ABSTRACT: Stemness-related factor Sall4 interacts with transcription factors Oct-3/4 and Sox2 and occupies Oct-Sox elements in mouse embryonic stem cells
Project description:A small number of transcription factors, including Oct-3/4 and Sox2, constitute the transcriptional network that maintains pluripotency in embryonic stem (ES) cells. Previous reports suggested that some of these factors form a complex that binds the Oct-Sox element, a composite sequence consisting of closely juxtaposed Oct-3/4-binding and Sox2-binding sites. However, little is known regarding the components of the complex. In this study, we show that Sall4, a member of the Spalt-like family of proteins, directly interacts with Sox2 and Oct-3/4. Sall4 in combination with Sox2 or Oct-3/4 simultaneously occupies the Oct-Sox elements in mouse ES cells. Sall4 knockdown led to differentiation of ES cells. Overexpression of Sall4 in ES cells increased reporter activities in a luciferase assay when the Pou5f1- or Nanog-derived Oct-Sox element was included in the reporter. Microarray analyses revealed that Sall4 and Sox2 bound to the same genes in ES cells significantly more frequently than expected from random coincidence. These factors appeared to bind the promoter regions of a subset of the Sall4- and Sox2-double-positive genes in precisely similar distribution patterns along the promoter regions, suggesting that Sall4 and Sox2 associate with such Sall4/Sox2-overlapping genes as a complex. Importantly, gene ontology analyses indicated that the Sall4/Sox2-overlapping gene set is enriched for genes involved in maintaining pluripotency. Sall4/Sox2/Oct-3/4-triple-positive genes identified by referring to a previous study identifying Oct-3/4-bound genes in ES cells were further enriched for pluripotency genes than Sall4/Sox2-double-positive genes. These results demonstrate that Sall4 contributes to the transcriptional network operating in pluripotent cells, together with Oct-3/4 and Sox2. ChIP-on-chip experiments using anti-Sall4 or anti-Sox2 antibody were performed.
Project description:A small number of transcription factors, including Oct-3/4 and Sox2, constitute the transcriptional network that maintains pluripotency in embryonic stem (ES) cells. Previous reports suggested that some of these factors form a complex that binds the Oct-Sox element, a composite sequence consisting of closely juxtaposed Oct-3/4-binding and Sox2-binding sites. However, little is known regarding the components of the complex. In this study, we show that Sall4, a member of the Spalt-like family of proteins, directly interacts with Sox2 and Oct-3/4. Sall4 in combination with Sox2 or Oct-3/4 simultaneously occupies the Oct-Sox elements in mouse ES cells. Sall4 knockdown led to differentiation of ES cells. Overexpression of Sall4 in ES cells increased reporter activities in a luciferase assay when the Pou5f1- or Nanog-derived Oct-Sox element was included in the reporter. Microarray analyses revealed that Sall4 and Sox2 bound to the same genes in ES cells significantly more frequently than expected from random coincidence. These factors appeared to bind the promoter regions of a subset of the Sall4- and Sox2-double-positive genes in precisely similar distribution patterns along the promoter regions, suggesting that Sall4 and Sox2 associate with such Sall4/Sox2-overlapping genes as a complex. Importantly, gene ontology analyses indicated that the Sall4/Sox2-overlapping gene set is enriched for genes involved in maintaining pluripotency. Sall4/Sox2/Oct-3/4-triple-positive genes identified by referring to a previous study identifying Oct-3/4-bound genes in ES cells were further enriched for pluripotency genes than Sall4/Sox2-double-positive genes. These results demonstrate that Sall4 contributes to the transcriptional network operating in pluripotent cells, together with Oct-3/4 and Sox2.
