Biology subjects

Malerba, A.

Publications and source records attributed to Malerba, A..

6 recordsLinked to original sources

bioRxiv2026

Chromatin topology control by a muscle-specific ribosomal protein

Three-dimensional genome organization stabilizes cell-type-specific gene expression, yet the tissue-restricted factors that maintain chromatin insulation remain poorly understood. Here, we identify the muscle-specific ribosomal protein Rpl3l as an unexpected nuclear regulator of genome architecture in atrial cardiomyocytes. Rpl3l is enriched in the nucleus and nucleolus, where it binds its own genomic locus and stabilizes a CTCF-anchored chromatin boundary that represses the T-type calcium channel gene Cacna1h. Loss of Rpl3l weakens local chromatin insulation, increases long-range contacts across the Rpl3l-Cacna1h locus, derepresses Cacna1h, and increases susceptibility to atrial fibrillation (AF), which is suppressed by pharmacological inhibition of T-type calcium channels. Furthermore, AF-associated RPL3L variants exhibit impaired nucleolar localization, reduced rRNA binding, and defective repression of CACNA1H in human iPSC-derived atrial cardiomyocytes. Together, these findings reveal a ribosomal protein-chromatin axis linking genome insulation to ion-channel dosage control and cardiac rhythm stability, expanding the repertoire of cell-type-specific genome architecture regulators. HighlightsThe muscle-specific ribosomal protein Rpl3l exhibits unexpected nuclear and nucleolar enrichment. Rpl3l stabilizes a CTCF-anchored chromatin boundary to maintain atrial-specific local genome insulation. Loss of Rpl3l derepresses Cacna1h which encodes a T-type Ca2+ channel and increases atrial fibrillation susceptibility. Atrial fibrillation-associated RPL3L variants impair nucleolar targeting and CACNA1H repression

physiology↗

bioRxiv2025

Periostin exon 17 skipping enhances the efficacy of local AAV-microdystrophin administration in a fibrotic model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a severe, progressive genetic disorder primarily affecting boys, characterized by muscle degeneration due to mutations in the DMD gene encoding dystrophin, a crucial protein for muscle fiber integrity. The disease leads to significant muscle weakness and eventually to loss of ambulation. AAV-microdystrophin gene therapy shows promise in preclinical and clinical settings. However, muscle fibrosis, a consequence of chronic inflammation and extracellular matrix (ECM) remodeling, exacerbates disease progression and may hinder therapeutic efficacy. Periostin, a matricellular protein involved in fibrosis, is upregulated in DMD rodent models and correlates with collagen deposition. We previously developed an antisense oligonucleotide strategy to induce exon 17 skipping and so reduce periostin expression and collagen accumulation in the fibrotic D2.mdx mouse model of DMD. Here, we investigated the combined effects of periostin modulation and AAV-microdystrophin (AAV-MD1) treatment. We found that systemic periostin splicing modulation with intramuscular AAV-MD1 administration significantly improved muscle function, assessed by grip strength and treadmill performance, compared to either single treatment. Importantly, periostin exon skipping increases the microdystrophin protein expression. These findings suggest that targeting periostin in conjunction with microdystrophin therapy could represent a valid therapeutic strategy for DMD.

pathology↗

bioRxiv2024

Understanding the structure and mechanics of the sheep calcaneal enthesis: a relevant animal model for tissue engineering applications

