101
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Fu Z, Geng C, Wang H, Yang Z, Weng C, Li H, Deng L, Liu L, Liu N, Ni J, Xie T. Twin Promotes the Maintenance and Differentiation of Germline Stem Cell Lineage through Modulation of Multiple Pathways. Cell Rep 2015; 13:1366-1379. [DOI: 10.1016/j.celrep.2015.10.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 08/12/2015] [Accepted: 10/05/2015] [Indexed: 11/28/2022] Open
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102
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Abstract
Pumilio is an RNA-binding protein originally identified in Drosophila, with a Puf domain made up of eight Puf repeats, three helix bundles arranged in a rainbow architecture, where each repeat recognizes a single base of the RNA-binding sequence. The eight-base recognition sequence can therefore be modified simply via mutation of the repeat that recognizes the base to be changed and this is understood in detail via high-resolution crystal structures. The binding mechanism is also altered in a variety of homologues from different species, with bases flipped out from the binding site to regenerate a consensus sequence. Thus Pumilios can be designed with bespoke RNA recognition sequences and can be fused to nucleases, split GFP, etc. as tools in vitro and in cells.
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103
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Mainpal R, Nance J, Yanowitz JL. A germ cell determinant reveals parallel pathways for germ line development in Caenorhabditis elegans. Development 2015; 142:3571-82. [PMID: 26395476 DOI: 10.1242/dev.125732] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Accepted: 09/01/2015] [Indexed: 02/01/2023]
Abstract
Despite the central importance of germ cells for transmission of genetic material, our understanding of the molecular programs that control primordial germ cell (PGC) specification and differentiation are limited. Here, we present findings that X chromosome NonDisjunction factor-1 (XND-1), known for its role in regulating meiotic crossover formation, is an early determinant of germ cell fates in Caenorhabditis elegans. xnd-1 mutant embryos display a novel 'one PGC' phenotype as a result of G2 cell cycle arrest of the P4 blastomere. Larvae and adults display smaller germ lines and reduced brood size consistent with a role for XND-1 in germ cell proliferation. Maternal XND-1 proteins are found in the P4 lineage and are exclusively localized to the nucleus in PGCs, Z2 and Z3. Zygotic XND-1 turns on shortly thereafter, at the ∼300-cell stage, making XND-1 the earliest zygotically expressed gene in worm PGCs. Strikingly, a subset of xnd-1 mutants lack germ cells, a phenotype shared with nos-2, a member of the conserved Nanos family of germline determinants. We generated a nos-2 null allele and show that nos-2; xnd-1 double mutants display synthetic sterility. Further removal of nos-1 leads to almost complete sterility, with the vast majority of animals without germ cells. Sterility in xnd-1 mutants is correlated with an increase in transcriptional activation-associated histone modification and aberrant expression of somatic transgenes. Together, these data strongly suggest that xnd-1 defines a new branch for PGC development that functions redundantly with nos-2 and nos-1 to promote germline fates by maintaining transcriptional quiescence and regulating germ cell proliferation.
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Affiliation(s)
- Rana Mainpal
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Jeremy Nance
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY 10016, USA Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA
| | - Judith L Yanowitz
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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104
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Positive mRNA Translational Control in Germ Cells by Initiation Factor Selectivity. BIOMED RESEARCH INTERNATIONAL 2015; 2015:327963. [PMID: 26357652 PMCID: PMC4556832 DOI: 10.1155/2015/327963] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/22/2015] [Indexed: 01/04/2023]
Abstract
Ultimately, the production of new proteins in undetermined cells pushes them to new fates. Other proteins hold a stem cell in a mode of self-renewal. In germ cells, these decision-making proteins are produced largely from translational control of preexisting mRNAs. To date, all of the regulation has been attributed to RNA binding proteins (RBPs) that repress mRNAs in many models of germ cell development (Drosophila, mouse, C. elegans, and Xenopus). In this review, we focus on the selective, positive function of translation initiation factors eIF4E and eIF4G, which recruit mRNAs to ribosomes upon derepression. Evidence now shows that the two events are not separate but rather are coordinated through composite complexes of repressors and germ cell isoforms of eIF4 factors. Strikingly, the initiation factor isoforms are themselves mRNA selective. The mRNP complexes of translation factors and RBPs are built on specific populations of mRNAs to prime them for subsequent translation initiation. Simple rearrangement of the partners causes a dormant mRNP to become synthetically active in germ cells when and where they are required to support gametogenesis.
