Ploidy influences cellular responses to gross chromosomal rearrangements in saccharomyces cerevisiae

<p>Abstract</p> <p>Background</p> <p>Gross chromosomal rearrangements (GCRs) such as aneuploidy are key factors in genome evolution as well as being common features of human cancer. Their role in tumour initiation and progression has not yet been completely elucidated and the effects of additional chromosomes in cancer cells are still unknown. Most previous studies in which <it>Saccharomyces cerevisiae </it>has been used as a model for cancer cells have been carried out in the haploid context. To obtain new insights on the role of ploidy, the cellular effects of GCRs were compared between the haploid and diploid contexts.</p> <p>Results</p> <p>A total number of 21 haploid and diploid <it>S. cerevisiae </it>strains carrying various types of GCRs (aneuploidies, nonreciprocal translocations, segmental duplications and deletions) were studied with a view to determining the effects of ploidy on the cellular responses. Differences in colony and cell morphology as well as in the growth rates were observed between mutant and parental strains. These results suggest that cells are impaired physiologically in both contexts. We also investigated the variation in genomic expression in all the mutants. We observed that gene expression was significantly altered. The data obtained here clearly show that genes involved in energy metabolism, especially in the tricarboxylic acid cycle, are up-regulated in all these mutants. However, the genes involved in the composition of the ribosome or in RNA processing are down-regulated in diploids but up-regulated in haploids. Over-expression of genes involved in the regulation of the proteasome was found to occur only in haploid mutants.</p> <p>Conclusion</p> <p>The present comparisons between the cellular responses of strains carrying GCRs in different ploidy contexts bring to light two main findings. First, GCRs induce a general stress response in all studied mutants, regardless of their ploidy. Secondly, the ploidy context plays a crucial role in maintaining the stoichiometric balance of the proteins: the translation rates decrease in diploid strains, whereas the excess protein synthesized is degraded in haploids by proteasome activity.</p

Combined transcriptome studies identify AFF3 as a mediator of the oncogenic effects of β-catenin in adrenocortical carcinoma

International audienceAdrenocortical cancer (ACC) is a very aggressive tumor, and genomics studies demonstrate that the most frequent alterations of driver genes in these cancers activate the Wnt/β-catenin signaling pathway. However, the adrenal-specific targets of oncogenic β-catenin-mediating tumorigenesis have not being established. A combined transcriptomic analysis from two series of human tumors and the human ACC cell line H295R harboring a spontaneous β-catenin activating mutation was done to identify the Wnt/β-catenin targets. Seven genes were consistently identified in the three studies. Among these genes, we found that AFF3 mediates the oncogenic effects of β-catenin in ACC. The Wnt response element site located at nucleotide position − 1408 of the AFF3 transcriptional start sites (TSS) mediates the regulation by the Wnt/β-catenin signaling pathway. AFF3 silencing decreases cell proliferation and increases apoptosis in the ACC cell line H295R. AFF3 is located in nuclear speckles, which play an important role in RNA splicing. AFF3 overexpression in adrenocortical cells interferes with the organization and/or biogenesis of these nuclear speckles and alters the distribution of CDK9 and cyclin T1 such that they accumulate at the sites of AFF3/speckles. We demonstrate that AFF3 is a new target of Wnt/β-catenin pathway involved in ACC, acting on transcription and RNA splicing

ChIPseq in Yeast Species: From Chromatin Immunoprecipitation to High-Throughput Sequencing and Bioinformatics Data Analyses.

International audienceChromatin immunoprecipitation (ChIP) followed by high-throughput sequencing (ChIPseq) is a powerful technique for the genome-wide location of protein DNA-binding sites. The ChIP experiment consists in treating living cells with a cross-linking agent to bind proteins to their DNA substrates. After fragmentation of DNA, specific fractions associated with a particular protein of interest are purified by immunoaffinity. They are next sequenced and identified on the reference genome using dedicated bioinformatics programs. Several technical aspects are important to obtain high-quality ChIPseq results. This includes the quality of antibodies, the sequencing protocols, the use of accurate controls and the careful choice of bioinformatics tools. We present here a general protocol to perform ChIPseq analyses in yeast species. This protocol has been optimized to identify target genes of specific transcription factors but can be used for any other DNA binding proteins

Corticosterone affects thyroid hormones induced modifications of the methylome.

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Stress sensitivity of limb development in Xenopus Tropicalis Tadpoles.

