No description available.

No description available.

The Golgi body is responsible for the modification and sorting of proteins and lipids in the secretory pathway. The Golgi must coordinate with other endomembrane compartments in order to target cargo to the correct destination. While our understanding of Golgi function is vast, we can extend our knowledge base by examining the functions of Golgi-associated proteins in developing animals. Lava lamp (Lva) is a Golgi-associated protein and a Drosophila golgin. Previously, Lva was shown to facilitate efficient membrane secretion required for cleavage furrow formation in early embryos. By acting as an adaptor molecule between Golgi and microtubule motility factors, Lva is thought to position Golgi bodies for targeted secretion during cellularization, the Drosophila cleavage stage of development. Here, I further characterize the role of Lva during animal development. I demonstrate that Lva is required for animal viability, and gamete production in females but not males. While Lva is expressed in many tissues, adult fat body cells are the most sensitive to decreased Lva activity, resulting in the disorganization of endomembrane compartments. Furthermore, this disruption in adult fat body cells correlates with a defect in neuroendocrine signaling, altering the activity of juvenile hormone. I propose that Lva activity in adult fat body cells is important for recognizing and/or processing juvenile hormone in order to support Drosophila oogenesis. Lva’s role in cellularization, which is a specialized form of cytokinesis in early embryos, provided insights into the combined processes of actomyosin-based contraction and membrane secretion. While some proteins have been implicated in cellularization, there are thought to be many more that have yet to be identified. In an effort to isolate additional genes involved in animal cell cytokinesis, we screened a unique collection of temperature sensitive (ts) mutations on the X-chromosome of Drosophila melanogaster. At the restrictive temperature, we identified five mutants that displayed a cellularization phenotype. For one of the mutants, fs(1)ts242, we narrowed the mutation to a region on the X chromosome consisting of 17 possible gene candidates. Identification of the gene should provide further elucidation of the mechanisms controlling actomyosin-based contraction and membrane secretion. / text

This study sought to examine the physiological correlates of migratory flight performance the North American migratory grasshopper Melanoplus sanguinipes Fabricius (Orthoptera: Acrididae) with a focus on mechanisms of resource allocation, the dynamics of hemolymph proteins, their interface with immune function, and the mechanism of flight-enhanced oogenesis. The performance of long duration flights has been shown previously to be of reproductive benefit to females who make them. Examination of possible mechanisms of resource compensation for the costs of flight showed no significant increase in either feeding, mating or digestion in females who performed long duration flight. A comparison of two populations of M. sanguinipes from Arizona and Colorado showed significant variation in body size, diapause regulation as well as internal and external morphology. The two populations did not differ in taxonomic characters or in short sequences of genomic and mitochondrial DNA. The follicle cell epithelium of ovaries from M. sanguinipes was examined for its relationship to juvenile hormone III (JH III). JH III induces patency in vitro in intercellular spaces of M. sanguinipes follicular epithelium as well as the characteristic apical endocytosis at the follicle cell oocyte interface. Exogenous JH III treatment of females on day 7 in lieu of flight reduced the threshold for induction of patency to 10-7 M JH III from 10-5 M JH III. These results indicate that JH III can act as a prime to the pump of oogenesis. An HPLC/LC-MS peptidomic survey of the hemolymph of M. sanguinipes following flight performance showed the presence of and changes in serine protease inhibitors. These peptides regulate numerous protease cascades involved in reproduction and immunity which suggested that flight might have a more broad impact than previously thought. Males who performed these flights showed a higher probability of surviving a bacterial challenge. The duration of flight performance was positively correlated in males with increases in titers of the hemolymph lipoproteins apolipophorin I and hexemerin. The exchangeable apolipophorin III showed no variation in correlation with flight. Females were not affected by flight performance in terms of hemolymph protein titers or the probability of surviving a bacterial challenge. These results suggest that the lipid transport system plays an important role in the immune response of this insect. / text

No description available.

No description available.

