Deletion of Pofut1 in Mouse Skeletal Myofibers Induces Muscle Aging-Related Phenotypes in cis and in trans

Predicting the pro-longevity or anti-longevity effect of model organism genes with enhanced Gaussian noise augmentation-based contrastive learning on protein-protein interaction networks

Ageing is a highly complex and important biological process that plays major roles in many diseases. Therefore, it is essential to better understand the molecular mechanisms of ageing-related genes. In this work, we proposed a novel enhanced Gaussian noise augmentation-based contrastive learning (EGsCL) framework to predict the pro-longevity or anti-longevity effect of four model organisms' ageing-related genes by exploiting protein-protein interaction (PPI) networks. The experimental results suggest that EGsCL successfully outperformed the conventional Gaussian noise augmentation-based contrastive learning methods and obtained state-of-the-art performance on three model organisms' predictive tasks when merely relying on PPI network data. In addition, we use EGsCL to predict 10 novel pro-/anti-longevity mouse genes and discuss the support for these predictions in the literature.

The association between sleep quality and telomere length: A systematic literature review

Several sleep parameters present an elevated risk for processes that contribute to cellular aging. Short sleep duration, sleep apnoea, and insomnia are significantly associated with shorter telomeres, a biological marker of cellular aging. However, there has been no review or analysis of studies that have examined the association between the psychological construct of sleep quality and telomere length. The present study aimed to provide a systematic review of the association between sleep quality and telomere length. A systematic review of English articles was conducted using MEDLINE/PubMed, PsycINFO, Google Scholar, and Web of Science electronic databases, with the final search conducted on 3rd September 2021. Search terms included sleep quality, poor sleep, insomnia, sleep difficulties, sleep issue*, non-restorative sleep, telomere*, cellular aging, and immune cell telomere length. Study eligibility criteria included human participants aged 18 years or older and a reproducible methodology. Study appraisal and synthesis were completed using a systematic search in line with a PICOS approach (P = Patient, problem, or population; I = Intervention, prognostic factor, exposure; C = Comparison, control, or comparator; O = Outcomes; S = Study designs). Twenty-two studies met review inclusion criteria. Qualitative synthesis of the literature indicated insufficient evidence overall to support a significant association between sleep quality and telomere length. Limitations across studies were addressed, such as the assessment of examined constructs. Findings highlight important targets for future research, including the standardised operationalisation of the sleep quality construct and experimental study designs. Research in this area has clinical significance by identifying possible mechanisms that increase the risk for age-related disease and mortality. PROSPERO Registration No.: CRD 42021233139.

Therapeutic efficacy of rscAAVrh74.miniCMV.LIPA gene therapy in a mouse model of lysosomal acid lipase deficiency

Lysosomal acid lipase deficiency (LAL-D) presents as one of two rare autosomal recessive diseases: Wolman disease (WD), a severe disorder presenting in infancy characterized by absent or very low LAL activity, and cholesteryl ester storage disease (CESD), a less severe, later onset disease form. Recent clinical studies have shown efficacy of enzyme replacement therapy for both forms of LAL-D; however, no gene therapy approach has yet been developed for clinical use. Here, we show that rscAAVrh74.miniCMV.LIPA gene therapy can significantly improve disease symptoms in the Lipa^−/− mouse model of LAL-D. Treatment dramatically lowered hepatosplenomegaly, liver and spleen triglyceride and cholesterol levels, and serum expression of markers of liver damage. Measures of liver inflammation and fibrosis were also reduced. Treatment of young adult mice was more effective than treatment of neonates, and enzyme activity was elevated in serum, consistent with possible bystander effects. These results demonstrate that adeno associated virus (AAV)-mediated LIPA gene-replacement therapy may be a viable option to treat patients with LAL-D, particularly patients with CESD.

