Epigenetic reprogramming of muscle progenitors: inspiration for clinical therapies

In the context of regenerative medicine, based on the potential of stem cells to restore diseased tissues, epigenetics is becoming a pivotal area of interest. Therapeutic interventions that promote tissue and organ regeneration have as primary objective the selective control of gene expression in adult stem cells. This requires a deep understanding of the epigenetic mechanisms controlling transcriptional programs in tissue progenitors. This review attempts to elucidate the principle epigenetic regulations responsible of stem cells differentiation. In particular we focus on the current understanding of the epigenetic networks that regulate differentiation of muscle progenitors by the concerted action of chromatin-modifying enzymes and noncoding RNAs. The novel exciting role of exosome-bound microRNA in mediating epigenetic information transfer is also discussed. Finally we show an overview of the epigenetic strategies and therapies that aim to potentiate muscle regeneration and counteract the progression of Duchenne Muscular Dystrophy (DMD)

Complex Illocutive Units in L-AcT: An Analysis of Non-Terminal Prosodic Breaks of Bound and Multiple Comments / Unidades Ilocucionárias Complexas na L-AcT: uma análise de quebras prosódicas não-terminais em Comentários Ligados e Comentários Múltiplos

Abstract: This work presents a pilot study for a prosodic analysis of two different spoken structures in spoken Italian within the theoretical framework of the Language into Act Theory (L-AcT): (i) chains of two or more Bound Comments (COB) that do not form a compositional informative and prosodic unit; (ii) compositional Information Units formed by two or more Multiple Comments (CMM), linked together by a conventional prosodic model that implements specific meta-illocutive structures. This work analyzes COBs and CMMs from the DB-IPIC Italian Minicorpus. Different prosodic cues are taken into account: f0 reset, pauses, final lengthening, intensity lowering and initial rush. The distinctive feature for COBs is a flat trend of f0 before the boundary, with a low number of f0 reset, while CMMs vary between different f0 shapes. Vowel elongation and a no rushing speech rate cooperate in perceiving the prolongation of one COB into another. Initial rush is a characteristic feature of CMMs, while the lengthening of the last vowel of the unit is easier to find at the end of a COB than in a CMM.Keywords: prosody; spontaneous speech segmentation; non-terminal breaks; L-AcT.Resumo: Este trabalho apresenta um estudo piloto sobre uma análise prosódica de duas estruturas distintas em italiano falado, sob a perspectiva da Teoria da Língua em Ato (L-AcT): (i) cadeiras de dois ou mais Comentários Ligados (COB) que não formam uma unidade informacional e prosódica composicional; (ii) unidades informacionais composicionais formadas por dois ou mais Comentários Múltiplos (CMM), ligados entre si por um modelo prosódico convencional que implementa estruturas metailocutivas específicas. Os COBs e CMMs analisados foram extraídos do minicorpus italiano disponível no DB-IPIC. Diferentes aspectos prosódicos são levados em conta: reset de f0, pausas, alongamento final, abaixamento de intensidade e rush inicial. O traço distintivo para os COBs é uma tendência a achatamento de f0 antes da fronteira, com um baixo número de reset de f0, enquanto os CMMs variam entre diferentes formatos de f0. Alongamento de vogal e uma velocidade de fala sem rushing cooperam na percepção do prolongamento de um COB naquele que o segue. O rush inicial é um traço característico dos CMMs, enquanto o alongamento da última vogal da unidade é mais fácil de encontrar ao final de um COB do que de um CMM.Palavras-chave: prosódia; segmentação da fala espontânea; quebras não-terminais; L-Ac

HDAC4 regulates satellite cell proliferation and differentiation by targeting P21 and Sharp1 genes

