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The Regulation of Muscle Structure and Metabolism by Mio/dChREBP in Drosophila.

Polak GL, Pasqualino A, Docherty JE, Beck SJ, DiAngelo JR - PLoS ONE (2015)

Bottom Line: Decreasing Mio levels using RNAi specifically in muscle results in increased thorax glycogen storage.Myofibril size is also decreased in flies just before emerging from their pupal cases, suggesting a role for Mio in myofibril development.Together, these data indicate a novel role for Mio in controlling muscle structure and metabolism and may provide a molecular link between nutrient availability and muscle function.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Hofstra University, Hempstead, NY, 11549, United States of America.

ABSTRACT
All cells require energy to perform their specialized functions. Muscle is particularly sensitive to the availability of nutrients due to the high-energy requirement for muscle contraction. Therefore the ability of muscle cells to obtain, store and utilize energy is essential for the function of these cells. Mio, the Drosophila homolog of carbohydrate response element binding protein (ChREBP), has recently been identified as a nutrient responsive transcription factor important for triglyceride storage in the fly fat body. However, the function of Mio in muscle is unknown. In this study, we characterized the role of Mio in controlling muscle function and metabolism. Decreasing Mio levels using RNAi specifically in muscle results in increased thorax glycogen storage. Adult Mio-RNAi flies also have a flight defect due to altered myofibril shape and size in the indirect flight muscles as shown by electron microscopy. Myofibril size is also decreased in flies just before emerging from their pupal cases, suggesting a role for Mio in myofibril development. Together, these data indicate a novel role for Mio in controlling muscle structure and metabolism and may provide a molecular link between nutrient availability and muscle function.

No MeSH data available.


Related in: MedlinePlus

Mio expression in muscle is necessary for normal glycogen storage.(A) Analysis of Mio expression from thoraxes of 5–7 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR flies compared to Mef2-Gal4>GFP controls (n = 8). Mio levels of the Mef2-Gal4>GFP controls were set to 1.0 and Mio levels of Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR animals were then calculated relative to their respective control. Values represent mean Mio expression±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test. (B) Glycogen/protein and (C) triglyceride/protein of thoraxes dissected from 5–8 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR male and female flies compared to their respective Mef2-Gal4>GFP controls (n = 6). Values represent mean±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test.
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pone.0136504.g001: Mio expression in muscle is necessary for normal glycogen storage.(A) Analysis of Mio expression from thoraxes of 5–7 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR flies compared to Mef2-Gal4>GFP controls (n = 8). Mio levels of the Mef2-Gal4>GFP controls were set to 1.0 and Mio levels of Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR animals were then calculated relative to their respective control. Values represent mean Mio expression±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test. (B) Glycogen/protein and (C) triglyceride/protein of thoraxes dissected from 5–8 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR male and female flies compared to their respective Mef2-Gal4>GFP controls (n = 6). Values represent mean±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test.

Mentions: Previous studies have shown that Mio expression in the fat body promotes triglyceride storage in Drosophila larvae and adults [18–20]. Mio is also expressed in other tissues [18] but its functions there remain unknown. In order to understand the tissue-specific functions of Mio, we decided to focus on Drosophila muscle, a highly metabolic and physiologically important tissue. To characterize the role of Mio in muscle, we performed experiments in which RNA interference (RNAi) was used to decrease Mio expression specifically in all muscles using Mef2-Gal4 [32] (Fig 1A). In order to achieve the desired knockdown we used two independent RNAi lines that provide lower levels of Mio. MiodsRNA uses double stranded RNA in order to activate the RNAi machinery while Mio-IR uses inverted repeats to activate RNAi. Using two independent RNAi transgenes allows us to control for any potential off target effects of the RNAi as well as any potential transgene insertion effects on the data presented here. Since Mio is important for triglyceride storage in the fat body and Mio’s mammalian homolog ChREBP has been implicated in the regulation of triglyceride and glycogen storage in liver and adipose tissue [10], we wanted to determine whether Mio acts in muscle to regulate macromolecule storage. To test this hypothesis, glycogen and triglyceride levels were measured from thoraxes of muscle-specific Mio-RNAi flies. Thoraxes from flies with decreased Mio levels in all muscles showed significantly higher glycogen levels when compared to GFP controls while no differences were observed in triglycerides (Fig 1B and 1C), suggesting that Mio plays a role specifically in glycogen storage in muscle.


The Regulation of Muscle Structure and Metabolism by Mio/dChREBP in Drosophila.