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105
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Laissue P. Aetiological coding sequence variants in non-syndromic premature ovarian failure: From genetic linkage analysis to next generation sequencing. Mol Cell Endocrinol 2015; 411:243-57. [PMID: 25960166 DOI: 10.1016/j.mce.2015.05.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/14/2015] [Accepted: 05/04/2015] [Indexed: 01/19/2023]
Abstract
Premature ovarian failure (POF) is a frequent pathology affecting 1-1.5% of women under 40 years old. Despite advances in diagnosing and treating human infertility, POF is still classified as being idiopathic in 50-80% of cases, strongly suggesting a genetic origin for the disease. Different types of autosomal and X-linked genetic anomalies can originate the phenotype in syndromic and non-syndromic POF cases. Particular interest has been focused on research into non-syndromic POF causative coding variants during the past two decades. This has been based on the assumption that amino acid substitutions might modify the intrinsic physicochemical properties of functional proteins, thereby inducing pathological phenotypes. In this case, a restricted number of mutations might originate the disease. However, like other complex pathologies, POF might result from synergistic/compensatory effects caused by several low-to-mildly drastic mutations which have frequently been classified as non-functional SNPs. Indeed, reproductive phenotypes can be considered as quantitative traits resulting from the subtle interaction of many genes. Although numerous sequencing projects have involved candidate genes, only a few coding mutations explaining a low percentage of cases have been described. Such apparent failure to identify aetiological coding sequence variations might have been due to the inherent molecular complexity of mammalian reproduction and to the difficulty of simultaneously analysing large genomic regions by Sanger sequencing. The purpose of this review is to present the molecular and cellular effects caused by non-synonymous mutations which have been formally associated, by functional tests, with the aetiology of hypergonadotropic non-syndromic POF. Considerations have also been included regarding the polygenic nature of reproduction and POF, as well as future approaches for identifying novel aetiological genes based on next generation sequencing (NGS).
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Affiliation(s)
- Paul Laissue
- Unidad de Genética, Grupo GENIUROS, Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia.
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106
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Yartseva V, Giraldez AJ. The Maternal-to-Zygotic Transition During Vertebrate Development: A Model for Reprogramming. Curr Top Dev Biol 2015; 113:191-232. [PMID: 26358874 DOI: 10.1016/bs.ctdb.2015.07.020] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cellular transitions occur at all stages of organismal life from conception to adult regeneration. Changing cellular state involves three main features: activating gene expression necessary to install the new cellular state, modifying the chromatin status to stabilize the new gene expression program, and removing existing gene products to clear out the previous cellular program. The maternal-to-zygotic transition (MZT) is one of the most profound changes in the life of an organism. It involves gene expression remodeling at all levels, including the active clearance of the maternal oocyte program to adopt the embryonic totipotency. In this chapter, we provide an overview of molecular mechanisms driving maternal mRNA clearance during the MZT, describe the developmental consequences of losing components of this gene regulation, and illustrate how remodeling of gene expression during the MZT is common to other cellular transitions with parallels to cellular reprogramming.
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Affiliation(s)
- Valeria Yartseva
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA.
| | - Antonio J Giraldez
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA; Yale Stem Cell Center, Yale University School of Medicine, New Haven, Connecticut, USA.
