@misc{SchurigUmehHenzeetal., author = {Schurig, Mona and Umeh, Obinna and Henze, Henriette and Jung, Marie Juliane and Gresing, Lennart and Blanchard, Veronique and Maltzahn, Julia von and H{\"u}bner, Christian and Franzka, Patricia}, title = {Consequences of GMPPB deficiency for neuromuscular development and maintenance}, series = {Frontiers in Molecular Neuroscience}, volume = {17}, journal = {Frontiers in Molecular Neuroscience}, issn = {1662-5099}, doi = {10.3389/fnmol.2024.1356326}, abstract = {Guanosine diphosphate-mannose pyrophosphorylase B (GMPPB) catalyzes the conversion of mannose-1-phosphate and GTP to GDP-mannose, which is required as a mannose donor for the biosynthesis of glycan structures necessary for proper cellular functions. Mutations in GMPPB have been associated with variable neuromuscular disorders such as muscular dystrophy and myasthenic syndromes. Here, we report that GMPPB protein abundance increases during brain and skeletal muscle development, which is accompanied by an increase in overall protein mannosylation. To model the human disorder in mice, we generated heterozygous GMPPB KO mice using CRISPR/Cas9. While we were able to obtain homozygous KO mice from heterozygous matings at the blastocyst stage, homozygous KO embryos were absent beyond embryonic day E8.5, suggesting that the homozygous loss of GMPPB results in early embryonic lethality. Since patients with GMPPB loss-of-function manifest with neuromuscular disorders, we investigated the role of GMPPB in vitro. Thereby, we found that the siRNA-mediated knockdown of Gmppb in either primary myoblasts or the myoblast cell line C2C12 impaired myoblast differentiation and resulted in myotube degeneration. siRNA-mediated knockdown of Gmppb also impaired the neuron-like differentiation of N2A cells. Taken together, our data highlight the essential role of GMPPB during development and differentiation, especially in myogenic and neuronal cell types.}, language = {en} } @misc{HuettnerHenzeElsteretal., author = {H{\"u}ttner, S{\"o}ren and Henze, Henriette and Elster, Dana and Koch, Philipp and Anderer, Ursula and Eyss, Bj{\"o}rn von and Maltzahn, Julia von}, title = {A dysfunctional miR-1-TRPS1-MYOG axis drives ERMS by suppressing terminal myogenic differentiation}, series = {Molecular Therapy}, volume = {31}, journal = {Molecular Therapy}, number = {9}, issn = {1525-0024}, doi = {10.1016/j.ymthe.2023.07.003}, pages = {2612 -- 2632}, abstract = {Rhabdomyosarcoma is the most common pediatric soft tissue tumor, comprising two major subtypes: the PAX3/7-FOXO1 fusion-negative embryonal and the PAX3/7-FOXO1 fusion-positive alveolar subtype. Here, we demonstrate that the expression levels of the transcriptional repressor TRPS1 are specifically enhanced in the embryonal subtype, resulting in impaired terminal myogenic differentiation and tumor growth. During normal myogenesis, expression levels of TRPS1 have to decrease to allow myogenic progression, as demonstrated by overexpression of TRPS1 in myoblasts impairing myotube formation. Consequentially, myogenic differentiation in embryonal rhabdomyosarcoma in vitro as well as in vivo can be achieved by reducing TRPS1 levels. Furthermore, we show that TRPS1 levels in RD cells, the bona fide model cell line for embryonal rhabdomyosarcoma, are regulated by miR-1 and that TRPS1 and MYOD1 share common genomic binding sites. The myogenin (MYOG) promoter is one of the critical targets of TRPS1 and MYOD1; we demonstrate that TRPS1 restricts MYOG expression and thereby inhibits terminal myogenic differentiation. Therefore, reduction of TRPS1 levels in embryonal rhabdomyosarcoma might be a therapeutic approach to drive embryonal rhabdomyosarcoma cells into myogenic differentiation, thereby generating postmitotic myotubes.}, language = {en} } @misc{HenzeHuettnerKochetal., author = {Henze, Henriette and H{\"u}ttner, S{\"o}ren S. and Koch, Philipp and Sch{\"u}ler, Svenja C. and Groth, Marco and von Eyss, Bj{\"o}rn and von Maltzahn, Julia}, title = {Denervation alters the secretome of myofibers and thereby affects muscle stem cell lineage progression and functionality}, series = {npj regenerative medicine}, volume = {9}, journal = {npj regenerative medicine}, number = {1}, publisher = {Nature Publishing Group UK}, address = {London}, issn = {2057-3995}, doi = {10.1038/s41536-024-00353-3}, pages = {1 -- 14}, abstract = {Skeletal muscle function crucially depends on innervation while repair of skeletal muscle relies on resident muscle stem cells (MuSCs). However, it is poorly understood how innervation affects MuSC properties and thereby regeneration of skeletal muscle. Here, we report that loss of innervation causes precocious activation of MuSCs concomitant with the expression of markers of myogenic differentiation. This aberrant activation of MuSCs after loss of innervation is accompanied by profound alterations on the mRNA and protein level. Combination of muscle injury with loss of innervation results in impaired regeneration of skeletal muscle including shifts in myogenic populations concomitant with delayed maturation of regenerating myofibers. We further demonstrate that loss of innervation leads to alterations in myofibers and their secretome, which then affect MuSC behavior. In particular, we identify an increased secretion of Osteopontin and transforming growth factor beta 1 (Tgfb1) by myofibers isolated from mice which had undergone sciatic nerve transection. The altered secretome results in the upregulation of early activating transcription factors, such as Junb , and their target genes in MuSCs. However, the combination of different secreted factors from myofibers after loss of innervation is required to cause the alterations observed in MuSCs after loss of innervation. These data demonstrate that loss of innervation first affects myofibers causing alterations in their secretome which then affect MuSCs underscoring the importance of proper innervation for MuSC functionality and regeneration of skeletal muscle.}, language = {en} }