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Muscle stem cell function has been suggested to be regulated by Acetyl-CoA and NAD+ availability, but the mechanisms remain unclear. Here we report the identification of two acetylation sites on PAX7 that positively regulate its transcriptional activity. Lack of PAX7 acetylation reduces DNA binding, specifically to the homeobox motif. The acetyltransferase MYST1 stimulated by Acetyl-CoA, and the deacetylase SIRT2 stimulated by NAD +, are identified as direct regulators of PAX7 acetylation and asymmetric division in muscle stem cells. Abolishing PAX7 acetylation in mice using CRISPR/Cas9 mutagenesis leads to an expansion of the satellite stem cell pool, reduced numbers of asymmetric stem cell divisions, and increased numbers of oxidative IIA myofibers. Gene expression analysis confirms that lack of PAX7 acetylation preferentially affects the expression of target genes regulated by homeodomain binding motifs. Therefore, PAX7 acetylation status regulates muscle stem cell function and differentiation potential to facilitate metabolic adaptation of muscle tissue. The acetyltransferase MYST1 stimulated by acetyl-CoA, and the deacetylase SIRT2 stimulated by NAD+, regulate PAX7 acetylation in muscle stem cells, which in turn, regulates stem cell self-renewal and regeneration following injury in mouse skeletal muscle.

Satellite cells are required for the growth, maintenance, and regeneration of skeletal muscle. Quiescent satellite cells possess a primary cilium, a structure that regulates the processing of the GLI family of transcription factors. Here we find that GLI3 processing by the primary cilium plays a critical role for satellite cell function. GLI3 is required to maintain satellite cells in a G 0 dormant state. Strikingly, satellite cells lacking GLI3 enter the G Alert state in the absence of injury. Furthermore, GLI3 depletion stimulates expansion of the stem cell pool. As a result, satellite cells lacking GLI3 display rapid cell-cycle entry, increased proliferation and augmented self-renewal, and markedly enhanced regenerative capacity. At the molecular level, we establish that the loss of GLI3 induces mTORC1 signaling activation. Therefore, our results provide a mechanism by which GLI3 controls mTORC1 signaling, consequently regulating muscle stem cell activation and fate. Primary cilia regulate the processing of the GLI transcription factors and Hedgehog signaling. Here, the authors show that cilia-related GLI3 controls both the quiescence-to-activation transition and self-renewal in muscle stem cells.

Loss of dystrophin causes Duchenne Muscular Dystrophy (DMD), a neuromuscular disease characterized by muscle fragility and muscle stem cell (MuSC) impairment. Conventional understanding is that DMD manifests after birth from cumulative muscle damage. Here, examination of mdx mouse embryos lacking dystrophin reveals no impairment of the primary myogenic program. By contrast, histological and single cell RNA-sequencing analysis during secondary myogenesis uncovers an increase in the proportion of fetal (f) MuSCs and a marked reduction in myogenic progenitors and myocytes, leading to fewer smaller-caliber myofibers. Wild type fMuSCs express full-length dystrophin that interacts with MARK2, whereas mdx fMuSCs downregulate MARK2 and NUMB, exhibiting reduced PARD3 polarization. Strikingly, deletion of the Numb Associated Kinase, AAK1, rescues polarization of NUMB and myogenic progenitor generation in mdx fetal muscle. Together, our results elucidate an acute disease pathology during DMD fetal development and the potential for therapeutic intervention by targeting AAK1. In mdx mouse fetuses, the lack of dystrophin markedly impairs secondary myogenesis due to reduced muscle stem cell polarity. AAK1 deletion restores polarity and rescues secondary myogenesis, revealing fetal onset in Duchenne muscular dystrophy.

Regeneration requires the precise integration of cues that initiate proliferation, direct differentiation, and ultimately re-pattern tissues to the proper size and scale. Yet how these processes are integrated with wounding responses remains relatively unknown. The freshwater planarian, Schmidtea mediterranea, is an ideal model to study the stereotyped proliferative and transcriptional responses to injury due to its high capacity for regeneration. Here, we characterize the effector of the Hippo signalling cascade, yorkie, during planarian regeneration and its role in restricting early injury responses. In yki(RNAi) regenerating animals, wound responses are hyper-activated such that both stem cell proliferation and the transcriptional wound response program are heighted and prolonged. Using this observation, we also uncovered novel wound-induced genes by RNAseq that were de-repressed in yki(RNAi) animals compared with controls. Additionally, we show that yki(RNAi) animals have expanded epidermal and muscle cell populations, which we hypothesize are the increased sources of wound-induced genes. Finally, we show that in yki(RNAi) animals, the sensing of the size of an injury by eyes or the pharynx is not appropriate, and the brain, gut, and midline cannot remodel or scale correctly to the size of the regenerating fragment. Taken together, our results suggest that yki functions as a key molecule that can integrate multiple aspects of the injury response including proliferation, apoptosis, injury-induced transcription, and patterning.

