Requirement of the fusogenic micropeptide myomixer for muscle formation in zebrafish

Proc Natl Acad Sci U S A. 2017 Nov 7;114(45):11950-11955. doi: 10.1073/pnas.1715229114. Epub 2017 Oct 23.


Skeletal muscle formation requires fusion of mononucleated myoblasts to form multinucleated myofibers. The muscle-specific membrane proteins myomaker and myomixer cooperate to drive mammalian myoblast fusion. Whereas myomaker is highly conserved across diverse vertebrate species, myomixer is a micropeptide that shows relatively weak cross-species conservation. To explore the functional conservation of myomixer, we investigated the expression and function of the zebrafish myomixer ortholog. Here we show that myomixer expression during zebrafish embryogenesis coincides with myoblast fusion, and genetic deletion of myomixer using CRISPR/Cas9 mutagenesis abolishes myoblast fusion in vivo. We also identify myomixer orthologs in other species of fish and reptiles, which can cooperate with myomaker and substitute for the fusogenic activity of mammalian myomixer. Sequence comparison of these diverse myomixer orthologs reveals key amino acid residues and a minimal fusogenic peptide motif that is necessary for promoting cell-cell fusion with myomaker. Our findings highlight the evolutionary conservation of the myomaker-myomixer partnership and provide insights into the molecular basis of myoblast fusion.

Keywords: fusogenic; micropeptide; myogenesis; myomaker; zebrafish.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • CRISPR-Cas Systems / genetics
  • Cell Fusion
  • Cell Line
  • Elephants / genetics
  • Membrane Proteins / genetics*
  • Muscle Development / genetics*
  • Muscle Development / physiology
  • Muscle Fibers, Skeletal / cytology*
  • Muscle Proteins / genetics*
  • Myoblasts / metabolism*
  • Sharks / genetics
  • Turtles / genetics
  • Zebrafish / embryology
  • Zebrafish / genetics
  • Zebrafish Proteins / genetics*


  • Membrane Proteins
  • Muscle Proteins
  • Zebrafish Proteins
  • mymk protein, zebrafish