Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB198

Poster Communications

the Epigenetic landscape of two phenotypic extreme skeletal muscles - Soleus and EDL

M. Bengtsen1, I. Winje1, J. Landskron2, L. Meza-Zepeda3, K. Gundersen1

1. Department of Biosciences, University of Oslo, Oslo, Norway. 2. Centre for Molecular Medicine Norway, University of Oslo, Oslo, Norway. 3. Institute for Cancer Research, Oslo University Hospital, Oslo, Oslo, Norway.

Introduction By varying the relative composition of different fibre-types within a muscle, an organism has the ability to fine-tune muscle function according to physiological demands. Skeletal muscle tissue is composed of approximately 40 - 60 % myonuclei, while the remaining are non-muscle cells with a different origin such as stromal and hematopoietic. Therefore, it is important to isolate the subpopulation of interest from the whole tissue, as a mixed-cell population are prone to increase the number of false-positive results. In this study, we present a novel method for isolating myonuclei from whole native muscle. The resulting pure myonuclear fraction allowed us to explore the epigenetic landscape for the two phenotypic extremes the oxidative Soleus and the glycolytic Extensor Digitorum Longus muscle (EDL). Methods Animals were sedated with gas anaesthesia with 2 % isoflurane. Surgically were initiated following the loss of the metatarsus reflex. A small incision where made on the posture side of the hind limb and the Soleus and EDL muscles were surgically removed and frozen in liquid nitrogen (n=6 Female NMRI mice, weighing 25-30 g). The myonuclei population was biochemically isolated and used to create the epigenetic map by Chromatin Immunoprecipitation coupled with next-generation sequencing (ChIP-Seq) and bioinformatic analyses. Results Using our novel method, we show that that the myonuclei epigenetic environment is significantly different compared to the whole tissue. Global analysis of the epigenetic landscape in the Soleus and EDL muscles show that there are large dynamic differences between the two muscle types which correlate with the myo-specific transcriptome and the properties of the muscles. Conclusion We have developed a novel method to isolate the myo-specific nuclei from skeletal muscle. We use the method to generate a global map of the epigenetic landscape of the two extremes, the oxidative Soleus and the glycolytic EDL muscles and find that their different physiological properties are reflected in their epigenome.

Where applicable, experiments conform with Society ethical requirements