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2011-2012

6 hits

  • Thumbnail for Investigation of the role of the ncl-1 gene in dendrite morphogenesis in C. elegans
    Investigation of the role of the ncl-1 gene in dendrite morphogenesis in C. elegans by Kerr, Genevieve

    Neurons are polarized cells with specialized processes known as dendrites that receive environmental stimuli and transduce that input to the cell body, or soma. Dendrites are important in generating action potentials for cell-to-cell communication and, in the case of sensory neurons, for sensing the environment. Despite the important role that dendrites play, the molecular mechanisms that regulate dendrite development, or morphogenesis, are poorly understood. Recent research indicates that dendrite morphogenesis is regulated by the localized control of messenger RNA (mRNA) in dendrites. mRNA localization and translational regulation is often mediated by RNA-binding proteins (RBPs), which recognize and bind to specific mRNAs. It is thought that regulating protein translation in dendrites, which are located far from the nucleus where mRNAs originate, is a faster and more efficient way to regulate dendrite morphogenesis than changing gene expression. A recent study has found that the RBP gene brat regulates dendrite morphogenesis in Drosophila. To determine if brat function is conserved, we studied the role of ncl-1, a C. elegans homolog of brat, in dendrite morphogenesis. Dendrite morphology in wild type and ncl-1 mutants was compared using a fluorescent marker that is expressed in the PVD mechanosensory neurons in C. elegans. We find that ncl-1 null mutant PVDs have fewer dendritic branches than wild type throughout development. Consistent with a role in PVD dendritic development, we find that ncl-1 is expressed in most neurons during development, likely including the PVD. Since NCL-1 may be involved in regulating mRNAs in dendrites we wanted to see where within neurons the NCL-1 protein is localized. We find that NCL-1 is localized to both axons and dendrites, but was excluded from the nucleus. Together, these results suggest that NCL-1 plays a conserved role as an RBP that regulates mRNAs important for dendrite elaboration and future studies will be aimed at learning which mRNAs NCL-1 binds and how it regulates them.

  • Thumbnail for Phylogenetic analysis of Pleurothallis (Orchidaceae) using the plastid sequence ycf1
    Phylogenetic analysis of Pleurothallis (Orchidaceae) using the plastid sequence ycf1 by Sheade, Nina Kiyomi

    The appropriate taxonomic organization of Pleurothallis (subtribe Pleurothallidinae, family Orchidaceae) and its subgenera has been debated for more than a century. Recent phylogenetic studies have suggested that subgenera previously elevated to the level of genus based on morphological studies are most appropriately considered subgenera of Pleurothallis. This study analyzed the hypothetical open reading frame ycf1, a plastid gene, in order first to determine its utility in phylogenetic study at the generic and infrageneric level, and second to test support for the existing models or suggest a new model for taxonomic organization of Pleurothallis. A 1,200 bp 5’ region and a 1,500 bp 3’ region of the ycf1 gene were sequenced for representative species of each of the morphologically-based groups within Pleurothallis sensu lato and phylogenetic trees were generated for each region using maximum-parsimony analysis. The tree generated from the 5’ region exhibited minimal topological structure, suggesting either that the species sequenced are too closely related to be segregated into unique genera or the 5’ region of the gene did not contain enough parsimony informative sites to be useful at this level of study. The 3’ ycf1 gene tree had considerably more topology but the small number of species sequenced limits the conclusions that can be drawn from the phylogenetic tree.

  • Thumbnail for Sythesis of a 15 residue polypeptide with potential to reactivate mutated tumor suppressor p53
    Sythesis of a 15 residue polypeptide with potential to reactivate mutated tumor suppressor p53 by Mamba, Senani Siphelele

    Changes to wild-type p53 that make it partially or completely lose or alter its function, to enable the progression of tumors, occur in ~ 50% cancers, highlighting the role of p53 as a significant tumor suppressor. Usually p53 is inactivated through the mutation of the gene in somatic cells and at times, through the disruption of pathways that are vital for p53 activation. Because of the prevalence of loss-of-p53 in most cancers, interventions to target the reactivation of defective p53 pathways are in progress. Since peptides are easier to synthesize, administer and are safer than most cancer drugs in the market, there is an interest in considering peptide derivatives in drug design. By synthesizing a small peptide from the C-terminal domain of p53 we tested if p53 would interact with this small peptide. This interaction is significant since the C-terminal domain of p53 is involved in the self-activation of p53 and the goal of peptide therapy in this case would be to restore p53 self-activation. The peptide was synthesized by solid-phase peptide synthesis and its affinity for p53 was tested using microarray printing technology. Based on the results, the C1 peptide, a small peptide with 15 amino acids, binds to p53. Our findings suggest that C1 should be investigated further, in order to develop it as an anti-cancer drug.

