The Role of Filamin in the Morphogenesis of the Skeletal Muscle Sarcomere

Citation

Gomer, Richard Hans (1983) The Role of Filamin in the Morphogenesis of the Skeletal Muscle Sarcomere. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/97M8-B306. https://resolver.caltech.edu/CaltechETD:etd-12212004-095323

Abstract

During chicken skeletal myogenesis in tissue culture, filamin is found on stress fibers in myoblasts and early myotubes. Approximately one day after fusion and shortly before α-actinin transits to Z lines, filamin disappears from the cells. The disappearance of filamin is correlated with a cessation of its synthesis. Approximately six days after fusion, filamin reappears at the Z lines of myogenic cells, shortly before desmin and vimentin transit to the Z line. In adult muscle, filamin is found at the periphery of the Z disk, along with desmin and vimentin. Peptide map analysis of the various filamins shows that gizzard and fibroblast filamins are identical while myoblast filamin is quite similar to these two filamins. Cultured myotube and adult myofibril filamins are virtually identical to each other and are quite different polypeptides when compared to gizzard, fibroblast and myoblast filamins. Analysis of terminally differentiated slow and fast muscle shows that both muscle types contain identical, skeletal muscle type filamins although in the slow muscle, filamin is distributed additionally on the I band. The molar filamin to actin ratio is 1:25 in gizzard and fibroblast, 1:54 in myoblasts, 1:820 in fast skeletal myofibrils and 1:82 in slow skeletal myofibrils.

These results offer several new insights into eucaryotic molecular morphogenesis. From the disappearance of filamin during myogenesis, we see that a morphogenetic process may involve the temporary removal of a family of proteins. The different distributions of identical filamin polypeptides in slow and fast muscle indicates that filamin may be synthesized at different times and rates in the two myogenic processes. It appears that, at least in the case of the skeletal muscle sarcomere, temporal control of protein synthesis may be an important part of eucaryotic molecular morphogenesis.

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