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von Saucken VE, Windner SE, Baylies MK. Postsynaptic BMP signaling regulates myonuclear properties in Drosophila larval muscles. bioRxiv 2024:2024.04.10.588944. [PMID: 38645063 PMCID: PMC11030338 DOI: 10.1101/2024.04.10.588944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The syncytial mammalian muscle fiber contains a heterogeneous population of (myo)nuclei. At the neuromuscular junction (NMJ), myonuclei have specialized positioning and gene expression. However, it remains unclear how myonuclei are recruited and what regulates myonuclear output at the NMJ. Here, we identify specific properties of myonuclei located near the Drosophila larval NMJ. These synaptic myonuclei have increased size in relation to their surrounding cytoplasmic domain (scaling), increased DNA content (ploidy), and increased levels of transcription factor pMad, a readout for BMP signaling activity. Our genetic manipulations show local BMP signaling affects muscle size, nuclear size, ploidy, and NMJ size and function. In support, RNA sequencing analysis reveals that pMad regulates genes involved in muscle growth, ploidy (i.e., E2f1), and neurotransmission. Our data suggest that muscle BMP signaling instructs synaptic myonuclear output that then positively shapes the NMJ synapse. This study deepens our understanding of how myonuclear heterogeneity supports local signaling demands to fine tune cellular function and NMJ activity.
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Affiliation(s)
- Victoria E. von Saucken
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065 USA
- Weill Cornell-Rockefeller-Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10065 USA
- Biochemistry, Cell & Developmental Biology, and Molecular Biology (BCMB) Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065 USA
| | - Stefanie E. Windner
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065 USA
| | - Mary K. Baylies
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065 USA
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Zapater I Morales C, Carman PJ, Soffar DB, Windner SE, Dominguez R, Baylies MK. Drosophila Tropomodulin is required for multiple actin-dependent processes within developing myofibers. Development 2023; 150:dev201194. [PMID: 36806912 PMCID: PMC10112908 DOI: 10.1242/dev.201194] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 02/09/2023] [Indexed: 02/22/2023]
Abstract
Proper muscle contraction requires the assembly and maintenance of sarcomeres and myofibrils. Although the protein components of myofibrils are generally known, less is known about the mechanisms by which they individually function and together synergize for myofibril assembly and maintenance. For example, it is unclear how the disruption of actin filament (F-actin) regulatory proteins leads to the muscle weakness observed in myopathies. Here, we show that knockdown of Drosophila Tropomodulin (Tmod), results in several myopathy-related phenotypes, including reduction of muscle cell (myofiber) size, increased sarcomere length, disorganization and misorientation of myofibrils, ectopic F-actin accumulation, loss of tension-mediating proteins at the myotendinous junction, and misshaped and internalized nuclei. Our findings support and extend the tension-driven self-organizing myofibrillogenesis model. We show that, like its mammalian counterpart, Drosophila Tmod caps F-actin pointed-ends, and we propose that this activity is crucial for cellular processes in different locations within the myofiber that directly and indirectly contribute to the maintenance of muscle function. Our findings provide significant insights to the role of Tmod in muscle development, maintenance and disease.
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Affiliation(s)
- Carolina Zapater I Morales
- Biochemistry, Cell & Developmental Biology, and Molecular Biology (BCMB) program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
| | - Peter J Carman
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David B Soffar
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
| | - Stefanie E Windner
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
| | - Roberto Dominguez
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mary K Baylies
- Biochemistry, Cell & Developmental Biology, and Molecular Biology (BCMB) program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering, Cancer Center, New York, NY 10065, USA
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Balakrishnan M, Yu SF, Chin SM, Soffar DB, Windner SE, Goode BL, Baylies MK. Cofilin Loss in Drosophila Muscles Contributes to Muscle Weakness through Defective Sarcomerogenesis during Muscle Growth. Cell Rep 2021; 32:107893. [PMID: 32697999 PMCID: PMC7479987 DOI: 10.1016/j.celrep.2020.107893] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 02/23/2020] [Accepted: 06/19/2020] [Indexed: 12/20/2022] Open
Abstract
Sarcomeres, the fundamental contractile units of muscles, are conserved structures composed of actin thin filaments and myosin thick filaments. How sarcomeres are formed and maintained is not well understood. Here, we show that knockdown of Drosophila cofilin (DmCFL), an actin depolymerizing factor, disrupts both sarcomere structure and muscle function. The loss of DmCFL also results in the formation of sarcomeric protein aggregates and impairs sarcomere addition during growth. The activation of the proteasome delays muscle deterioration in our model. Furthermore, we investigate how a point mutation in CFL2 that causes nemaline myopathy (NM) in humans affects CFL function and leads to the muscle phenotypes observed in vivo. Our data provide significant insights to the role of CFLs during sarcomere formation, as well as mechanistic implications for disease progression in NM patients. How sarcomeres are added and maintained in a growing muscle cell is unclear. Balakrishnan et al. observed that DmCFL loss in growing muscles affects sarcomere size and addition through unregulated actin polymerization. This results in a collapse of sarcomere and muscle structure, formation of large protein aggregates, and muscle weakness.
