscle.

Keywords: Biopsy; Human; Muscle; Myositis; Proteomics

DOI: https://doi.org/10.1007/s00011-025-01996-8

J Cachexia Sarcopenia Muscle. 2025 Feb;16(1): e13701

Skeletal Muscle Mitochondrial and Autophagic Dysregulation Are Modifiable in Spinal Muscular Atrophy.

Andrew I Mikhail, Sean Y Ng, Donald Xhuti, Magda A Lesinski, Jennifer Chhor, Marc-Olivier Deguise, Yves De Repentigny, Joshua P Nederveen, Rashmi Kothary, Mark A Tarnopolsky, Vladimir Ljubicic.

BACKGROUND: Spinal muscular atrophy (SMA) is a health- and life-limiting neuromuscular disorder. Although varying degrees of mitochondrial abnormalities have been documented in SMA skeletal muscle, the influence of disease progression on pathways that govern organelle turnover and dynamics are poorly understood. Thus, the purpose of this study was to investigate skeletal muscle mitochondria during SMA disease progression and determine the effects of therapeutic modalities on organelle biology.
METHODS: Smn2B/+ and Smn2B/- severe SMA-like mice were used to investigate mitochondrial turnover and dynamics signalling. Muscles were analysed at postnatal day 9 (P9), P13 or P21 to address pre-symptomatic, early symptomatic and late symptomatic periods of the disorder. Additionally, we utilized an acute dose of exercise and urolithin A (UA) to stimulate organelle remodelling in skeletal muscle of SMA mice in vivo and in SMA patient-derived myotubes in vitro, respectively.
RESULTS: Smn2B/+ and Smn2B/- mice demonstrated similar levels of muscle mitochondrial oxidative phosphorylation (OxPhos) proteins throughout disease progression. In contrast, at P21 the mRNA levels of upstream factors important for the transcription of mitochondrial genes encoded by the nuclear and mitochondrial DNA, including nuclear respiratory factor 2, sirtuin 1, mitochondrial transcription factor A and tumour protein 53, were upregulated (+31%-195%, p < 0.05) in Smn2B/- mice relative to Smn2B/+. Early and late symptomatic skeletal muscle from SMA-like mice showed greater autophagosome formation as denoted by more phosphorylated autophagy related 16-like 1 (p-ATG16L1Ser278) puncta (+60%-80%, p < 0.05), along with a build-up of molecules indicative of damaged mitochondria such as BCL2 interacting protein 3, Parkin and PTEN-induced kinase 1 (+100%-195%, p < 0.05). Furthermore, we observed a fragmented mitochondrial phenotype at P21 that was concomitant with abnormal splicing of Optic atrophy 1 transcripts (-53%, p < 0.05). A single dose of exercise augmented the expression of citrate synthase (+43%, p < 0.05) and corrected the over-assembly of autophagosomes (-64%, p < 0.05). In patient muscle cells, UA treatment stimulated autophagic flux, increased the expression of OxPhos proteins (+15%-47%, p < 0.05) and improved maximal oxygen consumption (+84%, p < 0.05).
CONCLUSIONS: Abnormal skeletal muscle mitochondrial turnover and dynamics are associated with disease progression in Smn2B/- mice despite compensatory elevations in upstream factors important for organelle synthesis and recycling. Exercise and UA enhance mitochondrial health in skeletal muscle, which indicates that lifestyle-based and pharmacological interventions may be effective countermeasures targeting the organelle for therapeutic remodelling in SMA.

Keywords: autophagy; biogenesis; dynamics; exercise; mitophagy; urolithin A

DOI: https://doi.org/10.1002/jcsm.13701

Noncoding RNA Res. 2025 Apr;11 188-199

Serum/glucose starvation enhances binding of miR-4745-5p and miR-6798-5p to HNRNPA1 mRNA 3'UTR: A novel method to identify miRNAs binding to mRNA 3'UTR using λN peptide-boxB sequence.

Tetsuyuki Takahashi, Mai Funamura, Shun Wakai, Takao Hijikata.

