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Open Access Publications from the University of California

Scholarly Works (5 results)

  • Thesis
  • Peer Reviewed
UC Riverside Electronic Theses and Dissertations (2016)

The organization and functionality of the fly olfactory system is orchestrated by complex molecular events, and the Drosophila model offers the tools necessary to understand the genetic basis of these events. This work aims to further characterize the molecular basis of olfactory driven behaviors in Drosophila. I will explore several topics to this end: The reliance of innate chemotaxis behavior on single receptor genes, the regulation of receptor gene choice, and a novel molecular mechanism required for olfactory learning and memory.

In Part I, I demonstrate that loss of single receptor genes can disrupt innate avoidance behaviors. First, I identify a novel aversive channel in the larvae governed by Or7a. Or7a mutants lose the ability to detect and respond to low concentrations of the food odorant E-(2)-hexenal. Secondly, I show that loss of Gr63a’s co-receptor Gr21a completely disrupts neuronal and behavioral response to carbon dioxide in adult flies. In both cases, I employed the emergent CRISPR/Cas9 system to create targeted knock-out mutations in Drosophila.

In Part II, I show that members of the chromatin modifying complex MMB/dREAM regulate expression of carbon dioxide receptors Gr63a and Gr21a. Using RNA-seq to analyze antennal transcriptomes, I observe differential expression of several other olfactory receptor genes in dREAM complex mutants, suggesting a broader role in olfactory receptor regulation for this multi-protein complex.

In Part III, I find that HDAC6, a largely cytoplasmic protein, is required for retention of olfactory memory in both larvae and adults. HDAC6 mutants also exhibit defects in synaptic plasticity at the larval neuromuscular junction, suggesting an interesting connection between molecular events at active zones and behavioral plasticity.

    Cover page: The Molecular Basis of Olfactory Driven Behaviors in Drosophila melanogaster
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2017)
    Histone deacetylases (HDACs) have been extensively studied as drug targets in neurodegenerative diseases, but less is known about their role in healthy neurons. We tested zinc-dependent HDACs using RNAi in Drosophila melanogaster and found memory deficits with RPD3 and HDAC6. We demonstrate that HDAC6 is required in both the larval and adult stages for normal olfactory memory retention. Neuronal expression of HDAC6 rescued memory deficits, and we demonstrate that the N-terminal deacetylase (DAC) domain is required for this ability. This suggests that deacetylation of synaptic targets associated with the first DAC domain, such as the active-zone scaffold Bruchpilot, is required for memory retention. Finally, electrophysiological experiments at the neuromuscular junction reveal that HDAC6 mutants exhibit a partial block of homeostatic plasticity, suggesting that HDAC6 may be required for the stabilization of synaptic strength. The learning deficit we observe in HDAC6 mutants could be a behavioral consequence of these synaptic defects.
      Cover page: The Role of Histone Deacetylase 6 in Synaptic Plasticity and Memory
      • Article
      • Peer Reviewed
      UC Riverside Previously Published Works (2020)
      The CO2 receptor in mosquitoes is broadly tuned to detect many diverse odorants. The receptor consists of three subunits (Gr1, Gr2, and Gr3) in mosquitoes but only two subunits in Drosophila: Gr21a (Gr1 ortholog) and Gr63a (Gr3 ortholog). We demonstrate that Gr21a is required for CO2 responses in Drosophila, as has been shown for Gr63a. Next, we generate a Drosophila double mutant for Gr21a and Gr63a, and in this background, we functionally express combinations of Aedes Gr1, Gr2, and Gr3 genes in the CO2 empty neuron. Only two subunits, Gr2 and Gr3, suffice for response to CO2. Addition of Gr1 increases sensitivity to CO2, whereas it decreases the response to pyridine. The inhibitory effect of the antagonist isobutyric acid is observed upon addition of Gr1. Gr1 therefore increases the diversity of ligands of the receptor and modulates the response of the receptor complex.
        Cover page: Contributions of the Conserved Insect Carbon Dioxide Receptor Subunits to Odor Detection
        • Article
        • Peer Reviewed
        UC Riverside Previously Published Works (2019)
        AbstractThe CO2 receptor in mosquitoes is broadly tuned to detect many diverse odorants. The receptor consists of three 7-TM subunits (Gr1, Gr2, and Gr3) in mosquitoes but only two subunits in Drosophila: Gr21a (Gr1 ortholog) and Gr63a (Gr3 ortholog). We demonstrate that Gr21a is required for CO2 responses in Drosophila as has been shown for Gr63a. Next, we generate a Drosophila double mutant for Gr21a and Gr63a, and in this background we functionally express combinations of Aedes Gr1, 2, and 3 genes in the “CO2 empty neuron.” Only two subunits, Gr2 and Gr3, suffice for response to CO2. Addition of Gr1 increases sensitivity to CO2 while it decreases the response to pyridine. The inhibitory effect of the antagonist isobutyric acid is observed upon addition of Gr1. Gr1 therefore increases the diversity of ligands of the receptor, and also modulates the response of the receptor complex.
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2018)
          Biomolecules exist and function in cellular microenvironments that control their spatial organization, local concentration, and biochemical reactivity. Due to the complexity of native cytoplasm, the development of artificial bioreactors and cellular mimics to compartmentalize, concentrate, and control the local physico-chemical properties is of great interest. Here, we employ self-assembling polypeptide coacervates to explore the partitioning of the ubiquitous cytoskeletal protein actin into liquid polymer-rich droplets. We find that actin spontaneously partitions into coacervate droplets and is enriched by up to ∼30-fold. Actin polymerizes into micrometer-long filaments and, in contrast to the globular protein BSA, these filaments localize predominately to the droplet periphery. We observe up to a 50-fold enhancement in the actin filament assembly rate inside coacervate droplets, consistent with the enrichment of actin within the coacervate phase. Together these results suggest that coacervates can serve as a versatile platform in which to localize and enrich biomolecules to study their reactivity in physiological environments.
            Cover page: Partitioning and Enhanced Self-Assembly of Actin in Polypeptide CoacervatesCreative Commons 'BY-NC-SA' version 4.0 license
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