Elsevier

Developmental Biology

Volume 357, Issue 1, 1 September 2011, Pages 108-116
Developmental Biology

Evolution of Developmental Control Mechanisms
Cellular and molecular investigations into the development of the pectoral girdle

https://doi.org/10.1016/j.ydbio.2011.06.031Get rights and content
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Abstract

The forelimbs of higher vertebrates are composed of two portions: the appendicular region (stylopod, zeugopod and autopod) and the less prominent proximal girdle elements (scapula and clavicle) that brace the limb to the main trunk axis.

We show that the formation of the muscles of the proximal limb occurs through two distinct mechanisms. The more superficial girdle muscles (pectoral and latissimus dorsi) develop by the “In–Out” mechanism whereby migration of myogenic cells from the somites into the limb bud is followed by their extension from the proximal limb bud out onto the thorax. In contrast, the deeper girdle muscles (e.g. rhomboideus profundus and serratus anterior) are induced by the forelimb field which promotes myotomal extension directly from the somites. Tbx5 inactivation demonstrated its requirement for the development of all forelimb elements which include the skeletal elements, proximal and distal muscles as well as the sternum in mammals and the cleithrum of fish. Intriguingly, the formation of the diaphragm musculature is also dependent on the Tbx5 programme. These observations challenge our classical views of the boundary between limb and trunk tissues. We suggest that significant structures located in the body should be considered as components of the forelimb.

Highlights

► Vertebrate forelimb girdle muscles develop through 3 mechanisms all. ► Tbx5 controls all components of the pectoral girdle. ► Muscular diaphragm development is controlled by Tbx5. ► Sternum development is controlled by Tbx5.

Keywords

Forelimb
Shoulder girdle
Muscle
Tbx5
Diaphragm
Sternum

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