Amniote somite derivatives

Abstract

Somites are segments of paraxial mesoderm that give rise to a multitude of tissues in the vertebrate embryo. Many decades of intensive research have provided a wealth of data on the complex molecular interactions leading to the formation of various somitic derivatives. In this review, we focus on the crucial role of the somites in building the body wall and limbs of amniote embryos. We give an overview on the current knowledge on the specification and differentiation of somitic cell lineages leading to the development of the vertebral column, skeletal muscle, connective tissue, meninges, and vessel endothelium, and highlight the importance of the somites in establishing the metameric pattern of the vertebrate body. Developmental Dynamics 236:2382-2396, 2007.

Extracellular matrix remodeling accompanies axial muscle development and morphogenesis in the mouse

“…Soon after their formation, somites undergo a compartmentalization giving rise to the sclerotome (origin of vertebrae, ribs, and tendons of back muscles) and the epithelial dermomyotome (origin of skeletal muscle, dermal, some endothelial, smooth muscle, and brown fat precursors; Kalcheim and Ben-Yair, 2005;Buckingham, 2006;Christ et al, 2007;Seale et al, 2008). Migratory muscle progenitors delaminate from the hypaxial lip of the dermomyotome at specific axial levels and migrate to their final destination (e.g., limbs, diaphragm).…”

Many routes to the same destination: lessons from skeletal muscle development

“…1). Somites are found throughout the chordates and are the source of all the skeletal muscle of the trunk and limbs as well as some head muscles, such as the tongue muscles (Noden et al 1999, Brent & Tabin 2002, Christ et al 2007. Somites begin forming at the anterior of the embryo and are added posteriorly as the embryo extends.…”

“…These include the sclerotome, which will give rise to vertebrae and ribs, the dermatome, which produces the dorsal dermis, the syndetome, from where axial tendons are derived, and the myotome, which is where muscle differentiation first occurs (Brent et al 2003, Christ et al 2007. Myogenic precursors can first be detected in the dermomyotome, a characteristic 'C'-shaped epithelial structure containing a mixture of myogenic and dermal progenitors (see Fig.…”

Cell lineages and early patterns of embryonic CNS vascularization

“…15 Of note, the dorsal aortas arise as paired structures from confluent blood islands and subsequently fuse into a single aorta along the a-p axis. Synchronous with neurulation, segmental epithelial blocks, the somites, 16 condense in the paraxial mesoderm, i.e., on either side of the NT and notochord. In each somite, 17,18 gene expression patterns establish an a-p and d-v axis, whereby a ventral sclerotome which expresses Pax1 is induced via Shh signaling from the notochord, and is separated from a dorsal dermamyotome (expressing Pax3, induced via Wnt signaling from the NT roof plate).…”