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Zinc Uptake and Storage During the Formation of the Cerebral Cortex in Mice

International audienceThe cerebral cortex (or neocortex) is a brain structure formed during embryogenesis. The present study seeks to provide a detailed characterization of the Zn homeostatic mechanisms during cerebral cortex formation and development. To reach that goal, we have combined high-throughput RNA-sequencing analysis of the whole murine genome, X-ray fluorescence nanoimaging (XRF), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and live-cell imaging of dissociated cortical neurons loaded with the Zn fluorescent probe FluoZin-3. The transcriptomic analysis was conducted from mRNAs isolated from cortices collected at embryonic (E) days 11 (E11), E13, and E17 and on postnatal day 1 (PN1) pups. This permitted to characterize the temporal pattern of expression of the main genes participating in the cellular transport, storage, and release of Zn during corticogenesis. It appears that cells of the immature cortex express a wide diversity of actors involved in Zn homeostasis with Zip7, SOD1, and metallothioneins being the most abundant transcripts throughout corticogenesis. The quantification of total Zn with XRF and ICP-AES reveals a reduction of Zn levels. Moreover, this is accompanied by a diminution of the size of the internal pools of mobilizable Zn. This study illustrates the tight temporal and spatial regulation of Zn homeostasis during cerebral brain development

Opposite T 3 Response of ACTG1-FOS Subnetwork Differentiate Tailfin Fate in Xenopus Tadpole and Post-hatching Axolotl

International audienceAmphibian post-embryonic development and Thyroid Hormones (TH) signaling are deeply and intimately connected. In anuran amphibians, TH induce the spectacular and complex process known as metamorphosis. In paedomorphic salamanders, at similar development time, raising levels of TH fail to induce proper metamorphosis, as many "larval" tissues (e.g., gills, tailfin) are maintained. Why does the same evolutionary conserved signaling pathway leads to alternative phenotypes? We used a combination of developmental endocrinology, functional genomics and network biology to compare the transcriptional response of tailfin to TH, in the post-hatching paedormorphic Axolotl salamander and Xenopus tadpoles. We also provide a technological framework that efficiently reduces large lists of regulated genes down to a few genes of interest, which is well-suited to dissect endocrine regulations. We first show that Axolotl tailfin undergoes a strong and robust TH-dependent transcriptional response at post embryonic transition, despite the lack of visible anatomical changes. We next show that Fos and Actg1, which structure a single and dense subnetwork of cellular sensors and regulators, display opposite regulation between the two species. We finally show that TH treatments and natural variations of TH levels follow similar transcriptional dynamics. We suggest that, at the molecular level, tailfin fate correlates with the alternative transcriptional states of an fos-actg1 sub-network, which also includes transcription factors and regulators of cell fate. We propose that this subnetwork is one of the molecular switches governing the initiation of distinct TH responses, with transcriptional programs conducting alternative tailfin fate (maintenance vs. resorption) 2 weeks post-hatching

In Saccharomyces cerevisae, ATP2 mRNA sorting to the vicinity of mitochondria is essential for respiratory function

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Unravelling the genes forming the wing pattern supergene in the polymorphic butterfly Heliconius numata

Background Unravelling the genetic basis of polymorphic characters is central to our understanding of the origins and diversification of living organisms. Recently, supergenes have been implicated in a wide range of complex polymorphisms, from adaptive colouration in butterflies and fish to reproductive strategies in birds and plants. The concept of a supergene is now a hot topic in biology, and identification of its functional elements is needed to shed light on the evolution of highly divergent adaptive traits. Here, we apply different gene expression analyses to study the supergene P that controls polymorphism of mimetic wing colour patterns in the neotropical butterfly Heliconius numata. Results We performed de novo transcriptome assembly and differential expression analyses using high-throughput Illumina RNA sequencing on developing wing discs of different H. numata morphs. Within the P interval, 30 and 17 of the 191 transcripts were expressed differentially in prepupae and day-1 pupae, respectively. Among these is the gene cortex, known to play a role in wing pattern formation in Heliconius and other Lepidoptera. Our in situ hybridization experiments confirmed the relationship between cortex expression and adult wing patterns. Conclusions This study found the majority of genes in the P interval to be expressed in the developing wing discs during the critical stages of colour pattern formation, and detect drastic changes in expression patterns in multiple genes associated with structural variants. The patterns of expression of cortex only partially recapitulate the variation in adult phenotype, suggesting that the remaining phenotypic variation could be controlled by other genes within the P interval. Although functional studies on cortex are now needed to determine its exact developmental role, our results are in accordance with the classical supergene hypothesis, whereby several genes inherited together due to tight linkage control a major developmental switch