Project description:Embryonic stem cell (ESCs) identity is orchestrated by co-operativity between the transcription factors (TFs) Sox2 and the class V POU-TF, Oct4 at composite Sox/Oct motifs. Neural stem cells (NSCs) lack Oct4 but express Sox2 and class III POU-TFs. This raises the question of how Sox2 interacts with POU-TFs to transcriptionally specify ESCs or NSCs. Here we show that Oct4 alone binds the Sox/Oct motif and the octamer-containing palindromic MORE equally well. Sox2 binding selectively increases the affinity of Oct4 for the Sox/Oct motif. In contrast, Oct6 binds preferentially to the MORE, and is unaffected by Sox2. ChIP-seq in NSCs shows the MORE to be the most enriched motif for class III POU-TFs, with MORE sub-types apparent, but no Sox/Oct motif enrichment. These results suggest that in NSCs, co-operativity between Sox2 and class III POU-TFs may not occur and that POU-TF driven transcription uses predominantly the MORE cis architecture. Thus, distinct interactions between Sox2 and POU-TF subclasses distinguish pluripotent ESCs from multipotent NSCs, providing molecular insight into how Oct4 alone can convert NSCs to pluripotency.
Project description:We show here by using genome-wide ChIP-sequencing that lineage segregation involves multiple Sox/Oct partnership. In undifferentiated ES cells Oct4 interacts with Sox2 and both TFs bind on the 'canonical' motif, whereas in cells commited to PrE lineage Oct4 switches from Sox2 to Sox17 interaction and this complex bind to a unique "compressed" motif. ChIP-sequencing has been done for Sox2, Sox17 and Oct4 in the pluripotent context or PrE context
Project description:We show here by using genome-wide ChIP-sequencing that lineage segregation involves multiple Sox/Oct partnership. In undifferentiated ES cells Oct4 interacts with Sox2 and both TFs bind on the 'canonical' motif, whereas in cells commited to PrE lineage Oct4 switches from Sox2 to Sox17 interaction and this complex bind to a unique "compressed" motif.
Project description:Stem cells self-renew or differentiate under the governance of a stem cell-specific transcriptional program with each transcription factor orchestrating the activities of a particular set of genes. Here we demonstrate that a single transcription factor is able to regulate distinct core circuitries in two different blastocyst-derived stem cell lines, embryonic stem (ES) and extra-embryonic endoderm (XEN) cells. The transcription factor, Sall4, is required for early embryonic development and for ES cell pluripotency. Sall4 is also expressed in XEN cells and depletion of Sall4 disrupts self-renewal and induces differentiation. Genome-wide analysis reveals Sall4 is regulating different gene sets in ES and XEN cells, and depletion of Sall4 targets in the respective cell types induces differentiation. With Oct4, Sox2 and Nanog, Sall4 forms a crucial interconnected auto-regulatory network in ES cells. In XEN cells, Sall4 regulates key XEN lineageassociated genes, Gata4, Gata6, Sox7 and Sox17. Our findings demonstrate how Sall4 functions as an essential stemness factor for two different stem cell lines. Keywords: ES/XEN comparison, ES Sall4 KD/control KD comparison, and XEN Sall4 KD/control KD comparison
Project description:The objective of this study was to identify genes regulated by canonical Wnt signaling in mouse embryonic stem cells (ESCs).Canonical Wnt signaling supports the pluripotency of mouse ESCs but also promotes differentiation of early mammalian cell lineages. To explain these paradoxical observations, we explored the gene regulatory networks at play. Canonical Wnt signaling is intertwined with the pluripotency network comprising Nanog, Oct4, and Sox2 in mouse ESCs. In defined media supporting the derivation and propagation of mouse ESCs, Tcf3 and ?-catenin interact with Oct4; Tcf3 binds to Sox motif within Oct-Sox composite motifs that are also bound by Oct4-Sox2 complexes. Further, canonical Wnt signaling up-regulates the activity of the Pou5f1 distal enhancer via the Sox motif in mouse ESCs. When viewed in the context of published studies on Tcf3 and ?-catenin mutants, our findings suggest that Tcf3 counters pluripotency by competition with Sox2 at these sites, and Tcf3 inhibition is blocked by ?-catenin entry into this complex. Wnt pathway stimulation also triggers ?-catenin association at regulatory elements with classic Lef/Tcf motifs associated with differentiation programs. The failure to activate these targets in the presence of a MEK/ERK inhibitor essential for mouse ESC culture suggests that MEK/ERK signaling and canonical Wnt signaling combine to promote mouse ESC differentiation. Triplicates of mouse embryonic stem cells cultured with GSK3 inhibitor CHIR99021 or with Wnt pathway inhibitor XAV939.
