1. The Cryptococcus neoformans Titan cell is an inducible and regulated morphotype underlying pathogenesis.
- Author
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Dambuza IM, Drake T, Chapuis A, Zhou X, Correia J, Taylor-Smith L, LeGrave N, Rasmussen T, Fisher MC, Bicanic T, Harrison TS, Jaspars M, May RC, Brown GD, Yuecel R, MacCallum DM, and Ballou ER
- Subjects
- Animals, Cryptococcosis microbiology, Cryptococcus neoformans genetics, Cyclic AMP metabolism, Disease Models, Animal, Female, Fungal Proteins metabolism, Host-Pathogen Interactions, Humans, Hyphae cytology, Hyphae growth & development, Hyphae pathogenicity, Lung microbiology, Lung Diseases, Fungal microbiology, Male, Mice, Mice, Inbred BALB C, Mice, Inbred C57BL, Microscopy, Electron, Transmission, Models, Biological, Morphogenesis, Polyploidy, Transcription Factors metabolism, Virulence, Cryptococcus neoformans cytology, Cryptococcus neoformans pathogenicity
- Abstract
Fungal cells change shape in response to environmental stimuli, and these morphogenic transitions drive pathogenesis and niche adaptation. For example, dimorphic fungi switch between yeast and hyphae in response to changing temperature. The basidiomycete Cryptococcus neoformans undergoes an unusual morphogenetic transition in the host lung from haploid yeast to large, highly polyploid cells termed Titan cells. Titan cells influence fungal interaction with host cells, including through increased drug resistance, altered cell size, and altered Pathogen Associated Molecular Pattern exposure. Despite the important role these cells play in pathogenesis, understanding the environmental stimuli that drive the morphological transition, and the molecular mechanisms underlying their unique biology, has been hampered by the lack of a reproducible in vitro induction system. Here we demonstrate reproducible in vitro Titan cell induction in response to environmental stimuli consistent with the host lung. In vitro Titan cells exhibit all the properties of in vivo generated Titan cells, the current gold standard, including altered capsule, cell wall, size, high mother cell ploidy, and aneuploid progeny. We identify the bacterial peptidoglycan subunit Muramyl Dipeptide as a serum compound associated with shift in cell size and ploidy, and demonstrate the capacity of bronchial lavage fluid and bacterial co-culture to induce Titanisation. Additionally, we demonstrate the capacity of our assay to identify established (cAMP/PKA) and previously undescribed (USV101) regulators of Titanisation in vitro. Finally, we investigate the Titanisation capacity of clinical isolates and their impact on disease outcome. Together, these findings provide new insight into the environmental stimuli and molecular mechanisms underlying the yeast-to-Titan transition and establish an essential in vitro model for the future characterization of this important morphotype., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2018
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