Spotlight on Research for 2004

January 2004 (historical)

"Humming" Toadfish Reveals Muscle Design Principles to NIAMS Scientists

Scientists in the NIAMS Intramural Research Program are discovering the latest in muscle design principles from a toadfish that hums.

Kuan Wang, Ph.D., and his colleagues in the Laboratory of Muscle Biology have been studying the plainfin midshipman type I male fish, a curious sea creature with poisonous spines, light-producing skin and impressive mating ritual. During the breeding season, the male fish attracts females by emitting loud, long hums. This mating sound is produced by the rapid vibration of certain sound-producing muscles, which causes the fish's air bladder to reverberate. These "sonic" muscles are among the fastest and most enduring muscles known, beating 6,000 times a minute and lasting hours without resting.

Using electron and other types of imaging techniques, Dr. Wang and his group have discovered an elaborate cytoskeletal network within the fish's specialized muscle cells that allow super-fast, high-endurance contraction. Included among the novel features of this network are the orientation and shape of myofibrils, which are structures in cells' cytoplasm that cause contractions; the distribution and abundant number of mitochondria, the energy-producing power plants of cells; formations of protein filaments that link myofibrils, mitochondria and nuclei; unique junctional complexes and extraordinarily wide Z bands where sarcomeres-the contracting units that make up myofibrils-come together. The scientists propose that the cytoskeletal network, the unique junctional complexes and the wide Z bands, are adaptations that make possible the high-frequency and high-endurance activity of the sonic muscles.

These special characteristics make the male midshipman type I sonic muscle a valuable model system, one which may even offer possible clues to the cause of nemaline myopathy, a muscle disease with at least one structural similarity to the midshipman sonic muscle. "Our work reveals the design and engineering principles of 'fast and furious' muscle," says Dr. Wang. "We see them as important parameters in tissue engineering for musculoskeletal systems."

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Lewis M, et. al. Concentric intermediate filament lattice links to specialized Z-band junctional complexes in sonic muscle fibers of the type I male midshipman fish. J Struct Biol 2003:143:56-71.