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ULTRASTRUCTURAL AND CYTOCHEMICAL STUDIES ON NORMAL AND RIBONUCLEASE-TREATED NUCLEI FROM THE LARVAE OF THE FRUIT FLY, DROSOPHILA MELANOGASTERSmith, William Jacland, 1939- January 1966 (has links)
No description available.
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Highwire coordinates synapse formation and maturation by regulating both a map kinase cascade and the ability of the axon to respond to external cues in the giant fiber system of Drosophila MelanogasterUnknown Date (has links)
The ubiquitin ligase Highwire is responsible for cell-autonomously promoting
synapse formation in the Drosophila Giant Fiber system. highwire mutants show defects
in synaptic function and extra branching at the axon terminal, corresponding to transient
branching that occur in the course of giant synapse formation during metamorphosis. The
MAP kinase pathway, including Wallenda and JNK/Basket, plus the transcription factor
Jun, act to suppress synaptic function and axon pruning in a dosage sensitive manner,
suggesting different molecular mechanisms downstream of the MAP kinase pathway
govern function and pruning. A novel role for Highwire is revealed, regulating the giant
fiber axon’s ability to respond to external cues regulated by Fos. When expression of the
transcription factor Fos is disrupted in the post-synaptic TTMn or surrounding midline
glia of highwire mutants, the giant fiber axons show a marked increase in axon overgrowth and midline crossing. However, synaptic function is rescued by the cell nonautonomous
manipulation of Fos, indicating distinct mechanisms downstream of Highwire regulating synaptic function and axon morphology. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Netrin-Frazzled signaling instructs synaptogenesis and plasticity at an identified central synapse in DrosophilaUnknown Date (has links)
The classic guidance molecules, Netrin and its receptor Frazzled (Fra), dictate the strength of
synaptic connections in the giant fiber system (GFS) of Drosophila melanogaster by regulating
gap junction localization in the pre-synaptic terminal. In Netrin mutant animals the synaptic
coupling between a giant interneuron and the jump motor neuron was weakened. Dye-coupling
between these two neurons was severely compromised or absent. These mutants exhibited
anatomically and physiologically defective synapses between the giant fiber (GF) and
tergotrochanteral motor neuron (TTMn). In cases where Netrin mutants displayed apparently
normal synaptic anatomy, half of the specimens exhibited physiologically defective synapses.
Dye-coupling between the giant fiber and the motor neuron was reduced or eliminated,
suggesting that gap junctions were disrupted in the Netrin mutants. When we examined the gap
junctions with antibodies to Shaking-B Innexin (ShakB), they were significantly decreased or
absent in the pre-synaptic terminal of the mutant GF. This data is the first to show that Netrin and
Frazzled regulate placement of gap junctions pre-synaptically at a central synapse. In the Drosophila Giant Fiber System, we demonstrate a mechanism that ensures the monoinnervation of two homologous motor neurons by two homologous interneurons. In a scenario where both interneurons could synapse with both motor neuron targets, each interneuron exclusively synapsed with only one target and the circuit functions at normal physiological levels. This innervation pattern depended on the ratio of netrin-to-frazzled expression. When Netrin was over expressed in the system, shifting the ratio in favor of Netrin,
both interneurons synapsed with both target motor neurons and physiological function was reduced. This resulted in the polyinnervationof a single target. In contrast, when Frazzled was over expressed in the system, one interneuron innervated both targets and excluded the remaining interneuron from making any synaptic contact. This resulted in a single interneuron mono-innervating both motor neurons and physiological function was mutant. The orphaned interneuron made no synaptic contact with either motor neuron target. Physiological function was only normal when the Netrin-Frazzled ratio was at endogenous levels and each GF monoinnervated one motor neuron. When we examined the gap junctions at this synapse in experimental animals, there was a significant reduction of gap junction hemichannels in the presynaptic terminal of axons that deviated from normal innervation patterns. While the synapse dyecoupled, the reduction in gap junction hemichannels reduced function in the circuit. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2013.
