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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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:
Zhai, Bing; Wozniak, Karen L; Masso-Silva, Jorge et al. (2015) Development of protective inflammation and cell-mediated immunity against Cryptococcus neoformans after exposure to hyphal mutants. MBio 6:e01433-15
Lin, Xiaorong; Chacko, Nadia; Wang, Linqi et al. (2015) Generation of stable mutants and targeted gene deletion strains in Cryptococcus neoformans through electroporation. Med Mycol 53:225-34
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Lin, Jianfeng; Idnurm, Alexander; Lin, Xiaorong (2015) Morphology and its underlying genetic regulation impact the interaction between Cryptococcus neoformans and its hosts. Med Mycol 53:493-504
Idnurm, Alexander; Lin, Xiaorong (2015) Rising to the challenge of multiple Cryptococcus species and the diseases they cause. Fungal Genet Biol 78:1-6
Xu, Xinping; Zhao, Youbao; Kirkman, Elyssa et al. (2015) Secreted Acb1 Contributes to the Yeast-to-Hypha Transition in Cryptococcus neoformans. Appl Environ Microbiol 82:1069-79
Wang, Linqi; Lin, Xiaorong (2015) The morphotype heterogeneity in Cryptococcus neoformans. Curr Opin Microbiol 26:60-4
Wang, Linqi; Tian, Xiuyun; Gyawali, Rachana et al. (2014) Morphotype transition and sexual reproduction are genetically associated in a ubiquitous environmental pathogen. PLoS Pathog 10:e1004185
Lin, Xiaorong; Alspaugh, J Andrew; Liu, Haoping et al. (2014) Fungal morphogenesis. Cold Spring Harb Perspect Med 5:a019679

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