Partial de-repression of the hyphal program does not restore hyphae formation in absence of a functional Arp2/3 complex
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ABSTRACT:
ORGANISM(S): Candida albicans
PROVIDER: GSE19582 | GEO | 2010/01/23
SECONDARY ACCESSION(S): PRJNA123967
REPOSITORIES: GEO
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Project description:Deleting components of the Arp2/3 complex in Candida albicans resulted in a global lack of hyphal specific gene induction. This observation suggests that the failure in hyphal growth of Arp2/3 complex mutants could be a result of failure to activate hyphal specific genes. If the hyphal defect was primarily due to failure to activate gene expression, de-repressing hyphal-specific gene expression by deleting the NRG1 repressor could potentially suppress the defect, as deletion of NRG1 leads to constitutive filamentous growth even in the absence of any hyphal induction signals (Garcia-Sanchez et al., 2005, Kadosh & Johnson, 2005). We therefore created an nrg1Î/Îarp2Î/Î mutant. When grown under non-inducing conditions, nrg1Î/Îarp2Î/Î cells showed the arp2Î/Î mutant morphology of round and swollen cells. When induced for hyphal growth, nrg1Î/Îarp2Î/Î cells also exhibited the arp2Î/Î cell morphology and did not form hyphae even after extended overnight incubation times. To determine if the hyphal-specific genes are de-repressed in the nrg1Î/Îarp2Î/Î mutant, we performed transcript profiling. We compared the nrg1Î/Îarp2Î/Î mutant grown under hyphal conditions to the arp2Î/Î mutant grown under the same conditions (10% serum, 37ï°C, three hours), and found that a significant number of hyphal-specific genes that are normally induced when WT cells are undergoing the yeast to hyphae switch (WT-HY) showed greater expression in the nrg1Î/Îarp2Î/Î mutant compared to arp2Î/Î cells (p-value 4.9x10-9). When we examined the set of NRG1-dependent hyphal-specific genes previously identified (Kadosh & Johnson, 2005), we found that seven of 28 genes (HYR1, SAP5, SAP4, KIP4, ORF19.6079, ALS3 and UME6) showed significantly increased expression (⥠2 fold) in nrg1Î/Îarp2Î/Î cells compared to arp2Î/Î cells, while a further four genes (IHD1, CBP1, ORF19.6705 and ALS10) showed moderately increased expression between 1.5 and 2-fold. Thus, while deleting a transcriptional repressor of the filamentation program leads to de-repression of many hyphal genes, the entire regulated gene set is not de-repressed; this presumably reflects the complex interplay that different transcriptional (co-) repressors exert on the yeast-to-hyphae transition (Garcia-Sanchez et al., 2005, Kadosh & Johnson, 2005). We further found that despite the increased induction of some hyphal genes in the nrg1Î/Îarp2Î/Î mutant, a few of those genes are not as highly induced as in WT cells. One gene that was induced in both the ânrg1Î/Îarp2Î/Î vs arp2Î/Îâ and the ânrg1Î/Îarp2Î/Î vs WTâ-comparisons is UME6, a recently identified key regulator of the hyphal program (Banerjee et al., 2008, Zeidler et al., 2009). Interestingly, although constitutive over-expression of UME6 in WT cells resulted in constitutive filamentous growth even in the absence of hyphae signals (Carlisle et al., 2009), the increased expression level of UME6 in the nrg1Î/Îarp2Î/Î mutant is not sufficient to restore filamentation in the absence of a functional Arp2/3 complex. Thus despite partial de-repression of the hyphal program, hyphae do not form, making it likely other roles of the Arp2/3 complex, such as its function in actin patch formation and actin branching, are required for hyphal development.
2010-01-22 | E-GEOD-19582 | biostudies-arrayexpress
Project description:Candida albicans is a diploid fungal pathogen lacking a defined complete sexual cycle, and thus has been refractory to standard forward genetic analysis. Instead, transcription profiling and reverse genetic strategies based on Saccharomyces cerevisiae have typically been used to link genes to functions. To overcome restrictions inherent in such indirect approaches, we have investigated a forward genetic mutagenesis strategy based on the UAU1 technology. We screened 4700 random insertion mutants for defects in hyphal development, and linked two new genes (ARP2 and VPS52) to hyphal growth. Deleting ARP2 abolished hyphal formation, generated round and swollen yeast phase cells, disrupted cortical actin patches and blocked virulence in mice. The mutants also showed a global lack of induction of hyphae-specific genes upon the yeast-to-hyphae switch. Surprisingly, both arp2Î/Î and arp2Î/Îarp3Î/Î mutants were still able to endocytose FM4-64 and Lucifer Yellow, although as shown by time-lapse movies internalization of FM4-64 was somewhat delayed in mutant cells. Thus the non-essential role of the Arp2/3 complex discovered by forward genetic screening in C. albicans showed that uptake of membrane components from the plasma membrane to vacuolar structures is not dependent on this actin nucleating machinery. By forward genetic screening, we have identified genes that are essential for hyphal formation. One of the hits is the Arp2/3 complex, which is essential for hyphal formation, but not for viability in Candida albicans. To gain insights into cellular processes affected by disrupting Arp2/3 complex functions, we performed transcriptional profiling under yeast growth conditions (YPD at 30°C for three hours) or hyphal induction (YPD + 10% FBS at 37°C for three hours) and compared transcriptional consequences of deleting ARP2 to MYO5 and SLA2 microarray data sets (Oberholzer et al., 2006).
