Biology subjects

Petrany, M.

Publications and source records attributed to Petrany, M..

5 recordsLinked to original sources

bioRxiv2024

The multimodal transcriptional response of denervated skeletal muscle involves alterations in cholesterol homeostasis impacting muscle size

The development and maintenance of the neuromuscular junction (NMJ) requires reciprocal signals between the nerve terminals and the multinucleated skeletal muscle fiber (myofiber). This interaction leads to highly specialized transcription in the sub-synaptic or NMJ myonuclei within mature myofibers leading to clustering of acetylcholine receptors (AChRs). Here, we utilized single-nucleus RNA sequencing (snRNA-seq) to delineate the transcriptional response of myonuclei to denervation. Through snRNA-seq on skeletal muscle from two independent mouse models of denervation, sciatic nerve transection and amyotrophic lateral sclerosis, we identify a multimodal transcriptional response of NMJ-enriched genes and an alteration in cholesterol homeostasis in both slow and fast myofibers. Gramd1, a family of genes involved in non-vesicular cholesterol transport, are enriched at the NMJ in innervated muscle and upregulated in both models of denervation by the NMJ and extrasynaptic myonuclei. In vivo gain and loss of function studies indicate that NMJ-enriched Gramd1 genes regulate myofiber sizes independent of an obvious impact on AChR clustering. We uncovered a dynamic transcriptional response of myonuclei to denervation and highlight a critical role for cholesterol transport to maintain myofiber sizes.

cell biology↗

bioRxiv2023

Lineage tracing of newly accrued nuclei in skeletal myofibers uncovers distinct transcripts and interplay between nuclear populations

Multinucleated skeletal muscle cells have an obligatory need to acquire additional nuclei through fusion with activated skeletal muscle stem cells when responding to both developmental and adaptive growth stimuli. A fundamental question in skeletal muscle biology has been the reason underlying this need for new nuclei in syncytial cells that already harbor hundreds of nuclei. To begin to answer this long-standing question, we utilized nuclear RNA-sequencing approaches and developed a lineage tracing strategy capable of defining the transcriptional state of recently fused nuclei and distinguishing this state from that of pre-existing nuclei. Our findings reveal the presence of conserved markers of newly fused nuclei both during development and after a hypertrophic stimulus in the adult. However, newly fused nuclei also exhibit divergent gene expression that is determined by the myogenic environment to which they fuse. Moreover, accrual of new nuclei through fusion is required for nuclei already resident in adult myofibers to mount a normal transcriptional response to a load-inducing stimulus. We propose a model of mutual regulation in the control of skeletal muscle development and adaptations, where newly fused and pre-existing myonuclear populations influence each other to maintain optimal functional growth.

cell biology↗

bioRxiv2023

Enveloped viruses pseudotyped with mammalian myogenic cell fusogens target skeletal muscle for gene delivery

Entry of enveloped viruses into cells is mediated by fusogenic proteins that form a complex between membranes to drive rearrangements needed for fusion. Skeletal muscle development also requires membrane fusion events between progenitor cells to form multinucleated myofibers. Myomaker and Myomerger are muscle-specific cell fusogens, but do not structurally or functionally resemble classical viral fusogens. We asked if the muscle fusogens could functionally substitute for viral fusogens, despite their structural distinctiveness, and fuse viruses to cells. We report that engineering of Myomaker and Myomerger on the membrane of enveloped viruses leads to specific transduction of skeletal muscle. We also demonstrate that locally and systemically injected virions pseudotyped with the muscle fusogens can deliver micro-Dystrophin (Dys) to skeletal muscle of a mouse model of Duchenne muscular dystrophy. Through harnessing the intrinsic properties of myogenic membranes, we establish a platform for delivery of therapeutic material to skeletal muscle.

cell biology↗

bioRxiv2020

Single-nucleus RNA-seq identifies transcriptional heterogeneity in multinucleated skeletal myofibers

While the majority of cells contain a single nucleus, cell types such as trophoblasts, osteoclasts, and skeletal myofibers require multinucleation. One advantage of multinucleation can be the assignment of distinct functions to different nuclei, but comprehensive interrogation of transcriptional heterogeneity within multinucleated tissues has been challenging due to the presence of a shared cytoplasm. Here, we utilized single-nucleus RNA-sequencing (snRNA-seq) to determine the extent of transcriptional diversity within multinucleated skeletal myofibers. Nuclei from mouse skeletal muscle were profiled across the lifespan, which revealed the emergence of distinct myonuclear populations in postnatal development and their reactivation in aging muscle. Our datasets also provided a platform for discovery of novel genes associated with rare specialized regions of the muscle cell, including markers of the myotendinous junction and functionally validated factors expressed at the neuromuscular junction. These findings reveal that myonuclei within syncytial muscle fibers possess distinct transcriptional profiles that regulate muscle biology.

cell biology↗

bioRxiv2017

Myomerger Induces Fusion Of Non-Fusogenic Cells And Is Required For Myoblast Fusion

Despite the importance of cell fusion for mammalian development and physiology, the factors critical for this process remain to be fully defined1. This lack of knowledge has severely limited our ability to reconstitute cell fusion, which is necessary to decipher the biochemical mechanisms driving plasma membrane merger. Myomaker (Tmem8c) is a muscle-specific protein required for myoblast fusion2,3. Expression of myomaker in fibroblasts drives their fusion with myoblasts, but not with other myomaker-fibroblasts, highlighting the requirement of additional myoblast-derived factors for fusion. Here, we demonstrate that Gm7325, named myomerger, induces the fusion of myomaker-expressing fibroblasts. Cell mixing experiments reveal that while myomaker renders cells fusion-competent, myomerger induces fusogenicity. Thus, myomaker and myomerger confer fusogenic activity to normally non-fusogenic cells. Myomerger is skeletal muscle-specific and only expressed during developmental and regenerative myogenesis. Disruption of myomerger in myoblast cell lines through Cas9-mutagenesis generated non-fusogenic myocytes. Genetic deletion of myomerger in mice results in a paucity of muscle fibers demonstrating a requirement for myomerger in normal muscle formation. Myomerger deficient myocytes exhibit an ability to differentiate and harbor organized sarcomeres, however remain mono-nucleated. These data identify myomerger as a fundamental myoblast fusion protein and establishes a system that begins to reconstitute mammalian cell fusion.

developmental biology↗