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107
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Zhang C, Robinson BS, Xu W, Yang L, Yao B, Zhao H, Byun PK, Jin P, Veraksa A, Moberg KH. The ecdysone receptor coactivator Taiman links Yorkie to transcriptional control of germline stem cell factors in somatic tissue. Dev Cell 2015; 34:168-80. [PMID: 26143992 DOI: 10.1016/j.devcel.2015.05.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 04/25/2015] [Accepted: 05/14/2015] [Indexed: 12/16/2022]
Abstract
The Hippo pathway is a conserved signaling cascade that modulates tissue growth. Although its core elements are well defined, factors modulating Hippo transcriptional outputs remain elusive. Here we show that components of the steroid-responsive ecdysone (Ec) pathway modulate Hippo transcriptional effects in imaginal disc cells. The Ec receptor coactivator Taiman (Tai) interacts with the Hippo transcriptional coactivator Yorkie (Yki) and promotes expression of canonical Yki-responsive genes. Tai enhances Yki-driven growth, while Tai loss, or a form of Tai unable to bind Yki, suppresses Yki-driven tissue growth. This growth suppression is not correlated with impaired induction of canonical Hippo-responsive genes but with suppression of a distinct pro-growth program of Yki-induced/Tai-dependent genes, including the germline stem cell factors nanos and piwi. These data reveal Hippo/Ec pathway crosstalk in the form a Yki-Tai complex that collaboratively induces germline genes as part of a transcriptional program that is normally repressed in developing somatic epithelia.
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Affiliation(s)
- Can Zhang
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Brian S Robinson
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Pathology & Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Wenjian Xu
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Liu Yang
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Bing Yao
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Heya Zhao
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Phil K Byun
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA; Graduate Program in Genetics and Molecular Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Peng Jin
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Alexey Veraksa
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Kenneth H Moberg
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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108
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Shapiro-Kulnane L, Smolko AE, Salz HK. Maintenance of Drosophila germline stem cell sexual identity in oogenesis and tumorigenesis. Development 2015; 142:1073-82. [PMID: 25758221 DOI: 10.1242/dev.116590] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Adult stem cells maintain tissue homeostasis by balancing self-renewal and differentiation. In Drosophila females, germline stem cells (GSCs) require Sex lethal (Sxl) to exit the stem cell state and to enter the differentiation pathway. Without Sxl GSCs do not differentiate and instead form tumors. Previous studies have shown that these tumors are not caused by a failure in the self-renewal/differentiation switch. Here, we show that Sxl is also necessary for the cell-autonomous maintenance of germ cell female identity and demonstrate that tumors are caused by the acquisition of male characteristics. Germ cells without Sxl protein exhibit a global derepression of testis genes, including Phf7, a male germline sexual identity gene. Phf7 is a key effector of the tumor-forming pathway, as it is both necessary and sufficient for tumor formation. In the absence of Sxl protein, inappropriate Phf7 expression drives tumor formation through a cell-autonomous mechanism that includes sex-inappropriate activation of Jak/Stat signaling. Remarkably, tumor formation requires a novel response to external signals emanating from the GSC niche, highlighting the importance of interactions between mutant cells and the surrounding normal cells that make up the tumor microenvironment. Derepression of testis genes, and inappropriate Phf7 expression, is also observed in germ cell tumors arising from the loss of bag of marbles (bam), demonstrating that maintenance of female sexual identity requires the concerted actions of Sxl and bam. Our work reveals that GSCs must maintain their sexual identity as they are reprogrammed into a differentiated cell, or risk tumorigenesis.