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Synaptic Rearrangements and the Role of Netrin-Frazzled Signaling in Shaping the Drosophila Giant Fiber CircuitUnknown Date (has links)
In the developing CNS, presynaptic neurons often have exuberant overgrowth and
form excess (and overlapping) postsynaptic connections. Importantly, these excess
connections are refined during circuit maturation so that only the appropriate connections
remain. This synaptic rearrangement phenomenon has been studied extensively in
vertebrates but many of those models involve complex neuronal circuits with multiple
presynaptic inputs and postsynaptic outputs. Using a simple escape circuit in Drosophila
melanogaster (the giant fiber circuit), we developed tools that enabled us to study the
molecular development of this circuit; which consists of a bilaterally symmetrical pair of
presynaptic interneurons and postsynaptic motorneurons. In the adult circuit, each
presynaptic interneuron (giant fiber) forms a single connection with the ipsilateral,
postsynaptic motorneuron (TTMn). Using new tools that we developed we labeled both
giant fibers throughout their development and saw that these neurons overgrew their targets and formed overlapping connections. As the circuit matured, giant fibers pruned
their terminals and refined their connectivity such that only a single postsynaptic
connection remained with the ipsilateral target. Furthermore, if we ablated one of the two
giant fibers during development in wildtype animals, the remaining giant fiber often
retained excess connections with the contralateral target that persisted into adulthood.
After demonstrating that the giant fiber circuit was suitable to study synaptic
rearrangement, we investigated two proteins that might mediate this process. First, we
were able to prevent giant fibers from refining their connectivity by knocking out
highwire, a ubiquitin ligase that prevented pruning. Second, we investigated whether
overexpressing Netrin (or Frazzled), part of a canonical axon guidance system, would
affect the refinement of giant fiber connectivity. We found that overexpressing Netrin (or
Frazzled) pre- & postsynaptically resulted in some giant fibers forming or retaining
excess connections, while exclusively presynaptic (or postsynaptic) expression of either
protein had no effect. We further showed that by simultaneously reducing (Slit-Robo)
midline repulsion and elevating Netrin (or Frazzled) pre- & postsynaptically, we
significantly enhanced the proportion of giant fibers that formed excess connections. Our
findings suggest that Netrin-Frazzled and Slit-Robo signaling play a significant role in
refining synaptic circuits and shaping giant fiber circuit connectivity. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
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A role for the Drosophila eIF4E binding protein during stress response /Jenkins, Mark, 1979- January 2004 (has links)
No description available.
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A role for the Drosophila eIF4E binding protein during stress response /Jenkins, Mark, 1979- January 2004 (has links)
The Drosophila melanogaster eIF4E binding protein (d4E-BP) inhibits translation initiation and is implicated in cell growth as a downstream effector of the Drosophila insulin signaling pathway. Since d4E-BP null flies show similar growth and development to control flies, the possibility of a conditional phenotype was explored through stress treatments. Adult d4E-BP null flies show sensitivity to oxidative stress, and d4E-BP null larvae die faster than controls under starvation and protein starvation. Expressing a mutant d4E-BP that doesn't bind to eIF4E in the d4E-BP null background does not rescue this stress sensitivity, which suggests that wild-type stress resistance requires binding of d4E-BP to eIF4E. / The Drosophila forkhead transcription factor dFOXO is a transcriptional activator of d4E-BP. There is a strong reduction of d4E-BP peptide in a dFOXO null background. dFOXO null flies are also sensitive to oxidative stress, and rescue of this sensitivity through ectopic expression of UAS-d4E-BP(wt) in a dFOXO null background suggests d4E-BP is a downstream mediator of dFOXO oxidative stress resistance.
