Falzarano, M. S. | Search bioRxiv

bioRxiv2024

Modulation of the JAK2-STAT3 pathway promotes expansion and maturation of human iPSCs-derived myogenic progenitor cells

Generation of in vitro induced pluripotent cells (hiPSCs)-derived skeletal muscle progenitor cells (SMPCs) holds great promise for regenerative medicine for skeletal muscle wasting diseases, as for example Duchenne Muscular Dystrophy (DMD). Multiple approaches, involving ectopic expression of key regulatory myogenic genes or small molecules cocktails, have been described by different groups to obtain SMPC towards cell-transplantation in vivo as a therapeutic approach to skeletal muscle diseases. However, hiPSCs-derived SMPC generated using transgene-free protocols are usually obtained in a low amount and resemble a more embryonal/fetal stage of differentiation. Here we demonstrate that modulation of the JAK2/STAT3 signaling pathway during an in vitro skeletal muscle differentiation protocol, increases the yield of PAX7+ and CD54+ SMPCs and drive them to a post- natal maturation stage, in both human ES and patient-derived iPSCs. Importantly, upon removal of the inhibition from the cultures, the obtained SMPCs are able to differentiate into multinucleated myotubes in vitro. These findings reveal that modulation of the JAK2/STAT3 signaling pathway is a potential therapeutic avenue to generate SMPCs in vitro with increase potential for cell-therapy approaches.

cell biology↗

bioRxiv2021

Dystrophin regulates peripheral circadian SRF signalling

Dystrophin is a sarcolemmal protein essential for muscle contraction and maintenance, absence of which leads to the devastating muscle wasting disease Duchenne muscular dystrophy (DMD)[1, 2]. Dystrophin has an actin-binding domain [3-5], which specifically binds and stabilises filamentous (F)-actin[6], an integral component of the RhoA-actin-serum response factor (SRF)-pathway[7]. The RhoA-actin-SRF-pathway plays an essential role in circadian signalling whereby the hypothalamic suprachiasmatic nucleus, transmits systemic cues to peripheral tissues, activating SRF and transcription of clock target genes[8, 9]. Given dystrophin binds F-actin and disturbed SRF-signalling disrupts clock entrainment, we hypothesised that dystrophin loss causes circadian deficits. Here we show for the first time alterations in the RhoA-actin-SRF-signalling-pathway, in both dystrophin-deficient myotubes and dystrophic mouse models. Specifically, we demonstrate reduced F/G-actin ratios and nuclear MRTF, dysregulation of core clock and downstream target-genes, and down-regulation of key circadian genes in muscle biopsies from DMD patients harbouring an array of mutations. Further, disrupted circadian locomotor behaviour was observed in dystrophic mice indicative of disrupted SCN signalling, and indeed dystrophin protein was absent in the SCN of dystrophic animals. Dystrophin is thus a critically important component of the RhoA-actin-SRF-pathway and a novel mediator of circadian signalling in peripheral tissues, loss of which leads to circadian dysregulation.

cell biology↗