  • Thumbnail for The effects of gender and brood size on the development of Flammulated Owl (Otus flammeolus) nestlings
    The effects of gender and brood size on the development of Flammulated Owl (Otus flammeolus) nestlings by Jones, Isabel

    Reversed sexual size dimorphism (RSSD), where females within a given species are larger than their male counterparts, is a phenomena observed across a few avian taxa including hawks and eagles (Accipitriformes), falcons (Falconiformes), waders (Charadriiformes), and owls (Strigiformes). While the mechanisms driving the evolution of this phenomenon are widely discussed, the proximate effects of RSSD on development and juvenile morphology are not well understood. Life history characteristics, such as brood size, influencing avian morphology are also important in understanding long-term patterns in development. I studied development of Flammulated Owls (Otus flammeolus), an RSSD species that tends to raise offspring in broods of 2-3 owlets, to better understand these relationships. I analyzed development using two measures: mass and wing feather length. First I determined the gender of all 2011 nestlings based on genetic analysis of blood samples collected from owlets captured and bled in 2011. Gender data since 2003 were already available. Growth analysis on a total of 189 owlets revealed that females reach a higher asymptotic mass than males. Broods consisting of three owlets reached a higher asymptotic mass than broods consisting of 2 owlets, an unexpected result based on previous research. The differences in maximum juvenile mass in broods of different sizes may be biased due to divergent sex ratios within broods; 57% of owlets in broods of three were female while 38% in broods of two were female. Even so, trends remained the same when males are compared with other males and females with other females in same-sized broods. Wing size differed little between the genders and broods. Juvenile body condition ultimately informs adult viability and fitness, thus it is important to understand these and other selective factors that influence avian development.

  • Thumbnail for Thermal reaction norms of metabolic scope in Madagascar hissing cockroaches
    Thermal reaction norms of metabolic scope in Madagascar hissing cockroaches by Wise, Kelsey Lane

    The “hotter is better” hypothesis states that the rate-depressing effects of low temperature cannot be compensated by acclimation or adaptation. In the present study we test this hypothesis by using metabolic rate and aerobic scope as performance indicators. Madagascar hissing cockroaches (Gromphadorhina portentosa) were acclimated to different temperatures for several weeks. After this acclimation period resting and maximal metabolic rates (RMR and MMR respectively) were measured via flow-through respirometry at temperatures ranging beyond the acclimation temperatures. RMR was obtained from animals kept in a dark chamber, at a given temperature, for at least 40 min. Following 1 min of vigorous shaking, MMR was calculated by using the highest continuous 30-sec running average of metabolic rate. Aerobic scope was determined as the difference between MMR and RMR. Preliminary results indicate that while the thermal reaction norms for RMR of cold acclimated animals are left-shifted compared to those of warm acclimated ones, the reaction norms for MMR displayed a reverse pattern, resulting in the warm acclimated animals having a higher aerobic scope. If confirmed, these results would lend support to the hotter is better hypothesis but also raise questions concerning the perception of metabolic rates as performance traits.

  • Thumbnail for ZK858.4 causes embryonic lethality but does not directly impact MEX-3 localization in an RNAi induced knockdown of E3 ubiquitin ligases in Caenorhabditis elegans
    ZK858.4 causes embryonic lethality but does not directly impact MEX-3 localization in an RNAi induced knockdown of E3 ubiquitin ligases in Caenorhabditis elegans by Reichard, Kathryn L.

    The ubiquitin proteosome system (UPS) functions in the cell to mark specific proteins for degradation. E3 ubiquitin ligases act as recognition factors and increase the specificity of the UPS. MEX-3 is an RNA binding protein in Caenorhabditis elegans that inhibits the translation of PAL-1, a posterior specifying protein, and contributes to development of the anterior of the embryo. MEX-3 is present throughout the oocyte, 1-cell, and 2-cell embryo. However, MEX-3 is then depleted in the posterior after the second cell division, and PAL-1 is then expressed in the two posterior blastomeres of the 4-cell embryo. MEX-3 is rapidly depleted from the entire embryo after the 8-cell stage. This degradation is location and time specific, and thus hypothesized to be caused by the UPS. MEX-3 is hypothesized to be targeted for degradation by a specific E3 ubiquitin ligase, and knockout of this protein should result in increase in universal MEX-3 expression in the early embryo. This study sought to determine the MEX-3 specific E3 ubiquitin ligase(s). Putative E3 ubiquitin ligases expressed during early embryonic development were knocked out in C. elegans, and phenotypes were determined. Of the knocked-out ligase genes, only one, ZK858.4 caused embryonic lethality at both 15˚ and 24˚ C. However, fluorescence microcopy of GFP::MEX-3 demonstrated that ZK858.4 knockout did not appear to increase global MEX-3 concentrations. Determining which protein targets MEX-3 degradation will provide more insight into the molecular mechanisms of determining anterior/posterior patterning in C. elegans early embryonic development.