Suppression of scant identifies Endos as a substrate of greatwall kinase and a negative regulator of protein phosphatase 2A in mitosis.

Protein phosphatase 2A (PP2A) plays a major role in dephosphorylating the targets of the major mitotic kinase Cdk1 at mitotic exit, yet how it is regulated in mitotic progression is poorly understood. Here we show that mutations in either the catalytic or regulatory twins/B55 subunit of PP2A act as enhancers of gwl(Scant), a gain-of-function allele of the Greatwall kinase gene that leads to embryonic lethality in Drosophila when the maternal dosage of the mitotic kinase Polo is reduced. We also show that heterozygous mutant endos alleles suppress heterozygous gwl(Scant); many more embryos survive.

Drosophila Larp associates with poly(A)-binding protein and is required for male fertility and syncytial embryo development.

As the influence of mRNA translation upon cell cycle regulation becomes clearer, we searched for genes that might specify such control in Drosophila. A maternal-effect lethal screen identified mutants in the Drosophila gene for Larp (La-related protein) which displayed maternal-effect lethality and male sterility. A role for La protein has already been implicated in mRNA translation whereas Larp has been proposed to regulate mRNA stability.

Girds 'n' cleeks o' cytokinesis: microtubule sticks and contractile hoops in cell division.

Microtubules maintain an intimate relationship with the rings of anillin, septins and actomyosin filaments throughout cytokinesis. In Drosophila, peripheral microtubules emanating from the spindle poles contact the equatorial cell cortex to deliver the signal that initiates formation of the cytokinetic furrow. Mutations that affect microtubule stability lead to ectopic furrowing because peripheral microtubules contact inappropriate cortical sites.

The Drosophila phosphatidylinositol transfer protein encoded by vibrator is essential to maintain cleavage-furrow ingression in cytokinesis.

Cytokinesis requires the coordination of cytoskeletal and plasma membrane dynamics. A role for phosphatidylinositol lipids has been proposed for the successful completion of cytokinesis but this is still poorly characterised. Here, we show mutants of the gene vibrator, previously found to encode the Drosophila phosphatidylinositol transfer protein, produce multinucleate cells indicative of cytokinesis failure in male meiosis.

Klp67A destabilises pre-anaphase microtubules but subsequently is required to stabilise the central spindle.

Klp67A is a member of the Kip3 subfamily of microtubule destabilising kinesins, the loss of which results in abnormally long and stable pre-anaphase microtubules. Here we examine its role during cytokinesis in Drosophila primary spermatocytes that require the coordinated interaction of an interior and peripheral set of central spindle microtubules. In mutants anaphase B spindles elongated with normal kinetics but bent towards the cortex.

Drosophila Klp67A is required for proper chromosome congression and segregation during meiosis I.

Drosophila Klp67A belongs to the Kip3 subfamily of Kinesin-type microtubule catastrophe factors. In primary spermatocytes, loss of klp67A leads to defects in karyokinesis and cytokinesis. We show that these cells formed disorganised, bipolar spindles that contained increased numbers of microtubules.

Drosophila dd4 mutants reveal that gammaTuRC is required to maintain juxtaposed half spindles in spermatocytes.

The weak spindle integrity checkpoint in Drosophila spermatocytes has revealed a novel function of the gamma-tubulin ring complex (gammaTuRC) in maintaining spindle bipolarity throughout meiosis. Bipolar and bi-astral spindles could form in Drosophila mutants for dd4, the gene encoding the 91 kDa subunit of gammaTuRC. However, these spindles collapsed around metaphase and began to elongate as if attempting anaphase B.

Mapping and identification of essential gene functions on the X chromosome of Drosophila.

The Drosophila melanogaster genome consists of four chromosomes that contain 165 Mb of DNA, 120 Mb of which are euchromatic. The two Drosophila Genome Projects, in collaboration with Celera Genomics Systems, have sequenced the genome, complementing the previously established physical and genetic maps. In addition, the Berkeley Drosophila Genome Project has undertaken large-scale functional analysis based on mutagenesis by transposable P element insertions into autosomes.