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ChIP-chip data for transcription factor binding in white and opaque cell types of Candida albicans

ABSTRACT: 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. Previous work identified six key transcriptional regulators important for white-opaque switching: Wor1, Wor2, Wor3, Czf1, Efg1, and Ahr1. In this work, we use a combination of genetic and genome-wide approaches to explore the topology of the transcriptional network that specifies each of the two cell types, and governs the ability to switch between them. In particular, we use a combination of genome-wide chromatin immunoprecipitation and gene expression profiling to determine the direct and indirect regulatory interactions that form the switch network. The six regulators are arranged together in a complex transcriptional network, and we propose that the topology of this network is responsible for both the epigenetic maintenance of the white and opaque states and for the switching between them. 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.

ORGANISM(S): Candida albicans

PROVIDER: GSE42837 | GEO | 2013/05/01

SECONDARY ACCESSION(S): PRJNA183912

REPOSITORIES: GEO

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ChIP-chip data for transcription factor binding in white and opaque cell types of Candida albicans

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. Previous work identified six key transcriptional regulators important for white-opaque switching: Wor1, Wor2, Wor3, Czf1, Efg1, and Ahr1. In this work, we use a combination of genetic and genome-wide approaches to explore the topology of the transcriptional network that specifies each of the two cell types, and governs the ability to switch between them. In particular, we use a combination of genome-wide chromatin immunoprecipitation and gene expression profiling to determine the direct and indirect regulatory interactions that form the switch network. The six regulators are arranged together in a complex transcriptional network, and we propose that the topology of this network is responsible for both the epigenetic maintenance of the white and opaque states and for the switching between them. 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

2013-05-01 | E-GEOD-42837 | biostudies-arrayexpress

Interlocking Transcriptional Feedback Loops Control White-Opaque Switching in Candida albicans

Project description:The human pathogen Candida albicans can assume either of two distinct cell types, designated ‘‘white’’ and ‘‘opaque.’’ Each cell type is maintained for many generations; switching between them is rare and stochastic, and occurs without any known changes in the nucleotide sequence of the genome. The two cell types differ dramatically in cell shape, colony appearance, mating competence, and virulence properties. In this work, we investigate the transcriptional circuitry that specifies the two cell types and controls the switching between them. First, we identify two new transcriptional regulators of white-opaque switching, Czf1 and white-opaque regulator 2 (Wor2). Analysis of a large set of double mutants and ectopic expression strains revealed genetic relationships between CZF1, WOR2, and two previously identified regulators of white-opaque switching, WOR1 and EFG1. Using chromatin immunoprecipitation, we show that Wor1 binds the intergenic regions upstream of the genes encoding three additional transcriptional regulators of white-opaque switching (CZF1, EFG1, and WOR2), and also occupies the promoters of numerous white- and opaque-enriched genes. Based on these interactions, we have placed these four genes in a circuit controlling white-opaque switching whose topology is a network of positive feedback loops, with the master regulator gene WOR1 occupying a central position. Our observations indicate that a key role of the interlocking feedback loop network is to stably maintain each epigenetic state through many cell divisions. Keywords: ChIP-chip

2007-10-01 | GSE8709 | GEO

Identification and characterization of Wor4, a new transcriptional regulator of white-opaque switching

Project description:The human fungal pathogen Candida albicans can switch between two cell types, “white” and “opaque,” each of which is heritable through many cell divisions. Switching between these two cell types is regulated by six transcriptional regulators which form a highly interconnected circuit with multiple feedback loops. Here, we identify a seventh regulator of white-opaque switching, which we have named Wor4. We show that ectopic expression of Wor4 is sufficient to drive switching from the white to the opaque cell type and that deletion of Wor4 blocks switching from the white to the opaque cell type. A combination of ectopic expression and deletion experiments indicates that Wor4 is positioned upstream of Wor1 and that it is formally an activator of the opaque cell type. The combination of ectopic expression and deletion phenotypes for Wor4 is unique; none of the other six white-opaque regulators show this pattern. We determined the pattern of Wor4 binding across the genome by ChIP-seq and found it is highly correlated with that of Wor1 and Wor2, indicating that Wor4 is tightly integrated into the existing white-opaque regulatory circuit. We previously proposed that white-to-opaque switching relies on the activation of a complex circuit of feedback loops that remains excited through many cell divisions. The identification of a new, central regulator of white-opaque switching supports this idea by indicating that the white-opaque switching mechanism is considerably more complex than those controlling conventional, non-heritable patterns of gene expression.

