Browsing by Subject "drosophila"
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Item HEM-protein regulates cell migration and asymmetric cell division during development of the ventral nerve cord in Drosophila melanogaster(2010-07-08) Zengrong Zhu; Krishna M. Bhat; Pomila Singh; Ping Wu; Kathleen M. Beckingham; Javier V. NavarroCell migration and asymmetric cell division are two of the key events during development of the nervous system. I have focused on a typical neuronal lineage, NB4-2→GMC-1→RP2/sib, in the ventral nerve cord (VNC) of the Drosophila embryo to investigate the regulation of neuronal migration and asymmetric cell division during development of the nervous system. I have discovered a migration defect of RP2 neurons in HEM-protein (Hem) mutants: RP2 neurons cross the midline and migrate from the initial hemi-segment to the opposite hemi-segment. The same migration defect is observed in WASP-family verprolin-homologous protein (WAVE/SCAR) and Abl tyrosine kinase (Abl) mutants, suggesting that these three genes might act together to regulate neuronal migration in the VNC. I have found that Hem is required for maintaining the protein level of WAVE in vivo and is necessary for its proper localization in the cell. In Hem mutants, WAVE is down regulated and mis-localized in RP2 neurons, resulting in the migration defect of RP2 neurons. Abl on the other hand negatively regulates the protein level of WAVE. When Abl is ectopically expressed, WAVE protein is down regulated. In Abl mutants, WAVE is up regulated and its hyperactivity may be responsible for the migration defect of RP2 neurons. Meanwhile, instead of asymmetric division in wild type embryos, a symmetric division of GMC-1 is observed in the “strong phenotype embryo†of HemJ4-48 mutants. It was not observed in other Hem mutants and Hem deficiency alleles. The truncated Hem protein (∆HemJ4-48) in HemJ4-48 allele may behave as a neomorphic protein, resulting in the symmetric division of GMC-1. In HemJ4-48 mutants, the apical localization of Inscuteable (Insc) is disrupted, suggesting that regulation of the asymmetric division of GMC-1 by Hem is mediated by Insc. The same symmetric division of GMC-1s was also observed in Abl mutants but not WAVE mutants, suggesting that Abl may act together with Hem to regulate the asymmetric division of GMC-1s. This study uses the Drosophila VNC as a model system and describes how neuronal migration and asymmetric cell division are regulated by Hem during development of the nervous system.Item The dynamics, interactions and phenotypes associated with the three members of the 14-3-3 family in Drosophila melanogaster(Texas A&M University, 2005-11-01) Acevedo, Summer FontaineIt has been proposed that the various 14-3-3 isotypes and isoforms present in all eukaryotes are largely functionally equivalent. However, this is not consistent with the conservation of multiple isoforms and isotypes, especially in vertebrates with seven 14-3-3 encoding genes and nine isotypes. The hypothesis tested in this thesis is that both isoform-specific and overlapping functions are likely mediated through tissue specific expression, colocalization and dimerization of 14-3-3 proteins occur in vivo. Drosophila melanogaster was selected because it offers a simple, but representative system to study these proteins functionally. This thesis focuses primarily on D14-3-3?, although the expression pattern and phenotypes associated with all three Drosophila 14-3-3s were determined. I first determined the expression pattern of the three different 14-3-3 isotypes (leoI, leoII and D14-3-3?) and described developmental phenotypes associated with mutations in 14-3-3 isotypes in Drosophila. I found that there is partial redundancy with respect to lethality. Both LEO and D14-3-3? appear required for normal germ-line and somatic gonadal development. However, they do not appear to be functionally equivalent with respect to this phenotype since LEO is unable to compensate for the loss of D14-3-3?. I also determined that D14-3-3? mutants have unique phenotypes including deficits in adult cross-vein formation and rapid habituation to olfactory and footshock stimuli. To further understand the unique role that D14-3-3? plays in the adult CNS, I mapped the areas in the brain involved in olfactory and footshock habituation. I found that although the mushroom bodies (MBs) are necessary to inhibit premature habituation such as that exhibited by D14-3-3? mutants, D14-3-3? expression specifically in the MBs is not sufficient to rescue premature habituation. Although the loss of either LEO or D14-3-3? appears to cause a deficit in olfactory associative learning, premature habituation is the cause of the deficit seen in D14-3-3? mutants. As leo mutants do not exhibit a premature habituation phenotype, it appears that within the MBs LEO and D14-3-3? are not functionally equivalent. Therefore, the data supports the hypothesis that 14-3-3s have functional specificity and redundancy likely to represent use of homo and heterodimers in different processes within the tissues of an organism.Item Tubulin in vitro, in vivo and in silico(Texas A&M University, 2005-02-17) Mershin, AndreasTubulin, microtubules and associated proteins were studied theoretically, computationally and experimentally in vitro and in vivo in order to elucidate the possible role these play in cellular information processing and storage. Use of the electric dipole moment of tubulin as the basis for binary switches (biobits) in nanofabricated circuits was explored with surface plasmon resonance, refractometry and dielectric spectroscopy. The effects of burdening the microtubular cytoskeleton of olfactory associative memory neurons with excess microtubule associated protein TAU in Drosophila fruitflies were determined. To investigate whether tubulin may be used as the substrate for quantum computation as a bioqubit, suggestions for experimental detection of quantum coherence and entanglement among tubulin electric dipole moment states were developed.