Muscle–Tendon Interactions in the Absence of Bones: Lessons from the Fruit Fly, Drosophila - Structural Interfaces and Attachments in Biology - page 124

at the cytoplasmic faces of the tendon-cell MTJ, where it promotes the polarized
organization of the plus ends of microtubules that are stretched between the MTJ and
the cuticle. Reduction at the levels of Shot leads to dissociation of the MT plus ends
from the MTJ and extensive elongation of the tendon cell. These results suggest that
the polarized array of MT within the tendon cells is critical for the tendon cell to resist
muscle contraction.
6.7 Conclusions
Analysis of the fly musculoskeletal system reveals unique solutions to overcome
issues shared with musculoskeletal assembly and function in vertebrates. For
example, instead of multiple tendon cells in vertebrates that share the muscle-
generated forces between many cell units, in Drosophila , the force is divided
between multiple MT-fibers within a single cell. Analysis of the fly musculo-
skeleton enables us to define the critical phases essential for the correct functional-
ity of this system. These include: (a) the precise encounter between muscles and
their corresponding tendon cells; (b) the critical role of the integrin receptors in the
formation of the MTJ, and the gradual construction of the MTJ to accommodate the
final morphology of the muscle and tendon ends; (c) the elasticity of the tendon
cells that is maintained by the MT system; and (d) the essential role of the ECM and
its precise assembly and deposition during MTJ formation.
Acknowledgment The studies described in this review were supported by a grant from the
Israel Science Foundation to T. Volk and a previous grant from the Minerva Foundation with
funding from the Federal German Ministry of Education and Research to T. Volk. I also thank
S. Schwarzbaum for her English corrections of this chapter.
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