2016-01-11 | GSE75124 | GEO

Identification and characterization of Wor4, a new transcriptional regulator of white-opaque switching

Project description:The human fungal pathogen Candida albicans can switch between two cell types, âwhiteâ and âopaque,â each of which is heritable through many cell divisions. Switching between these two cell types is regulated by six transcriptional regulators which form a highly interconnected circuit with multiple feedback loops. Here, we identify a seventh regulator of white-opaque switching, which we have named Wor4. We show that ectopic expression of Wor4 is sufficient to drive switching from the white to the opaque cell type and that deletion of Wor4 blocks switching from the white to the opaque cell type. A combination of ectopic expression and deletion experiments indicates that Wor4 is positioned upstream of Wor1 and that it is formally an activator of the opaque cell type. The combination of ectopic expression and deletion phenotypes for Wor4 is unique; none of the other six white-opaque regulators show this pattern. We determined the pattern of Wor4 binding across the genome by ChIP-seq and found it is highly correlated with that of Wor1 and Wor2, indicating that Wor4 is tightly integrated into the existing white-opaque regulatory circuit. We previously proposed that white-to-opaque switching relies on the activation of a complex circuit of feedback loops that remains excited through many cell divisions. The identification of a new, central regulator of white-opaque switching supports this idea by indicating that the white-opaque switching mechanism is considerably more complex than those controlling conventional, non-heritable patterns of gene expression. C. albicans Wor4-GFP versus untagged control in both white and opaque cell types. Cells grown in SD+aa+Uri at 25Â°C with three technical replicates of each strain/cell type (12 total).

2016-01-11 | E-GEOD-75124 | biostudies-arrayexpress

Ssn6 defines a new level of regulation of white-opaque switching in Candida albicans and is required for the stochasticity of the switch

Project description:The human commensal and opportunistic pathogen Candida albicans can switch between two distinct, heritable cell types, named “white” and “opaque,” which differ in morphology, mating abilities, metabolic preferences, and in their interactions with the host immune system. Previous studies revealed a highly interconnected group of transcriptional regulators that control switching between the two cell types. Here, we identify Ssn6, the C. albicans functional homolog of the Saccharomyces cerevisiae transcriptional co-repressor Cyc8, as a new regulator of white-opaque switching. In a or α mating type strains, deletion of SSN6 results in mass switching from the white to the opaque cell type. Transcriptional profiling of ssn6 deletion mutant strains reveals that Ssn6 represses part of the opaque cell transcriptional program in white cells and the majority of the white cell transcriptional program in opaque cells. Genome-wide chromatin immunoprecipitation experiments demonstrate that Ssn6 is tightly integrated into the opaque cell regulatory circuit and that the positions to which it is bound across the genome strongly overlap with those bound by Wor1 and Wor2, previously identified regulators of white-opaque switching. This work reveals the next layer in the white-opaque transcriptional circuitry by integrating a transcriptional regulator that does not bind DNA directly but instead associates with specific combinations of DNA-bound transcriptional regulators.

2015-12-28 | GSE74011 | GEO

Expression changes between C. albicans white and opaque cell types and mutant strains

2013-05-01 | GSE42134 | GEO

The gray phenotype in the human fungal pathogen Candida tropicalis

Project description:Phenotypic plasticity, the ability to switch between different morphological types, plays critical roles in environmental adaptation, leading to infections, and allowing for sexual reproduction in pathogenic Candida species. Candida tropicalis, which is both an emerging human fungal pathogen and an environmental fungus, can switch between two heritable cell types termed white and opaque. In this study, we report the discovery of a novel phenotype in C. tropicalis, named the gray phenotype. Similar to Candida albicans and Candida dubliniensis, white, gray, and opaque cell types of C. tropicalis also form a tristable switching system, where gray cells are relatively small and elongated. In C. tropicalis, gray cells exhibit intermediate levels of mating competency and virulence in a mouse systemic infection model compared to the white and opaque cell types, express a set of cell type-enriched genes, and exhibit both common and species-specific biological features. The key regulators of white-opaque transitions, Wor1 and Efg1, are not required for the gray phenotype. A comparative study of the gray phenotypes in C. tropicalis, C. albicans, and C. dubliniensis provides clues to explain the species differences in terms of virulence, ecological niches, and prevalence among these three species.

