Microtubule assembly in cultured myoblasts and myotubes following XXXX induced microtubule depolymerisation.

@entity10612 @entity16144 @entity43162 @entity9653
When myoblasts fuse into myotubes, the organisation of the cytoskeleton changes dramatically. For example, microtubules emanate in a radial array form the centrosome in myoblasts, but form linear arrays not linked to a centrosome in myotubes. It is not clear how these linear arrays are formed and nucleated. They could arise in a number of ways: by nucleation and release from centrosomal like structures, cytoplasmic assembly, breakage/severing or nucleation from non-centrosomal sites. To test which of the above mechanisms or combination of mechanisms are responsible we investigated the re-formation of microtubules after depolymerisation by @entity10612 , using antibodies against @entity16144 , gamma-tubulin, @entity43162 , and tyrosinated @entity9653 . In myoblasts, we found that when microtubules were allowed to recover after complete depolymerisation with @entity10612 , microtubule recovery began within 1 min and was complete after 5 min. Microtubules grew out from the centrosome, which was positively stained for gamma-tubulin or @entity16144 . In untreated myotubes, microtubules were arranged in linear arrays, with @entity43162 at their ends. The pericentriolar protein, @entity16144 was arranged in a band around the nucleus as well as discrete spots in the cytoplasm. In contrast, the microtubule nucleating protein gamma-tubulin was not found in a band around the nucleus, but was found in several punctuate spots throughout the cytoplasm. Further, when microtubules were allowed to recover, after complete depolymerisation with @entity10612 , recovery was not as rapid as that seen in myoblasts, and we found that regrowth began with the formation of short microtubule fragments throughout the cytoplasm. Gamma-tubulin was associated with these fragments. These results suggest that in myotubes, nucleation of microtubules can be non-centrosomal.
