Visualization of the transverse cytoskeletal network in insect-flight muscle by scanning-electron microscopy

Located at the level of the Z-line, the transverse cytoskeletal network of insect-flight muscle interconnects adjacent myofibrils with one another, and interconnects peripheral myofibrils with the cell membrane. This network has been presumed to keep myofibrils in register, or to distribute tension laterally among myofibrils. In this study, we used scanning-electron microscopy to reveal details of the three-dimensional arrangement of this network. The network is seen to interconnect longitudinal elements of the cytoskeletal network which surround each myofibril. The arrangement is not unlike that seen in vertebrate skeletal muscle. Interestingly, the transverse network makes contact with cell components such as dense bodies and mitochondria. Such contacts imply potential roles over and above those noted above. The network may be involved not only in mechanical function, but possibly also in intracellular communication.