This proposal is to identify and characterize factors in the fungus Cryptococcus neoformans that can be used as targets to compromise its pathogenicity. Cryptococcus is a dimorphic fungus: it generally causes diseases when it is in the yeast form and it is less virulent when it is in the filamentous form (pseudohyphae or hyphae). As the ability to regulate growth form in response to host cues is an essential requirement for many eukaryotic microbes to cause diseases, activating appropriate regulatory circuits for development is likely to be critical for the survival and propagation of Cryptococcus under host conditions. Unfortunately, the molecular bases underlying the link between dimorphism and virulence in Cryptococcus remain an enigma. Filamentation in Cryptococcus has historically been considered to be coupled with mating, which is suppressed under host conditions. Preliminary studies performed in the applicant's lab indicate that genetic manipulation can confer Cryptococcus filamentous growth under conditions that are host physiologically relevant. Znf2, a zinc finger transcription factor, is a master regulator of filamentation and it also dictates cell adhesion (flocculation). Importantly, Znf2 negatively impact Cryptococcus pathogenicity. Thus, Znf2 provides a link to understand the molecular bases of dimorphism and virulence in Cryptococcus. The central hypothesis of this proposal is that Znf2 mediates the ability of Cryptococcus to cause disease by controlling cell morphotype and other features normally associated with morphogenesis. Guided by strong preliminary data, the hypothesis will be tested by pursuing the following specific aims: 1). Establish the relationship between ZNF2 expression, the ability to undergo filamentation, cell adhesion, and Cryptococcus virulence. 2). Characterize additional determinants of filamentation and Znf2 targets, and determine their roles in virulence. The focus on factors that regulate the inherent ability to undergo filamentation in order to understand dimorphism and virulence in Cryptococcus represents a substantial departure from current approaches that are centered on the signaling pathways that lead to mating. Research based on this new vision is expected to generate mechanistic insights into novel virulence determinants in Cryptococcus. Given the divergence of Cryptococcus from other environmentally-acquired dimorphic pathogens (different phyla) that also show a similar inverse association between filamentation and virulence, it is highly likely that this research will identify conserved determinants necessary for fungal dimorphism. As Cryptococcus is both a clinically important pathogen and is amenable to genetic and molecular studies, this research will contribute to a broader understanding of cell-shape determination and the impact of morphotype on the survival of microbial pathogens. The long-term goals are to understand the fundamental requirements for morphogenesis and pathogenicity that are common to fungal pathogens, and to harness such knowledge to develop preventative and therapeutic measures against invasive mycoses.

Public Health Relevance

Systemic fungal infections, including cryptococcosis, have high mortality rates and are a worldwide problem that affects millions of people. This research will provide valuable information concerning the molecular mechanisms by which Cryptococcus and other fungi regulate cell morphotype and pathogenicity. These molecules are anticipated to represent promising therapeutic targets.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Pathogenic Eukaryotes Study Section (PTHE)
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Duncan, Rory A
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Texas A&M University
Schools of Arts and Sciences
College Station
United States
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Meng, Yunfang; Fan, Yumeng; Liao, Wanqing et al. (2018) Plant Homeodomain Genes Play Important Roles in Cryptococcal Yeast-Hypha Transition. Appl Environ Microbiol 84:
Zhao, Youbao; Upadhyay, Srijana; Lin, Xiaorong (2018) PAS Domain Protein Pas3 Interacts with the Chromatin Modifier Bre1 in Regulating Cryptococcal Morphogenesis. MBio 9:
Fan, Yumeng; Lin, Xiaorong (2018) Multiple Applications of a Transient CRISPR-Cas9 Coupled with Electroporation (TRACE) System in the Cryptococcus neoformans Species Complex. Genetics 208:1357-1372
Xu, Xinping; Lin, Jianfeng; Zhao, Youbao et al. (2017) Glucosamine stimulates pheromone-independent dimorphic transition in Cryptococcus neoformans by promoting Crz1 nuclear translocation. PLoS Genet 13:e1006982
Gyawali, Rachana; Upadhyay, Srijana; Way, Joshua et al. (2017) A Family of Secretory Proteins Is Associated with Different Morphotypes in Cryptococcus neoformans. Appl Environ Microbiol 83:
Gyawali, Rachana; Zhao, Youbao; Lin, Jianfeng et al. (2017) Pheromone independent unisexual development in Cryptococcus neoformans. PLoS Genet 13:e1006772
Xu, Xinping; Zhao, Youbao; Kirkman, Elyssa et al. (2016) Secreted Acb1 Contributes to the Yeast-to-Hypha Transition in Cryptococcus neoformans. Appl Environ Microbiol 82:1069-1079
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Chacko, Nadia; Zhao, Youbao; Yang, Ence et al. (2015) The lncRNA RZE1 Controls Cryptococcal Morphological Transition. PLoS Genet 11:e1005692

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