2010-10-08 | E-GEOD-19565 | biostudies-arrayexpress
Project description:Candida albicans is a diploid fungal pathogen lacking a defined complete sexual cycle, and thus has been refractory to standard forward genetic analysis. Instead, transcription profiling and reverse genetic strategies based on Saccharomyces cerevisiae have typically been used to link genes to functions. To overcome restrictions inherent in such indirect approaches, we have investigated a forward genetic mutagenesis strategy based on the UAU1 technology. We screened 4700 random insertion mutants for defects in hyphal development, and linked two new genes (ARP2 and VPS52) to hyphal growth. Deleting ARP2 abolished hyphal formation, generated round and swollen yeast phase cells, disrupted cortical actin patches and blocked virulence in mice. The mutants also showed a global lack of induction of hyphae-specific genes upon the yeast-to-hyphae switch. Surprisingly, both arp2Δ/Δ and arp2Δ/Δarp3Δ/Δ mutants were still able to endocytose FM4-64 and Lucifer Yellow, although as shown by time-lapse movies internalization of FM4-64 was somewhat delayed in mutant cells. Thus the non-essential role of the Arp2/3 complex discovered by forward genetic screening in C. albicans showed that uptake of membrane components from the plasma membrane to vacuolar structures is not dependent on this actin nucleating machinery.
2010-01-23 | GSE19565 | GEO
Project description:This SuperSeries is composed of the following subset Series: GSE19565: Arp2/3 complex mutants show a pronounced lack of hyphal specific gene expression in Candida albicans GSE19582: Partial de-repression of the hyphal program does not restore hyphae formation in absence of a functional Arp2/3 complex Refer to individual Series
2010-05-15 | E-GEOD-19583 | biostudies-arrayexpress
Project description:Our genetic screen reveals that deletion of CTM1, which abolishes the lysine trimethylation of cytochrome c (Cyc1), results in inhibition of hyphal morphogenesis in Candida albicans. Similar results are observed in the unmethylatable Cyc1 mutant (cyc1K79A). To elucidate how unmethylated Cyc1 inhibits hyphal growth, we performed RNA-Seq analysis by comparing WT (BWP17), ctm1∆/∆, and cyc1K79A cells grown in yeast and hyphal condition. Consistent with previous published data, many hyphal specific genes (HSGs), such as ALS3, ECE1, HWP1, and UME6, are upregulated while three major hyphal suppressor genes, TUP1, NRG1, and RFG1, are downregulated when WT cells switch from yeast to hyphal growth. Similar changes are observed in ctm1Δ/Δ and cyc1K79A cells upon hyphal induction, even though most mutant cells maintain yeast morphology throughout the induction. Further comparisons reveal that the basal transcriptional levels of HSGs are much lower in ctm1Δ/Δ and cyc1K79A cells than those in WT cells. Upon hyphal induction, the levels of HSGs in ctm1Δ/Δ and cyc1K79A cells increase but still remain lower than their basal levels in WT cells. In contrast, the hyphal suppressor genes (especially NRG1) exhibit much higher basal transcriptional levels in ctm1Δ/Δ and cyc1K79A cells than in WT cells. Their transcriptional levels reduce upon hyphal induction but still remain higher than the basal levels in WT cells. Together, these data suggest that unmethylated Cyc1 inhibits hyphal morphogenesis via transcriptional regulation of HSGs and hyphal suppressor genes.
