Histone deacetylase inhibitor trichostatin A enhances myogenesis by coordinating muscle regulatory factors and myogenic repressors
Histone deacetylase inhibitors (HDACIs) are known to promote skeletal muscle formation. However, their mechanisms that include effects on the expression of major muscle components such as the dystrophin-associated proteins complex (DAPC) or myogenic regulatory factors (MRFs) remain unknown. In this study, we investigated the effects of HDACIs on skeletal muscle formation using the C2C12 cell culture system. C2C12 myoblasts were exposed to trichostatin A (TSA), one of the most potent HDACIs, and differentiation was subsequently induced. We found that TSA enhances the expression of myosin heavy chain without affecting DAPC expression. In addition, TSA increases the expression of the early MRFs, Myf5 and MEF2, whereas it suppresses the expression of the late MRF, myogenin. Interestingly, TSA also enhances the expression of Id1, Id2, and Id3 (Ids). Ids are myogenic repressors that inhibit myogenic differentiation. These findings suggest that TSA promotes gene expression in proliferation and suppresses it in the differentiation stage of muscle formation. Taken together, our data demonstrate that TSA enhances myogenesis by coordinating the expression of MRFs and myogenic repressors.
Available from: Lena Smirnova
- "These results further support the findings on the miRNA level. It was previously shown that HDAC inhibitors, including VPA, enhance differentiation of myoblasts by regulation of MRFs , . This, together with the observation that ectopic expression of myogenic factors (such as Pax3, MoyD, Myf5 and myogenin) in neural tubes of chicken embryos activates muscle-specific gene expression and myogenesis in neural tissue  might explain the upregulation of myo-mirs and MRFs in our system and, as consequence, an activation of myogenesis by VPA during neural differentiation of mESCs. "
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ABSTRACT: Studying chemical disturbances during neural differentiation of murine embryonic stem cells (mESCs) has been established as an alternative in vitro testing approach for the identification of developmental neurotoxicants. miRNAs represent a class of small non-coding RNA molecules involved in the regulation of neural development and ESC differentiation and specification. Thus, neural differentiation of mESCs in vitro allows investigating the role of miRNAs in chemical-mediated developmental toxicity. We analyzed changes in miRNome and transcriptome during neural differentiation of mESCs exposed to the developmental neurotoxicant sodium valproate (VPA). A total of 110 miRNAs and 377 mRNAs were identified differently expressed in neurally differentiating mESCs upon VPA treatment. Based on miRNA profiling we observed that VPA shifts the lineage specification from neural to myogenic differentiation (upregulation of muscle-abundant miRNAs, mir-206, mir-133a and mir-10a, and downregulation of neural-specific mir-124a, mir-128 and mir-137). These findings were confirmed on the mRNA level and via immunochemistry. Particularly, the expression of myogenic regulatory factors (MRFs) as well as muscle-specific genes (Actc1, calponin, myosin light chain, asporin, decorin) were found elevated, while genes involved in neurogenesis (e.g. Otx1, 2, and Zic3, 4, 5) were repressed. These results were specific for valproate treatment and-based on the following two observations-most likely due to the inhibition of histone deacetylase (HDAC) activity: (i) we did not observe any induction of muscle-specific miRNAs in neurally differentiating mESCs exposed to the unrelated developmental neurotoxicant sodium arsenite; and (ii) the expression of muscle-abundant mir-206 and mir-10a was similarly increased in cells exposed to the structurally different HDAC inhibitor trichostatin A (TSA). Based on our results we conclude that miRNA expression profiling is a suitable molecular endpoint for developmental neurotoxicity. The observed lineage shift into myogenesis, where miRNAs may play an important role, could be one of the developmental neurotoxic mechanisms of VPA.
Available from: Marco Deguise
- "Interestingly, TSA treatment is also beneficial in the Smn2B/− mouse model that does not harbor the SMN2 transgene; however in this case there was no detectable increase in Smn. Furthermore, other studies have demonstrated that TSA treatment of C2C12 cells increased myoblast fusion, and that TSA can increase the expression of early myogenic regulatory factors (18,19). We therefore investigated whether TSA could increase myofiber size and ameliorate muscle maturity in Smn2B/− mice. "
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ABSTRACT: Mutations in the survival motor neuron (SMN1) gene lead to the neuromuscular disease spinal muscular atrophy (SMA). Although SMA is primarily considered as a motor neuron
disease, the importance of muscle defects in its pathogenesis has not been fully examined. We use both primary cell culture
and two different SMA model mice to demonstrate that reduced levels of Smn lead to a profound disruption in the expression
of myogenic genes. This disruption was associated with a decrease in myofiber size and an increase in immature myofibers,
suggesting that Smn is crucial for myogenic gene regulation and early muscle development. Histone deacetylase inhibitor trichostatin
A treatment of SMA model mice increased myofiber size, myofiber maturity and attenuated the disruption of the myogenic program
in these mice. Taken together, our work highlights the important contribution of myogenic program dysregulation to the muscle
weakness observed in SMA.
Available from: Alexandra C Senegaglia
- "We observed that desmin was increased in BM-MSCs and decreased in ADSCs after TSA
treatment. As TSA enhances myogenesis in C2C12 cells (26), we suppose that myogenesis could be favored in BM-MSCs
instead of adipogenesis. "
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ABSTRACT: Epigenetic mechanisms such as DNA methylation and histone modification are important in stem cell differentiation. Methylation is principally associated with transcriptional repression, and histone acetylation is correlated with an active chromatin state. We determined the effects of these epigenetic mechanisms on adipocyte differentiation in mesenchymal stem cells (MSCs) derived from bone marrow (BM-MSCs) and adipose tissue (ADSCs) using the chromatin-modifying agents trichostatin A (TSA), a histone deacetylase inhibitor, and 5-aza-2'-deoxycytidine (5azadC), a demethylating agent. Subconfluent MSC cultures were treated with 5, 50, or 500 nM TSA or with 1, 10, or 100 µM 5azadC for 2 days before the initiation of adipogenesis. The differentiation was quantified and expression of the adipocyte genes PPARG and FABP4 and of the anti-adipocyte gene GATA2 was evaluated. TSA decreased adipogenesis, except in BM-MSCs treated with 5 nM TSA. Only treatment with 500 nM TSA decreased cell proliferation. 5azadC treatment decreased proliferation and adipocyte differentiation in all conditions evaluated, resulting in the downregulation of PPARG and FABP4 and the upregulation of GATA2. The response to treatment was stronger in ADSCs than in BM-MSCs, suggesting that epigenetic memories may differ between cells of different origins. As epigenetic signatures affect differentiation, it should be possible to direct the use of MSCs in cell therapies to improve process efficiency by considering the various sources available.
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