In vivo partial reprogramming of myofibers promotes muscle regeneration by remodeling the stem cell niche

Short-term, systemic expression of the Yamanaka reprogramming factors (Oct-3/4, Sox2, Klf4 and c-Myc [OSKM]) has been shown to rejuvenate aging cells and promote tissue regeneration in vivo. However, the mechanisms by which OSKM promotes tissue regeneration are unknown. In this work, we focus on a specific tissue and demonstrate that local expression of OSKM, specifically in myofibers, induces the activation of muscle stem cells or satellite cells (SCs), which accelerates muscle regeneration in young mice. In contrast, expressing OSKM directly in SCs does not improve muscle regeneration. Mechanistically, expressing OSKM in myofibers regulates the expression of genes important for the SC microenvironment, including upregulation of p21, which in turn downregulates Wnt4. This is critical because Wnt4 is secreted by myofibers to maintain SC quiescence. Thus, short-term induction of the Yamanaka factors in myofibers may promote tissue regeneration by modifying the stem cell niche.

Short term systemic expression of the reprogramming factors Oct-3/4, Sox2, Klf4, c-Myc (OSKM) rejuvenates aging cells and promotes tissue regeneration. Here the authors show that myofiber-specific expression of OSKM accelerates muscle regeneration by reducing secretion of muscle stem cell quiescence promoting Wnt4.

Eukarion-134 Attenuates Endoplasmic Reticulum Stress-Induced Mitochondrial Dysfunction in Human Skeletal Muscle Cells

Maladaptive endoplasmic reticulum (ER) stress is associated with modified reactive oxygen species (ROS) generation and mitochondrial abnormalities; and is postulated as a potential mechanism involved in muscle weakness in myositis, an acquired autoimmune neuromuscular disease. This study investigates the impact of ROS generation in an in vitro model of ER stress in skeletal muscle, using the ER stress inducer tunicamycin (24 h) in the presence or absence of a superoxide dismutase/catalase mimetic Eukarion (EUK)-134. Tunicamycin induced maladaptive ER stress, which was mitigated by EUK-134 at the transcriptional level. ER stress promoted mitochondrial dysfunction, described by substantial loss of mitochondrial membrane potential, as well as a reduction in respiratory control ratio, reserve capacity, phosphorylating respiration, and coupling efficiency, which was ameliorated by EUK-134. Tunicamycin induced ROS-mediated biogenesis and fusion of mitochondria, which, however, had high propensity of fragmentation, accompanied by upregulated mRNA levels of fission-related markers. Increased cellular ROS generation was observed under ER stress that was prevented by EUK-134, even though no changes in mitochondrial superoxide were noticeable. These findings suggest that targeting ROS generation using EUK-134 can amend aspects of ER stress-induced changes in mitochondrial dynamics and function, and therefore, in instances of chronic ER stress, such as in myositis, quenching ROS generation may be a promising therapy for muscle weakness and dysfunction.

POFUT1 is dispensable for structure, function and survival of mouse podocytes

Pofut1 gene encodes a O-fucosyltransferase that adds fucose to the serine/threonine residue in the sequence of C²XXXX(S/T)C³ of EGF-like domain in a protein. O-fucosylation has been shown to be required for some EGF-like domain-containing proteins to function, e.g., Notch1, and POFUT1 deficiency could affect cellular function and cause diseases. Pofut1 is ubiquitously expressed, but its essentiality for most cell types is not known. In the present study, we examined the consequence of Pofut1 gene abrogation in mouse podocytes using Cre-loxP system, and found that the conditional knockout mice were indistinguishable from wild-type controls in urinary protein level, glomerular morphology, podocyte foot process ultrastructure, podocyte marker expression and podocyte numbers. These results indicated that POFUT1 is not essential for podocyte structure, function and survival in mice. To understand why POFUT1 is dispensable for podocytes, we searched mouse podocyte essential gene candidates (as determined by single-cell RNA-seq) and found only two POFUT1 substrates, NOTCH2 and tPA. It has been shown that abrogation of these genes does not cause podocyte injury, explaining dispensability of POFUT1 for mouse podocytes and demonstrating a feasibility to predict POFUT1 essentiality for a given cell type. At present, most mouse cell types have been subject to single-cell RNA-seq, making essential gene prediction and thus POFUT1 requirement prediction possible for the cell types.

