Project description:We investigated the gene expression profile changes after Ezh2 conditional knockout in the mouse retina at E16.5. Loss of Ezh2 leads to up-regulation of PRC2 targeted genes including cell cycle regulators and multiple genes which are not normally expressed in the retina, including many Hox genes. Loss of Ezh2 resulted in a dramatic decline in progenitor proliferation by postnatal day 3, such that there is an early end to neurogenesis, and disruption of laminar organization. Although there are only minor effects on embryonic retinal development, there is accelerated differentiation of several late born cell types postnatally, including photoreceptors and Mueller glia, which become reactive by postnatal day 14. Peripheral retina was dissected at E16.5 from Pax6alpha-Cre:Ezh2fl/+ and Pax6alpha-Cre:Ezh2fl/null mouse embryos. Total RNA was purified and RNA deep sequencing was done using 4 controls and 4 conditional knockout samples.
Project description:We investigated the gene expression profile changes after Ezh2 conditional knockout in the mouse retina at E16.5. Loss of Ezh2 leads to up-regulation of PRC2 targeted genes including cell cycle regulators and multiple genes which are not normally expressed in the retina, including many Hox genes. Loss of Ezh2 resulted in a dramatic decline in progenitor proliferation by postnatal day 3, such that there is an early end to neurogenesis, and disruption of laminar organization. Although there are only minor effects on embryonic retinal development, there is accelerated differentiation of several late born cell types postnatally, including photoreceptors and Mueller glia, which become reactive by postnatal day 14.
Project description:The histone methyltransferase complex PRC2 controls key steps in developmental transitions and cell fate choices. However, its roles in vertebrate eye development remain unknown. Here we report that in Xenopus PRC2 regulates the progression of retinal progenitors from proliferation to differentiation. We show that the PRC2 core components are enriched in retinal progenitors and downregulated with differentiation. Knockdown of the PRC2 core component Ezh2 leads to reduced retinal progenitor proliferation in part due to upregulation of the cdk inhibitor p15Ink4b. In addition, while PRC2 knockdown does not alter eye patterning, retinal progenitor gene expression or expression of the neural competence factor Sox2, it does cause suppression of proneural bHLH gene expression, indicating that PRC2 is critical for the initiation of neural differentiation in the retina. Consistent with this, knocking down or blocking PRC2 function constrains the generation of most retinal neural cell types and promotes a Mueller glial cell fate decision. We also show that Wnt/?-catenin signaling acting through the receptor Frizzled 5, but independent of Sox2, regulates expression of key PRC2 subunits in the developing retina. This is consistent with a role for this pathway in coordinating proliferation and the transition to neurogenesis in the Xenopus retina. Our data establishes PRC2 as a regulator of proliferation and differentiation during eye development. Xenopus embryos were injected at the 8-cell stage with 5ng Ezh2 ATG MO or 5ng control MO (scrambled sequence of Ezh2 ATG MO) together with 400 pg mRNA for GFP as a lineage tracer. At stage 27, GFP-positive eyes were isolated by microdissection. Pools of 20-25 eyes were used to prepare total RNA for each sample on the microarray. 4 control and 4 Ezh2 ATG MO samples were hybridized to Agilent 1-color microarrays.
Project description:The histone methyltransferase complex PRC2 controls key steps in developmental transitions and cell fate choices. However, its roles in vertebrate eye development remain unknown. Here we report that in Xenopus PRC2 regulates the progression of retinal progenitors from proliferation to differentiation. We show that the PRC2 core components are enriched in retinal progenitors and downregulated with differentiation. Knockdown of the PRC2 core component Ezh2 leads to reduced retinal progenitor proliferation in part due to upregulation of the cdk inhibitor p15Ink4b. In addition, while PRC2 knockdown does not alter eye patterning, retinal progenitor gene expression or expression of the neural competence factor Sox2, it does cause suppression of proneural bHLH gene expression, indicating that PRC2 is critical for the initiation of neural differentiation in the retina. Consistent with this, knocking down or blocking PRC2 function constrains the generation of most retinal neural cell types and promotes a Mueller glial cell fate decision. We also show that Wnt/β-catenin signaling acting through the receptor Frizzled 5, but independent of Sox2, regulates expression of key PRC2 subunits in the developing retina. This is consistent with a role for this pathway in coordinating proliferation and the transition to neurogenesis in the Xenopus retina. Our data establishes PRC2 as a regulator of proliferation and differentiation during eye development.
