Temperature sensitivity of muscle and neuron differentiation in embryonic cell cultures from the Drosophila mutant, shibire

Geographic information systems adoption model: A partial least square-structural equation modeling analysis approach

The ability of Geographic Information System (GIS) to organize, analyze, visualize and integrate spatial data has been at the top of its primary uses among professional industries. However, considering the extensive adoption of Information System (IS) throughout history for government organizations' or citizens' disaster response, the implementation of geographical elements is still minimal. Previous GIS models and framework studies, particularly in developing countries, were affected by pandemic pressure, competitiveness pressure, change management, and security factors. Thus, this study aims to develop a model for the successful adoption of GIS using the Technology Acceptance Model (TAM), and De Lone and Mc Lean Information Success Model and analyze the applicability of the existing factors to enhance the performance of Public Sector Organizations (PSOs). From the study, a new conceptual framework was proposed to examine the effects of factors on GIS adoption that impact performance among PSOs from the perspective of Saudi Arabia. Quantitative methods were used to collect data through a questionnaire distributed to 350 respondents from PSO, and only 272 were found to be valid. Partial Least Square Structural Equation Modeling (PLS-SEM) validated the GIS model. The finding revealed that system quality, service quality, change management, competitiveness pressure, perceived ease of use, perceived usefulness, and security factors significantly and positively affected GIS adoption. The study also showed that GIS adoption substantially affected PSO performance. The proposed model provides insight into how GIS adoption can eventually enhance performance among PSOs. In essence, the study contributes to the running of PSO and the decisions taken by policymakers.

Association of a dynamin-like protein with the Golgi apparatus in mammalian cells

Dynamins are a family of 100-kD GTPases comprised of at least three distinct gene products and multiple alternatively spliced variants. Homologies with the shibire gene product in Drosophila melanogaster and with Vps1p and Dnm1p in Saccharomyces cerevisiae suggest that dynamins play an important role in vesicular transport. Morphological studies have localized brain dynamin to coated pits and tubular invaginations at the plasma membrane, where it is believed to facilitate the formation of endocytic vesicles. Because similar membrane-budding events occur at the Golgi apparatus and multiple dynamin isoforms exist, we have studied the distribution of dynamins in mammalian cells. To this end, we generated and characterized peptide-specific antibodies directed against conserved regions of the dynamin family. By immunoblot analysis, these antibodies reacted specifically with a 100-kD protein in fibroblasts that sedimented with membranes and microtubules in vitro in a manner similar to brain dynamin. By immunofluorescence microscopy, these antibodies strongly labeled the Golgi complex in cultured fibroblasts and melanocytes, as confirmed by double labeling with a Golgi-specific antibody. Furthermore, Western blot analysis showed significant enrichment of a 100-kD dynamin band in Golgi fractions isolated from the liver. To substantiate these findings, we use a specific antidynamin antibody to immunoisolate Golgi membranes from subcellular Golgi fractions, as determined by EM and immunoblot analysis. This study provides the first morphological and biochemical evidence that a dynamin-like protein associates with the Golgi apparatus in mammalian cells, and suggests that dynamin-related proteins may have multiple cytoplasmic distributions. The potential contributions of dynamin to the secretory and endocytic pathways are discussed.

Induction of mutant dynamin specifically blocks endocytic coated vesicle formation

Dynamin is the mammalian homologue to the Drosophila shibire gene product. Mutations in this 100-kD GTPase cause a pleiotropic defect in endocytosis. To further investigate its role, we generated stable HeLa cell lines expressing either wild-type dynamin or a mutant defective in GTP binding and hydrolysis driven by a tightly controlled, tetracycline-inducible promoter. Overexpression of wild-type dynamin had no effect. In contrast, coated pits failed to become constricted and coated vesicles failed to bud in cells overexpressing mutant dynamin so that endocytosis via both transferrin (Tfn) and EGF receptors was potently inhibited. Coated pit assembly, invagination, and the recruitment of receptors into coated pits were unaffected. Other vesicular transport pathways, including Tfn receptor recycling, Tfn receptor biosynthesis, and cathepsin D transport to lysosomes via Golgi-derived coated vesicles, were unaffected. Bulk fluid-phase uptake also continued at the same initial rates as wild type. EM immunolocalization showed that membrane-bound dynamin was specifically associated with clathrin-coated pits on the plasma membrane. Dynamin was also associated with isolated coated vesicles, suggesting that it plays a role in vesicle budding. Like the Drosophila shibire mutant, HeLa cells overexpressing mutant dynamin accumulated long tubules, many of which remained connected to the plasma membrane. We conclude that dynamin is specifically required for endocytic coated vesicle formation, and that its GTP binding and hydrolysis activities are required to form constricted coated pits and, subsequently, for coated vesicle budding.

Identification of dynamin 2, an isoform ubiquitously expressed in rat tissues

Dynamin is a 100-kDa microtubule-activated GTPase originally isolated from mammalian brain that has been proposed to be crucial in the early steps of endocytosis. Previous studies on the primary structure, biochemical properties, and functional role of dynamin indicated that it was neuron-specific. However, using an antibody against a synthetic peptide representing an enzymatic region of rat brain dynamin (D100), we identified a 100-kDa protein doublet in rat liver, suggesting that dynamin exists as different isoforms that are distinct from the brain counterpart. We then initiated a search for distinctive dynamin isoforms with antibodies and cDNA probes. A 500-bp PCR-generated cDNA probe corresponding to the enzymatic region of the rat brain dynamin-encoding gene was used to isolate six overlapping clones from a rat liver cDNA library that together span the complete coding sequence of another dynamin gene, "Dyn2." Sequence analyses reveal that dynamin 2 (Dyn2) is 75% identical to brain dynamin at the DNA level and is 79% identical at the protein level. By Northern blot analysis and isoform-specific PCR, Dyn2 was found ubiquitously in adult rat tissues as two transcripts of 3.5 kb and 4 kb; the highest levels were found in testis. These results indicate that dynamin proteins are encoded by at least two genes expressed differentially in mammalian tissues and that the expression of Dyn2, and not of brain dynamin, accounts for the ubiquitous distribution of dynamin in rat tissues.

shibire, a neurogenic mutant of Drosophila

Embryos of the temperature-sensitive mutant shibirets 1 were given short exposures to the restrictive temperature during the stage when neuroblasts segregate from the presumptive epidermis. The resulting lethal phenotype, expansion of the nervous system at the expense of the epidermis, is characteristic of a group of mutants called neurogenic mutants. Exposures as short as 20 min were sufficient to promote the neurogenic phenotype. Cell masses from heat-pulsed embryos could be cultured in vivo as tumorous masses which retained some characteristics of neural tissue. An examination of the neurogenic region from heat-pulsed embryos revealed numerous packets of extracellular vesicles and coated pits blocked in endocytosis.

Genetics of the nervous system in Drosophila

The genetic analysis ofDrosophilaneurobiology has expanded into a considerable field. A host of genetic variants is now available for analyzing the development, structure, physiology, and chemistry of the fly's excitable cells and tissues and how they control the animal's behavior.