File:Muscle elongation.png

Cartoon of WT embryo showing the three phases of muscle elongation.

In the oldest/most anterior somites, myotubes have formed and are attached to the MTJs. The transition region contains cells intercalating by extending protrusions that are subsequently filled. Muscle precursor cells exhibit protrusive activity in all directions. A1: Magnification of a somite in panel A showing proteins concentrated at the MTJ and boundary capture of recently elongated cells.

B–B1) Cartoon of laminin mutant embryo at the same age as WT embryo in panel A showing the same three phases of muscle morphogenesis, but with a developmental delay. Cells in yellow are aberrantly long and have invaded into neighboring myotomes. B1: Magnification of two somites in panel B that depicts a model of how boundary crossing could occur in laminin mutant embryos. If laminin is absent, there may be randomly spaced locations at the MTJ devoid of proteins that function in boundary capture. Elongating muscle cells would invade the MTJ at these locations.

C) Cartoon model showing the two-step mechanism of elongating. We show that adhesion to the matrix is required for normal elongation and hypothesize that cells also utilize cell-cell adhesion to generate traction forces needed for protrusion extension and filling.

D) Model accounting for developmental delay in muscle morphogenesis that occurs in laminin mutants. Cartoon depicting a laminin mutant cell undergoing two-step elongation via protrusion extension and filling. Lack of the cell-matrix adhesion protein laminin results in less traction and therefore slower extension and/or filling.

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http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000219

Citation: Snow CJ, Goody M, Kelly MW, Oster EC, Jones R, et al. (2008) Time-Lapse Analysis and Mathematical Characterization Elucidate Novel Mechanisms Underlying Muscle Morphogenesis. PLoS Genet 4(10): e1000219. doi:10.1371/journal.pgen.1000219

Copyright: © 2008 Snow et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.