Project description:Alternative RNA splicing (AS) regulates proteome diversity, including isoform-specific expression of several pluripotency genes. Here, we integrated global gene expression and proteomic analyses and identified a molecular signature suggesting a central role for AS in maintaining human pluripotent stem cell (hPSC) self-renewal. We demonstrate the splicing factor SFRS2 is an OCT4 target gene required for pluripotency. SFRS2 regulates AS of the methyl-CpG-binding protein MBD2, whose isoforms play opposing roles in maintenance of, and reprogramming to, pluripotency. While both MDB2a and MBD2c are enriched at the OCT4 and NANOG promoters, MBD2a preferentially interacts with repressive NuRD chromatin remodeling factors and promotes hPSC differentiation, whereas overexpression of MBD2c enhances reprogramming of fibroblasts to pluripotency. The miR-301 and miR-302 families provide additional regulation by targeting SFRS2 and MDB2a. These data suggest that OCT4, SFRS2, and MBD2 participate in a positive feedback loop, regulating proteome diversity complexity in support of hPSC self-renewal and reprogramming. We isolated RNA from human fibroblasts and human embryonic stem cells for hybridization to the Affymetrix gene expression microarrays.
Project description:Using global gene expression and proteomic analyses, we identified a molecular signature in human embryonic and induced pluripotent stem cells that suggested a central regulatory role for RNA splicing in self-renewal. Through genetic and biochemical approaches, we established reciprocal functional links between the master regulatory factor OCT4 and SFRS2, a member of the serine/arginine-rich family of splicing factors. SFRS2 regulates expression of two isoforms of the methyl-CpG-binding protein MBD2 that play opposing roles in human ESC and during the reprogramming of fibroblasts. Both the MBD2a isoform expressed in fibroblasts and the MBD2c isoform found in pluripotent cells bind OCT4 and NANOG promoters in human ESC, but only MBD2a interacts with NuRD chromatin remodeling factors. Members of the miR-301 and miR-302 families provide additional regulation by targeting SFRS2 and the somatic specific MBD2a isoform. These data are consistent with a model in which OCT4, SFRS2, and MBD2 participate in a positive feedback loop to regulate proteome diversity in support of self-renewal in pluripotent cells. We isolated RNA from human iPS cells, different human fibroblasts and human embryonic stem cells for hybridization to the Affymetrix gene expression microarrays.
Project description:Alternative RNA splicing (AS) regulates proteome diversity, including isoform-specific expression of several pluripotency genes. Here, we integrated global gene expression and proteomic analyses and identified a molecular signature suggesting a central role for AS in maintaining human pluripotent stem cell (hPSC) self-renewal. We demonstrate the splicing factor SFRS2 is an OCT4 target gene required for pluripotency. SFRS2 regulates AS of the methyl-CpG-binding protein MBD2, whose isoforms play opposing roles in maintenance of, and reprogramming to, pluripotency. While both MDB2a and MBD2c are enriched at the OCT4 and NANOG promoters, MBD2a preferentially interacts with repressive NuRD chromatin remodeling factors and promotes hPSC differentiation, whereas overexpression of MBD2c enhances reprogramming of fibroblasts to pluripotency. The miR-301 and miR-302 families provide additional regulation by targeting SFRS2 and MDB2a. These data suggest that OCT4, SFRS2, and MBD2 participate in a positive feedback loop, regulating proteome diversity complexity in support of hPSC self-renewal and reprogramming.
Project description:Using global gene expression and proteomic analyses, we identified a molecular signature in human embryonic and induced pluripotent stem cells that suggested a central regulatory role for RNA splicing in self-renewal. Through genetic and biochemical approaches, we established reciprocal functional links between the master regulatory factor OCT4 and SFRS2, a member of the serine/arginine-rich family of splicing factors. SFRS2 regulates expression of two isoforms of the methyl-CpG-binding protein MBD2 that play opposing roles in human ESC and during the reprogramming of fibroblasts. Both the MBD2a isoform expressed in fibroblasts and the MBD2c isoform found in pluripotent cells bind OCT4 and NANOG promoters in human ESC, but only MBD2a interacts with NuRD chromatin remodeling factors. Members of the miR-301 and miR-302 families provide additional regulation by targeting SFRS2 and the somatic specific MBD2a isoform. These data are consistent with a model in which OCT4, SFRS2, and MBD2 participate in a positive feedback loop to regulate proteome diversity in support of self-renewal in pluripotent cells.
Project description:Pluripotent stem cells are defined by their self-renewal capacity, which is the ability of the stem cells to proliferate indefinitely while maintaining the pluripotent identity essential for their ability to differentiate into any somatic cell lineage. However, understanding the mechanisms that control stem cell fitness versus the pluripotent cell identity is challenging. To investigate the interplay between these two aspects of pluripotency, we performed four parallel genome-scale CRISPR-Cas9 loss-of-function screens interrogating stem cell fitness in hPSC self-renewal conditions, and the dissolution of the primed pluripotency identity during early differentiation. Comparative analyses led to the discovery of genes with distinct roles in pluripotency regulation, including mitochondrial and metabolism regulators crucial for stem cell fitness, and chromatin regulators that control pluripotent identity during early differentiation. We further discovered a core set of factors that control both stem cell fitness and pluripotent identity, including a network of chromatin factors that safeguard pluripotency. Our unbiased and systematic screening and comparative analyses disentangle two interconnected aspects of pluripotency, provide rich datasets for exploring pluripotent cell identity versus cell fitness, and offer a valuable model for categorizing gene function in broad biological contexts.
Project description:Chavez2009 - a core regulatory network of OCT4 in human embryonic stem cells
A core OCT4-regulated network has been identified as a test case, to analyase stem cell characteristics and cellular differentiation.
This model is described in the article:
In silico identification of a core regulatory network of OCT4 in human embryonic stem cells using an integrated approach.
Chavez L, Bais AS, Vingron M, Lehrach H, Adjaye J, Herwig R
BMC Genomics, 2009, 10:314
Abstract:
BACKGROUND: The transcription factor OCT4 is highly expressed in pluripotent embryonic stem cells which are derived from the inner cell mass of mammalian blastocysts. Pluripotency and self renewal are controlled by a transcription regulatory network governed by the transcription factors OCT4, SOX2 and NANOG. Recent studies on reprogramming somatic cells to induced pluripotent stem cells highlight OCT4 as a key regulator of pluripotency.
RESULTS: We have carried out an integrated analysis of high-throughput data (ChIP-on-chip and RNAi experiments along with promoter sequence analysis of putative target genes) and identified a core OCT4 regulatory network in human embryonic stem cells consisting of 33 target genes. Enrichment analysis with these target genes revealed that this integrative analysis increases the functional information content by factors of 1.3 - 4.7 compared to the individual studies. In order to identify potential regulatory co-factors of OCT4, we performed a de novo motif analysis. In addition to known validated OCT4 motifs we obtained binding sites similar to motifs recognized by further regulators of pluripotency and development; e.g. the heterodimer of the transcription factors C-MYC and MAX, a prerequisite for C-MYC transcriptional activity that leads to cell growth and proliferation.
CONCLUSION: Our analysis shows how heterogeneous functional information can be integrated in order to reconstruct gene regulatory networks. As a test case we identified a core OCT4-regulated network that is important for the analysis of stem cell characteristics and cellular differentiation. Functional information is largely enriched using different experimental results. The de novo motif discovery identified well-known regulators closely connected to the OCT4 network as well as potential new regulators of pluripotency and differentiation. These results provide the basis for further targeted functional studies.
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