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Affiliation(s)
- Laura Shapiro-Kulnane
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4955, USA
| | - Anne Elizabeth Smolko
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4955, USA
| | - Helen Karen Salz
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4955, USA
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109
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Laver JD, Li X, Ray D, Cook KB, Hahn NA, Nabeel-Shah S, Kekis M, Luo H, Marsolais AJ, Fung KY, Hughes TR, Westwood JT, Sidhu SS, Morris Q, Lipshitz HD, Smibert CA. Brain tumor is a sequence-specific RNA-binding protein that directs maternal mRNA clearance during the Drosophila maternal-to-zygotic transition. Genome Biol 2015; 16:94. [PMID: 25962635 PMCID: PMC4460960 DOI: 10.1186/s13059-015-0659-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/22/2015] [Indexed: 11/30/2022] Open
Abstract
Background Brain tumor (BRAT) is a Drosophila member of the TRIM-NHL protein family. This family is conserved among metazoans and its members function as post-transcriptional regulators. BRAT was thought to be recruited to mRNAs indirectly through interaction with the RNA-binding protein Pumilio (PUM). However, it has recently been demonstrated that BRAT directly binds to RNA. The precise sequence recognized by BRAT, the extent of BRAT-mediated regulation, and the exact roles of PUM and BRAT in post-transcriptional regulation are unknown. Results Genome-wide identification of transcripts associated with BRAT or with PUM in Drosophila embryos shows that they bind largely non-overlapping sets of mRNAs. BRAT binds mRNAs that encode proteins associated with a variety of functions, many of which are distinct from those implemented by PUM-associated transcripts. Computational analysis of in vitro and in vivo data identified a novel RNA motif recognized by BRAT that confers BRAT-mediated regulation in tissue culture cells. The regulatory status of BRAT-associated mRNAs suggests a prominent role for BRAT in post-transcriptional regulation, including a previously unidentified role in transcript degradation. Transcriptomic analysis of embryos lacking functional BRAT reveals an important role in mediating the decay of hundreds of maternal mRNAs during the maternal-to-zygotic transition. Conclusions Our results represent the first genome-wide analysis of the mRNAs associated with a TRIM-NHL protein and the first identification of an RNA motif bound by this protein family. BRAT is a prominent post-transcriptional regulator in the early embryo through mechanisms that are largely independent of PUM. Electronic supplementary material The online version of this article (doi:10.1186/s13059-015-0659-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- John D Laver
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Xiao Li
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada.
| | - Debashish Ray
- Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada.
| | - Kate B Cook
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada.
| | - Noah A Hahn
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Syed Nabeel-Shah
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Mariana Kekis
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada.
| | - Hua Luo
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Alexander J Marsolais
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Karen Yy Fung
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Timothy R Hughes
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada.
| | - J Timothy Westwood
- Department of Biology, University of Toronto, Mississauga, 3359 Mississauga Road, Mississauga, Ontario, L5L 1C6, Canada.
| | - Sachdev S Sidhu
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada.
| | - Quaid Morris
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Donnelly Centre, University of Toronto, 160 College Street, Toronto, Ontario, M5S 3E1, Canada. .,Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada. .,Department of Computer Science, University of Toronto, 40 St. George Street, Toronto, Ontario, M5S 2E4, Canada.
| | - Howard D Lipshitz
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
| | - Craig A Smibert
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada. .,Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
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110
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Zhang C, Zhu T, Chen Y, Xu EY. Loss of preimplantation embryo resulting from a Pum1 gene trap mutation. Biochem Biophys Res Commun 2015; 462:8-13. [PMID: 25896760 DOI: 10.1016/j.bbrc.2015.04.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 04/03/2015] [Indexed: 11/25/2022]
Abstract
Pumilio is a member of the highly conserved PUF family of RNA-binding proteins that function as a developmental regulator in diverse animal species. Two Pumilio genes, Pum1 and Pum2, have been identified in mammals and are found to be involved in sperm development, neuron development as well as human diseases such as neurodegeneration. Generation of animal models disrupting different parts of Pum protein could help to further dissect their physiological function. Here we described characterization and analysis of a mouse line possessing a gene trap mutation of the Pumilio1 (Pum1) gene. Mice homozygous for the mutation (Pum1(XE002)) cannot be recovered in the adult offspring, at birth or at different time points of embryonic development (E18, E14, E12). Careful analysis of preimplantation embryos showed that no homozygous blastocysts could be detected on day 3.5 of gestation. 96-hr in vitro culture of 1-cell embryos either by natural mating or in vitro fertilization between heterozygotes failed to uncover any homozygous blastocysts, suggesting an early loss of homozygous preimplantation embryos. The lack of Pum1 gene trap homozygotes suggests a role of Pum1 in very early embryonic development or fertilization. This novel animal model affecting the beginning of embryonic development could help to understand not only the genetic mechanism underlying preimplantation embryonic development but also the translational regulation in development and diseases.
