title: Loss of function of the Drosophila Ninein-related centrosomal protein Bsg25D causes mitotic defects and impairs embryonic development.
abstract: The centrosome-associated proteins Ninein (Nin) and Ninein-like protein (Nlp) play significant roles in microtubule stability, nucleation and anchoring at the centrosome in mammalian cells. Here, we investigate Blastoderm specific gene 25D (Bsg25D), which encodes the only Drosophila protein that is closely related to Nin and Nlp. In early embryos, we find that Bsg25D mRNA and Bsg25D protein are closely associated with centrosomes and astral microtubules. We show that sequences within the coding region and 3'UTR of Bsg25D mRNAs are important for proper localization of this transcript in oogenesis and embryogenesis. Ectopic expression of eGFP-Bsg25D from an unlocalized mRNA disrupts microtubule polarity in mid-oogenesis and compromises the distribution of the axis polarity determinant Gurken. Using total internal reflection fluorescence microscopy, we show that an N-terminal fragment of Bsg25D can bind microtubules in vitro and can move along them, predominantly toward minus-ends. While flies homozygous for a Bsg25D null mutation are viable and fertile, 70% of embryos lacking maternal and zygotic Bsg25D do not hatch and exhibit chromosome segregation defects, as well as detachment of centrosomes from mitotic spindles. We conclude that Bsg25D is a centrosomal protein that, while dispensable for viability, nevertheless helps ensure the integrity of mitotic divisions in Drosophila.
authors.affiliation: Department of Biology, McGill University, Montréal, Québec H3G 0B1, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Kowanda
authors.affiliation: RNA Biology Unit, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Bergalet
authors.affiliation: Department of Biology, McGill University, Montréal, Québec H3G 0B1, Canada.
authors.forename: Michal
authors.initials: M
authors.lastname: Wieczorek
authors.affiliation: Department of Biology, McGill University, Montréal, Québec H3G 0B1, Canada.
authors.forename: Gary
authors.initials: G
authors.lastname: Brouhard
authors.affiliation: RNA Biology Unit, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada Département de Biochimie, Université de Montréal, Montréal, Québec H3T 1J4, Canada Division of Experimental Medicine, McGill University, Montréal, Québec H3A 1A3, Canada.
authors.forename: Éric
authors.initials: É
authors.lastname: Lécuyer
authors.affiliation: Department of Biology, McGill University, Montréal, Québec H3G 0B1, Canada paul.lasko@mcgill.ca.
authors.forename: Paul
authors.identifier: http://orcid.org/0000-0002-4037-3501
authors.initials: P
authors.lastname: Lasko
keywords: Centrosome; Dynein; Pole plasm; RNA localization