Honors & Awards
Gilliam Fellowship Program, Howard Hughes Medical Institute (2016-2019)
Predoctoral Diversity Enrichment Program, Burroughs Wellcome Fund (2017-2019)
Boards, Advisory Committees, Professional Organizations
President, Duke University Bouchet Society (2017 - 2019)
Librarian, Duke Chapel Choir (2019 - Present)
PhD, Duke University School of Medicine, Cell Biology (2021)
MS, Mississippi State University, Biological Sciences (2014)
MA, Boston University, Applied Linguistics (2005)
BS, Millsaps College, Biology (1994)
John Pringle, Postdoctoral Faculty Sponsor
Current Research and Scholarly Interests
I am a biologist with broad biomedical research experience, ranging from longitudinal studies of cognitive aging to clinical trials of autoimmune disease - but my favorite biological problems have broad relevance to a variety of cell types, processes, and organisms. As a Ph.D. student in cell biology, I studied how budding yeast cells track chemical signals, a process that is critical for feeding, fertilization, and development (among many other things) in a wide variety of eukaryotes. As a postdoctoral fellow, I currently investigate actomyosin-independent mechanisms of cytokinesis in the alga Chlamydomonas reinhardtii.
Chemotropism and Cell-Cell Fusion in Fungi.
Microbiology and molecular biology reviews : MMBR
Fungi exhibit an enormous variety of morphologies, including yeast colonies, hyphal mycelia, and elaborate fruiting bodies. This diversity arises through a combination of polar growth, cell division, and cell fusion. Because fungal cells are nonmotile and surrounded by a protective cell wall that is essential for cell integrity, potential fusion partners must grow toward each other until they touch and then degrade the intervening cell walls without impacting cell integrity. Here, we review recent progress on understanding how fungi overcome these challenges. Extracellular chemoattractants, including small peptide pheromones, mediate communication between potential fusion partners, promoting the local activation of core cell polarity regulators to orient polar growth and cell wall degradation. However, in crowded environments, pheromone gradients can be complex and potentially confusing, raising the question of how cells can effectively find their partners. Recent findings suggest that the cell polarity circuit exhibits searching behavior that can respond to pheromone cues through a remarkably flexible and effective strategy called exploratory polarization.
View details for DOI 10.1128/mmbr.00165-21
View details for PubMedID 35138122
Exploratory polarization facilitates mating partner selection in Saccharomyces cerevisiae.
Molecular biology of the cell
2021; 32 (10): 1048-1063
Yeast decode pheromone gradients to locate mating partners, providing a model for chemotropism. How yeast polarize toward a single partner in crowded environments is unclear. Initially, cells often polarize in unproductive directions, but then they relocate the polarity site until two partners' polarity sites align, whereupon the cells "commit" to each other by stabilizing polarity to promote fusion. Here we address the role of the early mobile polarity sites. We found that commitment by either partner failed if just one partner was defective in generating, orienting, or stabilizing its mobile polarity sites. Mobile polarity sites were enriched for pheromone receptors and G proteins, and we suggest that such sites engage in an exploratory search of the local pheromone landscape, stabilizing only when they detect elevated pheromone levels. Mobile polarity sites were also enriched for pheromone secretion factors, and simulations suggest that only focal secretion at polarity sites would produce high pheromone concentrations at the partner's polarity site, triggering commitment.
View details for DOI 10.1091/mbc.E21-02-0068
View details for PubMedID 33689470
View details for PubMedCentralID PMC8101489
Mechanisms that ensure monogamous mating in Saccharomyces cerevisiae.
Molecular biology of the cell
2021; 32 (8): 638-644
Haploid cells of the budding yeast Saccharomyces cerevisiae communicate using secreted pheromones and mate to form diploid zygotes. Mating is monogamous, resulting in the fusion of precisely one cell of each mating type. Monogamous mating in crowded conditions, where cells have access to more than one potential partner, raises the question of how multiple-mating outcomes are prevented. Here we identify mutants capable of mating with multiple partners, revealing the mechanisms that ensure monogamous mating. Before fusion, cells develop polarity foci oriented toward potential partners. Competition between these polarity foci within each cell leads to disassembly of all but one focus, thus favoring a single fusion event. Fusion promotes the formation of heterodimeric complexes between subunits that are uniquely expressed in each mating type. One complex shuts off haploid-specific gene expression, and the other shuts off the ability to respond to pheromone. Zygotes able to form either complex remain monogamous, but zygotes lacking both can re-mate.
