Computational Analysis Reveals a Key Regulator of Cryptococcal Virulence and Determinant of Host Response.
Cryptococcus neoformans is a ubiquitous, opportunistic fungal pathogen that kills over 600,000 people annually. Here, we report integrated computational and experimental investigations of the role and mechanisms of transcriptional regulation in cryptococcal infection. Major cryptococcal virulence traits include melanin production and the development of a large polysaccharide capsule upon host entry; shed capsule polysaccharides also impair host defenses. We found that both transcription and translation are required for capsule growth and that Usv101 is a master regulator of pathogenesis, regulating melanin production, capsule growth, and capsule shedding. It does this by directly regulating genes encoding glycoactive enzymes and genes encoding three other transcription factors that are essential for capsule growth: GAT201, RIM101, and SP1. Murine infection with cryptococci lacking Usv101 significantly alters the kinetics and pathogenesis of disease, with extended survival and, unexpectedly, death by pneumonia rather than meningitis. Our approaches and findings will inform studies of other pathogenic microbes.


OBJECTIVE
Cryptococcus neoformans causes fatal meningitis in immunocompromised individuals, mainly HIV positive, killing over 600,000 each year. A unique feature of this yeast, which makes it particularly virulent, is its polysaccharide capsule; this structure impedes host efforts to combat infection. Capsule size and structure respond to environmental conditions, such as those encountered in an infected host. We have combined computational and experimental tools to elucidate capsule regulation, which we show primarily occurs at the transcriptional level. We also demonstrate that loss of a novel transcription factor alters virulence factor expression and host cell interactions, changing the lethal condition from meningitis to pneumonia with an exacerbated host response. We further demonstrate the relevant targets of regulation and kinetically map key regulatory and host interactions. Our work elucidates mechanisms of capsule regulation, provides methods and resources to the research community, and demonstrates an altered pathogenic outcome that resembles some human conditions.
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Stacey R
SR
Gish
Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri, USA Department of Computer Science and Engineering, Washington University, St. Louis, Missouri, USA.
Ezekiel J
EJ
Maier
Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri, USA Department of Computer Science and Engineering, Washington University, St. Louis, Missouri, USA.
Brian C
BC
Haynes
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Felipe H
FH
Santiago-Tirado
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Deepa L
DL
Srikanta
Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri, USA Department of Computer Science and Engineering, Washington University, St. Louis, Missouri, USA.
Cynthia Z
CZ
Ma
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Lucy X
LX
Li
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Matthew
M
Williams
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.
Erika C
EC
Crouch
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Shabaana A
SA
Khader
Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri, USA Department of Computer Science and Engineering, Washington University, St. Louis, Missouri, USA Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, USA brent@wustl.edu doering@wustl.edu.
Michael R
MR
Brent
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA brent@wustl.edu doering@wustl.edu.
Tamara L
TL
Doering
D000818:Animals; D019295:Computational Biology; D003453:Cryptococcosis / Q000382:microbiology*; D003455:Cryptococcus neoformans / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D005260:Female; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D053263:Gene Regulatory Networks; D006801:Humans; D008543:Melanins / Q000378:metabolism; D051379:Mice; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
D005656:Fungal Proteins; D008543:Melanins; D014157:Transcription Factors