Integrated expression analysis of muscle hypertrophy identifies Asb2 as a negative regulator of muscle mass
Jonathan R. Davey, … , David E. James, Paul Gregorevic
Jonathan R. Davey, … , David E. James, Paul Gregorevic
Published April 21, 2016
Citation Information: JCI Insight. 2016;1(5):e85477. https://doi.org/10.1172/jci.insight.85477.
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Research Article Aging Muscle biology

Integrated expression analysis of muscle hypertrophy identifies Asb2 as a negative regulator of muscle mass

Abstract

The transforming growth factor-β (TGF-β) signaling network is a critical regulator of skeletal muscle mass and function and, thus, is an attractive therapeutic target for combating muscle disease, but the underlying mechanisms of action remain undetermined. We report that follistatin-based interventions (which modulate TGF-β network activity) can promote muscle hypertrophy that ameliorates aging-associated muscle wasting. However, the muscles of old sarcopenic mice demonstrate reduced response to follistatin compared with healthy young-adult musculature. Quantitative proteomic and transcriptomic analyses of young-adult muscles identified a transcription/translation signature elicited by follistatin exposure, which included repression of ankyrin repeat and SOCS box protein 2 (Asb2). Increasing expression of ASB2 reduced muscle mass, thereby demonstrating that Asb2 is a TGF-β network–responsive negative regulator of muscle mass. In contrast to young-adult muscles, sarcopenic muscles do not exhibit reduced ASB2 abundance with follistatin exposure. Moreover, preventing repression of ASB2 in young-adult muscles diminished follistatin-induced muscle hypertrophy. These findings provide insight into the program of transcription and translation events governing follistatin-mediated adaptation of skeletal muscle attributes and identify Asb2 as a regulator of muscle mass implicated in the potential mechanistic dysfunction between follistatin-mediated muscle growth in young and old muscles.

Authors

Jonathan R. Davey, Kevin I. Watt, Benjamin L. Parker, Rima Chaudhuri, James G. Ryall, Louise Cunningham, Hongwei Qian, Vittorio Sartorelli, Marco Sandri, Jeffrey Chamberlain, David E. James, Paul Gregorevic

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Figure 5

ASB2 is not downregulated in aged muscle exposed to follistatin, but suppression is required for maximal follistatin response.

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ASB2 is not downregulated in aged muscle exposed to follistatin, but sup...
C57Bl/6 mice of indicated age were injected with rAAV:MCS in the left TA and rAAV:FST in the right TA. (A) Immunoblot analysis of ASB2 expression in response to indicated follistatin treatment. (B) Quantification of ASB2 expression presented in A (ratio-paired t test, P < 0.05, n = 6, ± SEM). (C) Quantitative PCR analysis of Asb2 mRNA from mice in A (ratio-paired t test; P < 0.05; 6 month, n = 4; 24 month, n = 5; ± SEM). (D) Immunoblot analysis of TBC1D1 expression in response to indicated follistatin treatment. (E) Quantification of TBC1D1 expression presented in D (ratio-paired t test, P < 0.05, n = 6, ± SEM). (F) C57Bl/6 mice were injected with rAAV:FST plus rAAV:MCS in the left TA and rAAV:FST plus rAAV:Asb2 in the right TA. The rAAV:FST plus rAAV:Asb2–coinjected muscles were compared against the rAAV:FST plus rAAV:MCS control muscles (ratio paired t test; P < 0.05; 14 days, n = 4; 28 days, n = 8; ± SEM). (G) Muscle fiber diameter in TA muscles examined 28 days after treatment with rAAV:FST plus rAAV:MCS or rAAV:FST plus rAAV:Asb2 (Holm-Sidak multiple t test, P < 0.05, n = 4, ± SEM). (H) Comparison in relative changes in muscle mass due to Asb2 expression in static (Figure 4E) versus follistatin (F) treatment (unpaired t test; P < 0.05; rAAV:Asb2 14 days, n = 5; rAAV:FST + rAAV:Asb2 14 days, n = 4; rAAV:Asb2 28 days, n = 4; rAAV:FST + rAAV:Asb2 28 days, n = 8; ± SEM). (I) C57Bl/6 mice underwent surgical denervation or sham operation on contralateral TA muscles. Immunoblot analysis of indicated time course after surgery for ASB2 expression. (J) Quantification of immunoblots from I for ASB2 expression (ratio-paired t test, P < 0.05, n = 4, ± SEM). Recombinant adeno-associated virus, rAAV; ankyrin repeat-containing protein with a suppressor of cytokine signaling box 2, Asb2; control construct, MCS; follistatin, FST; tibialis anterior muscle, TA; doxycycline, DOX; tetracycline responsive follistatin, indFST; TBC1 domain family member 1, TBC1D1.