Project description:Understanding the conditions that promote the evolution of reproductive isolation, and thus speciation. Here we empirically test some of the key predictions of speciation theory (Coyne 2004; Kohn 2005) by experimentally evolving the initial stages of speciation in yeast. After allowing replicate populations to adapt to two divergent environments, we observed the consistent, de novo evolution of two forms of postzygotic isolation: reduced rate of mitotic reproduction and reduced efficiency of meiotic reproduction. In general, divergent selection resulted in greater reproductive isolation than parallel selection, as predicted by ecological speciation theory. Our experimental system allowed for the first controlled comparison of the relative importance of ecological and genetic mechanisms of isolation, and the novel ability to quantify the effects of antagonistic epistasis. For mitotic reproduction, hybrid inferiority was conditional upon the selective environments and was both ecological and genetic in basis. In contrast, isolation associated with meiotic reproduction was unconditional and was caused solely by genetic mechanisms. Overall, our results show that adaption to divergent environments promotes the evolution of isolation through antagonistic epistasis, providing evidence of a plausible common avenue to speciation and adaptive radiation in nature (Schluter 2000,2001: Funk 2006) Keywords: Speciation, antagonistic epistasis, divergent adaptation
2007-06-21 | GSE6870 | GEO
Project description:Bradyrhizobia associated to native legumes in Australia
Project description:The importance of extrinsic regulation of hematopoietic stem cell activity is increasingly acknowledged. Here we report the generation of a new niche system, which supports expansion of mouse hematopoietic stem cells in vitro. Characterization of this niche revealed a transcriptional regulatory network including four critical factors, namely FOS, SPI1, KLF10 and TFEC. Interestingly, these factors are essential for osteoclastogenesis, thus revealing an osteoclastic network that supports hematopoietic stem cell self-renewal. Lentiviral vectors containing putative transcription factors regulating HSC expansion were transfected into GPE cells and gene expression values were compared to empty vector controls.
Project description:While cross-tissue metabolite variations are increasingly regarded as important readouts of tissue-level gene regulatory processes, these have rarely been explored by non-targeted metabolomics. Here we explore tissue-level metabolic specialization in Nicotiana attenuata, an ecological model with rich secondary metabolism by combining tissue-wide non-targeted mass spectral data acquisition, information theory analysis, and MS/MS molecular networks. This analysis was conducted for two different methanolic extracts of 14 tissues and deconvoluted 895 non-redundant MS/MS spectra. Using information theory analysis, anthers were found to harbor the most specialized metabolome and, through MS/MS molecular networks, most unique metabolites of anthers and other tissues were annotated. Finally, tissue-metabolite association maps were used to predict tissue-specific gene functions. Predictions for the function of two UDP-glycosyltransferases in flavonoid metabolism were confirmed by virus-induced gene-silencing. The present workflow allows biologists to amortize the vast amount of data produced by modern MS instrumentation for their quest to understand gene function.
Project description:Metastatic lesions are typically not found until patients self-report symptoms or they become radiologically evident. We have developed an engineered metastatic niche (scaffold) that recruits aggressive tumor cells prior to their colonization in other organs. The engineered niche can be monitored for dynamic gene expression, and changes at this site are analogous to those in a native metastatic site (lung) for triple negative breast cancer (4T1 cells). We were able to develop a 10-gene signature from the scaffold that accurately monitors disease progression and recurrence or resistance to resection therapy. This data set acts to dissect the heterogeneity of the cell populations in the engineered and native metastatic niche and identify the cell types that contribute to the success of the signature.
Project description:Multiple distinct cell types of the human lung and airways have been defined by single cell RNA sequencing (scRNAseq). Here we present a multi-omics spatial lung atlas to define novel cell types which we map back into the macro- and micro-anatomical tissue context to define functional tissue microenvironments. Firstly, we have generated single cell and nuclei RNA sequencing, VDJ-sequencing and Visium Spatial Transcriptomics data sets from 5 different locations of the human lung and airways. Secondly, we define additional cell types/states, as well as spatially map novel and known human airway cell types, such as adult lung chondrocytes, submucosal gland (SMG) duct cells, distinct pericyte and smooth muscle subtypes, immune-recruiting fibroblasts, peribronchial and perichondrial fibroblasts, peripheral nerve associated fibroblasts and Schwann cells. Finally, we define a survival niche for IgA-secreting plasma cells at the SMG, comprising the newly defined epithelial SMG-Duct cells, and B and T lineage immune cells. Using our transcriptomic data for cell-cell interaction analysis, we propose a signalling circuit that establishes and supports this niche. Overall, we provide a transcriptional and spatial lung atlas with multiple novel cell types that allows for the study of specific tissue microenvironments such as the newly defined gland-associated lymphoid niche (GALN).
