Sclerotome-derived slit1 drives directional migration and differentiation of robo2-expressing pioneer myoblasts

Osnat Halperin-Barlev, Chaya Kalcheim*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Pioneer myoblasts generate the first myotomal fibers and act as a scaffold to pattern further myotome development. From their origin in the medial epithelial somite, they dissociate and migrate towards the rostral edge of each somite, from which differentiation proceeds in both rostral-to-caudal and medial-to-lateral directions. The mechanisms underlying formation of this unique wave of pioneer myofibers remain unknown. We show that rostrocaudal or mediolateral somite inversions in avian embryos do not alter the original directions of pioneer myoblast migration and differentiation into fibers, demonstrating that regulation of pioneer patterning is somite-intrinsic. Furthermore, pioneer myoblasts express Robo2 downstream of MyoD and Myf5, whereas the dermomyotome and caudal sclerotome express Slit1. Loss of Robo2 or of sclerotome-derived Slit1 function perturbed both directional cell migration and fiber formation, and their effects were mediated through RhoA. Although myoblast specification was not affected, expression of the intermediate filament desmin was reduced. Hence, Slit1 and Robo2, via RhoA, act to pattern formation of the pioneer myotome through the regulation of cytoskeletal assembly.

Original languageAmerican English
Pages (from-to)2935-2945
Number of pages11
JournalJournal of Embryology and Experimental Morphology
Issue number14
StatePublished - 15 Jul 2011


  • Avian embryo
  • Dermomyotome
  • Desmin
  • Myf5
  • MyoD
  • Myofiber patterning
  • Myotome
  • Rho GTPases
  • Somite


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