LncRNA 2310043L19Rik inhibits differentiation and promotes proliferation of myoblast by sponging miR-125a-5p

Although many long non-coding RNAs (lncRNAs) have been identified in muscle, some of their physiological functions and regulatory mechanisms remain elusive. Here we report the functional identification and characterization of a novel lncRNA 2310043L19Rik (lnc-231), which is highly expressed in muscle. The expression level of lnc-231 in skeletal muscle of young mice is higher than that in aged mice. Functional analysis showed that overexpression of lnc-231 restrained differentiation and promoted proliferation of myoblast, while inhibition of lnc-231 revealed completely opposite effects in vitro. RNA molecules of lnc-231 acted mechanistically as competing endogenous RNAs (ceRNA) to target miR-125a-5p, whereas miR-125a-5p binds to the 3'-UTR of E2F3 mRNA to inhibit its function. Collectively, lncRNA 2310043L19Rik promotes proliferation and inhibits differentiation of myoblast cells by attenuating the function of miR-125a-5p.

A CTG repeat-selective chemical screen identifies microtubule inhibitors as selective modulators of toxic CUG RNA levels

A CTG repeat expansion in the DMPK gene is the causative mutation of myotonic dystrophy type 1 (DM1). Transcription of the expanded CTG repeat produces toxic gain-of-function CUG RNA, leading to disease symptoms. A screening platform that targets production or stability of the toxic CUG RNA in a selective manner has the potential to provide new biological and therapeutic insights. A DM1 HeLa cell model was generated that stably expresses a toxic r(CUG)480 and an analogous r(CUG)0 control from DMPK and was used to measure the ratio-metric level of r(CUG)480 versus r(CUG)0. This DM1 HeLa model recapitulates pathogenic hallmarks of DM1, including CUG ribonuclear foci and missplicing of pre-mRNA targets of the muscleblind (MBNL) alternative splicing factors. Repeat-selective screening using this cell line led to the unexpected identification of multiple microtubule inhibitors as hits that selectively reduce r(CUG)480 levels and partially rescue MBNL-dependent missplicing. These results were validated by using the Food and Drug Administration-approved clinical microtubule inhibitor colchicine in DM1 mouse and primary patient cell models. The mechanism of action was found to involve selective reduced transcription of the CTG expansion that we hypothesize to involve the LINC (linker of nucleoskeleton and cytoskeleton) complex. The unanticipated identification of microtubule inhibitors as selective modulators of toxic CUG RNA opens research directions for this form of muscular dystrophy and may shed light on the biology of CTG repeat expansion and inform therapeutic avenues. This approach has the potential to identify modulators of expanded repeat-containing gene expression for over 30 microsatellite expansion disorders.

Combination Treatment of Erythromycin and Furamidine Provides Additive and Synergistic Rescue of Mis-Splicing in Myotonic Dystrophy Type 1 Models

Myotonic dystrophy type 1 (DM1) is a multi-systemic disease that presents with clinical symptoms including myotonia, cardiac dysfunction and cognitive impairment. DM1 is caused by a CTG expansion in the 3' UTR of the DMPK gene. The transcribed expanded CUG repeat RNA sequester the muscleblind-like (MBNL) and up-regulate the CUG-BP Elav-like (CELF) families of RNA-binding proteins leading to global mis-regulation of RNA processing and altered gene expression. Currently, there are no disease-targeting treatments for DM1. Given the multi-step pathogenic mechanism, combination therapies targeting different aspects of the disease mechanism may be a viable therapeutic approach. Here, as proof-of-concept, we studied a combination of two previously characterized small molecules, erythromycin and furamidine, in two DM1 models. In DM1 patient-derived myotubes, rescue of mis-splicing was observed with little to no cell toxicity. In a DM1 mouse model, a combination of erythromycin and the prodrug of furamidine (pafuramidine), administered orally, displayed both additive and synergistic mis-splicing rescue. Gene expression was only modestly affected and over 40 % of the genes showing significant expression changes were rescued back toward WT expression levels. Further, the combination treatment partially rescued the myotonia phenotype in the DM1 mouse. This combination treatment showed a high degree of mis-splicing rescue coupled with low off-target gene expression changes. These results indicate that combination therapies are a promising therapeutic approach for DM1.

