title: Dgp71WD is required for the assembly of the acentrosomal Meiosis I spindle, and is not a general targeting factor for the γ-TuRC.
abstract: Dgp71WD/Nedd1 proteins are essential for mitotic spindle formation. In human cells, Nedd1 targets γ-tubulin to both centrosomes and spindles, but in other organisms the function of Dgp71WD/Nedd1 is less clear. In Drosophila cells, Dgp71WD plays a major part in targeting γ-tubulin to spindles, but not centrosomes, while in Xenopus egg extracts, Nedd1 acts as a more general microtubule (MT) organiser that can function independently of γ-tubulin. The interpretation of these studies, however, is complicated by the fact that some residual Dgp71WD/Nedd1 is likely present in the cells/extracts analysed. Here we generate a Dgp71WD null mutant lacking all but the last 12 nucleotides of coding sequence. The complete loss of Dgp71WD has no quantifiable effect on γ-tubulin or Centrosomin recruitment to the centrosome in larval brain cells. The recruitment of γ-tubulin to spindle MTs, however, is severely impaired, and spindle MT density is reduced in a manner that is indistinguishable from cells lacking Augmin or γ-TuRC function. In contrast, the absence of Dgp71WD leads to defects in the assembly of the acentrosomal female Meiosis I spindle that are more severe than those seen in Augmin or γ-TuRC mutants, indicating that Dgp71WD has additional functions that are independent of these complexes in oocytes. Moreover, the localisation of bicoid RNA during oogenesis, which requires γ-TuRC function, is unperturbed in Dgp71WD(120) mutants. Thus, Dgp71WD is not simply a general cofactor required for γ-TuRC and/or Augmin targeting, and it appears to have a crucial role independent of these complexes in the acentrosomal Meiosis I spindle.
authors.affiliation: Sir William Dunn School of Pathology, University of Oxford ,  South Parks Road, Oxford OX1 3RE ,  UK.
authors.forename: Richard F
authors.initials: RF
authors.lastname: Reschen
authors.forename: Nathalie
authors.initials: N
authors.lastname: Colombie
authors.forename: Lucy
authors.initials: L
authors.lastname: Wheatley
authors.forename: Jeroen
authors.initials: J
authors.lastname: Dobbelaere
authors.forename: Daniel
authors.initials: D
authors.lastname: St Johnston
authors.forename: Hiro
authors.initials: H
authors.lastname: Ohkura
authors.forename: Jordan W
authors.initials: JW
authors.lastname: Raff