Anastral spindle assembly and ?-tubulin in Drosophila oocytes.

ABSTRACT: Anastral spindles assemble by a mechanism that involves microtubule nucleation and growth from chromatin. It is still uncertain whether ?-tubulin, a microtubule nucleator essential for mitotic spindle assembly and maintenance, plays a role. Not only is the requirement for ?-tubulin to form anastral Drosophila oocyte meiosis I spindles controversial, but its presence in oocyte meiosis I spindles has not been demonstrated and is uncertain.We show, for the first time, using a bright GFP fusion protein and live imaging, that the Drosophila maternally-expressed ?Tub37C is present at low levels in oocyte meiosis I spindles. Despite this, we find that formation of bipolar meiosis I spindles does not require functional ?Tub37C, extending previous findings by others. Fluorescence photobleaching assays show rapid recovery of ?Tub37C in the meiosis I spindle, similar to the cytoplasm, indicating weak binding by ?Tub37C to spindles, and fits of a new, potentially more accurate model for fluorescence recovery yield kinetic parameters consistent with transient, diffusional binding.The FRAP results, together with its mutant effects late in meiosis I, indicate that ?Tub37C may perform a role subsequent to metaphase I, rather than nucleating microtubules for meiosis I spindle formation. Weak binding to the meiosis I spindle could stabilize pre-existing microtubules or position ?-tubulin for function during meiosis II spindle assembly, which follows rapidly upon oocyte activation and completion of the meiosis I division.

SUBMITTER: Endow SA 

PROVIDER: S-EPMC3022845 | biostudies-other | 2011 Jan

REPOSITORIES: biostudies-other