Dominant suppressor genes of p53-induced apoptosis in Drosophila melanogaster.

One of the major functions of programmed cell death (apoptosis) is the removal of cells that suffered oncogenic mutations, thereby preventing cancerous transformation. By making use of a Double-Headed-EP (DEP) transposon, a P element derivative made in our laboratory, we made an insertional mutagenesis screen in Drosophila melanogaster to identify genes that, when overexpressed, suppress the p53-activated apoptosis. The DEP element has Gal4-activatable, outward-directed UAS promoters at both ends, which can be deleted separately in vivo.

Vacuole dynamics in the salivary glands of Drosophila melanogaster during prepupal development.

A central function of the Drosophila salivary glands (SGs), historically known for their polytene chromosomes, is to produce and then release during pupariation the secretory glue used to affix a newly formed puparium to a substrate. This essential event in the life history of Drosophila is regulated by the steroid hormone ecdysone in the late-larval period. Ecdysone triggers a cascade of sequential gene activation that leads to glue secretion and initiates the developmentally-regulated programmed cell death (PCD) of the larval salivary glands, which culminates 16 h after puparium formation (APF).

Apocrine secretion in Drosophila salivary glands: subcellular origin, dynamics, and identification of secretory proteins.

In contrast to the well defined mechanism of merocrine exocytosis, the mechanism of apocrine secretion, which was first described over 180 years ago, remains relatively uncharacterized. We identified apocrine secretory activity in the late prepupal salivary glands of Drosophila melanogaster just prior to the execution of programmed cell death (PCD). The excellent genetic tools available in Drosophila provide an opportunity to dissect for the first time the molecular and mechanistic aspects of this process.

Drosophila Spag is the homolog of RNA polymerase II-associated protein 3 (RPAP3) and recruits the heat shock proteins 70 and 90 (Hsp70 and Hsp90) during the assembly of cellular machineries.

The R2TP is a recently identified Hsp90 co-chaperone, composed of four proteins as follows: Pih1D1, RPAP3, and the AAA(+)-ATPases RUVBL1 and RUVBL2. In mammals, the R2TP is involved in the biogenesis of cellular machineries such as RNA polymerases, small nucleolar ribonucleoparticles and phosphatidylinositol 3-kinase-related kinases. Here, we characterize the spaghetti (spag) gene of Drosophila, the homolog of human RPAP3.

Specific Cooperation Between Imp-α2 and Imp-β/Ketel in Spindle Assembly During Drosophila Early Nuclear Divisions.

The multifunctional factors Imp-α and Imp-β are involved in nuclear protein import, mitotic spindle dynamics, and nuclear membrane formation. Furthermore, each of the three members of the Imp-α family exerts distinct tasks during development. In Drosophila melanogaster, the imp-α2 gene is critical during oogenesis for ring canal assembly; specific mutations, which allow oogenesis to proceed normally, were found to block early embryonic mitosis.

Cytoskeletal proteins regulate chromatin access of BR-C transcription factor and Rpd3-Sin3A histone deacetylase complex in Drosophila salivary glands.

At the onset of Drosophila metamorphosis the steroid hormone ecdysone induces a process leading to a rapid degeneration of the larval salivary glands (SGs). Ecdysone acts through the ecdysone receptor heterodimer, which activates primary response genes. In particular these genes include the Broad-Complex (BR-C) gene encoding a set of BTB/POZ-transcription factors, among which the Z1 isoform is critical for SG cell death.

Discs large in the Drosophila testis: an old player on a new task.

Gamete development requires a coordinated soma-germ line interaction that ensures renewal and differentiation of germline and somatic stem cells. The physical contact between the germline and somatic cell populations is crucial because it allows the exchange of diffusible signals among them. The tumor suppressor gene discs large (dlg) encodes a septate junction protein with functions in epithelial cell polarity, asymmetric neuroblast division and formation of neuromuscular junctions.

discs large regulates somatic cyst cell survival and expansion in Drosophila testis.

Gonad development requires a coordinated soma-germline interaction that ensures renewal and differentiation of germline and somatic stem cells to ultimately produce mature gametes. The Drosophila tumour suppressor gene discs large (dlg) encodes a septate junction protein functioning during epithelial polarization, asymmetric neuroblast division, and formation of neuromuscular junctions. Here, we report the role of dlg in testis development and its critical function in somatic cyst cells (SCCs).

Arginine methyltransferase Capsuleen is essential for methylation of spliceosomal Sm proteins and germ cell formation in Drosophila.

Although arginine modification has been implicated in a number of cellular processes, the in vivo requirement of protein arginine methyltransferases (PRMTs) in specific biological processes remain to be clarified. In this study we characterize the Drosophila PRMT Capsuléen, homologous to human PRMT5. During Drosophila oogenesis, catalytic activity of Capsuléen is necessary for both the assembly of the nuage surrounding nurse cell nuclei and the formation of the pole plasm at the posterior end of the oocyte.

Domains of Importin-alpha2 required for ring canal assembly during Drosophila oogenesis.

Null-mutation in Drosophila importin-alpha2, such as the deficiency imp-alpha2(D14), causes recessive female sterility with the formation of dumpless eggs. In imp-alpha2(D14) the transfer of nurse cell components to the oocyte is interrupted and the Kelch protein, an oligomeric ring canal actin organizer, is normally produced but fails to associate with the ring canals resulting in their occlusion. To define domains regulating Kelch deposition on ring canals we performed site-directed mutagenesis on protein binding domains and putative phosphorylation sites of Imp-alpha2.