Polak GL, Pasqualino A, Docherty JE, Beck SJ, DiAngelo JR - PLoS ONE (2015)

Mio expression in muscle is necessary for normal glycogen storage.(A) Analysis of Mio expression from thoraxes of 5–7 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR flies compared to Mef2-Gal4>GFP controls (n = 8). Mio levels of the Mef2-Gal4>GFP controls were set to 1.0 and Mio levels of Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR animals were then calculated relative to their respective control. Values represent mean Mio expression±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test. (B) Glycogen/protein and (C) triglyceride/protein of thoraxes dissected from 5–8 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR male and female flies compared to their respective Mef2-Gal4>GFP controls (n = 6). Values represent mean±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4549115&req=5

pone.0136504.g001: Mio expression in muscle is necessary for normal glycogen storage.(A) Analysis of Mio expression from thoraxes of 5–7 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR flies compared to Mef2-Gal4>GFP controls (n = 8). Mio levels of the Mef2-Gal4>GFP controls were set to 1.0 and Mio levels of Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR animals were then calculated relative to their respective control. Values represent mean Mio expression±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test. (B) Glycogen/protein and (C) triglyceride/protein of thoraxes dissected from 5–8 day old Mef2-Gal4>MiodsRNA and Mef2-Gal4>Mio-IR male and female flies compared to their respective Mef2-Gal4>GFP controls (n = 6). Values represent mean±SEM. *p<0.05 by One-way ANOVA with post hoc Tukey test.
Mentions: Previous studies have shown that Mio expression in the fat body promotes triglyceride storage in Drosophila larvae and adults [18–20]. Mio is also expressed in other tissues [18] but its functions there remain unknown. In order to understand the tissue-specific functions of Mio, we decided to focus on Drosophila muscle, a highly metabolic and physiologically important tissue. To characterize the role of Mio in muscle, we performed experiments in which RNA interference (RNAi) was used to decrease Mio expression specifically in all muscles using Mef2-Gal4 [32] (Fig 1A). In order to achieve the desired knockdown we used two independent RNAi lines that provide lower levels of Mio. MiodsRNA uses double stranded RNA in order to activate the RNAi machinery while Mio-IR uses inverted repeats to activate RNAi. Using two independent RNAi transgenes allows us to control for any potential off target effects of the RNAi as well as any potential transgene insertion effects on the data presented here. Since Mio is important for triglyceride storage in the fat body and Mio’s mammalian homolog ChREBP has been implicated in the regulation of triglyceride and glycogen storage in liver and adipose tissue [10], we wanted to determine whether Mio acts in muscle to regulate macromolecule storage. To test this hypothesis, glycogen and triglyceride levels were measured from thoraxes of muscle-specific Mio-RNAi flies. Thoraxes from flies with decreased Mio levels in all muscles showed significantly higher glycogen levels when compared to GFP controls while no differences were observed in triglycerides (Fig 1B and 1C), suggesting that Mio plays a role specifically in glycogen storage in muscle.

Bottom Line: Decreasing Mio levels using RNAi specifically in muscle results in increased thorax glycogen storage.Myofibril size is also decreased in flies just before emerging from their pupal cases, suggesting a role for Mio in myofibril development.Together, these data indicate a novel role for Mio in controlling muscle structure and metabolism and may provide a molecular link between nutrient availability and muscle function.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Hofstra University, Hempstead, NY, 11549, United States of America.

ABSTRACT
All cells require energy to perform their specialized functions. Muscle is particularly sensitive to the availability of nutrients due to the high-energy requirement for muscle contraction. Therefore the ability of muscle cells to obtain, store and utilize energy is essential for the function of these cells. Mio, the Drosophila homolog of carbohydrate response element binding protein (ChREBP), has recently been identified as a nutrient responsive transcription factor important for triglyceride storage in the fly fat body. However, the function of Mio in muscle is unknown. In this study, we characterized the role of Mio in controlling muscle function and metabolism. Decreasing Mio levels using RNAi specifically in muscle results in increased thorax glycogen storage. Adult Mio-RNAi flies also have a flight defect due to altered myofibril shape and size in the indirect flight muscles as shown by electron microscopy. Myofibril size is also decreased in flies just before emerging from their pupal cases, suggesting a role for Mio in myofibril development. Together, these data indicate a novel role for Mio in controlling muscle structure and metabolism and may provide a molecular link between nutrient availability and muscle function.

No MeSH data available.


Related in: MedlinePlus