Skeletal muscle phenotyping of Hippo gene-mutated mice reveals that Lats1 deletion increases the percentage of type I muscle fibers

Fakhreddin Yaghoob Nezhad,Annett Riermeier,Lore Becker,Henning Wackerhage,Martin Schönfelder,Martin Hrabĕ De Angelis

doi:10.1007/s11248-021-00293-4

Abstract

The Hippo signal transduction network regulates transcription through Yap/Taz-Tead1-4 in many tissues including skeletal muscle. Whilst transgenic mice have been generated for many Hippo genes, the resultant skeletal muscle phenotypes were not always characterized. Here, we aimed to phenotype the hindlimb muscles of Hippo gene-mutated Lats1−/−, Mst2−/−, Vgll3−/−, and Vgll4+/− mice. This analysis revealed that Lats1−/− mice have 11% more slow type I fibers than age and sex-matched wild-type controls. Moreover, the mRNA expression of slow Myh7 increased by 50%, and the concentration of type I myosin heavy chain is 80% higher in Lats1−/− mice than in age and sex-matched wild-type controls. Second, to find out whether exercise-related stimuli affect Lats1, we stimulated C2C12 myotubes with the hypertrophy agent clenbuterol or the energy stress agent AICAR. We found that both stimulated Lats1 expression by 1.2 and 1.3 fold respectively. Third, we re-analyzed published datasets and found that Lats1 mRNA in muscle is 63% higher in muscular dystrophy, increases by 17–77% after cardiotoxin-induced muscle injury, by 41–71% in muscles during overload-induced hypertrophy, and by 19–21% after endurance exercise when compared to respective controls. To conclude, Lats1 contributes to the regulation of muscle fiber type proportions, and its expression is regulated by physiological and pathological situations in skeletal muscle.

Highlights

We use our &650 human skeletal muscles to move, stand, speak, generate heat, store glucose as glycogen, and amino acids as protein
To study the effect of transgenesis on skeletal muscle phenotype, we phenotyped hindlimb muscles of Lats1-/, Mst2-/, Vgll3-/, and Vgll4?/- mice versus sex- and age-matched wild-type mice as controls
The major finding of this analysis is that deleting Lats1-/- had 11% more type I fibers, 50% more Myh7 mRNA, and 80% more type I myosin heavy chain when compared to matched wild-type controls

Summary

Introduction

We use our &650 human skeletal muscles to move, stand, speak, generate heat, store glucose as glycogen, and amino acids as protein. Muscle size and function are regulated by many signaling pathways and depend on genetics. In the past two decades, the Hippo signal transduction network has been identified as a regulator of skeletal muscle development, regeneration, and size and is associated with diseases such as muscular dystrophy and rhabdomyosarcoma (Wackerhage et al 2014). Activated LATS1/2 inhibits the transcriptional co-factors YAP/TAZ by phosphorylation of multiple serines (Liang et al 2014; Zhao et al 2007). Unphosphorylated YAP/ TAZ can translocate to the nucleus to co-activate TEAD-1–4 transcription factors to initiate the transcription of target genes such as ANKRD1, CTGF, and CYR61 (Dong et al 2007; Liu et al 2010; Oh and Irvine 2008; Ren et al 2010; Zhao et al 2010). VGLL1–4 proteins can bind TEAD1–4 (Zhou et al 2016) and may compete for common binding interfaces with Yap and Taz (Figeac et al 2019; Hori et al 2020; Koontz et al 2013; Yamaguchi 2020)

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