Project description:During aging, the regenerative capacity of skeletal muscle decreases due to intrinsic changes in muscle stem cells (MuSCs) and alterations in their niche. Here, we used quantitative mass spectrometry to characterize intrinsic changes in the MuSC proteome and remodeling of the MuSC niche during aging. We generated a network connecting age-affected ligands located in the niche and cell surface receptors on MuSCs. Thereby, we revealed signaling via Integrins, Lrp1, Egfr and Cd44 as the major cell communication axes perturbed through aging. We investigated the effect of Smoc2, a secreted protein that accumulates with aging, originating from fibro-adipogenic progenitors. Increased levels of Smoc2 contribute to the aberrant Itgb1/MAPK signaling observed during aging, thereby causing impaired MuSC functionality and muscle regeneration. By connecting changes in the proteome of MuSCs to alterations of their niche, our work will enable a better understanding of how MuSCs are affected during aging.
Project description:During aging, the regenerative capacity of skeletal muscle decreases due to intrinsic changes in muscle stem cells (MuSCs) and alterations in their niche. Here, we used quantitative mass spectrometry to characterize intrinsic changes in the MuSC proteome and remodeling of the MuSC niche during aging. We generated a network connecting age-affected ligands located in the niche and cell surface receptors on MuSCs. Thereby, we revealed signaling via Integrins, Lrp1, Egfr and Cd44 as the major cell communication axes perturbed through aging. We investigated the effect of Smoc2, a secreted protein that accumulates with aging, originating from fibro-adipogenic progenitors. Increased levels of Smoc2 contribute to the aberrant Itgb1/MAPK signaling observed during aging, thereby causing impaired MuSC functionality and muscle regeneration. By connecting changes in the proteome of MuSCs to alterations of their niche, our work will enable a better understanding of how MuSCs are affected during aging.
Project description:Meiotic DSB, catalyzed by the Spo11 transesterase protein and accessory DSB proteins, form in the nucleosome depleted regions (NDR) at promoters, preferentially those located on the chromosome loops that shape meiotic chromosomes, whereas the DSB proteins are located on chromosome axes at the basis of these loops. Mechanisms bridging these two chromosomal regions for DSB formation have remained elusive. Here we show that Spp1, a conserved member of the histone H3K4 methyltransferase Set1 complex, is required for normal levels of DSB formation and is associated with chromosome axes in the DSB-rich domains during meiosis. Moreover, Spp1 physically interacts with the Mer2 axis-associated DSB protein, and uses its PHD finger as a magnet to read H3K4 trimethylation close to promoters, tether these regions to chromosome axes and activate cleavage in the nearby promoter by the DSB proteins. We further show that in the absence of Spp1 or the Set1 complex, DSB are introduced at a few new sites, located in promoters of transcriptionally induced genes, suggesting another selection mechanism of preferred DSB sequences. This paper provides the molecular mechanism linking H3K4me3 to the DSB forming machinery, by the meiosis-specific specialization of Spp1 as an active member of the DSB complex and a reader of H3K4me3, and opens perspectives for the study of DSB formation at mammalian recombination hotspots that are also enriched in H3K4me3. ChIP-chip experiment in vegetative or meiotic diploid SK1 yeast cells - two biological replicates
Project description:The importance of extrinsic regulation of hematopoietic stem cell activity is increasingly acknowledged. Here we report the generation of a new niche system, which supports expansion of mouse hematopoietic stem cells in vitro. Characterization of this niche revealed a transcriptional regulatory network including four critical factors, namely FOS, SPI1, KLF10 and TFEC. Interestingly, these factors are essential for osteoclastogenesis, thus revealing an osteoclastic network that supports hematopoietic stem cell self-renewal.