Skeletal muscle exhibits a high regenerative capacity, mainly due to the ability of satellite cells to replicate and differentiate in response to appropriate stimuli. Epigenetic control is effective at different stages of this process. It has been shown that the chromatin-remodeling factor HDAC4 is able to regulate satellite cell proliferation and commitment. However, its molecular targets are still uncovered. To explain the signaling pathways regulated by HDAC4 in satellite cells, we generated tamoxifen-inducible mice with conditional inactivation of HDAC4 in Pax7(+) cells (HDAC4 KO mice). We found that the proliferation and differentiation of HDAC4 KO satellite cells were compromised, although similar amounts of satellite cells were found in mice. Moreover, we found that the inhibition of HDAC4 in satellite cells was sufficient to block the differentiation process. By RNA-sequencing analysis we identified P21 and Sharp1 as HDAC4 target genes. Reducing the expression of these target genes in HDAC4 KO satellite cells, we also defined the molecular pathways regulated by HDAC4 in the epigenetic control of satellite cell expansion and fusion

Surface-Relief Gratings in Halogen-Bonded Polymer–Azobenzene Complexes: A Concentration-Dependence Study

In recent years, supramolecular complexes comprising a poly(4-vinylpyridine) backbone and azobenzene-based halogen bond donors have emerged as a promising class of materials for the inscription of light-induced surface-relief gratings (SRGs). The studies up to date have focused on building supramolecular hierarchies, i.e., optimizing the polymer–azobenzene noncovalent interaction for efficient surface patterning. They have been conducted using systems with relatively low azobenzene content, and little is known about the concentration dependence of SRG formation in halogen-bonded polymer–azobenzene complexes. Herein, we bridge this gap, and study the concentration dependence of SRG formation using two halogen-bond-donating azobenzene derivatives, one functionalized with a tetrafluoroiodophenyl and the other with an iodoethynylphenyl group. Both have been previously identified as efficient molecules in driving the SRG formation. We cover a broad concentration range, starting from 10 mol % azobenzene content and going all the way up to equimolar degree of complexation. The complexes are studied as spin-coated thin films, and analyzed by optical microscopy, atomic force microscopy, and optical diffraction arising during the SRG formation. We obtained diffraction efficiencies as high as 35%, and modulation depths close to 400 nm, which are significantly higher than the values previously reported for halogen-bonded polymer–azobenzene complexes

Non-Natural Linker Configuration in 2,6-Dipeptidyl-Anthraquinones Enhances the Inhibition of TAR RNA Binding/Annealing Activities by HIV-1 NC and Tat Proteins

The HIV-1 nucleocapsid (NC) protein represents an excellent molecular target for the development of antiretrovirals by virtue of its well-characterized chaperone activities, which play pivotal roles in essential steps of the viral life cycle. Our ongoing search for candidates able to impair NC binding/annealing activities led to the identification of peptidylanthraquinones as a promising class of nucleic acid ligands. Seeking to elucidate the inhibition determinants and increase the potency of this class of compounds, we have now explored the effects of chirality in the linker connecting the planar nucleus to the basic side chains. We show here that the non-natural linker configuration imparted unexpected TAR RNA targeting properties to the 2,6-peptidyl-anthraquinones and significantly enhanced their potency. Even if the new compounds were able to interact directly with the NC protein, they manifested a consistently higher affinity for the TAR RNA substrate and their TARbinding properties mirrored their ability to interfere with NC-TAR interactions. Based on these findings, we propose that the viral Tat protein, sharing the same RNA substrate but acting in distinct phases of the viral life cycle, constitutes an additional druggable target for this class of peptidyl-anthraquinones. The inhibition of Tat-TAR interaction for the test compounds correlated again with their TAR-binding properties, while simultaneously failing to demonstrate any direct Tat-binding capabilities. These considerations highlighted the importance of TAR RNA in the elucidation of their inhibition mechanism, rather than direct protein inhibition. We have therefore identified anti-TAR compounds with dual in vitro inhibitory activity on different viral proteins, demonstrating that it is possible to develop multitarget compounds capable of interfering with processes mediated by the interactions of this essential RNA domain of HIV-1 genome with NC and Tat proteins

