Key result
Vertebrate striated muscles exhibit either simple or superlattice forms of myosin filaments, which emerged during evolution and may lead to different contractile behaviors.
This historical review highlights the evolutionary emergence and functional differences between simple and superlattice forms of myosin filaments in vertebrate striated muscles.
No immediate clinical implications for cardiac care; leaves open whether lattice variants influence human contractile disorders.
Myosin filaments in vertebrate striated muscle have a long roughly cylindrical backbone with cross-bridge projections on the surfaces of both halves except for a short central bare zone. In the middle of this central region the filaments are cross-linked by the M-band which holds them in a well-defined hexagonal lattice in the muscle A-band. During muscular contraction the M-band-defined rotation of the myosin filaments around their long axes influences the interactions that the cross-bridges can make with the neighbouring actin filaments. We can visualise this filament rotation by electron microscopy of thin cross-sections in the bare-region immediately adjacent to the M-band where the filament profiles are distinctly triangular. In the muscles of teleost fishes, the thick filament triangular profiles have a single orientation giving what we call the simple lattice. In other vertebrates, for example all the tetrapods, the thick filaments have one of two orientations where the triangles point in opposite directions (they are rotated by 60° or 180°) according to set rules. Such a distribution cannot be developed in an ordered fashion across a large 2D lattice, but there are small domains of superlattice such that the next-nearest neighbouring thick filaments often have the same orientation. We believe that this difference in the lattice forms can lead to different contractile behaviours. Here we provide a historical review, and when appropriate cite recent work related to the emergence of the simple and superlattice forms by examining the muscles of several species ranging back to primitive vertebrates and we discuss the functional differences that the two lattice forms may have.
No takes yet. Share an insight, caveat, or question.
Luther et al. (2014) conducted a review in Vertebrate striated muscle structure. Myosin filament lattice forms (simple vs superlattice) was evaluated. Vertebrate striated muscles exhibit either simple or superlattice forms of myosin filaments, which emerged during evolution and may lead to different contractile behaviors.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: