Single cell dynamics of embryonic muscle progenitor cells in zebrafish

Abstract

statement: 25 Live imaging and single cell clonal analysis reveal dynamic behaviors of zebrafish embryonic 26 muscle progenitor cells in quiescence and activation. 27 2 ABSTRACT 28 29Muscle stem cells hold a great therapeutic potential in regenerating damaged muscles. 30However, the in vivo behavior of muscle stem cells during muscle growth and regeneration is 31 still poorly understood. Using zebrafish as a model, we describe the in vivo dynamics and 32 function of dermomyotome cells, a population of embryonic muscle progenitor cells. 33Dermomyotome cells are located in a superficial layer external to muscle fibers and express 34 many extracellular matrix (ECM) genes including col1a2. Utilizing a new col1a2 transgenic 35 line, we show that dermomyotome cells display a ramified morphology with dynamic cellular 36 processes. Cell lineage tracing demonstrates that col1a2 + dermomyotome cells contribute to 37 normal muscle growth as well as muscle injury repair. Combination of live imaging and single 38 cell clonal analysis reveals a highly-choreographed process of muscle regeneration. 39Activated dermomyotome cells change from the quiescent ramified morphology to a polarized 40 and elongated morphology and generate daughter cells that fuse with existing muscle fibers. 41

Origin and diversification of fibroblasts from the sclerotome in zebrafish

“…In nkx3.1 NTR-mCherry embryos, mCherry + cells can be seen populating both the dorsal and ventral regions in the major lobe of the fin fold (Fig 1B and S1B). Using a mosaic col1a2:Gal4; UAS:Kaede line (referred to as col1a2 Kaede ) (Sharma et al, 2019), we visualized the cell morphology at high resolution (Fig 1C). These Kaede + fin cells were characterized by extensive "treelike" cellular processes projecting towards the periphery of the fin fold (Fig 1B and 1C).…”

“…The copyright holder for this preprint (which this version posted April 19, 2021. ; https://doi.org/10.1101/2021.04.19.440421 doi: bioRxiv preprint 9 performed single cell clonal analysis on sclerotome progenitors as previously described (Sharma et al, 2019). We focused on the smaller dorsal domain to ensure precise single cell photoconversion and accurate cell tracing.…”

“…Zebrafish strains used in this study were maintained and raised under standard conditions. The following transgenic strains were used in this study: Tg(BRE:GFP)mw29 (Collery and Link, 2011), TgBAC(col1a2:Gal4)ca102 (Ma et al, 2018;Sharma et al, 2019), TgBAC(col1a2:GFP)ca103 , Tg(kdrl:EGFP)la163 (Choi et al, 2007), TgBAC(nkx3.1:Gal4)ca101 (Ma et al, 2018), Tg(UAS:Kaede)s1999t (Davison et al, 2007), and Tg(UAS:NTR-mCherry)c264 (Davison et al, 2007).…”

Stem cells in skeletal muscle growth and regeneration in amniotes and teleosts: Emerging themes

“…The second population of muscle stem cells resides in a teleost specific structure known as the external cell layer (ECL), which is formed during myogenesis from the anterior compartment of the somite, and subsequently sits on the lateral surface of the animal (Hollway et al, ; Stellabotte, Dobbs‐McAuliffe, Fernández, Feng, & Devoto, ). This structure serves a similar role to the amniote dermomyotome but unlike the latter it exists throughout the life of the animal and is critical for secondary myogenesis and growth of the teleost myotome (discussed below) (Marschallinger, Obermayer, Sänger, Stoiber, & Steinbacher, ; Nguyen et al, ; Sharma, Ruel, Kocha, Liao, & Huang, ). These stem cells are from here on referred to as growth‐specific stem cells.…”