2024-01-01 | GSE243813 | GEO
Project description:Mouse embryonic stem cells (mESCs), a model for differentiation into primed epiblast-like cells (EpiLCs), have revealed transcriptional and epigenetic control of early embryonic development. The control and significance of morphological changes, however, remain less defined. We show marked changes in morphology and actin architectures during differentiation that depend on Arp2/3 complex but not formin activity. Inhibiting Arp2/3 complex activity pharmacologically or genetically does not block exit from naive pluripotency but attenuates increases in EpiLC markers. We find that inhibiting Arp2/3 complex activity delays formative pluripotency and causes globally defective lineage specification as indicated by RNA-sequencing, with significant effects on TBX3-depedendent transcriptional programs. We also identify two previously unreported indicators of mESC differentiation; MRTF and FHL2, which have inverse Arp2/3 complex-dependent nuclear translocation. Our findings on Arp2/3 complex activity in differentiation and the established role of formins in EMT indicate that these two actin nucleators regulate distinct modes of epithelial plasticity
2022-04-01 | GSE175391 | GEO
Project description:Our understanding of transitions of human embryonic stem cells between distinct stages of pluripotency relies predominantly on regulation by transcriptional and epigenetic programs with limited insight on the role of established morphological changes. We report remodeling of the actin cytoskeleton of human embryonic stem cells (hESCs) as they transition from primed to naïve pluripotency that includes assembly of a ring of contractile actin filaments encapsulating colonies of naïve hESCs. Activity of the Arp2/3 complex is required for the actin ring, uniform cell mechanics within naïve colonies, nuclear translocation of the Hippo pathway effectors YAP and TAZ, and effective transition to naïve pluripotency. RNA-sequencing analysis confirms that Arp2/3 complex activity regulates Hippo signaling in hESCs, and impaired naïve pluripotency with inhibited Arp2/3 complex activity is rescued by expressing a constitutively active, nuclear-localized YAP-S127A. Moreover, expression of YAP-S127A partially restored in actin filament fence with Arp2/3 complex inhibition, suggesting that actin filament remodeling is both upstream and downstream of YAP activity. These new findings on the cell biology of hESCs reveal a mechanism for cytoskeletal dynamics coordinating cell mechanics to regulate gene expression and facilitate transitions between pluripotency states.
2024-09-11 | GSE276968 | GEO
Project description:Arp2/3 complex assembles branched actin filaments key to many cellular processes, but its organismal roles remain poorly understood. Here we employed conditional arpc4 knockout mice to study the function of the Arp2/3 complex in the epidermis.We found that depletion of the Arp2/3 complex by knockout of arpc4 results in skin abnormalities at birth that evolve into a severe psoriasis-like disease hallmarked by hyperactivation of transcription factor Nrf2. Knockout of arpc4 in cultured keratinocytes was sufficient to induce nuclear accumulation of Nrf2, upregulation of Nrf2-target genes and decreased filamentous actin levels. Furthermore, pharmacological inhibition of the Arp2/3 complex unmasked the role of branched actin filaments in Nrf2 regulation. Consistently, we unveiled that Nrf2 associates with the actin cytoskeleton in cells and binds to filamentous actin in vitro Finally, we discovered that Arpc4 is downregulated in both human and mouse psoriatic epidermis. Thus, the Arp2/3 complex affects keratinocytes' shape and transcriptome through an actin-based cell-autonomous mechanism that influences epidermal morphogenesis and homeostasis.
2017-11-23 | GSE107264 | GEO
Project description:Arp2/3 complex assembles branched actin filaments key to many cellular processes, but its organismal roles remain poorly understood. Here we employed conditional arpc4 knockout mice to study the function of the Arp2/3 complex in the epidermis.We found that depletion of the Arp2/3 complex by knockout of arpc4 results in skin abnormalities at birth that evolve into a severe psoriasis-like disease hallmarked by hyperactivation of transcription factor Nrf2. Knockout of arpc4 in cultured keratinocytes was sufficient to induce nuclear accumulation of Nrf2, upregulation of Nrf2-target genes and decreased filamentous actin levels. Furthermore, pharmacological inhibition of the Arp2/3 complex unmasked the role of branched actin filaments in Nrf2 regulation. Consistently, we unveiled that Nrf2 associates with the actin cytoskeleton in cells and binds to filamentous actin in vitro Finally, we discovered that Arpc4 is downregulated in both human and mouse psoriatic epidermis. Thus, the Arp2/3 complex affects keratinocytes' shape and transcriptome through an actin-based cell-autonomous mechanism that influences epidermal morphogenesis and homeostasis.
2017-11-23 | GSE107265 | GEO
Project description:Tunneling nanotubes (TNTs) connect distant cells and mediate cargo transfer for intercellular communication in physiological and pathological contexts. How the cell controls a common pool of proteins to generate these actin-mediated protrusions spanning length scales beyond those attainable by canonical filopodia remains unknown. Through a combination of surface micropatterning, microscopy and optical tweezer-based approaches, we found that Arp2/3-dependent pathways attenuate the extent with which actin polymerizes in nanotubes, limiting the formation and attainable lengths of TNTs. Upon Arp2/3 inhibition Epidermal growth factor receptor kinase substrate 8 (Eps8) exhibited heightened interactions with the inverted Bin/Amphiphysin/Rvs (I-BAR) domain protein IRSp53 resulting in increased TNTs. In these conditions, Eps8 interaction with proteins enhancing filament turnover and depolymerization were reduced. Our data reveals how common players in protrusions (Eps8 and IRSp53) drive outward linear actin extension to form TNTs, and that their interaction is enhanced when competing pathways overutilizing actin in branched Arp2/3 networks are inhibited, suggesting a shift in the equilibrium (and proteins usage) between branched and linear actin polymerization to form different cell protrusions.
2023-11-28 | PXD035976 | Pride