Monash University

DEV 2011 DEV2011 Lecture Note 14.Lecture 14

Developmental Biology - Gilbert
Chapter 9
 Mature somite contain 3 major compartments: scleotome, which forms the
vertebrate and rib cartilage; myotome, which forms the musculature of the
back, rub cage, and ventral body wall; and dermamyotome, which contains
skeletal muscle progenitor cells and the cells that generate the dermis of the
back.
 Important component of somitogenesis are: periodicity; fissure formation;
epithelialization; specification; differentiation.
 Somite formation begin as paraxial mesoderm cells become organized into
whorls of cells called somitomeres
 Somite formation depends on oscillating signal provided by Notch and Wnt
pathways, and rostral-to-caudal gradient provides a moving “wave” of an FGF
that sets the somite boundaries.
Separation of somites from the unsegmented mesoderm
 Two proteins critical for fissure formation and somite separation are the Eph
tyrosine kinases and their ligants, the ephrin protein.
Differentiation of Somites