Project description:Reactivation of the pluripotency network during somatic cell reprogramming by exogenous transcription factors involves chromatin remodeling and the recruitment of RNA polymerase II (Pol II) to target loci. Here, we report that Pol II is engaged at pluripotency promoters in reprogramming but remains paused and inefficiently released. We also show that bromodomain-containing protein 4 (BRD4) stimulates productive transcriptional elongation of pluripotency genes by dissociating the pause release factor P-TEFb from an inactive complex containing HEXIM1. Consequently, BRD4 overexpression enhances reprogramming efficiency and HEXIM1 suppresses it, whereas Brd4 and Hexim1 knockdown do the opposite. We further demonstrate that the reprogramming factor KLF4 helps recruit P-TEFb to pluripotency promoters. Our work thus provides a mechanism for explaining the reactivation of pluripotency genes in reprogramming and unveils an unanticipated role for KLF4 in transcriptional pause release. Pol II ChIP-seq for MEFs, ESCs and bulk populations of OSKM reprogramming intermediates at two time points.
Project description:Purposes: (1) compare the SUMO chromatin landscape between mouse embryonic fibroblasts (MEFs) and embryonic stem cells (ESc) (2) Decipher how hyposumoylation enhances MEF to induced pluripotent stem cells (iPSc) reprogramming (3) Decipher how hyposumoylation enhances ESc to 2C-like cells conversion. Methods : (1) ChIP-seq in MEFs and ESc for SUMO isoforms and histone marks. (2) ChIP-seq for transcription factors and histone marks at day 4 of MEF to iPSc reprogramming comparing wild type (shCtrl) and hyposumoylated cells (shUbc9). ATAC-Seq at day 4 of MEF to iPSc reprogramming comparing wild type (shCtrl) and hyposumoylated cells (shUbc9). RNA-Seq in MEFs, iPSc, at day 4 and day 7 of MEF to iPSc reprogramming comparing wild type (shCtrl) and hyposumoylated cells (shUbc9). (3) RNA-Seq in ESc comparing wild-type (siCtrl) and hyposumoylated cells (siUbc9). Results: (1) SUMO chromatin landscape is highly different between MEFs and ESc and associates to distinct chromatin marks. (2) Hyposumoylation enhances MEFs to iPSc reprogramming by favoring the extinction of the MEF transcriptional program and redistributing pluripotency factors from MEF enhancers toward ES enhancers. (3) Hyposumoylation enhances ES to 2C-like conversion by destabilizing heterochromatin thus resulting in an activation of the 2-cell transcriptional program. Conclusion: SUMO at chromatin is gate-keeper of cell-identity.
Project description:This SuperSeries is composed of the following subset Series: GSE30995: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [RNA-Seq] GSE31006: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [ChIP-Seq] GSE31007: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [protein binding microarray] GSE31948: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [AS microarray] Refer to individual Series
Project description:Reactivation of the pluripotency network during somatic cell reprogramming by exogenous transcription factors involves chromatin remodeling and the recruitment of RNA polymerase II (Pol II) to target loci. Here, we report that Pol II is engaged at pluripotency promoters in reprogramming but remains paused and inefficiently released. We also show that bromodomain-containing protein 4 (BRD4) stimulates productive transcriptional elongation of pluripotency genes by dissociating the pause release factor P-TEFb from an inactive complex containing HEXIM1. Consequently, BRD4 overexpression enhances reprogramming efficiency and HEXIM1 suppresses it, whereas Brd4 and Hexim1 knockdown do the opposite. We further demonstrate that the reprogramming factor KLF4 helps recruit P-TEFb to pluripotency promoters. Our work thus provides a mechanism for explaining the reactivation of pluripotency genes in reprogramming and unveils an unanticipated role for KLF4 in transcriptional pause release. Refer to individual Series
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.