Approaching the functional annotation of fungal virulence factors using cross-species genetic interaction profiling

• Published in: PLoS genetics 2012-12, Vol.8 (12), p.e1003168
• Main Authors: Brown, Jessica C S, Madhani, Hiten D
• Format: Article
• Language: English
• Subjects: Acquired immune deficiency syndrome; AIDS; Biology; Brewer's yeast; Cryptococcus; Cryptococcus neoformans - genetics; Cryptococcus neoformans - pathogenicity; Endosomes - genetics; Endosomes - metabolism; Fungi - genetics; Fungi - pathogenicity; Gene Expression Profiling; Gene Expression Regulation, Fungal; Genes; Genetic aspects; Genetics; Golgi Apparatus - genetics; Golgi Apparatus - metabolism; Health aspects; Humans; Microbial genetics; Microbiology; Molecular Sequence Annotation; Physiological aspects; Proteins; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Sequence Deletion; Virulence (Microbiology); Virulence Factors - genetics; Yeast
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1003168

In many human fungal pathogens, genes required for disease remain largely unannotated, limiting the impact of virulence gene discovery efforts. We tested the utility of a cross-species genetic interaction profiling approach to obtain clues to the molecular function of unannotated pathogenicity factors in the human pathogen Cryptococcus neoformans. This approach involves expression of C. neoformans genes of interest in each member of the Saccharomyces cerevisiae gene deletion library, quantification of their impact on growth, and calculation of the cross-species genetic interaction profiles. To develop functional predictions, we computed and analyzed the correlations of these profiles with existing genetic interaction profiles of S. cerevisiae deletion mutants. For C. neoformans LIV7, which has no S. cerevisiae ortholog, this profiling approach predicted an unanticipated role in the Golgi apparatus. Validation studies in C. neoformans demonstrated that Liv7 is a functional Golgi factor where it promotes the suppression of the exposure of a specific immunostimulatory molecule, mannose, on the cell surface, thereby inhibiting phagocytosis. The genetic interaction profile of another pathogenicity gene that lacks an S. cerevisiae ortholog, LIV6, strongly predicted a role in endosome function. This prediction was also supported by studies of the corresponding C. neoformans null mutant. Our results demonstrate the utility of quantitative cross-species genetic interaction profiling for the functional annotation of fungal pathogenicity proteins of unknown function including, surprisingly, those that are not conserved in sequence across fungi.