Muscle–Tendon Interactions in the Absence of Bones: Lessons from the Fruit Fly, Drosophila - Structural Interfaces and Attachments in Biology - page 114

Chapter 6
Muscle-Tendon Interactions in the Absence
of Bones: Lessons from the Fruit Fly, Drosophila

Talila Volk

6.1 Introduction

Invertebrates provide a unique system in which to study how the musculoskeletal
system operates and functions in the absence of bone structures. The fruit fly
Drosophila Melanogaster has been used as an exciting animal model to study and
elucidate various aspects of embryonic development, including the initial steps of
muscle and tendon development and patterning [ 1 - 3 ].
Whereas Drosophila does not contain cartilage/bone elements, the muscles are
connected to specialized muscle attachment cells that are part of the epidermal cell
layer, which together with the cuticle, form the exoskeleton [ 1 , 4 ]. These epidermal
cells function as muscle attachment sites and develop into a specialized subset of
epidermal cells, referred to as tendons. Despite the fact that these tendon cells
appear considerably different from the collagen fiber-rich, multicellular tendons of
vertebrates, some of the principles of tendon cell determination, and especially their
cross-talk with muscles and the formation of the myotendinous junction (MTJ),
appear to be conserved in evolution; therefore, tendon formation in the fly can serve
as a paradigm for the corresponding processes in the vertebrate embryo.
Two unique features of the musculoskeletal system in flies that are not present in
vertebrates are the absence of bones and the one-to-two relationship between a
single muscle cell and its corresponding two tendon cells that connect both ends of
the muscle. In such a scenario, the mechanical force produced by muscle contrac-
tion is transmitted directly to the two tendon cells at both its ends. Therefore, the
structure of these tendons must be robust to resist muscle contractions and to
maintain the integrity of the entire ectoderm.
The following chapter describes the origin as well as the differentiation
pathway promoting tendon development in Drosophila embryonic development,

T. Volk ( * )
Department of Molecular Genetics, Weizmann Institute, Rehovot, Israel
e-mail: [e-mail]