title: The Drosophila calcipressin sarah is required for several aspects of egg activation.
abstract: Activation of mature oocytes initiates development by releasing the prior arrest of female meiosis, degrading certain maternal mRNAs while initiating the translation of others, and modifying egg coverings. In vertebrates and marine invertebrates, the fertilizing sperm triggers activation events through a rise in free calcium within the egg. In insects, egg activation occurs independently of sperm and is instead triggered by passage of the egg through the female reproductive tract ; it is unknown whether calcium signaling is involved. We report here that mutations in sarah, which encodes an inhibitor of the calcium-dependent phosphatase calcineurin, disrupt several aspects of egg activation in Drosophila. Eggs laid by sarah mutant females arrest in anaphase of meiosis I and fail to fully polyadenylate and translate bicoid mRNA. Furthermore, sarah mutant eggs show elevated cyclin B levels, indicating a failure to inactivate M-phase promoting factor (MPF). Taken together, these results demonstrate that calcium signaling is involved in Drosophila egg activation and suggest a molecular mechanism for the sarah phenotype. We also find the conversion of the sperm nucleus into a functional male pronucleus is compromised in sarah mutant eggs, indicating that the Drosophila egg's competence to support male pronuclear maturation is acquired during activation.
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Vanessa L
authors.initials: VL
authors.lastname: Horner
authors.forename: Andreas
authors.initials: A
authors.lastname: Czank
authors.forename: Janet K
authors.initials: JK
authors.lastname: Jang
authors.forename: Navjot
authors.initials: N
authors.lastname: Singh
authors.forename: Byron C
authors.initials: BC
authors.lastname: Williams
authors.forename: Jaakko
authors.initials: J
authors.lastname: Puro
authors.forename: Eric
authors.initials: E
authors.lastname: Kubli
authors.forename: Steven D
authors.initials: SD
authors.lastname: Hanes
authors.forename: Kim S
authors.initials: KS
authors.lastname: McKim
authors.forename: Mariana F
authors.initials: MF
authors.lastname: Wolfner
authors.forename: Michael L
authors.initials: ML
authors.lastname: Goldberg
mesh_terms: D000705:Anaphase / Q000235:genetics; D000818:Animals; D002135:Calcium-Binding Proteins; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D019926:Cyclin B / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008297:Male; D008540:Meiosis / Q000502:physiology; D008954:Models, Biological; D009154:Mutation; D010063:Ovum / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D026723:Polyadenylation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D013094:Spermatozoa / Q000166:cytology / Q000648:ultrastructure; D014817:Vitelline Membrane / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D019926:Cyclin B; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; C513393:Sra protein, Drosophila