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Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Merced Electronic Theses and Dissertations (2021)

Candida albicans is a commensal member of the human microbiota that is also capable of causing superficial and disseminated infections and is known to be the predominant fungal pathogen of humans in clinical settings. Mucosal linings are critical for protecting the host against infections, and it is the biological and viscoelastic properties of mucus, predominantly attributed to glycoproteins called mucins, that provide this protection. Chapter 1 introduces how mucins are involved in maintaining a healthy microbial balance on mucosal linings when directly interacting with microorganisms. Oftentimes, invading microorganisms colonize mucosal surfaces by forming microbial communities called biofilms. Biofilms can have detrimental impacts on the host because, once formed, they are highly resistant to chemical and mechanical perturbations. Chapter 2 aims to discover novel regulators that mediate the ability of C. albicans to interact with mucin in the context of biofilms. We screened a library of 211 transcription factor deletion mutants using in vitro biofilm assays in the presence of mucin to identify the regulators involved in governing C. albicans interactions with mucin. A total of 12 “master” regulators were found to play roles in interacting with mucins. Using a combination of genetic and genome-wide approaches, we mapped the regulatory connections of each transcription factor to one another and to downstream target genes to determine the regulatory network controlling the ability of C. albicans to interact with mucin. Understanding how C. albicans modulates its interactions with mucin will shed new light on the regulatory control that evolved to mediate this important interaction with the host. In Chapter 3, we introduce a host-pathogen model system to study the interactions between C. albicans and the flatworm Schmidtea mediterranea. This model is a unique invertebrate model that allows for the study of an early C. albicans epithelial infection in the presence of secreted mucus produced by the flatworm. Using this model, we identified two C. albicans proteins that mediate epithelial infection in S. mediterranea as well as a comprehensive host response facilitated by diverse host tissues to clear the infection.

    Cover page: Identifying the regulatory network controlling Candida albicans interactions with host mucinsCreative Commons 'BY' version 4.0 license
    • Article
    • Peer Reviewed
    UC Merced Previously Published Works (2022)
    Regulatory transcription factors control many important biological processes, including cellular differentiation, responses to environmental perturbations and stresses, and host-pathogen interactions. Determining the genome-wide binding of regulatory transcription factors to DNA is essential to understanding the function of transcription factors in these often complex biological processes. Cleavage under targets and release using nuclease (CUT&RUN) is a modern method for genome-wide mapping of in vivo protein-DNA binding interactions that is an attractive alternative to the traditional and widely used chromatin immunoprecipitation followed by sequencing (ChIP-seq) method. CUT&RUN is amenable to a higher-throughput experimental setup and has a substantially higher dynamic range with lower per-sample sequencing costs than ChIP-seq. Here, a comprehensive CUT&RUN protocol and accompanying data analysis workflow tailored for genome-wide analysis of transcription factor-DNA binding interactions in the human fungal pathogen Candida albicans are described. This detailed protocol includes all necessary experimental procedures, from epitope tagging of transcription factor-coding genes to library preparation for sequencing; additionally, it includes a customized computational workflow for CUT&RUN data analysis.
      Cover page: Genome-wide Profiling of Transcription Factor-DNA Binding Interactions in Candida albicans: A Comprehensive CUT&RUN Method and Data Analysis Workflow.
      • Article
      • Peer Reviewed
      UC Merced Previously Published Works (2022)
      Mucins are large gel-forming polymers inside the mucus barrier that inhibit the yeast-to-hyphal transition of Candida albicans, a key virulence trait of this important human fungal pathogen. However, the molecular motifs in mucins that inhibit filamentation remain unclear despite their potential for therapeutic interventions. Here, we determined that mucins display an abundance of virulence-attenuating molecules in the form of mucin O-glycans. We isolated and cataloged >100 mucin O-glycans from three major mucosal surfaces and established that they suppress filamentation and related phenotypes relevant to infection, including surface adhesion, biofilm formation and cross-kingdom competition between C. albicans and the bacterium Pseudomonas aeruginosa. Using synthetic O-glycans, we identified three structures (core 1, core 1 + fucose and core 2 + galactose) that are sufficient to inhibit filamentation with potency comparable to the complex O-glycan pool. Overall, this work identifies mucin O-glycans as host molecules with untapped therapeutic potential to manage fungal pathogens.
        Cover page: Mucin O-glycans are natural inhibitors of Candida albicans pathogenicity
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