ABSTRACT: The Sin3a/HDAC co-repressor complex cooperates with Nanog in promoting stem cell pluripotency and somatic cell reprogramming [Microarray Expression]
Project description:Despite the requirement of Sin3a for survival of early embryos and embryonic stem cells (ESCs), mechanistic action of Sin3a in the maintenance and establishment of pluripotency remains unexplored. Here we report the transcriptional regulatory roles of Sin3a in maintaining ESC pluripotency and in reprogramming somatic cells towards full pluripotency. Sin3a/HDAC complex members were enriched in an extended Nanog interactome and exhibited a predominant transcriptional co-activator role at a global level in ESCs. We also established a critical role for Sin3a in efficient reprogramming of somatic cells towards full pluripotency. Nanog and Sin3a co-localize at almost all of their genome-wide targets in pre-iPSCs, and both factors are required to directly induce a synergistic transcriptional program wherein pluripotency genes are activated and reprogramming barrier genes are repressed. Our results, for the first time, establish positive roles of the Sin3a/HDAC complex in the maintenance and establishment of pluripotency.
Project description:Despite the requirement of Sin3a for survival of early embryos and embryonic stem cells (ESCs), mechanistic action of Sin3a in the maintenance and establishment of pluripotency remains unexplored. Here we report the transcriptional regulatory roles of Sin3a in maintaining ESC pluripotency and in reprogramming somatic cells towards full pluripotency. Sin3a/HDAC complex members were enriched in an extended Nanog interactome and exhibited a predominant transcriptional co-activator role at a global level in ESCs. We also established a critical role for Sin3a in efficient reprogramming of somatic cells towards full pluripotency. Nanog and Sin3a co-localize at almost all of their genome-wide targets in pre-iPSCs, and both factors are required to directly induce a synergistic transcriptional program wherein pluripotency genes are activated and reprogramming barrier genes are repressed. Our results, for the first time, establish positive roles of the Sin3a/HDAC complex in the maintenance and establishment of pluripotency.
Project description:Sin3a is the central scaffold protein of the prototypical Hdac1/2 chromatin repressor complex, crucially required during early embryonic development for the growth of pluripotent cells of the inner cell mass. Here, we explore the endogenous composition of the Sin3a-Hdac complex in pluripotent embryonic stem (ES) and differentiated cells. To do this, we established an endogenous double immunoprecipitation strategy coupled with quantitative mass spectrometry (ENDIP-MS) allowing us to define the precise composition of the Sin3a complex in multiple cell types. We identify the Fam60a subunit as a key defining feature of a variant Sin3a complex present in ES cells, but not in differentiated cells. Fam60a co-occupies H3K4me3 positive promoters with Sin3a and is essential to maintain it on chromatin. Consistent with this, Fam60a depletion phenocopies the loss of Sin3a, leading to decreased proliferation, an extended G1-phase and the deregulation of genes associated with differentiation. Taken together, our data characterise Fam60a as an essential core subunit of a variant Sin3a complex in ES cells required to promote rapid proliferation and to prevent unscheduled differentiation.
Project description:Cerebellar granule cells (GCs) are critical for motor and cognitive functions. Lineage tracing studies have identified a hierarchical developmental progression of GC neurogenesis, transitioning from Sox2+ stem-like quiescent cells to Atoh1+ rapidly proliferating granule cell precursors (GCPs), and ultimately to NeuN+ mature GCs. However, the molecular mechanisms governing these transitions remain poorly understood. Here, we demonstrate that Sin3A, a core component of the histone deacetylase (Hdac) complex, plays a sequentially essential role in driving GC lineage progression across distinct precursor stages. In Sox2+ cells, Sin3A facilitates their transition to GCPs by repressing Sox2 expression. In GCPs, Sin3A suppresses Atoh1 transcriptional activity by recruiting Neurod1 as a co-repressor, thereby promoting GCP differentiation. Additionally, Sin3A ensures the survival and specification of GCPs by repressing non-lineage-specific gene expression. Our findings highlight the central role of the Sin3A complex in orchestrating distinct stages of cerebellar GC lineage development.