POFUT1 promotes colorectal cancer development through the activation of Notch1 signaling

Copy number variations (CNVs) are key drivers of colorectal cancer (CRC). Our previous studies revealed that protein O-fucosyltransferase 1 (POFUT1) overexpression is driven by CNVs during CRC development. The potential role and underlying mechanisms of POFUT1 in CRC were not investigated. In this study, we analyzed the expression of POFUT1 in CRC from cosmic and TCGA databases and confirmed that POFUT1 is highly expressed in CRC. We used well characterized CRC cell lines, including SW620 and HCT116 to establish a model POFUT1 knockdown cell line. Using these cells, we investigated the role of POFUT1 in CRC. Our data revealed that silencing POFUT1 in CRC cells inhibits cell proliferation, decreases cell invasion and migration, arrests cell cycle progression, and stimulates CRC cell apoptosis in vitro. We further demonstrate that POFUT1 silencing dramatically suppresses CRC tumor growth and transplantation in vivo. We additionally reveal new mechanistic insights into the role of POFUT1 during CRC, through demonstrating that POFUT1 silencing inhibits Notch1 signaling. Taken together, our findings demonstrate that POFUT1 is a tumor activating gene during CRC development, which positively regulates CRC tumor progression through activating Notch1.

Furamidine Rescues Myotonic Dystrophy Type I Associated Mis-Splicing through Multiple Mechanisms

Myotonic dystrophy type 1 (DM1) is an autosomal dominant, CTG•CAG microsatellite expansion disease. Expanded CUG repeat RNA sequester the muscleblind-like (MBNL) family of RNA-binding proteins, thereby disrupting their normal cellular function which leads to global mis-regulation of RNA processing. Previously, the small molecule furamidine was shown to reduce CUG foci and rescue mis-splicing in a DM1 HeLa cell model and to rescue mis-splicing in the HSA^LR DM1 mouse model, but furamidine's mechanism of action was not explored. Here we use a combination of biochemical, cell toxicity, and genomic studies in DM1 patient-derived myotubes and the HSA^LR DM1 mouse model to investigate furamidine's mechanism of action. Mis-splicing rescue was observed in DM1 myotubes and the HSA^LR DM1 mouse with furamidine treatment. Interestingly, while furamidine was found to bind CTG•CAG repeat DNA with nanomolar affinity, a reduction in expanded CUG repeat transcript levels was observed in the HSA^LR DM1 mouse but not DM1 patient-derived myotubes. Further investigation in these cells revealed that furamidine treatment at nanomolar concentrations led to up-regulation of MBNL1 and MBNL2 protein levels and a reduction of ribonuclear foci. Additionally, furamidine was shown to bind CUG RNA with nanomolar affinity and disrupted the MBNL1 -CUG RNA complex in vitro at micromolar concentrations. Furamidine's likely promiscuous interactions in vitro and in vivo appear to affect multiple pathways in the DM1 mechanism to rescue mis-splicing, yet surprisingly furamidine was shown globally to rescue many mis-splicing events with only modest off-target effects on gene expression in the HSA^LR DM1 mouse model. Importantly, over 20% of the differentially expressed genes were shown to be returned, to varying degrees, to wild-type expression levels.