Fgf regulates dedifferentiation during skeletal muscle regeneration in adult zebrafish.
Fibroblast growth factors (Fgfs) regulate critical biological processes such as embryonic development, tissue homeostasis, wound healing, and tissue regeneration. In zebrafish, Fgf signaling plays an important role in the regeneration of the spinal cord, liver, heart, fin, and photoreceptors, although its exact mechanism of action is not fully understood. Utilizing an adult zebrafish extraocular muscle (EOM) regeneration model, we demonstrate that blocking Fgf receptor function using either a chemical inhibitor (SU5402) or a dominant-negative transgenic construct (dnFGFR1a:EGFP) impairs muscle regeneration. Adult zebrafish EOMs regenerate through a myocyte dedifferentiation process, which involves a muscle-to-mesenchyme transition and cell cycle reentry by differentiated myocytes. Blocking Fgf signaling reduced cell proliferation and active caspase 3 levels in the regenerating muscle with no detectable levels of apoptosis, supporting the hypothesis that Fgf signaling is involved in the early steps of dedifferentiation. Fgf signaling in regenerating myocytes involves the MAPK/ERK pathway: inhibition of MEK activity with U0126 mimicked the phenotype of the Fgf receptor inhibition on both muscle regeneration and cell proliferation, and activated ERK (p-ERK) was detected in injured muscles by immunofluorescence and western blot. Interestingly, following injury, ERK2 expression is specifically induced and activated by phosphorylation, suggesting a key role in muscle regeneration. We conclude that the critical early steps of myocyte dedifferentiation in EOM regeneration are dependent on Fgf signaling.
Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA.
Alfonso
A
Saera-Vila
Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA.
Phillip E
PE
Kish
Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA. Electronic address: akahana@med.umich.edu.
Alon
A
Kahana
D000375:Aging / Q000502:physiology*; D000818:Animals; D054337:Cell Dedifferentiation; D049109:Cell Proliferation; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000502:physiology*; D009801:Oculomotor Muscles; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000378:metabolism; D012038:Regeneration; D015027:Zebrafish / Q000502:physiology*
C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D005346:Fibroblast Growth Factors; D051496:Receptor, Fibroblast Growth Factor, Type 1
Cell cycle; Cell reprogramming; Heat-shock; MMT; Strabismus