Project description:Among ~5,000,000 fungal species on Earth, Candida albicans is exceptional in its lifelong association with humans, where it exists either as a benign component of the gastrointestinal microbiome or as an invasive pathogen. Although it is generally assumed that invasiveness results from a breakdown of host immunity , it is also possible that specific fungal programs control the transition between these divergent lifestyles. Here, we report that exposure of C. albicans to the mammalian gut triggers a developmental switch, driven by the Wor1 transcription factor, to a commensal cell type. Wor1 has been thought to occur only in unique genetic backgrounds, but we show that WOR1 expression is triggered when wild-type cells are propagated in a murine gastrointestinal infection model. Similar to Wor1’s role in a white-opaque switch for mating, WOR1 overexpression within the host induces a novel switch affecting cell and colony morphology and conferring commensal fitness. However, these hyperfit GUT (Gastrointestinally-IndUced Transition) cells lack the functional hallmarks of opaque cells, which they resemble morphologically, whereas bona fide opaque cells are defective for commensalism. Instead, the GUT cell transcriptome is optimized for the environment of the distal mammalian digestive tract. The GUT cell type switch illuminates how a single organism can utilize distinct genetic programs to transition between commensalism and invasive tissue pathogenesis Candida albicans strains including the Wild type strain (SN425), WOR1OE -White (a/a, SN1044), WOR1OE -GUT (a/a, SN1045), White (a/a, SN966) and Opaque (a/a, SN967) were grown at room temperature in SC medium supplemented with 100ug/ml adenine; 2-4 biological replicates were performed per strain. RNA was prepared from these strains and samples were hybridized on custom Agilent C. albicans ORF arrays (15,000 spots/array, 70-mer probes).
Project description:Among ~5,000,000 fungal species on Earth, Candida albicans is exceptional in its lifelong association with humans, where it exists either as a benign component of the gastrointestinal microbiome or as an invasive pathogen. Although it is generally assumed that invasiveness results from a breakdown of host immunity , it is also possible that specific fungal programs control the transition between these divergent lifestyles. Here, we report that exposure of C. albicans to the mammalian gut triggers a developmental switch, driven by the Wor1 transcription factor, to a commensal cell type. Wor1 has been thought to occur only in unique genetic backgrounds, but we show that WOR1 expression is triggered when wild-type cells are propagated in a murine gastrointestinal infection model. Similar to Wor1’s role in a white-opaque switch for mating, WOR1 overexpression within the host induces a novel switch affecting cell and colony morphology and conferring commensal fitness. However, these hyperfit GUT (Gastrointestinally-IndUced Transition) cells lack the functional hallmarks of opaque cells, which they resemble morphologically, whereas bona fide opaque cells are defective for commensalism. Instead, the GUT cell transcriptome is optimized for the environment of the distal mammalian digestive tract. The GUT cell type switch illuminates how a single organism can utilize distinct genetic programs to transition between commensalism and invasive tissue pathogenesis
Project description:The study asked the question whether commensalism or pathogenicity of an opportunistic pathogen like Candida albicans, depend on strain specific traits or on the phenotypic and genomic plasticity of the genus as a whole. Transcriptional analysis performed upon different medium conditions (RPMI in presence or absence of FBS) indicated differentially expressed genes involved in adhesion, filamentous growth and biofilm formation. Both genome sequence and gene expression highlighted concordant changes in pathways related to invasiveness and filamentation. These results reflected marked differences in term of morphological features, environment adaptation and survival to phagocytosis. The results indicate that the genetic background of C. albicans may greatly affect its behaviour in terms of in vitro susceptibility to immune effector cells. Based on this approach, a more in depth understanding of fungal genetic makeup is achievable, thus allowing to establish the virulence potential of a given isolate and possibly to predict the outcome of C. albicans infection.
Project description:The ability to undergo heritable switching between cell states is well recognized in microbial species. In the human fungal pathogen Candida albicans, cells can stably exist in several alternative states that show differential interactions with the mammalian host. Here, we demonstrate that gene dosage of the master transcription factor, Efg1, controls access to distinct cell states in diploid C. albicans cells. Thus, cells that are hemizygous for EFG1 can stably differentiate into a cell state that is not available to cells with two functional copies of the EFG1 gene. Strikingly, we reveal that a number of clinical isolates of C. albicans encode polymorphisms that produce a hemizygous EFG1 genotype and that this enables access to the novel cell state. Furthermore, we show that C. albicans cells in different cell states each exhibit unique interactions with the mammalian host, with consequences for both commensalism and pathogenesis.
Project description:The human fungal pathogen Candida albicans can switch between two phenotypic cell types, termed “white” and “opaque.” Both cell types are heritable for many generations, and the switch between the two types occurs epigenetically, that is, without a change in the DNA sequence of the genome. In this work we describe that SSN6, the C. albicans functional homolog of Saccharomyces cerevisiae Cyc8, is a regulator of the white-opaque switch. Chromatin IP's were performed using the protocol described by Hernday et al (Methods Enzymol. 2010;470:737-58. ). Briefly, log phase cultures were crosslinked with formaldehyde prior to cell lysis, chromatin shearing, and transcription-factor immunoprecipitation. Recovered DNA was amplified, dye-coupled, and competitively hybridized to a 244k-probe tiling array with a non-enriched genomic DNA reference.
Project description:We use high-throughput sequencing to profile the response of the opportunistic fungal pathogen Candida albicans to mucins from the mucosal niche. We find that C. albicans undergoes a genome-wide phenotypic shift in response to mucins suppressing virulence-associated pathways.
Project description:The human fungal pathogen Candida albicans can switch between two phenotypic cell types, termed “white” and “opaque.” Both cell types are heritable for many generations, and the switch between the two types occurs epigenetically, that is, without a change in the DNA sequence of the genome. In this work we describe that SSN6, the C. albicans functional homolog of Saccharomyces cerevisiae Cyc8, is a regulator of the white-opaque switch. Chromatin IP's were performed using the protocol described by Hernday et al (Methods Enzymol. 2010;470:737-58. ). Briefly, log phase cultures were crosslinked with formaldehyde prior to cell lysis, chromatin shearing, and transcription-factor immunoprecipitation. Recovered DNA was amplified, dye-coupled, and competitively hybridized to a 244k-probe tiling array with a non-enriched genomic DNA reference. Immunoprecipitated chromatin was hybridized against a non-enriched genomic DNA reference to identify transcription-factor binding sites
Project description:The opportunistic human fungal pathogen, Candida albicans, undergoes morphological and transcriptional adaptation in the switch from commensalism to pathogenicity. Although previous gene-knockout studies have identified many factors involved in this transformation, it remains unclear how these factors are regulated to coordinate the switch. Investigating morphogenetic control by post-translational phosphorylation has generated important regulatory insights into this process, especially focusing on coordinated control by the cyclin-dependent kinase Cdc28. Here we have identified the Fkh2 transcription factor as a regulatory target of both Cdc28 and the cell wall biosynthesis kinase Cbk1, in a role distinct from its conserved function in cell cycle progression. Transcript profiling of Fkh2 deletion and non-phosphrylatable mutants in yeast and hypae revealed that the the hyphal-specific shift in the phosphorylation profile is required for the expression of genes involved in pathogenesis, host interaction and biofilm formation. We confirmed that these changes in gene expression resulted in corresponding defects in pathogenic processes