Background Duchenne muscular dystrophy (DMD) is a devastating disease characterized by progressive muscle wasting that leads to diminished lifespan. In addition to the inherent weakness of dystrophin‐deficient muscle, the dysfunction of resident muscle stem cells (MuSC) significantly contributes to disease progression. Methods Using the mdx mouse model of DMD, we performed an in‐depth characterization of disease progression and MuSC function in dystrophin‐deficient skeletal muscle using immunohistology, isometric force measurements, transcriptomic analysis and transplantation assays. We examined the architectural and functional changes in mdx skeletal muscle from 13 and 52 weeks of age and following acute cardiotoxin (CTX) injury. We also studied MuSC dynamics and function under homeostatic conditions, during regeneration post‐acute injury, and following engraftment using a combination of histological and transcriptomic analyses. Results Dystrophin‐deficient skeletal muscle undergoes progressive changes with age and delayed regeneration in response to acute injury. Muscle hypertrophy, deposition of collagen and an increase in small myofibres occur with age in the tibialis anterior (TA) and diaphragm muscles in mdx mice. Dystrophic mdx mouse TA muscles become hypertrophic with age, whereas diaphragm atrophy is evident in 1‐year‐old mdx mice. Maximum tetanic force is comparable between genotypes in the TA, but maximum specific force is reduced by up to 38% between 13 and 52 weeks in the mdx mouse. Following acute injury, myofibre hyperplasia and hypotrophy and delayed recovery of maximum tetanic force occur in the mdx TA. We also find defective MuSC polarity and reduced numbers of myocytes in mdx muscle following acute injury. We observed a 50% and 30% decrease in PAX7+ and MYOG+ cells, respectively, at 5 days post CTX injury (5 dpi) in the mdx TA. A similar decrease in mdx progenitor cell proportion is observed by single cell RNA sequencing of myogenic cells at 5 dpi. The global expression of commitment‐related genes is also reduced at 5 dpi. We find a 46% reduction in polarized PARD3 in mdx MuSCs. Finally, mdx MuSCs exhibit elevated PAX7+ cell engraftment with significantly fewer donor‐derived myonuclei in regenerated myofibres. Conclusions Our study provides evidence that dystrophin deficiency in MuSCs and myofibres together contributes to progression of DMD. Ongoing muscle damage stimulates MuSC activation; however, aberrant intrinsic MuSC polarity and stem cell commitment deficits due to the loss of dystrophin impair muscle regeneration. Our study provides in vivo validation that dystrophin‐deficient MuSCs undergo fewer asymmetric cell divisions, instead favouring symmetric expansion.

Injured axons must regenerate to restore nervous system function, and regeneration is regulated in part by external factors from non-neuronal tissues. Many of these extrinsic factors act in the immediate cellular environment of the axon to promote or restrict regeneration, but the existence of long-distance signals regulating axon regeneration has not been clear. Here we show that the Rab GTPase rab-27 inhibits regeneration of GABAergic motor neurons in C . elegans through activity in the intestine. Re-expression of RAB-27, but not the closely related RAB-3, in the intestine of rab-27 mutant animals is sufficient to rescue normal regeneration. Several additional components of an intestinal neuropeptide secretion pathway also inhibit axon regeneration, including NPDC1/ cab-1 , SNAP25/ aex-4 , KPC3/ aex-5 , and the neuropeptide NLP-40, and re-expression of these genes in the intestine of mutant animals is sufficient to restore normal regeneration success. Additionally, NPDC1/ cab-1 and SNAP25/ aex-4 genetically interact with rab-27 in the context of axon regeneration inhibition. Together these data indicate that RAB-27-dependent neuropeptide secretion from the intestine inhibits axon regeneration, and point to distal tissues as potent extrinsic regulators of regeneration.

Despite an increase in treatment options, and substantial reductions in cardiovascular mortality over the past half-century, atherosclerosis remains the most prevalent cause of premature mortality worldwide. The development of innovative new therapies is crucial to further minimize atherosclerosis-related deaths. The diverse array of cell phenotypes derived from vascular smooth muscle cells (SMCs) and macrophages within atherosclerotic plaques are increasingly becoming recognized for their beneficial and detrimental roles in plaque stability and disease burden. This review explores how contemporary transcriptomics and fate-mapping studies have revealed vascular cell plasticity as a relatively unexplored target for therapeutic intervention. Recent literature for this narrative review was obtained by searching electronic databases (ie, Google Scholar, PubMed). Additional studies were sourced from reference lists and the authors’ personal databases. The lipid-rich and inflammatory plaque milieu induces SMC phenotypic switching to both beneficial and detrimental phenotypes. Likewise, macrophage heterogeneity increases with disease burden to a variety of pro-inflammatory and anti-inflammatory activation states. These vascular cell phenotypes are determinants of plaque structure stability, and it is therefore highly likely that they influence clinical outcomes. Development of clinical treatments targeting deleterious phenotypes or promoting pro-healing phenotypes remains in its infancy. However, existing treatments (statins) have shown beneficial effects toward macrophage polarization, providing a rationale for more targeted approaches. In contrast, beneficial SMC phenotypic modulation with these pharmacologic agents has yet to be achieved. The range of modulated vascular cell phenotypes provides a multitude of novel targets and the potential to reduce future adverse events. Vascular cell phenotypic heterogeneity must continue to be explored to lower cardiovascular events in the future. The rapidly increasing weight of evidence surrounding the role of SMC plasticity and macrophage polarity in plaque vulnerability provides a strong foundation upon which development of new therapeutics must follow. This approach may prove to be crucial in reducing cardiovascular events and improving patient benefit in the future.

