IRE1α regulates skeletal muscle regeneration through myostatin mRNA decay
Shengqi He, … , Zhenji Gan, Yong Liu
Shengqi He, … , Zhenji Gan, Yong Liu
Published July 20, 2021
Citation Information: J Clin Invest. 2021;131(17):e143737. https://doi.org/10.1172/JCI143737.
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Research Article Muscle biology

IRE1α regulates skeletal muscle regeneration through myostatin mRNA decay

Abstract

Skeletal muscle can undergo a regenerative process in response to injury or disease to preserve muscle mass and function, which are critically influenced by cellular stress responses. Inositol-requiring enzyme 1 (IRE1) is an ancient endoplasmic reticulum stress sensor and mediates a key branch of the unfolded protein response. In mammals, IRE1α is implicated in the homeostatic control of stress responses during tissue injury and regeneration. Here, we show that IRE1α serves as a myogenic regulator in skeletal muscle regeneration in response to injury and muscular dystrophy. We found in mice that IRE1α was activated during injury-induced muscle regeneration, and muscle-specific IRE1α ablation resulted in impaired regeneration upon cardiotoxin-induced injury. Gain- and loss-of-function studies in myocytes demonstrated that IRE1α acts to sustain both differentiation in myoblasts and hypertrophy in myotubes through regulated IRE1-dependent decay (RIDD) of mRNA encoding myostatin, a key negative regulator of muscle repair and growth. Furthermore, in the mouse model of Duchenne muscular dystrophy, loss of muscle IRE1α resulted in augmented myostatin signaling and exacerbated the dystrophic phenotypes. These results reveal a pivotal role for the RIDD output of IRE1α in muscle regeneration, offering insight into potential therapeutic strategies for muscle loss diseases.

Authors

Shengqi He, Tingting Fu, Yue Yu, Qinhao Liang, Luyao Li, Jing Liu, Xuan Zhang, Qian Zhou, Qiqi Guo, Dengqiu Xu, Yong Chen, Xiaolong Wang, Yulin Chen, Jianmiao Liu, Zhenji Gan, Yong Liu

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Figure 1

Injury-induced IRE1α activation affects skeletal muscle regeneration and myostatin signaling.

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Injury-induced IRE1α activation affects skeletal muscle regeneration and...
(A–C) Muscle injury induces IRE1α activation. TA muscle of adult male mice was injected with CTX to induce acute muscle injury (n = 5 mice at each time point). (A) Immunoblot analysis of the phosphorylation of IRE1α and eIF2α, and protein expression of BiP and eMyHC in muscle extracts. Each lane represents 1 individual mouse. Averaged p-IRE1α/IRE1α and p-eIF2α/eIF2α ratios are shown from densitometric quantification. (B and C) Quantitative RT-PCR analysis of Xbp1 mRNA splicing and the abundance of mRNAs encoding the indicated genes. (D–J) IRE1α abrogation impairs muscle regeneration and enhances myostatin signaling. TA muscles of male Ern1fl/fl and Myod1-Cre control and Ern1fl/fl Myod1-Cre mice were subjected to CTX-induced injuries (n = 5 mice at each time point). (D) TA muscle weight relative to tibia length. (E) Representative H&E staining of TA muscles from mice of the indicated genotypes. (F) Percentage of regenerated myofibers in the indicated cross-sectional areas of TA muscles at 12 days after CTX injection. Myofibers containing centralized nuclei were quantified by ImageJ from 500 myofibers of the TA muscle in each mouse. (G) Representative laminin (green) and eMyHC (red) immunostaining of TA muscles at 8 days after CTX injection. (H) Quantification of the percentage of eMyHC+ myofibers within laminin staining. (I) Quantitative RT-PCR analysis of Xbp1 mRNA splicing and Mstn mRNA abundance in TA muscles. Data are shown as relative to the value for Ern1fl/fl TA muscle at day 0 after normalization to Gapdh as the internal control. (J) Immunoblot analysis of TA muscle lysates. Averaged p-Smad/Smad ratios are shown after normalization to the value for Ern1fl/fl TA muscle at day 0. All data are presented as mean ± SEM. Significance was calculated by 1-way (A–C and H) or 2-way (D, F, I, and J) ANOVA with Bonferroni’s multiple-comparison test. *P < 0.05, **P < 0.01, ***P < 0.001 vs. day 0 or Ern1fl/fl. #P < 0.05, ###P < 0.001 vs. Myod1-Cre. Scale bars: 100 μm.