Gonad-related factors promote muscle performance gain during postnatal development in male and female mice

To better define the role of male and female gonad-related factors (MGRF, presumably testosterone, and FGRF, presumably estradiol, respectively) on mouse hindlimb skeletal muscle contractile performance/function gain during postnatal development, we analyzed the effect of castration initiated before puberty in male and female mice. We found that muscle absolute and specific (normalized to muscle weight) maximal forces were decreased in 6-mo-old male and female castrated mice compared with age- and sex-matched intact mice, without alteration in neuromuscular transmission. Moreover, castration decreased absolute and specific maximal powers, another important aspect of muscle performance, in 6-mo-old males, but not in females. Absolute maximal force was similarly reduced by castration in 3-mo-old muscle fiber androgen receptor (AR)-deficient and wild-type male mice, indicating that the effect of MGRF was muscle fiber AR independent. Castration reduced the muscle weight gain in 3-mo mice of both sexes and in 6-mo females but not in males. We also found that bone morphogenetic protein signaling through Smad1/5/9 was not altered by castration in atrophic muscle of 3-mo-old mice of both sexes. Moreover, castration decreased the sexual dimorphism regarding muscle performance. Together, these results demonstrated that in the long term, MGRF and FGRF promote muscle performance gain in mice during postnatal development, independently of muscle growth in males, largely via improving muscle contractile quality (force and power normalized), and that MGFR and FGRF also contribute to sexual dimorphism. However, the mechanisms underlying MGFR and FGRF actions remain to be determined

MHO1, an Evolutionarily Conserved Gene, Is Synthetic Lethal with PLC1; Mho1p Has a Role in Invasive Growth

The novel protein Memo (Mediator of ErbB2 driven cell motility) was identified in a screen for ErbB2 interacting proteins and found to have an essential function in cell motility. Memo is evolutionarily conserved with homologs found in all branches of life; the human and yeast proteins have a similarity of >50%. In the present study we used the model organism S. cerevisiae to characterize the Memo-homologue Mho1 (Yjr008wp) and to investigate its function in yeast. In a synthetic lethal screen we found MHO1 as a novel synthetic lethal partner of PLC1, which encodes the single phospholipase C in yeast. Double-deleted cells lacking MHO1 and PLC1, proliferate for up to ten generations. Introduction of human Memo into the memoΔplc1Δ strain rescued the synthetic lethal phenotype suggesting that yeast and human proteins have similar functions. Mho1 is present in the cytoplasm and the nucleus of yeast cells; the same distribution of Memo was found in mammalian cells. None of the Memo homologues have a characteristic nuclear localization sequence, however, a conserved nuclear export sequence is found in all. In mammalian cells, blocking nuclear export with Leptomycin B led to nuclear Memo accumulation, suggesting that it is actively exported from the nucleus. In yeast MHO1 expression is induced by stress conditions. Since invasive growth in S. cerevisiea is also stress-induced, we tested Mho1's role in this response. MHO1 deletion had no effect on invasion induced by nutrient deprivation, however, Mho1 overexpression blocked the invasive ability of yeast cells, suggesting that Mho1 might be acting in a dominant negative manner. Taken together, our results show that MHO1 is a novel synthetic lethal interactor with PLC1, and that both gene products are required for proliferation. Moreover, a role for Memo in cell motility/invasion appears to be conserved across species

Regulation of muscular functions by glucocorticoids and androgens

L’utilisation de glucocorticoïdes (GC) pour le traitement de maladies inflammatoires ou d’antagonistes des androgènes pour le cancer de la prostate est limitée par l’induction d’effets secondaires, tels que l’atrophie musculaire. Comme les mécanismes sous-jacents étaient mal connus, nous avons caractérisé le rôle de ces hormones dans la régulation des fonctions musculaires. Nos résultats montrent que le récepteur aux GC des myofibres contrôle négativement la masse musculaire par des actions distinctes en présence de concentrations physiologiques et pharmacologiques de GC. De plus, notre étude a permis d’identifier de nouveaux réseaux de gènes contrôlés par les GC dans le muscle. Nous avons également démontré que les androgènes favorisent le gain de performance musculaire via l’amélioration de la force. Ainsi, cette étude a clarifié les mécanismes régulant l’homéostasie musculaire et ouvre des perspectives prometteuses pour identifier de nouvelles cibles thérapeutiques.The use of glucocorticoids (GC) to treat inflammatory diseases or androgen antagonists for prostate cancer is limited by the occurrence of side effects such as muscle atrophy. As the underlying mechanisms were unclear, we characterized the effects of GC and androgens on muscle mass and function. Our results demonstrate that myofiber GC receptor negatively controls muscle mass by distinct actions under physiological and pharmacological levels of GC. Moreover, our data identified many genes and networks controlled by GC in myofibers. We also showed that androgens promote the gain in muscle performance during postnatal development via the improvement of specific maximal force and power. Thus, this study allowed to clarify the molecular and cellular mechanisms regulating muscle homeostasis, and paves the way to identify new therapeutic targets