Project description:HUES24 cell line was nucleofected with POU5f1 cDNA to overexpress OCT4; This leads to the formation of mesendodermal cells Short- and Long-scales intra- and inter-chromosomal interactions are linked to gene transcription, but the molecular event underlying these structures and how it affects cell fate decision during embryonic development are poorly understood. One of the first embryonic cell fate decisions (i.e mesendoderm determination) is driven by the POU factor OCT4, acting in concert with the high mobility group genes SOX-2 and SOX-17. Here, we identify novel chromatin remodelling mechanism and enhancer function driven by both OCT4 and SALL4 that mediate cell fate switching. We found that OCT4 alters the higher-order chromatin structure at both Sox-2 and Sox-17 loci. OCT4 titrates out cohesin and switches the Sox-17 enhancer from a locked (within an inter-chromosomal Sox-2 enhancer/CTCF/cohesin loop) to an active (within an intra-chromosomal Sox-17 promoter/enhancer/cohesin loop) state. SALL4 concomitantly mobilizes the polycomb complexes at the Soxs loci. Thus, OCT4/SALL4-driven cohesin-and polycombs-mediated changes in higher order chromatin structure mediate instruction of early cell fate in embryonic cells. ChIP anti-OCT4 on chip. results_v2.xls file description: Enriched binding sites. Mutant means oct4 overexpressing cells , wt GFP nucleofected cells.
Project description:HUES24 cell line was nucleofected with POU5f1 cDNA to overexpress OCT4; This leads to the formation of mesendodermal cells Short- and Long-scales intra- and inter-chromosomal interactions are linked to gene transcription, but the molecular event underlying these structures and how it affects cell fate decision during embryonic development are poorly understood. One of the first embryonic cell fate decisions (i.e mesendoderm determination) is driven by the POU factor OCT4, acting in concert with the high mobility group genes SOX-2 and SOX-17. Here, we identify novel chromatin remodelling mechanism and enhancer function driven by both OCT4 and SALL4 that mediate cell fate switching. We found that OCT4 alters the higher-order chromatin structure at both Sox-2 and Sox-17 loci. OCT4 titrates out cohesin and switches the Sox-17 enhancer from a locked (within an inter-chromosomal Sox-2 enhancer/CTCF/cohesin loop) to an active (within an intra-chromosomal Sox-17 promoter/enhancer/cohesin loop) state. SALL4 concomitantly mobilizes the polycomb complexes at the Soxs loci. Thus, OCT4/SALL4-driven cohesin-and polycombs-mediated changes in higher order chromatin structure mediate instruction of early cell fate in embryonic cells.
Project description:The functional consequences of cancer-associated missense mutations are unclear for majority of proteins, here we interrogated cancer mutation databases and identified recurrently mutated positions at structural contact interface of DNA-binding domains of SOX and POU family transcription factors. We used conversion of mouse embryonic fibroblasts (MEFs) to induced pluripotent stem cells (iPSCs) as a functional read out. In this study we identified several gain-of-function mutations that enhance cellular pluripotency reprogramming by SOX2 and OCT4. Wild type SOX17 does not support pluripotency reprogramming while recurrent missense mutation SOX17-V118M converts SOX17 into a pluripotency inducer, viability of cancer cells and provides protein stability. Here, we conclude that mutational profile of SOX and OCT family factors in cancer association can give direction to design high-performance reprogramming factors.