Pumilio proteins utilize distinct regulatory mechanisms to achieve complementary functions required for pluripotency and embryogenesis

Gene regulation in embryonic stem cells (ESCs) has been extensively studied at the epigenetic-transcriptional level, but not at the posttranscriptional level. Pumilio (Pum) proteins are among the few known translational regulators required for stem-cell maintenance in invertebrates and plants. Here we report the essential function of two murine Pum proteins, Pum1 and Pum2, in ESCs and early embryogenesis. Pum1/2 double-mutant ESCs display severely reduced self-renewal and differentiation, and Pum1/2 double-mutant mice are developmentally delayed at the morula stage and lethal by embryonic day 8.5. Remarkably, Pum1-deficient ESCs show increased expression of pluripotency genes but not differentiation genes, whereas Pum2-deficient ESCs show decreased pluripotency markers and accelerated differentiation. Thus, despite their high homology and overlapping target messenger RNAs (mRNAs), Pum1 promotes differentiation while Pum2 promotes self-renewal in ESCs. Pum1 and Pum2 achieve these two complementary aspects of pluripotency by forming a negative interregulatory feedback loop that directly regulates at least 1,486 mRNAs. Pum1 and Pum2 regulate target mRNAs not only by repressing translation, but also by promoting translation and enhancing or reducing mRNA stability of different target mRNAs. Together, these findings reveal distinct roles of individual mammalian Pum proteins in ESCs and their essential functions in ESC pluripotency and embryogenesis.

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Oct4GiP Reporter Assay to Study Genes that Regulate Mouse Embryonic Stem Cell Maintenance and Self-renewal

Journal of Visualized Experiments ◽

10.3791/3987 ◽

2012 ◽

Cited By ~ 2

Author(s):

Xiaofeng Zheng ◽

Guang Hu

Keyword(s):

Stem Cell ◽

Embryonic Stem Cell ◽

Embryonic Stem ◽

Mouse Embryonic Stem Cell ◽

Reporter Assay ◽

Self Renewal ◽

Stem Cell Maintenance ◽

Cell Maintenance

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Chromatin plasticity in pluripotent cells

Essays in Biochemistry ◽

10.1042/bse0480245 ◽

2010 ◽

Vol 48 ◽

pp. 245-262 ◽

Cited By ~ 30

Author(s):

Shai Melcer ◽

Eran Meshorer

Keyword(s):

Embryonic Stem ◽

Nuclear Architecture ◽

Nuclear Lamina ◽

Cell Types ◽

Blastocyst Stage ◽

Pluripotent Cells ◽

Self Renewal ◽

Stem Cell Maintenance ◽

Undifferentiated State ◽

Stage Embryo

ESCs (embryonic stem cells), derived from the blastocyst stage embryo, are characterized by an indefinite ability for self-renewal as well as pluripotency, enabling them to differentiate into all cell types of the three germ layers. In the undifferentiated state, ESCs display a global promiscuous transcriptional programme which is restricted gradually upon differentiation. Supporting transcriptional promiscuity, chromatin in pluripotent cells is more ‘plastic’ or ‘open’, with decondensed heterochromatin architecture, enrichment of active histone modifications, and a hyperdynamic association of chromatin proteins with chromatin. During ESC differentiation, nuclear architecture and chromatin undergo substantial changes. Heterochromatin foci appear smaller, more numerous and more condensed in the differentiated state, the nuclear lamina becomes more defined and chromatin protein dynamics becomes restricted. In the present chapter we discuss chromatin plasticity and epigenetics and the mechanisms that regulate the various chromatin states, which are currently a central theme in the studies of stem cell maintenance and differentiation, and which will no doubt assist in delineating the secrets of pluripotency and self-renewal.