Project description:Differentiation of mouse embryonic stem cells (mESCs) is accompanied by global changes in replication timing. To elucidate this reorganization process and explore its potential impact on mouse development, we constructed genome-wide replication-timing profiles of 15 independent mouse cell types representing nine different stages of early mouse development, including all three germ layers. Overall, 45% of the genome exhibits significant changes in replication timing between cell types, indicating that replication-timing regulation is more extensive than previously estimated from neural differentiation. Intriguingly, analysis of early and late epiblast cell culture models suggest that the earliest changes in development include extensive lineage-independent early-to-late replication switches that are completed at a stage equivalent to the post-implantation epiblast, prior to germ layer specification and down-regulation of key pluripotency transcription factors (Oct4/Nanog/Sox2). These changes were stable in all subsequent lineages and involved a class of irreversibly silenced genes that were re-positioned closer to the nuclear periphery. Lineage-specific, late-to-early and early-to-late replication switches followed, which created cell-type specific replication profiles. Importantly, partially reprogrammed induced pluripotent stem cells (piPSCs) failed to restore ESC-specific replication timing and transcription programs particularly within regions of lineage-independent early-to-late replication changes, as well as the inactive X-chromosome. We conclude that lineage-independent, early-to-late replication-timing switches that occur in the post-implantation epiblast embody an epigenetic commitment to differentiation prior to germ layer specification. 22 cell lines, with a total of 36 individual replicates (i.e. 14 in duplicates, 8 in single replicates)
Project description:Androgen receptor (AR) is a hormone-activated transcription factor that plays important roles in prostate development, function, as well as malignant transformation. The downstream pathways of AR, however, are incompletely understood. AR has been primarily known as a transcriptional activator inducing prostate-specific gene expression. Through integrative analysis of genome-wide AR occupancy and androgen-regulated gene expression, here we report AR as a globally acting transcriptional repressor. This repression is mediated by androgen responsive elements (ARE) and dictated by Polycomb group protein EZH2 and repressive chromatin remodeling. In embryonic stem cells, AR-repressed genes are occupied by EZH2 and harbor bivalent H3K4me3 and H3K27me3 modifications that are characteristic of differentiation regulators, the silencing of which maintains the undifferentiated state. Concordantly, these genes are silenced in castration-resistant prostate cancer rendering a stem cell-like lack of differentiation and tumor progression. Collectively, our data reveal an unexpected role of AR as a transcriptional repressor inhibiting non-prostatic differentiation and, upon excessive signaling, resulting in cancerous de-differentiation. It provides an innovative mechanism for castration resistance and highlights novel therapeutic strategies to treat advanced prostate cancer. Keywords: Genetic Modification compare gene expression in different cell lines with or without androgen treatment or EZH2 knockdown
Project description:Differentiation of mouse embryonic stem cells (mESCs) is accompanied by global changes in replication timing. To elucidate this reorganization process and explore its potential impact on mouse development, we constructed genome-wide replication-timing profiles of 15 independent mouse cell types representing nine different stages of early mouse development, including all three germ layers. Overall, 45% of the genome exhibits significant changes in replication timing between cell types, indicating that replication-timing regulation is more extensive than previously estimated from neural differentiation. Intriguingly, analysis of early and late epiblast cell culture models suggest that the earliest changes in development include extensive lineage-independent early-to-late replication switches that are completed at a stage equivalent to the post-implantation epiblast, prior to germ layer specification and down-regulation of key pluripotency transcription factors (Oct4/Nanog/Sox2). These changes were stable in all subsequent lineages and involved a class of irreversibly silenced genes that were re-positioned closer to the nuclear periphery. Lineage-specific, late-to-early and early-to-late replication switches followed, which created cell-type specific replication profiles. Importantly, partially reprogrammed induced pluripotent stem cells (piPSCs) failed to restore ESC-specific replication timing and transcription programs particularly within regions of lineage-independent early-to-late replication changes, as well as the inactive X-chromosome. We conclude that lineage-independent, early-to-late replication-timing switches that occur in the post-implantation epiblast embody an epigenetic commitment to differentiation prior to germ layer specification.
Project description:Purpose: Piwi family protein Aubergine (Aub) maintains genome integrity in late germ cells of the Drosophila ovary through piRNA-mediated repression of transposon activities. Although it is highly expressed in germline stem cells (GSCs) and early progeny, it remains unclear if it plays any roles in early GSC lineage development. Results: The study reveals a novel function of Aub in GSCs and their progeny, which promotes translation of self-renewal and differentiation factors by directly binding to its target mRNAs and interacting with translational initiation factors.
Project description:Clinical and genetic heterogeneity associated with retinal diseases makes stem cell-based therapies an attractive strategy for personalized medicine. However, we have limited understanding of the timing of key events in the developing human retina, and in particular the factors critical for generating the unique architecture of the fovea and surrounding macula. Here we define three key epochs in the transcriptome dynamics of human retina from fetal day (D) 52 to 150. Coincident histological analyses confirmed the cellular basis of transcriptional changes and highlighted the dramatic acceleration of development in the fovea compared to peripheral retina. Human and mouse retinal transcriptomes show remarkable similarity in developmental stages, though morphogenesis was greatly expanded in humans. Integration of DNA accessibility data allowed us to reconstruct transcriptional networks controlling photoreceptor differentiation. Our studies provide insights into human retinal development and serve as resource for molecular staging of human stem cell-derived retinal organoids.