Dynamic transcriptomic analysis reveals suppression of PGC1α/ERRα drives perturbed myogenesis in facioscapulohumeral muscular dystrophy.

Christopher R S Banerji,Maryna Panamarova,Efthymios Fidanis,Alka Saxena,Husam Hebaishi,Julian Contet,Simone Severini,Peter S Zammit,Sabrina Sacconi,Johanna Pruller,Nicolas Figeac

doi:10.1093/hmg/ddy405

Abstract

Facioscapulohumeral muscular dystrophy (FSHD) is a prevalent, incurable myopathy, linked to epigenetic derepression of D4Z4 repeats on chromosome 4q, leading to ectopic DUX4 expression. FSHD patient myoblasts have defective myogenic differentiation, forming smaller myotubes with reduced myosin content. However, molecular mechanisms driving such disrupted myogenesis in FSHD are poorly understood. We performed high-throughput morphological analysis describing FSHD and control myogenesis, revealing altered myogenic differentiation results in hypotrophic myotubes. Employing polynomial models and an empirical Bayes approach, we established eight critical time points during which human healthy and FSHD myogenesis differ. RNA-sequencing at these eight nodal time points in triplicate, provided temporal depth for a multivariate regression analysis, allowing assessment of interaction between progression of differentiation and FSHD disease status. Importantly, the unique size and structure of our data permitted identification of many novel FSHD pathomechanisms undetectable by previous approaches. For further analysis here, we selected pathways that control mitochondria: of interest considering known alterations in mitochondrial structure and function in FSHD muscle, and sensitivity of FSHD cells to oxidative stress. Notably, we identified suppression of mitochondrial biogenesis, in particular via peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1α), the cofactor and activator of oestrogen-related receptor α (ERRα). PGC1α knock-down caused hypotrophic myotubes to form from control myoblasts. Known ERRα agonists and safe food supplements biochanin A, daidzein or genistein, each rescued the hypotrophic FSHD myotube phenotype. Together our work describes transcriptomic changes in high resolution that occur during myogenesis in FSHD ex vivo, identifying suppression of the PGC1α-ERRα axis leading to perturbed myogenic differentiation, which can effectively be rescued by readily available food supplements.

Highlights

Facioscapulohumeral muscular dystrophy (FSHD) is a prevalent (12/100000 [1]) skeletal myopathy, for which there is currently no cure
Suppression of mitochondrial biogenesis genes regulated by ERR and proliferator-activated receptor gamma coactivator 1- (PGC1) is a general feature of FSHD myogenesis Of the many pathways that we found perturbed during myogenesis in FSHD (Tables S2-7), we decided to focus on the ERR /PGC1 pathway, of interest considering the sensitivity of FSHD cells to oxidative stress and know mitochondrial dysfunction [21, 45, 46] Further examination revealed that in addition to insufficient activation of PGC1 ERR target genes, there was significant suppression of ERR transcripts in differentiating FSHD 54-12 myoblasts, beginning from around 24 hours of differentiation (Figure 3C)
Of the many transcriptional changes identified in this comprehensive description of myogenesis in FSHD, we concentrated on the finding that suppression of PGC1 leads to a dynamic repression of ERR from day 1 of differentiation, driving FSHD hypotrophic myotube formation

Summary

Introduction

Facioscapulohumeral muscular dystrophy (FSHD) is a prevalent (12/100000 [1]) skeletal myopathy, for which there is currently no cure. The condition presents most notably as a descending skeletal muscle weakness and atrophy, beginning in facial muscles (such as the orbicularis oculi and orbicularis oris), and progressing to the biceps brachii and muscles of the shoulder girdle, before affecting specific lower limb muscles such as the tibialis anterior [2, 3]. There is often a marked left-right asymmetry in the degree that muscles are affected. FSHD is associated with extra-muscular features including retinal telangiectasia and sensorineural hearing loss [4,5,6]. FSHD is highly heterogeneous, with presentations varying dramatically between first degree relatives and even mono-zygotic twins [7, 8]. There is a differential penetrance between males and females, with males typically presenting earlier in life [9]

Methods

Results

Conclusion