Lineage-Specific Differences and Inference of Regulatory Networks Governing Human Chondrocyte Development
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ABSTRACT: In-vitro differentiation of chondrocyte populations recapitulate in-vivo behaviours, and reveal gene regulatory networks involved in chondrocyte development
Project description:To address large gaps in our understanding of the molecular regulation of articular and growth plate cartilage development in humans, we used our directed differentiation approach to generate these distinct cartilage tissues from human embryonic stem cells. The resulting transcriptomic profiles of hESC-derived articular and growth plate chondrocytes were similar to fetal epiphyseal and growth plate chondrocytes, with respect to genes both known and previously unknown to cartilage biology. With the goal to characterize the regulatory landscapes accompanying these respective transcriptomes, we mapped chromatin accessibility in hESC-derived chondrocyte lineages, and mouse embryonic chondrocytes, using ATAC-sequencing. Integration of the expression dataset with the differentially accessible genomic regions revealed lineage-specific gene regulatory networks. We validated functional interactions of two transcription factors (TFs) (RUNX2 in growth plate chondrocytes and RELA in articular chondrocytes) with their predicted genomic targets. The maps we provide thus represent a framework for probing regulatory interactions governing chondrocyte differentiation. This work constitutes a substantial step towards comprehensive and comparative molecular characterizations of distinct chondrogenic lineages and sheds new light on human cartilage development and biology.
Project description:Elucidation of cellular and gene regulatory networks (GRNs) governing organ development will accelerate progress toward tissue replacement. Here, we have compiled reference GRNs underlying pancreas development from data mining that integrates multiple approaches, including mutant analysis, lineage tracing, cell purification, gene expression and enhancer analysis, and biochemical studies of gene regulation. Using established computational tools, we integrated and represented these networks in frameworks that should enhance understanding of the surging output of genomic-scale genetic and epigenetic studies of pancreas development and diseases such as diabetes and pancreatic cancer. We envision similar approaches would be useful for understanding the development of other organs.
Project description:We compared Sox9-association at chondrocyte targets to a broad catalogue of regulatory indicators of chromatin organization and transcriptional activity to determine Sox9’s direct regulatory actions in normal developing chondrocytes. Sox9-associated regions resolve into two distinct regulatory categories. Class I regions closely associate with transcriptional start sites (TSSs). Their targets reflect general regulators of basal cell activities that Sox9 engages indirectly though a likely association with the basal transcriptional complex. In contrast, Class II regions outside of the local TSS domains highlight evolutionarily conserved, active enhancers directing expression of chondrocyte specific target genes, though DNA binding of Sox9-dimers at target sites with sub-optimal binding affinity. The level of associated chondrocyte gene expression correlates with the number of enhancer modules around the target gene and grouping into super-enhancer clusters. Comparison of Sox9 programs between neural crest and mesoderm-derived chondrocytes points to similar modes of chondrocyte specification in distinct chondrocyte lineages. These data provide the first insight into mammalian Sox family actions at the genome scale in the vivo setting. The resulting enhancer sets provide a key resource for further dissection of the regulatory programs of mammalian chondrogenesis. Incorportation of ChIP-seq data of Sox9 and histone modification marks for chromatin status together with microrarray gene expression profiling in neonatal mice chondrocytes to uncover Sox9 regulatory system
Project description:We compared Sox9-association at chondrocyte targets to a broad catalogue of regulatory indicators of chromatin organization and transcriptional activity to determine Sox9’s direct regulatory actions in normal developing chondrocytes. Sox9-associated regions resolve into two distinct regulatory categories. Class I regions closely associate with transcriptional start sites (TSSs). Their targets reflect general regulators of basal cell activities that Sox9 engages indirectly through a likely association with the basal transcriptional complex. In contrast, Class II regions outside of the local TSS domains highlight evolutionarily conserved, active enhancers directing expression of chondrocyte specific target genes, though DNA binding of Sox9-dimers at target sites with sub-optimal binding affinity. The level of associated chondrocyte gene expression correlates with the number of enhancer modules around the target gene and grouping into super-enhancer clusters. Comparison of Sox9 programs between neural crest and mesoderm-derived chondrocytes points to similar modes of chondrocyte specification in distinct chondrocyte lineages. These data provide the first insight into mammalian Sox family actions at the genome scale in the vivo setting. The resulting enhancer sets provide a key resource for further dissection of the regulatory programs of mammalian chondrogenesis. Incorportation of ChIP-seq data of Sox9 and histone modification marks for chromatin status together with micorarray gene expression profiling in neonatal mice chondrocytes to uncover Sox9 regulatory system. Overexpression of Sox9 with a control of EGFP in human fibroblasts to identify the direct targets of Sox9 regulatory system