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Affiliation(s)
- Mridula Balakrishnan
- Biochemistry & Structural Biology, Cell & Developmental Biology, and Molecular Biology (BCMB) Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA; Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Shannon F Yu
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Samantha M Chin
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - David B Soffar
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Stefanie E Windner
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Mary K Baylies
- Biochemistry & Structural Biology, Cell & Developmental Biology, and Molecular Biology (BCMB) Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA; Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
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Windner SE, Doris RA, Ferguson CM, Nelson AC, Valentin G, Tan H, Oates AC, Wardle FC, Devoto SH. Tbx6, Mesp-b and Ripply1 regulate the onset of skeletal myogenesis in zebrafish. Development 2015; 142:1159-68. [PMID: 25725067 PMCID: PMC4360180 DOI: 10.1242/dev.113431] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 01/27/2015] [Indexed: 12/20/2022]
Abstract
During embryonic development, the paraxial mesoderm becomes segmented into somites, within which proliferative muscle progenitors and muscle fibers establish the skeletal musculature. Here, we demonstrate that a gene network previously implicated in somite boundary formation, involving the transcriptional regulators Tbx6, Mesp-b and Ripply1, also confers spatial and temporal regulation to skeletal myogenesis in zebrafish. We show that Tbx6 directly regulates mesp-b and ripply1 expression in vivo, and that the interactions within the regulatory network are largely conserved among vertebrates. Mesp-b is necessary and sufficient for the specification of a subpopulation of muscle progenitors, the central proportion of the Pax3(+)/Pax7(+) dermomyotome. Conditional ubiquitous expression indicates that Mesp-b acts by inhibiting myogenic differentiation and by inducing the dermomyotome marker meox1. By contrast, Ripply1 induces a negative-feedback loop by promoting Tbx6 protein degradation. Persistent Tbx6 expression in Ripply1 knockdown embryos correlates with a deficit in dermomyotome and myotome marker gene expression, suggesting that Ripply1 promotes myogenesis by terminating Tbx6-dependent inhibition of myogenic maturation. Together, our data suggest that Mesp-b is an intrinsic upstream regulator of skeletal muscle progenitors and that, in zebrafish, the genes regulating somite boundary formation also regulate the development of the dermomyotome in the anterior somite compartment.
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Affiliation(s)
| | - Rosemarie A Doris
- Department of Biology, Wesleyan University, Middletown, CT 06459, USA
| | | | - Andrew C Nelson
- Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - Guillaume Valentin
- MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Haihan Tan
- Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - Andrew C Oates
- MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Fiona C Wardle
- Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - Stephen H Devoto
- Department of Biology, Wesleyan University, Middletown, CT 06459, USA
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Abstract
During myogenesis, cells gradually transition from mesodermal precursors to myoblasts, myocytes, and then to muscle fibers. The molecular characterization of this process requires the ability to identify each of these cell types and the factors that regulate the transitions between them. The most versatile technique for assaying cell identities in situ is immunocytochemistry, because multiple independent molecular markers of differentiation can be assayed simultaneously. The zebrafish has developed into a popular model for the study of myogenesis, and immunocytochemical techniques have been critical. We have adapted existing protocols to optimize immunocytochemistry in zebrafish, and have tested many antibodies developed against mouse, chick, and frog muscle antigens for their cross-reactivity in zebrafish. Here, we present protocols for whole mount immunocytochemistry on both formaldehyde and Carnoy's fixed embryos as well as on sectioned zebrafish tissue. We include a table of antibodies useful for experiments on the molecular biology of myogenesis in zebrafish.
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Affiliation(s)
- Nathan C Bird
- Department of Biology, Wesleyan University, Hall-Atwater Laboratories, Middletown, CT, USA
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Windner SE, Steinbacher P, Obermayer A, Kasiba B, Zweimueller-Mayer J, Stoiber W. Distinct modes of vertebrate hypaxial muscle formation contribute to the teleost body wall musculature. Dev Genes Evol 2011; 221:167-78. [PMID: 21720828 DOI: 10.1007/s00427-011-0369-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 06/14/2011] [Indexed: 11/28/2022]
Abstract
The formation of the body wall musculature in vertebrates is assumed to be initiated by direct ventral extension of the somites/myotomes. This contrasts to the formation of limb muscles and muscles involved in feeding or respiration/ventilation, which are founded by migratory muscle precursors (MMPs) distant to the somites. Here, we present evidence from morphology and expression of molecular markers proposing that the formation of the two muscle layers of the teleost body wall involves both of the above mechanisms: (1) MMPs from somites 5 and 6 found an independent muscle primordium-the so-called posterior hypaxial muscle (PHM)-which subsequently gives rise to the most anterior two segments of the medial obliquus inferioris (OI) muscle. (2) Direct epithelial extension of the hypaxial myotomes generates the OI segments from somite 7 caudalward and the entire lateral obliquus superioris (OS) muscle. The findings are discussed in relation to the evolution of hypaxial myogenic patterning including functional considerations. We hypothesise that the potential of the most anterior somites to generate migratory muscle precursors is a general vertebrate feature that has been differently utilised in the evolution in vertebrate groups.
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Affiliation(s)
- Stefanie E Windner
- Division of Zoology, Department of Organismic Biology, University of Salzburg, Austria
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Windner SE, Devoto SH. Myotome patterning and growth in zebrafish - The role of tbx24. Dev Biol 2010. [DOI: 10.1016/j.ydbio.2010.05.147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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