Serum/glucose starvation causes complete loss of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) without altering mRNA levels. However, the mechanisms driving hnRNP A1 downregulation during serum/glucose starvation are not yet well understood. Using the novel interaction between the λN peptide and boxB sequence (λN/boxB system) and miRNA microarray analysis, we aimed to identify specific-binding microRNAs (miRs or miRNAs) targeting HNRNPA1 mRNA 3'UTR under serum/glucose-starved conditions. Four miRNAs were identified as serum/glucose starvation-driven miRNAs for HNRNPA1 mRNA 3'UTR. Reporter assays, anti-miRNA and mutated miRNA-based assays, photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation/reverse transcribed-quantitative polymerase chain reaction, and transient overexpression of miRNAs showed that miR-4745-5p and miR-6798-5p suppress hnRNP A1 protein levels via enhancement of binding to HNRNPA1 mRNA 3'UTR under serum/glucose-starved condition. miR-4745-5p and miR-6798-5p overexpression significantly decreased growth rates, which was rescued by co-transfection with anti-miRNA for miR-4745-5p and miR-6798-5p. Anti-miRNA transfection for miR-4745-5p and miR-6798-5p significantly increased growth rates under serum/glucose-starved conditions. Furthermore, hnRNP A1 overexpression recovered miR-4745-5p- and miR-6798-5p-induced growth suppression. These findings indicated that miR-4745-5p and miR-6798-5p are serum/glucose starvation-driven miRNAs for hnRNP A1 and validated the λN/boxB system as a simple and useful method for detecting mRNA 3'UTR-bound miRNA.

Keywords: Microarray; Serum/glucose starvation; hnRNP A1; miR-4745-5p; miR-6798-5p; microRNA; λN/boxB system

DOI: https://doi.org/10.1016/j.ncrna.2025.01.001

Skelet Muscle. 2025 Feb 05. 15(1): 3

Neuromuscular electrical stimulation training induces myonuclear accretion and hypertrophy in mice without overt signs of muscle damage and regeneration.

Aurélie Fessard, Aliki Zavoriti, Natacha Boyer, Jules Guillemaud, Masoud Rahmati, Peggy Del Carmine, Christelle Gobet, Bénédicte Chazaud, Julien Gondin.

BACKGROUND: Skeletal muscle is a plastic tissue that adapts to increased mechanical loading/contractile activity through fusion of muscle stem cells (MuSCs) with myofibers, a physiological process referred to as myonuclear accretion. However, it is still unclear whether myonuclear accretion is driven by increased mechanical loading per se, or occurs, at least in part, in response to muscle injury/regeneration. Here, we developed a non-damaging protocol to evaluate contractile activity-induced myonuclear accretion/hypertrophy in physiological conditions.
METHODS: Contractile activity was generated by applying repeated electrical stimuli over the mouse plantar flexor muscles. This method is commonly referred to as NeuroMuscular Electrical Simulation (NMES) in Human. Each NMES training session consisted of 80 isometric contractions delivered at ∼15% of maximal tetanic force to avoid muscle damage. C57BL/6J male mice were submitted to either a short (i.e., 6 sessions) or long (i.e., 12 sessions) individualized NMES training program while unstimulated mice were used as controls. Histological investigations were performed to assess the impact of NMES on MuSC number and status, myonuclei content and muscle tissue integrity, typology and size.
RESULTS: NMES led to a robust proliferation of MuSCs and myonuclear accretion in the absence of overt signs of muscle damage/regeneration. NMES-induced myonuclear accretion was specific to type IIB myofibers and was an early event preceding muscle hypertrophy inasmuch as a mild increase in myofiber cross-sectional area was only observed in response to the long-term NMES training protocol.
CONCLUSION: We conclude that NMES-induced myonuclear accretion and muscle hypertrophy are driven by a mild increase in mechanical loading in the absence of overt signs of muscle injury.

Keywords: Contractile activity; Force production; Muscle stem cells; Resistance training; Skeletal muscle plasticity

DOI: https://doi.org/10.1186/s13395-024-00372-0