Histone deacetylases: molecular mechanisms and therapeutic implications for muscular dystrophies

Histone deacetylases (HDACs) are enzymes that regulate the deacetylation of numerous histone and non-histone proteins, thereby affecting a wide range of cellular processes. Deregulation of HDAC expression or activity is often associated with several pathologies, suggesting potential for targeting these enzymes for therapeutic purposes. For example, HDAC expression and activity are higher in dystrophic skeletal muscles. General pharmacological blockade of HDACs, by means of pan-HDAC inhibitors (HDACi), ameliorates both muscle histological abnormalities and function in preclinical studies. A phase II clinical trial of the pan-HDACi givinostat revealed partial histological improvement and functional recovery of Duchenne Muscular Dystrophy (DMD) muscles; results of an ongoing phase III clinical trial that is assessing the long-term safety and efficacy of givinostat in DMD patients are pending. Here we review the current knowledge about the HDAC functions in distinct cell types in skeletal muscle, identified by genetic and -omic approaches. We describe the signaling events that are affected by HDACs and contribute to muscular dystrophy pathogenesis by altering muscle regeneration and/or repair processes. Reviewing recent insights into HDAC cellular functions in dystrophic muscles provides new perspectives for the development of more effective therapeutic approaches based on drugs that target these critical enzymes

HDAC4 is necessary for satellite cell differentiation and muscle regeneration

In response to injury, skeletal muscle exhibits high capacity to regenerate and epigenetics controls multiple steps of this process (Giordani et al., 2013). It has been demonstrated in vitro that completion of muscle differentiation requires shuttling of histone deacetylase 4 (HDAC4), a member of class IIa HDACs, from the nucleus to the cytoplasm and consequent activation of MEF2-dependent differentiation genes (McKinsey et al., 2000). In vivo, HDAC4 expression is up-regulated in skeletal muscle upon injury, suggesting a role for this protein in muscle regeneration. With the aim to elucidate the role of HDAC4 in skeletal muscle regeneration, we generate mice lacking HDAC4 in the satellite cells (HDAC4fl/fl;Pax7CE Cre). Lack of HDAC4 inhibits satellite cell differentiation. Despite having similar amount of sorted cells, HDAC4 KO satellite cells proliferate less and have less pax7 than controls. Importantly, muscle regeneration in vivo is impaired in HDAC4fl/fl;Pax7CE Cre mice. These results are confirmed by molecular analyses of the expression of myogenic markers. All together, these data delineate the importance of HDAC4 in muscle regeneration and suggest a protective role in response to muscle damage

Anti-metastatic Properties of Naproxen-HBTA in a Murine Model of Cutaneous Melanoma

The beneficial effects of H2S-release and of COXs-inhibition have been exploited in the design of novel anti-inflammatory drugs, the H2S-releasing non-steroidal anti-inflammatory drugs (H2S-NSAIDs), showing promising potential for chemoprevention in cancers. Here, we evaluated the efficacy of a new H2S-releasing derivative of naproxen, named naproxen-4-hydroxybenzodithioate (naproxen-HBTA), in reducing metastatic melanoma features, both in vitro and in vivo. The novel H2S donor has been prepared following a synthetic scheme that provided high yields and purity. In particular, we investigated the effect of naproxen-HBTA in vitro on several metastatic features of human melanoma cells such as proliferation, migration, invasion, and colonies formation and in vivo in a model of cutaneous melanoma. Cell culture studies demonstrated that naproxen-HBTA induced caspase 3-mediated apoptosis and inhibited motility, invasiveness, and focus formation. Finally, daily oral treatment with naproxen-HBTA significantly suppressed melanoma growth and progression in mice. In conclusion, by using this dual approach we propose that the COX-2 and H2S pathways could be regarded as novel therapeutic targets/tools to generate new treatment options based on “combination therapy” for melanoma