Fragile X Protein (FMRP) is an RNA binding protein linked to the most common form of inherited mental retardation, Fragile X syndrome (FraX). Despite its ubiquitous expression and presence of non-neuronal phenotypes, FMRP function remains understudied outside of neural and synaptic development. In addition to severe cognitive deficits, FraX etiology also includes postpubescent macroorchidism, which is thought to occur due to overproliferation of the germline. Using a Drosophila model for FraX, I have shown that FMRP controls germline proliferation as well as dorso-ventral polarity during oogenesis. dFmr1 null ovaries exhibit egg chambers with increased numbers of germ cells and ventralized embryos. The number of cyclin E and phosphohistone H3 positive cells is increased in dFmr1 germaria compared to wild-type, suggesting that the mutant germline cells exhibit defects in proliferation. In addition, BrdU incorporation is increased during vitellogenesis, consistent with a prolonged S phase for endoreplicating nurse cells. Here I report the FMRP controls the levels of cbl mRNA in the ovary and that the overproliferation and polarity defects found in dFmr1 ovaries can be rescued by reducing cbl dosage in half. These data suggest a model whereby FMRP regulates cellular proliferation and polarity during oogenesis by controlling the E3 ubiquitin ligase cbl.

Bicaudal-C (Bic-C) encodes a KH-type RNA binding protein required maternally for anterior patterning of the Drosophila oocyte and correct migration of the centripetal follicle cells. In Drosophila, premature translation of the germ-plasm determinant Oskar in Bic-C mutant oocytes suggests a function for Bic-C in post-transcriptional gene regulation. / Purification and microarray analysis of Bic-C containing ribonucleoprotein complexes revealed that Bic-C associates with multiple transcripts encoding functionally-related components of the Wnt/Frizzled/Dishevelled signaling pathway that regulate actin dynamics, in addition to its own mRNA. Using transgenic reporter constructs, Bic-C was demonstrated to destabilize its own mRNA via cis-acting 5' UTR elements. When auto-regulation was bypassed and Bic-C was over-expressed in the female germline, premature cytoplasmic streaming was induced, disrupting axial patterning through displacement of both Gurken (Grk) and oskar. These phenotypes can also be induced by disruption of the actin cytoskeleton with pharmacological agents and are similar to those described for hypomorphic mutant alleles of orb, which encodes a CPEB-like protein that promotes polyadenylation of target mRNAs. The Bic-C overexpression phenotypes require its RNA binding activity, are substantially enhanced by mutations affecting orb and poly(A) polymerase, and are suppressed by mutations affecting the deadenylase CCR4 and its accessory protein NOT3. Co-immunoprecipitation experiments demonstrate that Bic-C associates with components of the deadenylase complex and with components of an ER-associated RNP complex that includes Me31B, PABP and Trailer-hitch. The latter complex is involved in Grk exocytosis. Accordingly, Grk secretion is defective in Bic-C mutants. / Taken together, these results support a model whereby Bic-C antagonizes Orb function by negatively regulating the expression of Orb target mRNAs, through recruitment of the deadenylase machinery, that are involved in coordinating cytoplasmic movements. Furthermore, this work identifies a novel function of Bic-C in dorsal/ventral patterning by promoting Grk secretion.

Recently, the timing of oocyte loss during murine development has been brought into question as authors using mouse vasa homologue (MVH) as a germ cell marker did not observe a loss of oocytes during fetal life. Instead the major loss was observed in the days following birth, after chromosome pairing has occurred. / In this study the controversy was addressed by establishing a new and reliable method to quantify murine oocytes in meiotic prophase, as well as to determine the gestation age and meiotic prophase stage of oocyte loss. Earlier limitations were overcome through the use of Germ Cell Nuclear Antigen-1 (GCNA-1) antibody as a germ cell specific marker, and the novel addition of a cytospin centrifugation step to the method. Progress through meiotic prophase was examined in chromosome spread preparations where meiotic stages were assessed using an antiserum against synaptonemal complex (SC) proteins. Quantification was accomplished by counting the number of GCNA-1 immunoreactive cells in chromosome spread preparations and estimated in histological sections using the ratio estimation model. (Abstract shortened by UMI.)

H1 histones are potentially significant to nuclear reprogramming during the oocyte-to-embryo transition. One characteristic distinguishing the H1 subtypes is that the somatic H1 histones are found primarily in dividing cells, whereas the H10 subtype is predominantly found in differentiated cells. The H1 complement in mouse oocytes and preimplantation embryos from wild-type and H10-/- animals was investigated. / Immunocytochemistry of wild-type cells demonstrated that H10 was predominant in oocytes while somatic H1 began accumulating in the 2-cell embryo. In H10-/- cells H10 was not detected, but, surprisingly, somatic H1 was detected beginning at the 1-cell stage. Radiolabeling of wild-type and H10-/- cells revealed that somatic H1 synthesis intensified after meiotic maturation, and therefore prior to its detection in embryos. The functional study found that loss of H10 impaired oogenesis but enhanced embryogenesis. The patterns of H1 immunodetection and synthesis are integrated, and the significance of H1 composition in development is discussed.