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Affiliation(s)
- Chenwang Zhang
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, China
| | - Tong Zhu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, China
| | - Yanmei Chen
- Department of Obstetrics, Gynecology and Reproductive Sciences, Northwestern University, USA
| | - Eugene Yujun Xu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, China.
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111
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Abstract
Stem cells give rise to tissues and organs during development and maintain their integrity during adulthood. They have the potential to self-renew or differentiate at each division. To ensure proper organ growth and homeostasis, self-renewal versus differentiation decisions need to be tightly controlled. Systematic genetic studies in Drosophila melanogaster are revealing extensive regulatory networks that control the switch between stem cell self-renewal and differentiation in the germline. These networks, which are based primarily on mutual translational repression, act via interlocked feedback loops to provide robustness to this important fate decision.
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Affiliation(s)
- Maija Slaidina
- Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016 Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Ruth Lehmann
- Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016 Howard Hughes Medical Institute and Kimmel Center for Biology and Medicine of the Skirball Institute, Department of Cell Biology, New York University School of Medicine, New York, NY 10016
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112
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Adaptive evolution of genes involved in the regulation of germline stem cells in Drosophila melanogaster and D. simulans. G3-GENES GENOMES GENETICS 2015; 5:583-92. [PMID: 25670770 PMCID: PMC4390574 DOI: 10.1534/g3.114.015875] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Population genetic and comparative analyses in diverse taxa have shown that numerous genes involved in reproduction are adaptively evolving. Two genes involved in germline stem cell regulation, bag of marbles (bam) and benign gonial cell neoplasm (bgcn), have been shown previously to experience recurrent, adaptive evolution in both Drosophila melanogaster and D. simulans. Here we report a population genetic survey on eight additional genes involved in germline stem cell regulation in D. melanogaster and D. simulans that reveals all eight of these genes reject a neutral model of evolution in at least one test and one species after correction for multiple testing using a false-discovery rate of 0.05. These genes play diverse roles in the regulation of germline stem cells, suggesting that positive selection in response to several evolutionary pressures may be acting to drive the adaptive evolution of these genes.
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113
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Russo J, Olivas WM. Conditional regulation of Puf1p, Puf4p, and Puf5p activity alters YHB1 mRNA stability for a rapid response to toxic nitric oxide stress in yeast. Mol Biol Cell 2015; 26:1015-29. [PMID: 25631823 PMCID: PMC4357503 DOI: 10.1091/mbc.e14-10-1452] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Puf RNA-binding proteins regulate mRNA stability and translation. This work elucidates the role of three yeast Puf proteins in regulating YHB1 mRNA stability in response to cell stress. Without stress, a precise balance of Puf1p, Puf4p, and Puf5p promotes decay of YHB1. Stress conditions inactivate Pufs to stabilize YHB1 and promote cell fitness. Puf proteins regulate mRNA degradation and translation through interactions with 3′ untranslated regions (UTRs). Such regulation provides an efficient method to rapidly alter protein production during cellular stress. YHB1 encodes the only protein to detoxify nitric oxide in yeast. Here we show that YHB1 mRNA is destabilized by Puf1p, Puf4p, and Puf5p through two overlapping Puf recognition elements (PREs) in the YHB1 3′ UTR. Overexpression of any of the three Pufs is sufficient to fully rescue wild-type decay in the absence of other Pufs, and overexpression of Puf4p or Puf5p can enhance the rate of wild-type decay. YHB1 mRNA decay stimulation by Puf proteins is also responsive to cellular stress. YHB1 mRNA is stabilized in galactose and high culture density, indicating inactivation of the Puf proteins. This condition-specific inactivation of Pufs is overcome by Puf overexpression, and Puf4p/Puf5p overexpression during nitric oxide exposure reduces the steady-state level of endogenous YHB1 mRNA, resulting in slow growth. Puf inactivation is not a result of altered expression or localization. Puf1p and Puf4p can bind target mRNA in inactivating conditions; however, Puf5p binding is reduced. This work demonstrates how multiple Puf proteins coordinately regulate YHB1 mRNA to protect cells from nitric oxide stress.
