BIOL303 Lecture Notes - Paraxial Mesoderm, Notch Signaling Pathway, Fgf8
19 Dec 2013
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Document Summary
A somite is a segment/ball of mesoderm derived from paraxial mesoderm adjacent to the notochord. It will initially differentiate into the sclerotome and the dermamyotome, the latter becomes the dermatome and myotome. Paraxial mesoderm is set up noggin, a bmp antagonist which blocks bmp signalling: the presomitic mesoderm shows an oscillating pattern of gene expression with respect to the c-hairy1 (as well as some other genes) in the chick embryo. Experiments were shown that waves of c-hairy1 expression corresponded to the timing of somite formation. However, it was confirmed through cell labelling experiments that cells did not move to generate these pattern differences and surgical experiments showed that there was no propagation of any activating signals. The notch signalling pathway is involved in establishing somite boundaries by separating them into anterior and posterior regions. Chimeric embryos were useful in establishing the mechanism by which somite boundaries are established because it proved that the same method existed in other species.