2017-01-30 | GSE81514 | GEO

Expression changes between C. albicans white and opaque cell types and mutant strains

Project description:The goal of this study is to characterize the transcriptional regulatory network that controls white-opaque cell-type switching in Candida albicans. This dataset includes microarrays comparing expression levels in wild-type white and opaque cell types, as well as 6 different transcription factor deletion strains. All samples were hybridized against a common mixed reference to allow for comparison between any two datasets within this study. Gene expression arrays were performed on wild-type and transcription factor deletion white and opaque a/a cell types . High and low intensity scans were performed. Background and saturated spots were filtered out, as indicated by null. Data from each scan was normalized by lowess normalization to enable transformation across any pair of datasets. All data presented are log2 ratios of Cy5/Cy3 Each sample was hybridized against a mixed reference sample to allow for transformation between any of the individual samples (white vs. opaque, wild-type vs. mutant)

2013-05-01 | E-GEOD-42134 | biostudies-arrayexpress

TOS9 Regulates White-Opaque Switching in Candida albicans

Project description:In Candida albicans, the a1-alpha2 complex represses white-opaque switching as well as mating. A ChIP-chip strategy was, therefore, used to screen for genes with a1-alpha2 binding sites and expression patterns consistent with a master switch gene (MSG). Of 51 genes identified with an a1-alpha2 binding site, one gene, TOS9, also referred to as EAP2, exhibited an expression pattern consistent with a MSG. TOS9 is expressed in opaque, not white a/a and alpha/alpha cells and Tos9p localizes to the opaque cell nucleus. Deletion of TOS9 blocks cells in the white phase, and misexpression in the white phase of the parent tos9+/tos9+ strain results in mass conversion to opaque. Expression of TOS9 under control of a MET promoter rescues the TOS9 null mutant tos9-/tos9- phenotype. Temperature-induced mass conversion of opaque to white in the parent strain results in the immediate cessation of TOS9 transcription, and loss of Tos9p prior to the point of commitment to white (the switch event), which occurs at the time of the second cell doubling. Misexpression of TOS9, as well as inhibition of the second round of DNA replication inhibits the temperature-induced switch from opaque to white. Based on these observations, a model is developed for the regulation and role of TOS9 in switching. Keywords: ChIP chip

2006-09-19 | GSE5493 | GEO

A white to opaque like phenotypic switch in the yeast Torulaspora microellipsoides

Project description:Torulaspora microellipsoides is a unicellular budding yeast of the Saccharomycetaceae family and is primarily associated with viticulture, however it has not been studied with regards to growth morphology or phenotypic switching. We discovered that T. microellipsoides undergoes a low-frequency morphological switch from small budding haploid (white) yeast to larger, higher ploidy (opaque) yeast. Genome sequencing of both cell types did not reveal any conspicuous differences, but comparison of transcriptomes by mRNA-seq revealed 511 differentially regulated genes, with white cells having greater expression of genes involved in stress resistance and complex carbohydrate utilization, and opaque cells up-regulating genes involved in ribosome biogenesis. Growth experiments showed that white cells are in general physiologically more resistant to stationary phase conditions and oxidative stress than opaque cells, but the latter performed better under some conditions and are more tolerant to cold temperatures. Opaque cells are also phenotypically more unstable than white cells and give rise to derivatives with diverse phenotypes and different total DNA content. We propose that ability of T. microellipsoides to switch phenotype is an ecological adaptation to specific niches, as has been suggested for similar morphological switching phenomena in distantly related species such as C. albicans, and suggest switching of this nature may be a more a more broadly utilized biological strategy among yeasts than previously thought.

2020-01-10 | GSE136991 | GEO

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