Tendon/enthesis injuries are a worldwide clinical problem. Along the enthesis, collagen fibrils show a progressive loss of anisotropy and an increase in mineralization reaching the bone. This causes gradients of mechanical properties. The design of scaffolds to regenerate these load-bearing tissues requires of being validated in vivo in relevant large animal models. The sheep tendon of triceps surae muscle is an optimal animal model for this scope with limited knowledge about its structure and mechanics. We decided to understand in-depth its structure and full-field mechanics. Collagen fibrils morphology was investigated via scanning electron microscopy revealing a marked change in orientation/dimensions passing from tendon to enthesis. Backscatter electron images and nanoindentation at the enthesis/bone marked small gradients of mineralization at the mineralized fibrocartilage reaching 27%wt and indentation modulus around 17-30 GPa. The trabecular bone instead had indentation modulus around 15-22 GPa. Mechanical tensile tests with digital image correlation confirmed the typical non-linear behavior of tendons (failure strain = 8.2{+/-}1.0%; failure force = 1369{+/-}187 N) with maximum principal strains reaching mean values of {varepsilon}p1[~]7%. The typical auxetic behavior of tendon was highlighted by the minimum principal strains ({varepsilon}p2[~]5%), progressively dampened at the enthesis. Histology revealed that this behavior was caused by a local thickening of the epitenon. Cyclic tests showed a force loss of 21{+/-}7 % at the last cycle. These findings will be fundamental for biofabrication and clinicians interested in designing the new generation of scaffolds for enthesis regeneration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/630234v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@143f0a8org.highwire.dtl.DTLVardef@16cb394org.highwire.dtl.DTLVardef@181be61org.highwire.dtl.DTLVardef@f9f2d9_HPS_FORMAT_FIGEXP M_FIG C_FIG Statement of SignificanceTendon and enthesis lesions are a clinical problem. To validate scaffolds for these applications large animal models are needed. Sheep tendon of triceps surae muscle is an optimal site for this scope. However, little is known about its extracellular matrix structure and mechanical properties. This work investigates the structure and mechanics of this tissue from different points of view. Scanning electron microscopy and histology studied its extracellular matrix morphology and composition. Backscattered electron images and nanoindentation assessed gradients of mineralization and stiffness at the enthesis. Mechanical tensile and cyclic tests coupled with digital image correlation elucidated its mechanics and superficial strain distribution. These findings will be fundamental for biofabrication and clinician experts to design innovative scaffolds to regenerate the enthesis.

bioengineering↗

bioRxiv2024

Different outcomes of endurance and resistance exercise in skeletal muscles of Oculopharyngeal muscular dystrophy.

BackgroundExercise is widely considered to have beneficial impact on skeletal muscle aging. In addition, there are also several studies demonstrating a positive effect of exercise on muscular dystrophies. Oculopharyngeal muscular dystrophy (OPMD) is a late-onset autosomal dominant inherited neuromuscular disorder caused by mutations in the PAPBN1 gene. These mutations consist in short (1-8) and meiotically stable GCN trinucleotide repeat expansions in its coding region responsible for the formation of PAPBN1 intranuclear aggregates. This study aims to characterize the effects of two types of chronic exercise, resistance and endurance, on the OPMD skeletal muscle phenotype using a relevant murine model of OPMD. MethodsIn this study, we tested two protocols of exercise. In the first, based on endurance exercise, FvB (wild-type) and A17 (OPMD) mice underwent a 6-week-long motorized treadmill protocol consisting in 3 sessions per week of running 20cm/s for 20 minutes. In the second protocol, based on resistance exercise generated by chronic mechanical overload (OVL), surgical removal of gastrocnemius and soleus muscles was performed, inducing hypertrophy of the plantaris muscle. In both types of exercise, muscles of A17 and FvB mice were compared to those of respective sedentary mice. For all the groups, force measurement, muscle histology and molecular analyses were conducted. ResultsFollowing the endurance exercise protocol, we did not observe any major changes in the muscle physiological parameters, but an increase in the number of PABPN1 intranuclear aggregates and enhanced collagen deposition in the exercised A17 OPMD mice. In the resistance overload protocol, we also observed an increased collagen deposition in the A17 OPMD mice which was associated with larger muscle mass and fiber cross sectional area and increased absolute maximal force as well as a reduction in PABPN1 aggregate number. ConclusionsRunning exercise and mechanical overload led to very different outcome in skeletal muscles of A17 mice. Both types of exercise enhanced collagen deposition but while the running protocol increased aggregates, the OVL reduced them. More importantly OVL reversed muscle atrophy and maximal force in the A17 mice. Our study performed in a relevant model gives an indication of the effect of different types of exercise on OPMD muscle which should be further evaluated in humans for future recommendations as a part of the lifestyle of individuals with OPMD.