View details for DOI 10.1091/mbc.E20-12-0757
View details for PubMedID 33596113
View details for PubMedCentralID PMC8108519
Ratiometric GPCR signaling enables directional sensing in yeast.
2019; 17 (10): e3000484
Accurate detection of extracellular chemical gradients is essential for many cellular behaviors. Gradient sensing is challenging for small cells, which can experience little difference in ligand concentrations on the up-gradient and down-gradient sides of the cell. Nevertheless, the tiny cells of the yeast Saccharomyces cerevisiae reliably decode gradients of extracellular pheromones to find their mates. By imaging the behavior of polarity factors and pheromone receptors, we quantified the accuracy of initial polarization during mating encounters. We found that cells bias the orientation of initial polarity up-gradient, even though they have unevenly distributed receptors. Uneven receptor density means that the gradient of ligand-bound receptors does not accurately reflect the external pheromone gradient. Nevertheless, yeast cells appear to avoid being misled by responding to the fraction of occupied receptors rather than simply the concentration of ligand-bound receptors. Such ratiometric sensing also serves to amplify the gradient of active G protein. However, this process is quite error-prone, and initial errors are corrected during a subsequent indecisive phase in which polarity clusters exhibit erratic mobile behavior.
View details for DOI 10.1371/journal.pbio.3000484
View details for PubMedID 31622333
View details for PubMedCentralID PMC6818790
The contribution of set switching and working memory to sentence processing in older adults.
Experimental aging research
2011; 37 (5): 516-38
This study evaluates the involvement of switching skills and working-memory capacity in auditory sentence processing in older adults. The authors examined 241 healthy participants, aged 55 to 88 years, who completed four neuropsychological tasks and two sentence-processing tasks. In addition to age and the expected contribution of working memory, switching ability, as measured by the number of perseverative errors on the Wisconsin Card Sorting Test, emerged as a strong predictor of performance on both sentence-processing tasks. Individuals with both low working-memory spans and more perseverative errors achieved the lowest accuracy scores. These findings are consistent with compensatory accounts of successful performance in older age.
View details for DOI 10.1080/0361073X.2011.619858
View details for PubMedID 22091580
View details for PubMedCentralID PMC3227002
Bilateral brain regions associated with naming in older adults
BRAIN AND LANGUAGE
2010; 113 (3): 113-123
To determine structural brain correlates of naming abilities in older adults, we tested 24 individuals aged 56-79 on two confrontation-naming tests (the Boston Naming Test (BNT) and the Action Naming Test (ANT)), then collected from these individuals structural Magnetic-Resonance Imaging (MRI) and Diffusion Tensor Imaging (DTI) data. Overall, several regions showed that greater gray and white matter volume/integrity measures were associated with better task performance. Left peri-Sylvian language regions and their right-hemisphere counterparts, plus left mid-frontal gyrus correlated with accuracy and/or negatively with response time (RT) on the naming tests. Fractional anisotropy maps derived from DTI showed robust positive correlations with ANT accuracy bilaterally in the temporal lobe and in right middle frontal lobe, as well as negative correlations with BNT RT, bilaterally, in the white matter within middle and inferior temporal lobes. We conclude that those older adults with relatively better naming skills can rely on right-hemisphere peri-Sylvian and mid-frontal regions and pathways, in conjunction with left-hemisphere peri-Sylvian and mid-frontal regions, to achieve their success.
View details for DOI 10.1016/j.band1.2010.03.001
View details for Web of Science ID 000277548600002
View details for PubMedID 20399492
View details for PubMedCentralID PMC2975055
- Language and Communication in Aging Encyclopedia of Gerontology Elsevier. 2007; 2: 1-8
- Language Disorders: General Encyclopedia of Gerontology Elsevier. 2007; 2: 16-23
- BUCLD 29: Proceedings Supplement Boston University Conference on Language Development. 2005 ; BUCLD Proceedings Supplements (2):
- BUCLD 29: Proceedings of the 29th Annual Boston University Conference on Language Development Boston University Conference on Language Development Cascadilla Press. 2005