Rab11 is required during Drosophila eye development.

In an effort to identify the role of Rab11, a small GTP binding protein, during Drosophila differentiation, phenotypic manifestations associated with different alleles of Rab11 were studied. The phenotypes ranged from eye-defects, bristle abnormalities and sterility to lethality during various developmental stages. In this paper, our focus is targeted on eye defects caused by Rab11 mutations.

Valois, a component of the nuage and pole plasm, is involved in assembly of these structures, and binds to Tudor and the methyltransferase Capsuléen.

Using the Capsuleen (Csul) methyltransferase as bait in the yeast two-hybrid system, we have identified a novel Drosophila protein containing multiple WD repeats and encoded by the valois (vsl) gene, which acts in pole plasm function. Vls is homologous to human MEP50, which forms a complex with the PRMT5 methyltransferase--the human homologue of Csul. We found that Vls localizes to the nuage in the nurse cells and to the pole plasm in the oocyte.

Requirements for scribble expression in newly formed gonads of Drosophila embryos.

The tumour suppressor gene scribble (scrib) is required for epithelial polarity and growth control in Drosophila, and encodes two protein isoforms. Here, we report the pattern of Scrib1 synthesis in pole cells and embryonic gonads. We found that Scrib1 synthesis became strongly enhanced in pole cells at the time of gonad formation and was also detectable in cortical domains of gonadal mesodermal cells adjacent to pole cells.

Knockout targeting of the Drosophila nap1 gene and examination of DNA repair tracts in the recombination products.

We used ends-in gene targeting to generate knockout mutations of the nucleosome assembly protein 1 (Nap1) gene in Drosophila melanogaster. Three independent targeted null-knockout mutations were produced. No wild-type NAP1 protein could be detected in protein extracts.

Patterns of importin-alpha expression during Drosophila spermatogenesis.

Importin-alpha proteins do not only mediate the nuclear import of karyophilic proteins but also regulate spindle assembly during mitosis and the assembly of ring canals during Drosophila oogenesis. Three importin-alpha genes are present in the genome of Drosophila. To gain further insights into their function we analysed their expression during spermatogenesis by using antibodies raised against each of the three Importin-alpha proteins identified in Drosophila, namely, Imp-alpha1, -alpha2, and -alpha3.

Temporal regulation of Drosophila salivary gland degeneration by the Broad-Complex transcription factors.

The destruction of obsolete larval tissues at the onset of insect metamorphosis is a complex process triggered by the steroid hormone ecdysone. Among the genes required for the implementation of salivary gland (SG) degeneration the reduced bristles on palpus (rbp) gene of the Broad-Complex (BR-C) locus plays a critical role. This gene encodes the BR-C Z1 transcription factor and its expression is directly regulated by ecdysone through the ecdysone receptor (EcR/Usp).

Importin-alpha 2 is critically required for the assembly of ring canals during Drosophila oogenesis.

The interstitial deletion D14 affecting the importin-alpha 2 gene of Drosophila, or imp-alpha 2(D14), causes recessive female sterility characterized by a block of nurse cell-oocyte transport during oogenesis. In wild-type egg chambers, the Imp-alpha 2 protein is uniformly distributed in the nurse cell cytoplasm with a moderate accumulation along the oocyte cortex. Cytochalasin D treatment of wild-type egg chambers disrupts the in vivo association of Imp-alpha 2 with F-actin and results in its release from the oocyte cortex and its transfer into nurse cell nuclei.

Regulation of cytosolic malate dehydrogenase by juvenile hormone in Drosophila melanogaster.

The Drosophila malate dehydrogenase, or malic enzyme (ME) encoded by the Men gene, is a non-mitochondrial enzyme recovered in the cytosolic fraction. By using mutation in the Men gene and deficiencies uncovering this locus, we could show that the ME activity recovered in cytosolic fractions originates exclusively from the Men gene located at map position 87D-1 on the right arm of the 3rd chromosome. We found that juvenile hormone (JH) can induce ME activity by two mechanisms.

P elements inserted in the vicinity of or within the Drosophila snRNP SmD3 gene nested in the first intron of the Ornithine Decarboxylase Antizyme gene affect only the expression of SmD3.

The Drosophila gene for snRNP SmD3 (SmD3) is contained in reverse orientation within the first intron of the Ornithine Decarboxylase Antizyme (AZ) gene. Previous studies show that two closely linked P elements cause the gutfeeling phenotype characterized by embryonic lethality and aberrant neuronal and muscle cell differentiation. However, the exact nature of the gene(s) affected in the gutfeeling phenotype remained unknown.

Stage-specific chromosomal association of Drosophila dMBD2/3 during genome activation.

The Drosophila gene dMBD2/3 encodes a protein with significant homologies to the mammalian methyl-DNA binding proteins MBD2 and MBD3. These proteins are essential components of chromatin complexes involved in epigenetic gene regulation. Because the available in vitro data on dMBD2/3 are conflicting we have started an in vivo characterization of dMBD2/3.

Kremen proteins are Dickkopf receptors that regulate Wnt/beta-catenin signalling.

The Wnt family of secreted glycoproteins mediate cell cell interactions during cell growth and differentiation in both embryos and adults. Canonical Wnt signalling by way of the beta-catenin pathway is transduced by two receptor families. Frizzled proteins and lipoprotein-receptor-related proteins 5 and 6 (LRP5/6) bind Wnts and transmit their signal by stabilizing intracellular beta-catenin.