Drosophila embryos spatially sort their nutrient stores to facilitate their utilization.

Animal embryos are provided by their mothers with a diverse nutrient supply that is crucial for development. In Drosophila, the three most abundant nutrients (triglycerides, proteins and glycogen) are sequestered in distinct storage structures: lipid droplets (LDs), yolk vesicles (YVs) and glycogen granules (GGs). Using transmission electron microscopy as well as live and fixed sample fluorescence imaging, we find that all three storage structures are dispersed throughout the egg but are then spatially allocated to distinct tissues by gastrulation: LDs largely to the peripheral epithelium, YVs and GGs to the central yolk cell.

Indispensable pre-mitotic endocycles promote aneuploidy in the Drosophila rectum.

The endocycle is a modified cell cycle that lacks M phase. Endocycles are well known for enabling continued growth of post-mitotic tissues. By contrast, we discovered pre-mitotic endocycles in precursors of Drosophila rectal papillae (papillar cells).

Genetic studies of spectrin in the larval fat body of Drosophila melanogaster: evidence for a novel lipid uptake apparatus.

Spectrin cytoskeleton defects produce a host of phenotypes affecting the plasma membrane, cell polarity, and secretory membrane traffic. However, many of the underlying molecular mechanisms remain unexplained by prevailing models. Here we used the larval fat body of Drosophila melanogaster as a genetic model system to further elucidate mechanisms of αβ-spectrin function.

A Rab10-dependent mechanism for polarized basement membrane secretion during organ morphogenesis.

Basement membranes (BMs) are specialized extracellular matrices that are essential for epithelial structure and morphogenesis. However, little is known about how BM proteins are delivered to the basal cell surface or how this process is regulated during development. Here, we identify a mechanism for polarized BM secretion in the Drosophila follicle cells.

Niche-associated activation of rac promotes the asymmetric division of Drosophila female germline stem cells.

Background: Drosophila female germline stem cells (GSCs) reside adjacent to a cellular niche that secretes Bone Morphogenetic Protein (BMP) ligands and anchors the GSCs through adherens junctions. The GSCs divide asymmetrically such that one daughter remains in the niche as a GSC, while the other is born away from the niche and differentiates. However, given that the BMP signal can be diffusible, it remains unclear how a local extracellular asymmetry is sufficient to result in a robust pattern of asymmetric division.

The receptor tyrosine phosphatase Lar regulates adhesion between Drosophila male germline stem cells and the niche.

The stem cell niche provides a supportive microenvironment to maintain adult stem cells in their undifferentiated state. Adhesion between adult stem cells and niche cells or the local basement membrane ensures retention of stem cells in the niche environment. Drosophila male germline stem cells (GSCs) attach to somatic hub cells, a component of their niche, through E-cadherin-mediated adherens junctions, and orient their centrosomes toward these localized junctional complexes to carry out asymmetric divisions.

Neurotransmitter Transporter-Like: a male germline-specific SLC6 transporter required for Drosophila spermiogenesis.

The SLC6 class of membrane transporters, known primarily as neurotransmitter transporters, is increasingly appreciated for its roles in nutritional uptake of amino acids and other developmentally specific functions. A Drosophila SLC6 gene, Neurotransmitter transporter-like (Ntl), is expressed only in the male germline. Mobilization of a transposon inserted near the 3' end of the Ntl coding region yields male-sterile mutants defining a single complementation group.

Asymmetric inheritance of mother versus daughter centrosome in stem cell division.

Adult stem cells often divide asymmetrically to produce one self-renewed stem cell and one differentiating cell, thus maintaining both populations. The asymmetric outcome of stem cell divisions can be specified by an oriented spindle and local self-renewal signals from the stem cell niche. Here we show that developmentally programmed asymmetric behavior and inheritance of mother and daughter centrosomes underlies the stereotyped spindle orientation and asymmetric outcome of stem cell divisions in the Drosophila male germ line.

Establishment of stable cell lines of Drosophila germ-line stem cells.

Each Drosophila ovariole has three independent sets of stem cells: germ-line stem cells (GSCs) and escort stem cells, located at the anterior tip of the germarium, and somatic stem cells (SSCs), located adjacent to the newly formed 16-cell cysts. Decapentaplegic (Dpp) is required to maintain the anterior stem cells, whereas Hedgehog is required for maintenance and cell division of the SCCs. In an effort to establish a new in vitro system to analyze intrinsic and extrinsic factors regulating the division and differentiation of GSCs of Drosophila, we tested various culture conditions for growing GSCs, derived from bag of marbles (bam) mutant ovaries.

Ovarian cystocytes can repopulate the embryonic germ line and produce functional gametes.

Ovarian tumors are formed either in the absence of Bam (bag-of-marbles) in germ-line cells or the overexpression of Dpp (decapentaplegic) in ovarian somatic cells. These tumor cells contain spectrosomes characteristic of ovarian germ-line stem cells and the immediate descendents called cystoblasts. We show that pole cells can successfully populate the gonad after transplantation to the dorsal mesoderm of host embryos following germ-band extension.

One of the two cytoplasmic actin isoforms in Drosophila is essential.

Actin is a highly conserved protein found in all eukaryotic organisms. Most organisms have multiple cytoplasmic actin genes that encode isoforms with slightly different amino acid sequences. These different isoforms are coexpressed in many cell types.

The LEF1/beta -catenin complex activates movo1, a mouse homolog of Drosophila ovo required for epidermal appendage differentiation.

