Mitochondrial Activity Is Involved in the Regulation of Myoblast Differentiation through Myogenin Expression and Activity of Myogenic Factors

Abstract

To characterize the regulatory pathways involved in the inhibition of cell differentiation induced by the impairment of mitochondrial activity, we investigated the relationships occurring between organelle activity and myogenesis using an avian myoblast cell line (QM7). The inhibition of mitochondrial translation by chloramphenicol led to a potent block of myoblast differentiation. Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone and oligomycin, which affect the organelle at different levels, exerted a similar influence. In addition, we provided evidence that this phenomenon was not the result of an alteration in cell viability. Conversely, overexpression of the mitochondrial T3 receptor (p43) stimulated organelle activity and strongly potentiated myoblast differentiation. The involvement of mitochondrial activity in an actual regulation of myogenesis is further supported by results demonstrating that the muscle regulatory gene myogenin, in contrast to CMD1 (chicken MyoD) and myf5, is a specific transcriptional target of mitochondrial activity. Whereas myogenin mRNA and protein levels were down-regulated by chloramphenicol treatment, they were up-regulated by p43 overexpression, in a positive relationship with the expression level of the transgene. We also found that myogenin or CMD1 overexpression in chloramphenicol-treated myoblasts did not restore differentiation, thus indicating that an alteration in mitochondrial activity interferes with the ability of myogenic factors to induce terminal differentiation.Recent studies emphasize that mitochondria, in addition to their well known involvement in the regulation of energy metabolism, are implicated in the regulation of cell growth and differentiation. In particular, mitochondrial events are involved in the preliminary steps of apoptosis (1), and inhibition of mitochondrial activity, either by deleting mtDNA (rho°cells) or by blocking translation in the organelle, has been shown to stop or decrease the proliferation of different cell lines (2-4). Furthermore, the general activity of the organelle, not restricted to energy production, is implicated in such regulation (5, 6). In addition, mitochondrial protein synthesis inhibition is associated with the impairment of differentiation of different cell lines, such as mouse erythroleukemia (7) and mastocytoma cells (8), neurons (9), and human (10), avian (11) or murine myoblasts (12). In agreement with these data, several pathologies are associated with mitochondrial disorders, even if the links between mitochondrial genome rearrangements or activity and pathological symptoms are not always clearly established. Despite these reports, little is known about the molecular mechanisms involved in these regulations. First, the exclusive use of inhibitors of mitochondrial function in previous reports was not fully adapted to demonstrating the occurrence of an actual regulatory pathway involving mitochondrial activity in the regulation of cell differentiation. Second, the nature of the molecular signals underlying the...

Thyroid hormone action in mitochondria

“…In contrast, chloramphenicol, a drug inducing the opposite influence to p43 by reducing mitochondrial protein synthesis, inhibits myoblast withdrawal from the cell cycle and their differentiation. In this study (Rochard et al 2000), we obtained good evidence that changes in ATP production were not involved in this myogenic influence. More interestingly, we found that myogenin expression was increased by p43 overexpression and decreased by chloramphenicol, events elicited at transcriptional level, thus establishing the existence of an actual regulation of myoblast differentiation by mitochondrial activity.…”

“…To clarify this point, we studied the influence of the direct mitochondrial T3 pathway on myoblast differentiation (Rochard et al 2000). First, T3 is a major regulator of myoblast differentiation (Marchal et al 1993), through mechanisms involving its c-Erb A nuclear receptors .…”

Mitochondrial biogenesis is decreased in skeletal muscle of pig fetuses exposed to maternal high-energy diets

“…Besides, recent studies have shown that mitochondria play a prominent role in the regulation of skeletal myogenesis (Rochard et al, 2000;Wagatsuma and Sakuma, 2013). Increased mitochondrial mass, mitochondrial DNA (mtDNA) copy number and mitochondrial respiration have been observed during C2C12 myogenic differentiation (Remels et al, 2010), suggesting the increased mitochondrial function may be essential for skeletal myogenesis.…”

“…Increased mitochondrial mass, mitochondrial DNA (mtDNA) copy number and mitochondrial respiration have been observed during C2C12 myogenic differentiation (Remels et al, 2010), suggesting the increased mitochondrial function may be essential for skeletal myogenesis. Moreover, blocking mitochondrial biogenesis inhibits myogenic differentiation (Rochard et al, 2000). Our previous study using a pig model indicated that moderately increased maternal dietary energy intake delayed fetal skeletal muscle differentiation and maturity on day 90 of gestation through changing myogenic gene expression and muscle fiber characteristics (Zou et al, 2016).…”

Hypothyroidism alters mitochondrial morphology and induces release of apoptogenic proteins during rat cerebellar development

“…Several of the identified genes were of mitochondrial origin, known to be involved in energy metabolism (Denver et al 1997). Recently, demonstration of the TH receptor in mitochondria and its involvement in controlling gene expression in mitochondria by different groups further potentiate the role of TH in energy metabolism (Hashizume & Ichikawa 1982, Wrutnaik et al 1995, Enriquez et al 1999, Rochard et al 2000. Establishment of the mitochondria's key role in apoptosis, a cardinal feature of neurogenesis, indicates that mitochondria may also play an important role in brain development (Oppenheim 1991, Yuan & Yanker 2000.…”