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| Assembly of Myofibrils in Developing Chick Myotubes |
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| N.M. McKenna, C.S. Johnson and Y.-l. Wang (1986) |
| J. Cell Biol. 103:2163-2171. |
| Mature muscle cells contain highly organized myofibrils, which consist of well aligned contractile units of sarcomeres. During embryonic development, sarcomere assembly starts as randomly distributed contractile units, which gradually turn into organized array of myofibrils. To study this process, fluorescently labeled alpha-actinin was microinjected into developing chick myotubes to label the Z-lines, where actin filaments are anchored along myofibrils, and their precursors. |
| Formation and Alignment of Z Lines in Developing Myotubes |
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Size = 272 x 136 pixels.
Size = 304 x 96 pixels.
Size = 256 x 232 pixels.| The precursor of Z-lines consists of many punctate structures referred to as Z-bodies. During development these Z-bodies merge into short lines with a characteristic spacing. Neighboring short Z-lines then merge to form long Z-lines across the myotube. The alignment of Z-lines is a trial-and-error process: Z-lines of neighboring myofibrils constantly associate and dissociate. Misaligned associations are unstable and are gradually replaced by correct, more stable associations. |