Nebulin and Lmod2 are critical for specifying thin-filament length in skeletal muscle

Kiss, Balázs; Gohlke, Jochen; Tonino, Paola; Hourani, Zaynab; Kolb, Justin; Strom, Joshua; Alekhina, Olga V.; Smith, John E.; Ottenheijm, Coen A.C.; Gregorio, Carol C.; Granzier, Henk

doi:10.1126/sciadv.abc1992

Cited by 29 publications

(64 citation statements)

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“…Instead, it has been suggested that nebulin contributes to the regulation of the Z-disk width ( Witt et al, 2006 ; Li et al, 2015 ). This is supported by the correlation between the number of nebulin Z-repeats and the Z-disk width that has been found ( Kiss et al, 2020 ) and the widened Z-disks that locally exist in nebulin-deficient muscle ( Witt et al, 2006 ; Tonino et al, 2010 ; Li et al, 2015 ).…”

Section: Introductionmentioning

confidence: 62%

“…Owing to alternative splicing events in the Z-repeat region and in super-repeat 12, there are often multiple annotated nebulin splice variants. Because gel electrophoresis and gene expression data from mice indicate that the majority of transcripts include all annotated super-repeat and Z-repeat exons ( Kiss et al, 2020 ), the longest isoform was selected for further analysis. Species were chosen based on completeness of the nebulin genomic sequence, as reflected by the absence of gaps that might indicate missing exons in the annotation.…”

Section: Methodsmentioning

confidence: 99%

“…Its absence in skeletal muscle in nebulin-deficient mouse muscle ( Witt et al, 2006 ; Bang et al, 2009 ; Ottenheijm et al, 2013 ; Li et al, 2015 ; Joureau et al, 2017 ; Kawai et al, 2018 ) and nebulin-based NEM ( Ottenheijm et al, 2009 , 2010 ; Lawlor et al, 2011 ) is likely to contribute to their deficit in force production. Using mouse models in which the number of super-repeats was varied, it was shown recently that nebulin’s super-repeat region strictly regulates thin filament length (TFL) in fast muscle; in slow muscle, nebulin collaborates with Lmod2 (leiomodin-2), with Lmod2 regulating the length of a distal nebulin-free thin filament segment ( Kiss et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

“…We refer to them as Z-repeats for their likely localization within the Z-disk region. A recent RNA sequencing study showed that Z-repeats are expressed at low and high levels in extensor digitorum longus (EDL) and soleus muscles of the mouse, respectively ( Kiss et al, 2020 ). These muscle types are rich in type I (soleus) and IIB (EDL) fibers, implying a fiber type–dependent expression of these exons.…”

Section: Introductionmentioning

confidence: 99%

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The number of Z-repeats and super-repeats in nebulin greatly varies across vertebrates and scales with animal size

Gohlke

Tonino

Lindqvist

et al. 2020

Journal of General Physiology

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Nebulin is a skeletal muscle protein that associates with the sarcomeric thin filaments and has functions in regulating the length of the thin filament and the structure of the Z-disk. Here we investigated the nebulin gene in 53 species of birds, fish, amphibians, reptiles, and mammals. In all species, nebulin has a similar domain composition that mostly consists of ∼30-residue modules (or simple repeats), each containing an actin-binding site. All species have a large region where simple repeats are organized into seven-module super-repeats, each containing a tropomyosin binding site. The number of super-repeats shows high interspecies variation, ranging from 21 (zebrafish, hummingbird) to 31 (camel, chimpanzee), and, importantly, scales with body size. The higher number of super-repeats in large animals was shown to increase thin filament length, which is expected to increase the sarcomere length for optimal force production, increase the energy efficiency of isometric force production, and lower the shortening velocity of muscle. It has been known since the work of A.V. Hill in 1950 that as species increase in size, the shortening velocity of their muscle is reduced, and the present work shows that nebulin contributes to the mechanistic basis. Finally, we analyzed the differentially spliced simple repeats in nebulin's C terminus, whose inclusion correlates with the width of the Z-disk. The number of Z-repeats greatly varies (from 5 to 18) and correlates with the number of super-repeats. We propose that the resulting increase in the width of the Z-disk in large animals increases the number of contacts between nebulin and structural Z-disk proteins when the Z-disk is stressed for long durations.