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Pumilio Proteins Exert Distinct Biological Functions and Multiple Modes of Post-Transcriptional Regulation in Embryonic Stem Cell Pluripotency and Early Embryogenesis

10.1101/751909 ◽

2019 ◽

Cited By ~ 1

Author(s):

Katherine E. Uyhazi ◽

Yiying Yang ◽

Na Liu ◽

Hongying Qi ◽

Xiao A. Huang ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Feedback Loop ◽

Embryonic Stem ◽

Early Embryogenesis ◽

Self Renewal ◽

Target Mrnas ◽

Regulatory Feedback Loop ◽

Post Transcriptional Regulation ◽

Pluripotency Genes

ABSTRACTGene regulation in embryonic stem cells (ESCs) has been extensively studied at the epigenetic-transcriptional levels, but not at the post-transcriptional levels. Pumilio (Pum) proteins are among the few known translational regulators required for stem cell maintenance in invertebrates and plants. Here we report the essential function of two murine Pum proteins, Pum1 and Pum2, in ESCs and early embryogenesis. Pum1/2 double mutants are developmentally delayed at the morula stage and lethal by embryonic day 8.5 (e8.5). Correspondingly, Pum1/2 double mutant ESCs display severely reduced self-renewal and differentiation, revealing the combined function of Pum1 and Pum2 in ESC pluripotency. Remarkably, Pum1-deficient ESCs show increased expression of pluripotency genes but not differentiation genes, indicating that Pum1 mainly promote differentiation; whereas Pum2-deficient ESCs show decreased expression of pluripotency genes and accelerated differentiation, indicating that Pum2 promotes self-renewal. Thus, Pum1 and Pum2 each uniquely contributes to one of the two complementary aspects of pluripotency. Furthermore, we show that Pum1 and Pum2 achieve ESC functions by forming a negative auto- and inter-regulatory feedback loop that directly regulates at least 1,486 mRNAs. Pum1 and Pum2 regulate target mRNAs not only by repressing translation as expected but also by promoting translation and enhancing or reducing mRNA stability of different target mRNAs. Together, these findings reveal the distinct roles of individual mammalian Pum proteins in ESCs and their collectively essential functions in ESC pluripotency and embryogenesis. Moreover, they demonstrate three novel modes of regulation of Pum proteins towards target mRNAs.SIGNIFICANCE STATEMENTThis report demonstrates the essential functions of mammalian Pumilio (Pum) proteins for embryonic stem cells (ESCs) pluripotency and embryogenesis. Moreover, it reveals the contrasting but complementary function of individual Pum proteins in regulating distinct aspects of ESC pluripotency, despite their largely overlapping expression and extremely high homology. Furthermore, it unravels a complex regulatory network in which Pum1 and Pum2 form a negative auto- and inter-regulatory feedback loop that regulates 1,486 mRNAs not only by translational repression as expected but also by promoting translation and enhancing or reducing stability of different target mRNAs, which reveals novel modes of post-transcriptional regulation mediated by Pum.

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The Yb protein defines a novel organelle and regulates male germline stem cell self-renewal in Drosophila melanogaster

The Journal of Cell Biology ◽

10.1083/jcb.200903034 ◽

2009 ◽

Vol 185 (4) ◽

pp. 613-627 ◽

Cited By ~ 64

Author(s):

Akos Szakmary ◽

Mary Reedy ◽

Hongying Qi ◽

Haifan Lin

Keyword(s):

Drosophila Melanogaster ◽

Stem Cell ◽

Double Mutant ◽

Terminal Region ◽

Germline Stem Cell ◽

Self Renewal ◽

Stem Cell Maintenance ◽

Male Germline ◽

Cytoplasmic Structures ◽

Cell Maintenance

Yb regulates the proliferation of both germline and somatic stem cells in the Drosophila melanogaster ovary by activating piwi and hh expression in niche cells. In this study, we show that Yb protein is localized as discrete cytoplasmic spots exclusively in the somatic cells of the ovary and testis. These spots, which are different from all known cytoplasmic structures in D. melanogaster, are evenly electron-dense spheres 1.5 µm in diameter (herein termed the Yb body). The Yb body is frequently associated with mitochondria and a less electron-dense sphere of similar size that appears to be RNA rich. There are one to two Yb bodies/cell, often located close to germline cells. The N-terminal region of Yb is required for hh expression in niche cells, whereas the C-terminal region is required for localization to Yb bodies. The entire Yb protein is necessary for piwi expression in niche cells. A double mutant of Yb and a novel locus show male germline loss, revealing a function for Yb in male germline stem cell maintenance.

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