Project description:Recent reports have proposed a new paradigm for obtaining mature somatic cell types from fibroblasts without going through a pluripotent state, by briefly expressing canonical iPSC reprogramming factors Oct4, Sox2, Klf4 and c-Myc (abbreviated as OSKM), in cells expanded in lineage differentiation promoting conditions. Here we apply genetic lineage tracing for endogenous Nanog, Oct4 and X chromosome reactivation during OSKM induced trans-differentiation, as these molecular events mark final stages for acquisition of induced pluripotency. Remarkably, the vast majority of reprogrammed cardiomyocytes or neural stem cells derived from mouse fibroblasts via OSKM mediated trans-differentiation were attained after transient acquisition of pluripotency, and followed by rapid differentiation. Our findings underscore a molecular and functional coupling between inducing pluripotency and obtaining “trans-differentiated” somatic cells via OSKM induction, and have implications on defining molecular trajectories assumed during different cell reprogramming methods. poly RNA-Seq was measured before, during and after conversion of mouse embryonic fibroblasts to neural stem cells using OSKM trans-differentiation method.
Project description:Recent reports have proposed a new paradigm for obtaining mature somatic cell types from fibroblasts without going through a pluripotent state, by briefly expressing canonical iPSC reprogramming factors Oct4, Sox2, Klf4 and c-Myc (abbreviated as OSKM), in cells expanded in lineage differentiation promoting conditions. Here we apply genetic lineage tracing for endogenous Nanog, Oct4 and X chromosome reactivation during OSKM induced trans-differentiation, as these molecular events mark final stages for acquisition of induced pluripotency. Remarkably, the vast majority of reprogrammed cardiomyocytes or neural stem cells derived from mouse fibroblasts via OSKM mediated trans-differentiation were attained after transient acquisition of pluripotency, and followed by rapid differentiation. Our findings underscore a molecular and functional coupling between inducing pluripotency and obtaining “trans-differentiated” somatic cells via OSKM induction, and have implications on defining molecular trajectories assumed during different cell reprogramming methods. poly RNA-Seq and Chromatin accesibility (ATAC-seq) were measured during conversion of mouse embryonic fibroblasts to neural stem cells using OSKM trans-differentiation method, as well as in mouse emrbyonic fibroblasts, iPSCs and mouse ESCs.
Project description:Recent reports have proposed a new paradigm for obtaining mature somatic cell types from fibroblasts without going through a pluripotent state, by briefly expressing canonical iPSC reprogramming factors Oct4, Sox2, Klf4 and c-Myc (abbreviated as OSKM), in cells expanded in lineage differentiation promoting conditions. Here we apply genetic lineage tracing for endogenous Nanog, Oct4 and X chromosome reactivation during OSKM induced trans-differentiation, as these molecular events mark final stages for acquisition of induced pluripotency. Remarkably, the vast majority of reprogrammed cardiomyocytes or neural stem cells derived from mouse fibroblasts via OSKM mediated trans-differentiation were attained after transient acquisition of pluripotency, and followed by rapid differentiation. Our findings underscore a molecular and functional coupling between inducing pluripotency and obtaining “trans-differentiated” somatic cells via OSKM induction, and have implications on defining molecular trajectories assumed during different cell reprogramming methods. WGBS (Whole-Genome-Bisulfite-sequencing) were measured during conversion of mouse embryonic fibroblasts to neural stem cells using OSKM trans-differentiation method, as well as in mouse emrbyonic fibroblasts, and mouse ESCs.
Project description:ChIP coupled with NGS identifies genome-wide binding sites of a ES cells specific Sin3a/Hdac complex. The aim of these experiments is to study the role of Fam60a in the Sin3a/Hdac complex. ChIP-Seq experiments reveal that Fam60a is required to maintain high levels of Sin3a binding on target genes in mESCs. Depletion of Fam60a causes a drop of Sin3a binding to target sites. Underlining the function of Fam60a in mES cells, ChIP-seq analysis of Sin3a and Fam60a in mouse fibroblasts reveal strikingly low global binding level of Sin3a to its target genes while Fam60a is absent at these sites.