Project description:We compared Sox9-association at chondrocyte targets to a broad catalogue of regulatory indicators of chromatin organization and transcriptional activity to determine Sox9’s direct regulatory actions in normal developing chondrocytes. Sox9-associated regions resolve into two distinct regulatory categories. Class I regions closely associate with transcriptional start sites (TSSs). Their targets reflect general regulators of basal cell activities that Sox9 engages indirectly though a likely association with the basal transcriptional complex. In contrast, Class II regions outside of the local TSS domains highlight evolutionarily conserved, active enhancers directing expression of chondrocyte specific target genes, though DNA binding of Sox9-dimers at target sites with sub-optimal binding affinity. The level of associated chondrocyte gene expression correlates with the number of enhancer modules around the target gene and grouping into super-enhancer clusters. Comparison of Sox9 programs between neural crest and mesoderm-derived chondrocytes points to similar modes of chondrocyte specification in distinct chondrocyte lineages. These data provide the first insight into mammalian Sox family actions at the genome scale in the vivo setting. The resulting enhancer sets provide a key resource for further dissection of the regulatory programs of mammalian chondrogenesis. Incorportation of ChIP-seq data of Sox9 and histone modification marks for chromatin status together with micorarray gene expression profiling in neonatal mice chondrocytes to uncover Sox9 regulatory system. Overexpression of Sox9 with a control of EGFP in human fibroblasts to identify the direct targets of Sox9 regulatory system
Project description:BackgroundInference of protein interaction networks from various sources of data has become an important topic of both systems and computational biology. Here we present a supervised approach to identification of gene expression regulatory networks.ResultsThe method is based on a kernel approach accompanied with genetic programming. As a data source, the method utilizes gene expression time series for prediction of interactions among regulatory proteins and their target genes. The performance of the method was verified using Saccharomyces cerevisiae cell cycle and DNA/RNA/protein biosynthesis gene expression data. The results were compared with independent data sources. Finally, a prediction of novel interactions within yeast gene expression circuits has been performed.ConclusionResults show that our algorithm gives, in most cases, results identical with the independent experiments, when compared with the YEASTRACT database. In several cases our algorithm gives predictions of novel interactions which have not been reported.
Project description:Glycopeptides (GPAs) are an important class of antibiotics, with vancomycin and teicoplanin being used in the last 40 years as drugs of last resort to treat infections caused by Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus. A few new GPAs have since reached the market. One of them is dalbavancin, a derivative of A40926 produced by the actinomycete Nonomuraea sp. ATCC 39727, recently classified as N. gerenzanensis. This review summarizes what we currently know on the multilevel regulatory processes governing production of the glycopeptide A40926 and the different approaches used to increase antibiotic yields. Some nutrients, e.g., valine, l-glutamine and maltodextrin, and some endogenous proteins, e.g., Dbv3, Dbv4 and RpoBR, have a positive role on A40926 biosynthesis, while other factors, e.g., phosphate, ammonium and Dbv23, have a negative effect. Overall, the results available so far point to a complex regulatory network controlling A40926 in the native producing strain.
Project description:Next-generation sequencing (NGS) has revolutionized systems-based analysis of cellular pathways. The goals of this study are to compare undamage chondrocyte and damage chondrocyte whole transcriptomes
Project description:A variety of cell cultures models and in vivo approaches have been used to study gene expression during chondrocyte differentiation. The extent to which the in vitro models reflect bona fide gene regulation in the growth plate has not been quantified. In addition, studies that evaluate global gene expression changes among different growth plate zones are limited. To address these issues, we completed a microarray screen of three growth plate zones derived from manually segmented embryonic mouse tibiae. Classification of genes differentially expressed between each respective growth plate zone, functional categorization as well as characterization of gene expression patterns, cytogenetic loci, signaling pathways and functional motifs confirmed documented data and pointed to novel aspects of chondrocyte differentiation. Parallel comparisons of the microdissected tibiae data set to our previously completed micromass culture screen further corroborated the suitability of micromass cultures for modeling gene expression in chondrocyte development. The micromass culture system demonstrated striking similarities to the in vivo microdissected tibiae screen; however, the micromass system was unable to accurately distinguish gene expression differences in the hypertrophic and mineralized zones of the growth plate. These studies will allow us to better understand zone-specific gene expression patterns in the growth plate. Ultimately, this work will help define both the genomic context in which genes are expressed in the long bones and the extent to which the micromass culture system is able to recapitulate chondrocyte development in endochondral ossification. Experiment Overall Design: Tibiae from 15.5 day old mouse embryos were isolated and partitioned into three distinct zones. Total RNA was isolated from each segment and the individual segments pooled within a litter. Experiment Overall Design: Samples were hybridized to Affymetrix MOE 430 2.0 mouse chips for analysis. Four independent trials were executed for each zone. Experiment Overall Design: Number of time points: 1 Experiment Overall Design: Number of treatments: 0 Experiment Overall Design: Number of Samples: 4 replicates per zone Experiment Overall Design: Affymetrix chip: MOE 430 2.0 Experiment Overall Design: Tissue or origin: Tibiae Experiment Overall Design: Species E15.5 mice Experiment Overall Design: Samples: Total RNA