Molecular Mechanisms Governing Early Myogenesis of Mouse Tongue

Abstract

The tongue muscle develops from myogenic precursor cells that undergo long-range migration from the occipital somites to tongue primordium. In this article, we aimed to overview cellular and molecular events taking place during the migration of tongue myogenic precursor cells in embryonic mice. Immunohistochemical techniques were used to determine the chronology and positions of desmin expression during early tongue development. Based on the three-dimensional (3D) reconstruction of serial desmin-immunostained images, we defined the discrete migration pathway of myogenic precursor cells as follows: occipital somites→mesenchyme of trunk→ventral areas of the fourth→third and second branchial arches before arriving at the median mandibular arches around E10.3. The migrating myogenic precursor cells were characterized as desmin-positive/MyoD-negative cells with the development of lamellipodia and expression of Rho family genes. Once within the tongue primordium, myogenic precursor cells were ready to switch off their migratory phenotypes and express myogenic regulatory factors (MRFs). Although multiple signaling cues have been supposed to exert effects on the migration and terminal differentiation of tongue myogenic precursor cells, the exact molecular mechanisms and cellular interactions remain to be elucidated.