Clifton A. Poodry

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.

Control of the developmental timer forDrosophila pupariation

SummaryIn the insectDrosophila, formation of the puparium marks the onset of metamorphosis and serves as a useful marker for developmental progress. The cells of the adult remain diploid and divide during the larval stage while the larval cells become polytene and do not divide. We use a high dose of gamma-irradiation (10 krad) to selectively delete the imaginal lineage from the developing larvae ofDrosophila melanogaster. We find that animals depleted of imaginal cells including those of the imaginal brain pupariate only if the larval cells are allowed to mature, demonstrating that the larval cells harbor the primary developmental timer for this process. However, proliferating imaginal cells can exert a negative influence on the timing of pupariation.

The shibirets mutant of Drosophila: A probe for the study of embryonic development☆

A temperature-sensitive mutant strain (shibire) has been used to probe the normal developmental process in Drosophila melanogaster. At high temperatures lethality occurs during embryonic development. Heat pulses given early disrupt cellular blastoderm formation in these mutants. Even in the absence of cells, the embryo begins morphogenetic movements characteristic of gastrulation. With heat pulses given later, the embryonic cells proliferate without normal differentiation.

Pole cell formation in Drosophila melanogaster.

The development of the pole cells of Drosophila melanogaster has been investigated in a temperature-sensitive developmental mutant strain, shibirets. Shibire (shits) mutants have periods of temperature sensitivity in early embryogenesis; embryos shifted to 29°C during those periods subsequently lack pole cells. The temperature-sensitivity profiles of four independently isolated alleles indicate that the shibire mutation is responsible for this defect in development. Carefully timed heat pulses established that there is a broad range in times of sensitivity extending even to the stage when the pole cells have begun to form. Scanning electron microscopy of the heattreated embryos was compared to that of controls to illustrate the extent of the defects in mutants. Transmission electron microscopy of sectioned embryos lacking pole cells revealed normal stage-specific morphology of polar granules in the posterior end. Speculations are presented on the significance of pole cell formation as a means of segregating germ cell determinants.

Varicella-zoster virus envelope glycoproteins: biochemical characterization and identification in clinical material.

Varicella-zoster virus (VZV)-infected human foreskin fibroblasts synthesize viral glycoproteins of 125,000 (gp125), 118,000 (gp118), 92,000 (gp92), 63,000 (gp63), 59,000 (gp59), and 47,000 (gp47) Da. In biochemical studies, all of these VZV glycoproteins were shown to contain asparagine-linked (N-linked) oligosaccharide chains and, except for gp125 and gp47, to be sialoglycoproteins. Experiments with endo-beta-N-acetylglucosaminidase H (endo H) demonstrated that gp92 contained only complex type (endo H-resistant) N-linked glycosyl chains, while the other mature glycoproteins contained both high-mannose (endo H-sensitive) and complex-type oligosaccharides. Monoclonal antibodies recognizing multiple glycoproteins, gp63/gp125 or gp92/gp59/gp47, neutralized virus infection, suggesting the glycoproteins were important components of the virus envelope. This was confirmed for gp92/gp59/gp47 by immunoelectron microscopy, which revealed dense staining localized exclusively to the virion envelope and to the plasma membrane of virus-producer cells. The mature forms of all of these glycoproteins were also present in viral material isolated from vesicles of varicella and zoster patients, indicating that in infected individuals the viral glycoproteins are synthesized and processed in a manner similar to that in tissue culture cells.

A temporal pattern in the development of sensory bristles inDrosophila

SummaryA temporal pattern of decrease in radiosensitivity among the precursors of cells of the imaginal epidermis and muscles ofDrosophila was found. These changes are interpreted as marking the end of cell division in the precursors of specific structures.

A reversible temperature-induced developmental arrest in Drosophila

Abstract Temperatures between 35.5 and 38°C cause a reversible arrest of imaginal development of wildtype and temperature-sensitive Drosophila melanogaster. A temperature-sensitive mutant, shibire-temperature sensitive 1, which develops abnormally when exposed to 29°C heat pulses during various sensitive periods, fails to produce its ususal mutant phenotypes when exposed to heat pulses of 35–38°C during the same sensitive periods. The results indicate that developmental progress is required for the reversible temperature-sensitive cellular effect of shibire to cause a permanent developmental lesion.

Pattern formation inDrosophila melanogaster: The effects of mutations on polarity in the developing leg

SummaryThe effects of the mutations eyeless dominant (eyD) and shibire (shi) on bristle pattern in the legs ofDrosophila melanogaster were examined. Both mutations cause gaps in the intersegmental membranes which separate leg segments and often alter the position of these membranes. It was observed that pattern disturbances including reversed bristle polarity and duplication of structures such as sex combs and transverse rows were associated with defects in the intersegmental membranes. The alterations in bristle polarity and most of the duplication of structures could be accounted for by a segmentally reiterated gradient in the legs which controls bristle polarity and which requires the integrity of the intersegmental membrane. A computer simulation of this gradient model was devised which accounted for the observed results. The possible role of cell death as a cause of the gaps in the intersegmental membrane and of some of the pattern disturbances was examined.

Ovary-autonomous maternal inheritance at a developmental locus in Drosophila

Abstract The sex-linked temperature-sensitive mutation shibirets of Drosophila melanogaster shows a maternal effect causing embryonic lethality at 29°C. The maternal influence is due to gene action autonomous to the ovary. Embryos carrying the paternally derived wild-type gene can survive at 29°C but only if heat pulses are begun at least 9 hr after oviposition. The paternal rescue is presumably due to zygotic gene action at this locus beginning part way through embryogenesis. A maternal wild-type genome, however, can produce shi embryos that have sufficient shi+ product to support embryogenesis up to the hatching stage even at 29°C.

Alterations in the cell surface proteins of drosophila during morphogenesis

SummaryUnevaginated and evaginated Drosophila imaginal discs were surface-labeled with 125I. Relative labeling was greater in eleven peptides and lower in three peptides of evaginated discs compared to unevaginated discs. These results are compared to the effects of 20-hydroxyecdysone (20-HOE) on metabolic labeling of membrane proteins fractionated from imaginal discs, and on cell surface labeling of a hormone-responsive Drosophila tissue culture line. A group of 35S-methionine labeled membrane fraction peptides whose metabolic labeling is 20-HOE dependent have isoelectric points and apparent molecular weights very similar to those of a group of proteins only labeled in iodinated evaginated discs, supporting the conclusion that these are hormone-dependent, cell surface proteins (Rickoll and Fristrom 1983). Based upon two-dimensional gel electrophoretic and immunological criteria three of the proteins showing increased labeling in evaginated discs are related to three proteins induced by 20-HOE in tissue culture cells. Two different subsets of radiolabeled peptides were observed in the imaginal discs based upon detergent solubility. Some of the proteins which are soluble in NP-40 plus urea but insoluble in NP-40 alone may be localized in the basal lamina of the imaginal discs, a structure which labels heavily with 125I and is lacking in tissue culture cells. In discs, the majority of hormone-dependent changes in radiolabeled peptides were seen in the fraction solubilized by NP-40 and urea with a sulfhydryl reducing agent, while in tissue culture cells, the majority of differences is seen in the fraction solubilized by NP-40 only. We speculate that these proteins may be involved in similar processes, e.g., cell rearrangement, that occur during both disc morphogenesis and 20-HOE induced aggregation in tissue culture cells.