Régulation des fonctions musculaires par les glucocorticoïdes et les androgènes

The use of glucocorticoids (GC) to treat inflammatory diseases or androgen antagonists for prostate cancer is limited by the occurrence of side effects such as muscle atrophy. As the underlying mechanisms were unclear, we characterized the effects of GC and androgens on muscle mass and function. Our results demonstrate that myofiber GC receptor negatively controls muscle mass by distinct actions under physiological and pharmacological levels of GC. Moreover, our data identified many genes and networks controlled by GC in myofibers. We also showed that androgens promote the gain in muscle performance during postnatal development via the improvement of specific maximal force and power. Thus, this study allowed to clarify the molecular and cellular mechanisms regulating muscle homeostasis, and paves the way to identify new therapeutic targets.L’utilisation de glucocorticoïdes (GC) pour le traitement de maladies inflammatoires ou d’antagonistes des androgènes pour le cancer de la prostate est limitée par l’induction d’effets secondaires, tels que l’atrophie musculaire. Comme les mécanismes sous-jacents étaient mal connus, nous avons caractérisé le rôle de ces hormones dans la régulation des fonctions musculaires. Nos résultats montrent que le récepteur aux GC des myofibres contrôle négativement la masse musculaire par des actions distinctes en présence de concentrations physiologiques et pharmacologiques de GC. De plus, notre étude a permis d’identifier de nouveaux réseaux de gènes contrôlés par les GC dans le muscle. Nous avons également démontré que les androgènes favorisent le gain de performance musculaire via l’amélioration de la force. Ainsi, cette étude a clarifié les mécanismes régulant l’homéostasie musculaire et ouvre des perspectives prometteuses pour identifier de nouvelles cibles thérapeutiques

The effect of constitutive inactivation of the myostatin gene on the gain in muscle strength during postnatal growth in two murine models

International audienceThe effect of constitutive inactivation of the gene encoding myostatin on the gain in muscle performance during postnatal growth hsa not been well characterized. Methods. We analyzed 2 murine myostatin knockout (KO) models: i) the Lee model (KOLee) and ii) the Grobet model (KOGrobet), and measured the contraction of tibialis anterior muscle in situ. Results. Absolute maximal isometric force was increased in 6-month old KOLee and KOGrobet mice, as compared to wild-type mice. Similarly, absolute maximal power was increased in 6-month old KOLee mice. In contrast, specific maximal force (relative maximal force per unit of muscle mass was decreased in all 6-month old male and female KO mice, except in 6-month old female KOGrobet mice, whereas specific maximal power was reduced only in male KOLee mice. Discussion. Genetic inactivation of myostatin increases maximal force and power, but in return it reduces muscle quality, particularly in male mice

Gonad-related factors promote muscle performance gain during postnatal development in male and female mice

To better define the role of male and female gonad-related factors (MGRF, presumably testosterone, and FGRF, presumably estradiol, respectively) on mouse hindlimb skeletal muscle contractile performance/function gain during postnatal development, we analyzed the effect of castration initiated before puberty in male and female mice. We found that muscle absolute and specific (normalized to muscle weight) maximal forces were decreased in 6-mo-old male and female castrated mice compared with age- and sex-matched intact mice, without alteration in neuromuscular transmission. Moreover, castration decreased absolute and specific maximal powers, another important aspect of muscle performance, in 6-mo-old males, but not in females. Absolute maximal force was similarly reduced by castration in 3-mo-old muscle fiber androgen receptor (AR)-deficient and wild-type male mice, indicating that the effect of MGRF was muscle fiber AR independent. Castration reduced the muscle weight gain in 3-mo mice of both sexes and in 6-mo females but not in males. We also found that bone morphogenetic protein signaling through Smad1/5/9 was not altered by castration in atrophic muscle of 3-mo-old mice of both sexes. Moreover, castration decreased the sexual dimorphism regarding muscle performance. Together, these results demonstrated that in the long term, MGRF and FGRF promote muscle performance gain in mice during postnatal development, independently of muscle growth in males, largely via improving muscle contractile quality (force and power normalized), and that MGFR and FGRF also contribute to sexual dimorphism. However, the mechanisms underlying MGFR and FGRF actions remain to be determined

<i>A. gossypii</i> strains used in this study.

<p><i>A. gossypii</i> strains used in this study.</p

Cytoskeleton analysis of wild-type and <i>memoΔ</i> strains of <i>S. cerevisiae.</i>

<p>(A) To stain the tubulin cytoskeleton, a GFP-tagged TUB1 expression vector, under its endogenous promoter was introduced into wild type and <i>memoΔ</i> cells. The arrows indicate (1) nuclear microtubules, (2) astral microtubules, and (3) the spindle pole body. (B) Phalloidin-OregonGreen was used to stain wild type and <i>memoΔ</i> cells. Two actin structures are stained: (1) cortical actin patches and (2) actin cables. There are no obvious differences in the microtubule structures or the actin cytoskeleton comparing wild-type and <i>memoΔ</i> cells.</p

Overexpression of Mho1 abolishes invasive growth in the haploid Σ1278B strain.

<p>(A) Mho1 was overexpressed in the invasive yeast strain Σ1278B by integrating the pRS416_pGAL_<i>6HIS-MHO1</i> and the BYintURA_pGAL_<i>MHO1</i> plasmids. The <i>mho1Δ</i> strains were made by replacing the endogenous gene with <i>kanMX</i> or <i>URA3MX</i>. (B) Overexpression of 6His-Mho1 is shown by western blotting using a His-tag specific antiserum. Mcm2 levels were used as a loading control. The lysates were: 1) Σ1278B wt grown on YPD, 2) Σ1278B wt grown on YPGal, 3) Σ1278B 6His-Mho1 OE grown on YPD, and 4) Σ1278B 6His-Mho1 OE grown on YPGal. (C) To test for invasive growth potential in Mho1-lacking or overexpressing strains, the indicated strains were streaked out on YPD or YPGal (overexpressing conditions) agar plates. As controls, the wt Σ1278B or Σ1278B harbouring the empty pRS416_pGAL and BYintURA_pGAL plasmid were used. After four days, the plates were washed under the water tap. Only cells overexpressing Mho1 on the YPGal plates were washed off the plates, showing that overexpression blocks haploid invasive growth.</p

Plasmids used in this study.

<p>Plasmids used in this study.</p