Wac: a new Augmin subunit required for chromosome alignment but not for acentrosomal microtubule assembly in female meiosis

The bipolar spindle forms without centrosomes naturally in female meiosis and by experimental manipulation in mitosis. Augmin is a recently discovered protein complex required for centrosome-independent microtubule generation within the spindle in Drosophila melanogaster cultured cells. Five subunits of Augmin have been identified so far, but neither their organization within the complex nor their role in developing organisms is known. In this study, we report a new Augmin subunit, wee Augmin component (Wac). Wac directly interacts with another Augmin subunit, Dgt2, via its coiled-coil domain. Wac depletion in cultured cells, especially without functional centrosomes, causes severe defects in spindle assembly. We found that a wac deletion mutant is viable but female sterile and shows only a mild impact on somatic mitosis. Unexpectedly, mutant female meiosis showed robust microtubule assembly of the acentrosomal spindle but frequent chromosome misalignment. For the first time, this study establishes the role of an Augmin subunit in developing organisms and provides an insight into the architecture of the complex

Anastral spindle assembly and γ-tubulin in Drosophila oocytes

<p>Abstract</p> <p>Background</p> <p>Anastral spindles assemble by a mechanism that involves microtubule nucleation and growth from chromatin. It is still uncertain whether γ-tubulin, a microtubule nucleator essential for mitotic spindle assembly and maintenance, plays a role. Not only is the requirement for γ-tubulin to form anastral <it>Drosophila </it>oocyte meiosis I spindles controversial, but its presence in oocyte meiosis I spindles has not been demonstrated and is uncertain.</p> <p>Results</p> <p>We show, for the first time, using a bright GFP fusion protein and live imaging, that the <it>Drosophila </it>maternally-expressed γTub37C 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 γTub37C, extending previous findings by others. Fluorescence photobleaching assays show rapid recovery of γTub37C in the meiosis I spindle, similar to the cytoplasm, indicating weak binding by γTub37C to spindles, and fits of a new, potentially more accurate model for fluorescence recovery yield kinetic parameters consistent with transient, diffusional binding.</p> <p>Conclusions</p> <p>The FRAP results, together with its mutant effects late in meiosis I, indicate that γTub37C 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 γ-tubulin for function during meiosis II spindle assembly, which follows rapidly upon oocyte activation and completion of the meiosis I division.</p

Are blogs edited? A linguistic survey of Italian blogs using search engines

Many blogs are written by people with no formal training in public writing; this could suggest a low level of editing and general correctness. A quantitative analysis of misspellings, however, shows that in their orthography Italian blogs are as well revised as conventional Italian newspaper texts. On the other hand, their editing is more careful than the editing of the average of Italian web pages

La lingua moderna dei romanzi storici

Diversi romanzi storici italiani pubblicati a partire dagli anni Novanta hanno fatto ricorso a un linguaggio diverso da quello tradizionale della narrativa di genere. In particolare, dai lavori dei Wu Ming fino a quelli di Alan D. Altieri, i dialoghi di storie ambientate a secoli di distanza sono stati resi con molti tratti di italiano colloquiale contemporaneo. Il contributo esamina questi tratti, particolarmente in rapporto all'italiano neostandard, confrontandoli con quelli di testi analoghi provenienti da altre tradizioni