Drosophila ovo/svb (dovo) is required for epidermal cuticle/denticle differentiation and is genetically downstream of the wg signaling pathway. Similarly, a mouse homolog of dovo, movo1, is required for the proper formation of hair, a mammalian epidermal appendage. Here, we provide biochemical evidence that movo1 encodes a nuclear DNA binding protein (mOvo1a) that binds to DNA sequences similar to those that dOvo binds to, further supporting the notion that mOvo1a and dOvo are genetically and biochemically homologous proteins.

A germline-specific gap junction protein required for survival of differentiating early germ cells.

Germ cells require intimate associations and signals from the surrounding somatic cells throughout gametogenesis. The zero population growth (zpg) locus of Drosophila encodes a germline-specific gap junction protein, Innexin 4, that is required for survival of differentiating early germ cells during gametogenesis in both sexes. Animals with a null mutation in zpg are viable but sterile and have tiny gonads.

Maelstrom is required to position the MTOC in stage 2-6 Drosophila oocytes.

The factors that determine intracellular polarity are largely unknown. In Drosophila oocytes one of the earliest polar events is the positioning of the microtubule-organizing center (MTOC). Here we present data that are consistent with the hypothesis that maelstrom is required for posterior positioning of the MTOC.

Assembly of the Drosophila germ plasm.

The Drosophila melanogaster germ plasm has become the paradigm for understanding both the assembly of a specific cytoplasmic localization during oogenesis and its function. The posterior ooplasm is necessary and sufficient for the induction of germ cells. For its assembly, localization of gurken mRNA and its translation at the posterior pole of early oogenic stages is essential for establishing the posterior pole of the oocyte.

Regulation of the vitellogenin receptor during Drosophila melanogaster oogenesis.

In many insects, development of the oocyte arrests temporarily just before vitellogenesis, the period when vitellogenins (yolk proteins) accumulate in the oocyte. Following hormonal and environmental cues, development of the oocyte resumes, and endocytosis of vitellogenins begins. An essential component of yolk uptake is the vitellogenin receptor.

The ovo gene required for cuticle formation and oogenesis in flies is involved in hair formation and spermatogenesis in mice.

The Drosophila svb/ovo gene gives rise to differentially expressed transcripts encoding a zinc finger protein. svb/ovo has two distinct genetic functions: shavenbaby (svb) is required for proper formation of extracellular projections that are produced by certain epidermal cells in late-stage differentiation; ovo is required for survival and differentiation of female germ cells. We cloned a mouse gene, movo1 encoding a nuclear transcription factor that is highly similar to its fly counterpart in its zinc-finger sequences.

The gastrulation defective gene of Drosophila melanogaster is a member of the serine protease superfamily.

The establishment of dorsal-ventral polarity in the oocyte involves two sets of genes. One set belongs to the gurken-torpedo signaling pathway and affects the development of the egg chorion as well as the polarity of the embryo. The second set of genes affects only the dorsal-ventral polarity of the embryo but not the eggshell.

Brainiac encodes a novel, putative secreted protein that cooperates with Grk TGF alpha in the genesis of the follicular epithelium.

brainiac (brn) is involved in a number of developmental events. In addition to being required zygotically for segregation of neuroblasts from epidermoblasts, it is essential for a series of critical steps during oogenesis which also depend upon gurken (grk), a TGF alpha homolog. Animals harboring strong mutations of either grk or EGF receptor tyrosine kinase (Egfr) or doubly mutant for brn and weak grk or Egfr mutations produce ovarian follicles with multiple sets of nurse cell-oocyte complexes.

Eggshell assembly in Drosophila: processing and localization of vitelline membrane and chorion proteins.

The Drosophila eggshell consists of three major proteinaceous layers: the vitelline membrane, the inner chorionic layer, and the outer endochorion. During the latter stages of oogenesis, the proteins that comprise these layers are synthesized and secreted by epithelial follicle cells which surround the maturing oocyte. While there is considerable knowledge of the structural units which comprise the eggshell layers, there is little knowledge of how individual proteins function or interact with one another to form the structure.

Multiple signaling pathways establish both the individuation and the polarity of the oocyte follicle in Drosophila.

The development of the Drosophila oocyte depends upon a sequential series of interactions between the germline cells and the somatically derived follicle cells to produce individual follicles with appropriate polarities. In the germarium the control of germline cell division depends upon a proper interaction with somatic cells adjacent to the germline stem cells. Both gurken and brainiac are required in the germline, and the Egfr, daughterless, Notch, and Delta genes are required in the somatic cells to produce individual egg chambers with a continuous follicular epithelium.

The Drosophila yolkless gene encodes a vitellogenin receptor belonging to the low density lipoprotein receptor superfamily.

Sequence comparisons of vitellogenins from a wide range of organisms have identified regions of similarity not only to each other but also to vertebrate apolipoproteins (e.g. apoB-100 and apoE).

Identification of regions interacting with ovoD mutations: potential new genes involved in germline sex determination or differentiation in Drosophila melanogaster.

Only a few Drosophila melanogaster germline sex determination genes are known, and there have been no systematic screens to identify new genes involved in this important biological process. The ovarian phenotypes produced by females mutant for dominant alleles of the ovo gene are modified in flies with altered doses of other loci involved in germline sex determination in Drosophila (Sex-lethal+, sans fille+ and ovarian tumor+). This observation constitutes the basis for a screen to identify additional genes required for proper establishment of germline sexual identity.

Multiple products from the shavenbaby-ovo gene region of Drosophila melanogaster: relationship to genetic complexity.

The Drosophila melanogaster shavenbaby (svb)-ovo gene region is a complex locus, containing two distinct but comutable genetic functions. ovo is required for survival and differentiation of female germ line cells and plays a role in germ line sex determination. In contrast, svb is required in both male and female embryos for the production of epidermal locomotor and sensory structures.