Nearly two-thirds of cancer patients are treated with radiation therapy (RT), often with the intent to achieve complete and permanent tumor regression (local control). RT is the primary treatment modality used to achieve local control for many malignancies, including locally advanced cervical cancer, head and neck cancer, and lung cancer. The addition of concurrent platinum-based radiosensitizing chemotherapy improves local control and patient survival. Enhanced outcomes with concurrent chemoradiotherapy may result from increased direct killing of tumor cells and effects on nontumor cell populations. Many patients treated with concurrent chemoradiotherapy exhibit a decline in neutrophil count, but the effects of neutrophils on radiation therapy are controversial. To investigate the clinical significance of neutrophils in the response to RT, we examined patient outcomes and circulating neutrophil counts in cervical cancer patients treated with definitive chemoradiation. Although pretreatment neutrophil count did not correlate with outcome, lower absolute neutrophil count after starting concurrent chemoradiotherapy was associated with higher rates of local control, metastasis-free survival, and overall survival. To define the role of neutrophils in tumor response to RT, we used genetic and pharmacological approaches to deplete neutrophils in an autochthonous mouse model of soft tissue sarcoma. Neutrophil depletion prior to image-guided focal irradiation improved tumor response to RT. Our results indicate that neutrophils promote resistance to radiation therapy. The efficacy of chemoradiotherapy may depend on the impact of treatment on peripheral neutrophil count, which has the potential to serve as an inexpensive and widely available biomarker.

Background To distinguish and co-detect aneuploid CD31 − tumor cells (TCs) and CD31 + tumor endothelial cells (TECs) may have significant diagnostic values for cervical cancer screening. However, there are very few relevant studies. In the present study, a novel “immunofluorescence staining integrated with fluorescence in situ hybridization (iFISH)” tumor tissue biopsy platform was applied to comprehensively investigate the clinical utilities of aneuploid TCs and TECs in all-stage cervical lesion smear specimens. Methods A total of 196 patients were enrolled in this study. Immunofluorescence staining of p16 and Ki67 combined with FISH was applied to quantitatively co-detect and characterize subcategorized aneuploid CD31 − TCs and CD31 + TECs in cervical cytological specimens. The Kruskal‒Wallis H test was used to compare the distributions of aneuploid TCs and TECs among all stages of cervical lesions and among the different high-risk HPV types (HPV16/18 and non-HPV16/18). The diagnostic value of detecting aneuploid TCs and TECs for high-grade squamous intraepithelial lesions (HSIL + ) was investigated via receiver operating characteristic curve analysis. Results The number of total aneuploid CD31 − TCs and their p16 + and/or Ki67 + (p16/Ki67 + ) subtypes increased markedly with the severity of cervical lesions, although a similar trend was not observed for aneuploid CD31 + TECs. The increase in aneuploid TCs resulted from HPV16/18 infection was mainly concentrated in low-grade squamous intraepithelial lesion(LSIL), whereas the increase caused by non-HPV16/18 infection was mainly concentrated in HSIL. To identify HSIL + , the area under the curve (AUC) of tetraploid TCs was the largest (0.739), followed by multiploid (≥ pentaploid) TCs (0.724) and triploid TCs (0.699). For the combined subtypes, the AUC of ≥ tetraploid TCs was 0.745, and their unique diagnostic value was clinically reflected by their high specificity. Conclusion The quantity of CD31 − aneuploid TCs was associated with the severity of cervical lesions. In HPV16/18 positive patients, aneuploid CD31 − TCs were significantly increased in the LSIL. Moreover, aneuploid CD31 − TCs exhibited remarkable specificity for detecting HSIL + . Further studies are required to expand the potential clinical utility of detecting CD31 − aneuploid TCs.

Living cells employ dynamic networks for intercellular communication and cooperation, leading to tissue-wide activity. One emerging challenge in the field of bottom-up synthetic biology is emulating such sophisticated behaviors in liposome-based synthetic cells (SCs). Fabricating communication networks in lipid bilayer-based SCs remains a challenge, as signaling molecules must transit through two consecutive membranes to transfer information between different SCs. Here, we address this obstacle by engineering connexin channels that directly connect the lumens of adhering SC membranes. We focus on orthogonal channel-forming connexins, namely connexin 43 and connexin 32, and redesign their channel activity to be UV- and near IR-responsive, respectively. By combining engineered connexins into a single SC assembly, we demonstrate orthogonal transfer of reactive signaling molecules between SCs, giving rise to unique reaction products and network states in a wavelength-dependent manner – an important step toward synthetic communication networks. Replicating intercellular communication in synthetic cells is challenging. Here, the authors report on engineered connexin nanopores that can be controlled with light to exchange distinct chemical signals between synthetic cells, creating programmable communication networks that mimic cellular interactions.