POSTER SESSION 1
The bab Locus Model for Synergistic Gene Regulatory Interactions in Development and Evolution. Presenter(s): Eric M Camino, Kaitlyn R Francis, Jordan E Vellky Advisor(s): Thomas M Williams Biology - Graduate Research
Complex spatial and temporal patterns of gene expression (production of a gene’s encoded protein) are crucial to animal development and changes in expression patterns are a common mode of evolutionary innovation. Thus, understanding development requires answering: (1) what are the DNA elements, so called CREs, controlling expression, (2) how the DNA sequences of CREs encode gene regulatory capabilities, (3) whether and how CREs work together to make complex expression patterns, and (4) how CRE sequences identify their gene target(s) of regulation in a 3-dimensional nucleus? These answers will aid studies to reveal the mechanisms of gene expression, and thus animal, evolution. A model to address these questions is the bab locus of fruit flies. This locus contains the duplicate bab1 and bab2 genes that shape a derived pattern of pigmentation in the species Drosophila melanogaster. The relevant bab expression pattern is controlled by two CREs which we found to interact in a non-additive, or synergistic, way to yield this pattern. Ongoing studies seek to trace: when and how CRE synergism evolved, which CRE sequences encode their synergistic activity, how these CREs interact with the bab genes, and whether synergism is limited to these genes. Ultimately, this work aims to connect how animal form is programmed into 1-dimensional DNA sequence and how this program evolves.
The Effects of Silver Nanoparticles on Mouse Embryonic Cell Renewal and Cell Cycle Presenter(s): Christopher J Stucke Advisor(s): Yiling Hong Biology - Honors Thesis
The use of silver nanoparticles in commercially made products is rapidly increasing, and there is no regulation on the disposal of these nanoparticles. As human exposure to silver nanoparticles rises, this study determines the effects of this exposure on stem cell factor gene expression and stem cell fate. This was accomplished by introducing varying concentrations of silver nanoparticles into mouse embryonic stem cells for varying amounts of time. Western blot and immunoprecipitation techniques were run on these cells to determine how the responses of stem cell factors Oct4, Nanog, P53, SirT1, and Rb differ from their normal function within the cell. In addition, this study also determines whether programmed cell death is occurring in response to the silver nanoparticle treatment. The results of the research provided necessary scientific data to improve or eliminate potential toxicity of nanoparticles, and information for relevant authority when approving products for consumer uses.
The mutations, molecular mechanisms, and constraints directing the evolution of a Drosophila cis-regulatory element Presenter(s): William A Rogers, Joseph R Salomone, David J Tacy Advisor(s): Thomas M Williams Biology - Graduate Research
A major goal of evolutionary developmental biology research is to illuminate how evolution acts on development to cause phenotypic change. A wealth of data implicates changes in gene expression as the predominant means by which morphological traits evolve, and likely via mutations in cis-regulatory elements (CREs) that specify gene expression patterns. Each expression pattern is encoded in a CRE as a regulatory logic comprised of a collection and organization of binding sites for certain transcription factor (TF) proteins. While several case studies have identified instances of CRE evolution, how encoded regulatory logics evolve remains poorly understood. An intraspecific comparison of Drosophila melanogaster sexually dimorphic abdominal pigmentation patterns presents an opportune situation to reveal how regulatory logics evolve. The degree of female pigmentation varies between populations and this variation stems from genetic variation at the bric-a-brac (bab) locus, which encodes the Bab TF proteins that act as repressors of pigmentation development. Bab expression in females is controlled by a CRE known as the dimorphic element. We identified four dimorphic element alleles that possess different gene regulatory capabilities. By determining the sequence and function of the CRE possessed by the most recent common ancestor of these extant populations we were able demonstrate how few mutations were necessary and sufficient to alter the function of the derived alleles. Ongoing studies seek to reveal how these few mutations of a relatively large effect modify an ancestral regulatory logic. 33