File:Somite patterning.jpg

Somite Patterning and Fate

Somite development involves two patterning systems operating along the A-P and D-V axes. (i) Unsegmented presomite mesoderm and nascent somites showing the oscillations and gradients of gene activity that determine A-P polarity prior to overt somite formation (green: anterior half-somite; red: posterior half-somite). (ii) Transverse section through an A-half-epithelial somite (esm, left) and a differentiated somite (right). Patterning along the D-V axis sub-divides the somite into dermatome (dr), myotome (m) and sclerotome (s). The sclerotome is further sub-divided into ventral (v), central (s, red) and (d) dorsal regions. (iii) Representation of two somites viewed laterally, showing the central sclerotome A-P sub-division. Only the anterior-half (green) is permissive for PNS components. (iv) In differentiated vertebrae, posterior-central sclerotomes form the paired transverse processes and pedicles of the neural arches (red) that encase the spinal cord and provide attachment points for epaxial muscles. Anterior central-sclerotome derivatives (green) contribute to peripheral nerve sheaths and prefigure the positions of the intervertebral foraminae (ivf). Spinous process (sp), intervertebral disc (ivd), vertebral body (vb).

Reference

Hughes et al. BMC Developmental Biology 2009 9:30 doi:10.1186/1471-213X-9-30 The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-213X/9/30

Original Image name: 1471-213X-9-30-1.jpg 1471-213X-9-30-1.jpg

© 2009 Hughes et al; licensee BioMed Central Ltd.

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