pathology↗

bioRxiv2021

Systemic antisense therapeutics inhibiting DUX4 expression improves muscle function in an FSHD mouse model

Aberrant expression of the double homeobox 4 (DUX4) gene in skeletal muscle causes muscle deterioration and weakness in Facioscapulohumeral Muscular Dystrophy (FSHD). Since the presence of a permissive pLAM1 polyadenylation signal is essential for stabilization of DUX4 mRNA and translation of DUX4 protein, disrupting the function of this structure can prevent expression of DUX4. We and others have shown promising results using antisense approaches to reduce DUX4 expression in vitro and in vivo following local intramuscular administration. Our group has developed further the antisense chemistries, and demonstrate here enhanced in vitro antisense efficacy. The optimal chemistry was conjugated to a cell-penetrating moiety, and for the first time in FSHD research has been systemically administered into a double-transgenic mouse model of FSHD. After four weekly treatments, mRNA quantities of DUX4 and target genes were reduced by 50% that led to a 5% increase in muscle mass, a 52% improvement in in situ muscle strength, and reduction of muscle fibrosis by 17%. Systemic DUX4 inhibition also improved the locomotor activity significantly and reduced the fatigue level by 22%. Our data overall demonstrate that the optimized antisense approach can contribute to future development of a therapeutic strategy for FSHD.

molecular biology↗

bioRxiv2018

Guanabenz treatment improves Oculopharyngeal muscular dystrophy phenotype

Oculopharyngeal muscular dystrophy (OPMD) is a rare late onset genetic disease affecting most profoundly eyelid and pharyngeal muscles, leading respectively to ptosis and dysphagia, and proximal limb muscles at later stages. A short abnormal (GCG) triplet expansion in the polyA- binding protein nuclear 1 (PABPN1) gene leads to PABPN1-containing aggregates in the muscles of OPMD patients. It is commonly accepted that aggregates themselves, the aggregation process and/or the early oligomeric species of PABPN1 are toxic in OPMD. Decreasing PABPN1 aggregate load in animal models of OPMD ameliorates the muscle phenotype. In order to identify a potential therapeutic molecule that would prevent and reduce aggregates, we tested guanabenz acetate (GA), an FDA-approved antihypertensive drug, in OPMD cells as well as in the A17 OPMD mouse model. We demonstrate that treating mice with GA reduces the size and number of nuclear aggregates, improves muscle force, protects myofibres from the pathology-derived turnover and decreases fibrosis. GA is known to target various cell processes, including the unfolded protein response (UPR), which acts to attenuate endoplasmic reticulum (ER) stress. Here we used a cellular model of OPMD to demonstrate that GA increases both the phosphorylation of the eukaryotic translation initiator factor 2 subunit (eIF2) and the splicing of Xbp1, key components of the UPR. Altogether these data suggest that modulation of protein folding regulation can be beneficial for OPMD and support the further development of guanabenz or its derivatives for treatment of OPMD in humans.\n\nSignificance StatementOculopharyngeal muscular dystrophy (OPMD) is a rare late onset incurable genetic disease characterized by the formation of insoluble aggregates in skeletal muscles. It has been shown that the reduction of aggregates correlates with an improvement of the disease. Here we used a mouse model of OPMD to show that Guanabenz acetate, the active constituent of a marketed but recently discontinued drug for hypertension, decreases the number and the size of aggregates after systemic delivery and improves many aspects of the disease. We also describe experimental evidences explaining the mechanism behind the efficacy of such compound for OPMD.

pathology↗