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Section: Introductionmentioning

confidence: 62%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The number of Z-repeats and super-repeats in nebulin greatly varies across vertebrates and scales with animal size

Gohlke

Tonino

Lindqvist

et al. 2020

Journal of General Physiology

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“…In addition, muscle viability and proliferative status were evaluated using fast and slow myosin protein staining. These proteins represent proliferative and apoptotic muscle cells, respectively 55 . The findings show that muscle structure atrophy is alleviated and muscle viability is increased significantly.…”

Section: Discussionmentioning

confidence: 99%

Preclinical assessment on neuronal regeneration in the injury-related microenvironment of graphene-based scaffolds

et al. 2021

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As the application of graphene nanomaterials gets increasingly attractive in the field of tissue engineering and regenerative medicine, the long-term evaluation is necessary and urgent as to their biocompatibility and regenerative capacity in different tissue injuries, such as nerve, bone, and heart. However, it still remains controversial about the potential biological effects of graphene on neuronal activity, especially after severe nerve injuries. In this study, we establish a lengthy peripheral nerve defect rat model and investigate the potential toxicity of layered graphene-loaded polycaprolactone scaffold after implantation during 18 months in vivo. In addition, we further identify possible biologically regenerative effects of this scaffold on myelination, axonal outgrowth, and locomotor function recovery. It is confirmed that graphene-based nanomaterials exert negligible toxicity and repair large nerve defects by dual regulation of Schwann cells and astroglia in the central and peripheral nervous systems. The findings enlighten the future of graphene nanomaterial as a key type of biomaterials for clinical translation in neuronal regeneration.

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Characterization of NEB pathogenic variants in patients reveals novel nemaline myopathy disease mechanisms and omecamtiv mecarbil force effects

Karimi,

Gohlke,

van der Borgh

et al. 2024

Acta Neuropathol

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Nebulin, a critical protein of the skeletal muscle thin filament, plays important roles in physiological processes such as regulating thin filament length (TFL), cross-bridge cycling, and myofibril alignment. Pathogenic variants in the nebulin gene (NEB) cause NEB-based nemaline myopathy (NEM2), a genetically heterogeneous disorder characterized by hypotonia and muscle weakness, currently lacking curative therapies. In this study, we examined a cohort of ten NEM2 patients, each with unique pathogenic variants, aiming to understand their impact on mRNA, protein, and functional levels. Results show that pathogenic truncation variants affect NEB mRNA stability and lead to nonsense-mediated decay of the mutated transcript. Moreover, a high incidence of cryptic splice site activation was found in patients with pathogenic splicing variants that are expected to disrupt the actin-binding sites of nebulin. Determination of protein levels revealed patients with either relatively normal or markedly reduced nebulin. We observed a positive relation between the reduction in nebulin and a reduction in TFL, or reduction in tension (both maximal and submaximal tension). Interestingly, our study revealed a pathogenic duplication variant in nebulin that resulted in a four-copy gain in the triplicate region of NEB and a much larger nebulin protein and longer TFL. Additionally, we investigated the effect of Omecamtiv mecarbil (OM), a small-molecule activator of cardiac myosin, on force production of type 1 muscle fibers of NEM2 patients. OM treatment substantially increased submaximal tension across all NEM2 patients ranging from 87 to 318%, with the largest effects in patients with the lowest level of nebulin. In summary, this study indicates that post-transcriptional or post-translational mechanisms regulate nebulin expression. Moreover, we propose that the pathomechanism of NEM2 involves not only shortened but also elongated thin filaments, along with the disruption of actin-binding sites resulting from pathogenic splicing variants. Significantly, our findings highlight the potential of OM treatment to improve skeletal muscle function in NEM2 patients, especially those with large reductions in nebulin levels.

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Nebulin and Lmod2 are critical for specifying thin-filament length in skeletal muscle

Cited by 29 publications

References 50 publications

The number of Z-repeats and super-repeats in nebulin greatly varies across vertebrates and scales with animal size

The number of Z-repeats and super-repeats in nebulin greatly varies across vertebrates and scales with animal size

Preclinical assessment on neuronal regeneration in the injury-related microenvironment of graphene-based scaffolds

Characterization of NEB pathogenic variants in patients reveals novel nemaline myopathy disease mechanisms and omecamtiv mecarbil force effects

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