Establishment of the epaxial–hypaxial boundary in the avian myotome
Version of Record online: 5 MAY 2006
Copyright © 2006 Wiley-Liss, Inc.
Volume 235, Issue 7, pages 1884–1894, July 2006
How to Cite
Ahmed, M. U., Cheng, L. and Dietrich, S. (2006), Establishment of the epaxial–hypaxial boundary in the avian myotome. Dev. Dyn., 235: 1884–1894. doi: 10.1002/dvdy.20832
- Issue online: 22 MAY 2006
- Version of Record online: 5 MAY 2006
- Manuscript Accepted: 24 MAR 2006
- Human Frontier Science Program. Grant Number: R6Y0056/2004-C201
- European Network of Excellence Myores. Grant Number: EU LSHG-CT-2004-511978 MYORES
- Association Française contre les Myopathies. Grant Numbers: CL/NM/2005.2088/, 11378, A07/06/05, 01/07/05, DRM05/BUIOCE/REFAP/MUSAI/ANGLE.
- skeletal muscle;
- chick embryo
Trunk skeletal muscles are segregated into dorsomedial epaxial and ventrolateral hypaxial muscles, separated by a myoseptum. In amniotes, they are generated from a transient structure, the dermomyotome, which lays down muscle, namely the myotome underneath. However, the dermomyotome and myotome are dorsoventrally continuous, with no morphologically defined epaxial–hypaxial boundary. The transcription factors En1 and Sim1 have been shown to molecularly subdivide the amniote dermomyotome, with En1 labeling the epaxial dermomyotome and Sim1 the hypaxial counterpart. Here, we demonstrate that En1 and Sim1 expression persists in cells leaving the dermomyotome, superimposing the expression boundary onto muscle and skin. En1-expressing cells colonize the myotome initially from the rostral and caudal lips, and slightly later, directly from the de-epithelializing dermomyotomal center. En1 expression in the myotome is concomitant with the appearance of Fgfr4/Pax7-expressing mitotically active myoblasts. This finding suggests that Fgfr4+/Pax7+/En1+ cells carry their expression with them when entering the myotome. Furthermore, it suggests that the epaxial–hypaxial boundary of the myotome is established through the late arising, mitotically active myoblasts. Developmental Dynamics 235:1884–1894, 2006. © 2006 Wiley-Liss, Inc.