An Efficient Protocol for CUT&RUN Analysis of FACS-Isolated Mouse Satellite Cells

Summary

Presented here is an efficient protocol for the fluorescence-activated cell sorting (FACS) isolation of mouse limb muscle satellite cells adapted to the study of transcription regulation in muscle fibers by cleavage under targets and release using nuclease (CUT&RUN).

Abstract

Genome-wide analyses with small cell populations are a major constraint for studies, particularly in the stem cell field. This work describes an efficient protocol for the fluorescence-activated cell sorting (FACS) isolation of satellite cells from the limb muscle, a tissue with a high content of structural proteins. Dissected limb muscles from adult mice were mechanically disrupted by mincing in medium supplemented with dispase and type I collagenase. Upon digestion, the homogenate was filtered through cell strainers, and cells were suspended in FACS buffer. Viability was determined with fixable viability stain, and immunostained satellite cells were isolated by FACS. Cells were lysed with Triton X-100 and released nuclei were bound to concanavalin A magnetic beads. Nucleus/bead complexes were incubated with antibodies against the transcription factor or histone modifications of interest. After washes, nucleus/bead complexes were incubated with protein A-micrococcal nuclease, and chromatin cleavage was initiated with CaCl₂. After DNA extraction, libraries were generated and sequenced, and the profiles for genome-wide transcription factor binding and covalent histone modifications were obtained by bioinformatic analysis. The peaks obtained for the various histone marks showed that the binding events were specific for satellite cells. Moreover, known motif analysis unveiled that the transcription factor was bound to chromatin via its cognate response element. This protocol is therefore adapted to study gene regulation in adult mice limb muscle satellite cells.

Introduction

Skeletal striated muscles represent on average 40% of the weight of the total human body¹. Muscle fibers exhibit a remarkable capacity for regeneration upon injury, which is described by the fusion of newly formed myocytes and the generation of new myofibers that replace the damaged ones². In 1961, Alexander Mauro reported a population of mononuclear cells that he termed as satellite cells³. These stem cells express the transcription factor paired box 7 (PAX7), and are located between the basal lamina and the sarcolemma of muscle fibers⁴. They were reported to express the c....

Protocol

Mice were kept in an accredited animal house, in compliance with National Animal Care Guidelines (European Commission directive 86/609/CEE; French decree no.87-848) on the use of laboratory animals for research. Intended manipulations were submitted to the Ethical committee (Com'Eth, Strasbourg, France) and to the French Research Ministry (MESR) for ethical evaluation and authorization according to the 2010/63/EU directive under the APAFIS number #22281.

1. Preparation of cell suspension for isolation of satellite cells by fluorescence-activated cell sorting (FACS) (Figure 1)....

Results

Satellite cells from mouse skeletal muscles were isolated by combining the protocols of Gunther et al. (hereafter Protocol 1)¹² and of Liu et al.²³ (hereafter Protocol 2). Since non-digested muscle fibers were observed after digestion when using the concentration of collagenase and dispase proposed in Protocol 1, the quantity of enzymes was increased to improve muscle fiber dissociation, as described in steps 1.2.1 and 1.2.3. As indicated in Protocol 2, the samples were sub.......

Discussion

The present study reports a standardized, reliable, and easy-to-perform method for the isolation and culture of mouse satellite cells, as well as the assessment of transcriptional regulation by the CUT&RUN method.

This protocol involves several critical steps. The first is muscle disruption and fiber digestion to ensure a high number of collected cells. Despite the increased enzyme concentration, more living cells were obtained than using Protocol 1. Satellite cells express a specific patt.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1.5 mL microtube	Eppendorf	2080422
2 mL microtube	Star Lab	S1620-2700
5 mL tubes	CORNING-FALCON	352063
50 mL tubes	Falcon	352098
anti-AR	abcam	ab108341
anti-CD11b	eBioscience	25-0112-82
anti-CD31	eBioscience	12-0311-82
anti-CD34	eBioscience	48-0341-82
anti-CD45	eBioscience	12-0451-83
anti-CXCR4	eBioscience	17-9991-82
anti-DMD	abcam	ab15277
anti-H3K27ac	Active Motif	39133
anti-H3K4me2	Active Motif	39141
anti-ITGA7	MBL	k0046-4
anti-PAX7	DSHB	AB_528428
anti-TER119	BD Pharmingen TM	553673
Beads	Polysciences	86057-3	BioMag®Plus Concanavalin A
Cell Strainer 100 µm	Corning®	431752
Cell Strainer 40 µm	Corning®	431750
Cell Strainer 70 µm	Corning®	431751
Centrifuge 1	Eppendorf	521-0011	Centrifuge 5415 R
Centrifuge 2	Eppendorf	5805000010	Centrifuge 5804 R
Chamber Slide System	ThermoFischer	171080	Système Nunc™ Lab-Tek™ Chamber Slide
Cleaning agent	Sigma	SLBQ7780V	RNaseZAPTM
Collagenase, type I	Thermo Fisher	17100017	10 mg/mL
Dispase	STEMCELL technologies	7913	5 U/mL
DynaMag™-2 Aimant	Invitrogen	12321D
Fixable Viability Stain	BD Biosciences	565388
Flow cytometer	BD FACSAria™ Fusion Flow Cytometer	23-14816-01
Fluoromount G with DAPI	Invitrogen	00-4959-52
Genome browser	IGV		http://software.broadinstitute.org/software/igv/
Glycerol	Sigma-Aldrich	G9012
Hydrogel	Corning®	354277	Matrigel hESC qualified matrix
Image processing software	Image J®		V 1.8.0
Laboratory film	Sigma-Aldrich	P7793-1EA	PARAFILM® M
Liberase LT	Roche	5401020001
Propyl gallate	Sigma-Aldrich	2370
Sequencer	Illumina Hiseq 4000	SY-401-4001
Shaking water bath	Bioblock Scientific polytest 20	18724