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Regulation of CAK activity of Cdk7 in Drosophila melanogasterChen, Jian, 1969- January 2003 (has links)
Cdk7 (Cyclin-dependent kinase 7) is conserved from yeast to human and involved in multiple functions. Cdk7 acts as a CAK (Cdk activating kinase) in a trimeric complex with Cyclin H and Mat1. The CAK activity is required for the full activation of the Cdks that directly regulate the cell cycle transitions. In addition, Cdk7 is the kinase subunit of TFIIH, the general transcription/DNA repair factor IIH. TFIIH is required for the general transcription of messenger RNAs by RNA polymerase II and for the transcription-coupled nucleotide excision repair functions. As in other systems, Drosophila Cdk7 has multiple functions. In order to understand how different functions of Cdk7 are regulated, I performed genetic screens to identify the regulators or downstream factors of multiple functions of Cdk7. Several candidate dominant suppressors and enhancers were identified in these screens. One strong suppressor of cdk7, xpd, encodes another subunit of TFIIH. The genetic suppression by xpd attracted me to further characterize the biological significance of this interaction. I showed that Xpd does have a novel function in regulating CAK activity of cdk7 , it down-regulates mitotic CAK activity. Furthermore, I found that Xpd protein levels are cell cycle dependent, being down-regulated at the beginning of the mitosis. Based on these data, I propose a model that mitotic down-regulation of Xpd results in increased CAK activity, positively regulating mitotic progression. Simultaneously, this down-regulation can be expected to contribute to the mechanisms of mitotic silencing of basal transcription.
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Regulation of CAK activity of Cdk7 in Drosophila melanogasterChen, Jian, 1969- January 2003 (has links)
No description available.
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Comprehensive study of the ZAD family of zinc finger transcription factors in Drosophila melanogasterUnknown Date (has links)
The zinc finger associated domain (ZAD) family of transcription factors from Drosophila melanogaster is not well described in the literature, in part because it is very difficult to study by traditional mutagenesis screens. Bioinformatic studies indicate this is due to overlapping functions remaining after a recent evolutionary divergence. I set out to use in vitro-binding techniques to identify the characteristics of the ZAD family and test this theory. I have constructed glutathione S-transferase (GST)-ZAD domain chimeric proteins for use in pull down protein binding assays,and GST-Zinc finger (ZnF) array domain chimera for electrophoretic mobility shift assays (EMSA). Protein binding assays indicated two putative conserved interactors, similar to the analogous KRAB system in mammals. ... Competitive bindings were carried out to show a specificity of binding conferred by the identified conserved positions. While the consensus binding sites show relatively few similarities, the predicted target genes identified by the consensus binding sites show significant overlap. The nature of this overlap conforms to the known characteristics of the ZAD family but points to a more positive selection to maintain conservation of function. / by Joseph Krystel. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
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Identification and characterization of mutations in the Drosophila mitochondrial translation elongation factor iconoclastUnknown Date (has links)
Mitochondrial disorders resulting from defects in oxidative phosphorylation are the most common form of inherited metabolic disease. Mutations in the human mitochondrial translation elongation factor GFM1 have recently been shown to cause the lethal pediatric disorder Combined Oxidative Phosphorylation Deficiency Syndrome (COXPD1). Children harboring mutations in GFM1 exhibit severe developmental, metabolic and neurological abnormalities. This work describes the identification and extensive characterization of the first known mutations in iconoclast (ico), the Drosophila orthologue of GFM1. Expression of human GFM1 can rescue ico null mutants, demonstrating functional conservation between the human and fly proteins. While point mutations in ico result in developmental defects and death during embryogenesis, animals null for ico survive until the second or third instar larval stage. These results indicate that in addition to loss-of-function consequences, point mutations in ico appear to produce toxic proteins with antimorphic or neomorphic effects. Consistent with this hypothesis, transgenic expression of a mutant ICO protein is lethal when expressed during development and inhibits growth when expressed in wing discs. In addition, animals with a single copy of an ico point mutation are more sensitive to acute hyperthermic or hypoxic stress. Removal of the positively-charged tail of the protein abolishes the toxic effects of mutant ICO, demonstrating that this domain is necessary for the harmful gain-of-function phenotypes observed in ico point mutants. / Further, expression of GFP-tagged constructs indicates that the C-terminal tail enhances ectopic nuclear localization of mutant ICO, suggesting that mislocalization of the protein may play a role in the antimorphic effects of mutant ICO. Taken together, these results illustrate that in addition to loss-of-function effects, gain-of-function effects can contribute significantly to the pathology caused by mutation in mitochondrial translation elongation factors. / by Catherine F. Trivigno. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.
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