The dermomyotome ventrolateral lip is essential for the hypaxial myotome formation

Qin Pu,Beate Brand-Saberi,Aisha Abduelmula,Dieter Schwandulla,Ruijin Huang,Maryna Masyuk,Carsten Theiss,Ketan Patel,Michael Hans

doi:10.1186/1471-213x-13-37

Abstract

BackgroundThe myotome is the primitive skeletal muscle that forms within the embryonic metameric body wall. It can be subdivided into an epaxial and hypaxial domain. It has been shown that the formation of the epaxial myotome requires the dorsomedial lip of the dermomyotome (DML). Although the ventrolateral lip (VLL) of the dermomyotome is believed to be required for the formation of the hypaxial myotome, experimentally evidence for this statement still needs to be provided. Provision of such data would enable the resolution of a debate regarding the formation of the hypaxial dermomyotome. Two mechanisms have been proposed for this tissue. The first proposes that the intermediate dermomyotome undergoes cellular expansion thereby pushing the ventral lateral lip in a lateral direction (translocation). In contrast, the alternative view holds that the ventral lateral lip grows laterally.ResultsUsing time lapse confocal microscopy, we observed that the GFP-labelled ventrolateral lip (VLL) of the dermomyotome grows rather than translocates in a lateral direction. The necessity of the VLL for lateral extension of the myotome was addressed by ablation studies. We found that the hypaxial myotome did not form after VLL ablation. In contrast, the removal of an intermediate portion of the dermomyotome had very little effect of the hypaxial myotome. These results demonstrate that the VLL is required for the formation of the hypaxial myotome.ConclusionOur study demonstrates that the dermomyotome ventrolateral lip is essential for the hypaxial myotome formation and supports the lip extension model. Therefore, despite being under independent signalling controls, both the dorsomedial and ventrolateral lip fulfil the same function, i.e. they extend into adjacent regions permitting the growth of the myotome.

Highlights

The myotome is the primitive skeletal muscle that forms within the embryonic metameric body wall
The dermomyotome ventrolateral lip grows into the somatopleura To view the cell movement of the VLL, a Green fluorescent protein (GFP)-expressing vector was introduced into the lateral part of epithelial somites at the interlimb level of chick embryos of about HH-16 by electroporation
Based on the observation that the width of the GFP-labelled cell layer increased continuously and the position of its medial border was relatively constant, we propose that the VLL grows actively in a lateral direction rather than being pushed by the intermediate part of the dermomyotome

Summary

Introduction

The myotome is the primitive skeletal muscle that forms within the embryonic metameric body wall. It can be subdivided into an epaxial and hypaxial domain. The ventrolateral lip (VLL) of the dermomyotome is believed to be required for the formation of the hypaxial myotome, experimentally evidence for this statement still needs to be provided. Provision of such data would enable the resolution of a debate regarding the formation of the hypaxial dermomyotome. The hypaxial component includes muscles of the ventrolateral body wall, girdle, limb and tongue. The myotome, is the primitive skeletal muscle that forms within embryonic metameric structures called the somite. The dorsal portion remains as an epithelium and forms a cell sheath, called the dermomyotome, which contributes to the formationof the dorsal dermis and skeletal muscle

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