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Affiliation(s)
- Joseph Russo
- Department of Biology, University of Missouri-St. Louis, St. Louis, MO 63121-4499
| | - Wendy M Olivas
- Department of Biology, University of Missouri-St. Louis, St. Louis, MO 63121-4499
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114
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Laws KM, Sampson LL, Drummond-Barbosa D. Insulin-independent role of adiponectin receptor signaling in Drosophila germline stem cell maintenance. Dev Biol 2015; 399:226-36. [PMID: 25576925 DOI: 10.1016/j.ydbio.2014.12.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 12/02/2014] [Accepted: 12/29/2014] [Indexed: 10/24/2022]
Abstract
Adipocytes have key endocrine roles, mediated in large part by secreted protein hormones termed adipokines. The adipokine adiponectin is well known for its role in sensitizing peripheral tissues to insulin, and several lines of evidence suggest that adiponectin might also modulate stem cells/precursors. It remains unclear, however, how adiponectin signaling controls stem cells and whether this role is secondary to its insulin-sensitizing effects or distinct. Drosophila adipocytes also function as an endocrine organ and, although no obvious adiponectin homolog has been identified, Drosophila AdipoR encodes a well-conserved homolog of mammalian adiponectin receptors. Here, we generate a null AdipoR allele and use clonal analysis to demonstrate an intrinsic requirement for AdipoR in germline stem cell (GSC) maintenance in the Drosophila ovary. AdipoR null GSCs are not fully responsive to bone morphogenetic protein ligands from the niche and have a slight reduction in E-cadherin levels at the GSC-niche junction. Conversely, germline-specific overexpression of AdipoR inhibits natural GSC loss, suggesting that reduction in adiponectin signaling might contribute to the normal decline in GSC numbers observed over time in wild-type females. Surprisingly, AdipoR is not required for insulin sensitization of the germline, leading us to speculate that insulin sensitization is a more recently acquired function than stem cell regulation in the evolutionary history of adiponectin signaling. Our findings establish Drosophila female GSCs as a new system for future studies addressing the molecular mechanisms whereby adiponectin receptor signaling modulates stem cell fate.
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Affiliation(s)
- Kaitlin M Laws
- Department of Biochemistry and Molecular Biology, Division of Reproductive Biology, Baltimore, MD, USA
| | - Leesa L Sampson
- Department of Biochemistry and Molecular Biology, Division of Reproductive Biology, Baltimore, MD, USA
| | - Daniela Drummond-Barbosa
- Department of Biochemistry and Molecular Biology, Division of Reproductive Biology, Baltimore, MD, USA; Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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115
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Dosch R. Next generation mothers: Maternal control of germline development in zebrafish. Crit Rev Biochem Mol Biol 2014; 50:54-68. [DOI: 10.3109/10409238.2014.985816] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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116
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Narita R, Takahasi K, Murakami E, Hirano E, Yamamoto SP, Yoneyama M, Kato H, Fujita T. A novel function of human Pumilio proteins in cytoplasmic sensing of viral infection. PLoS Pathog 2014; 10:e1004417. [PMID: 25340845 PMCID: PMC4207803 DOI: 10.1371/journal.ppat.1004417] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 08/21/2014] [Indexed: 12/24/2022] Open
Abstract
RIG-I-like receptor (RLR) plays a pivotal role in the detection of invading pathogens to initiate type I interferon (IFN) gene transcription. Since aberrant IFN production is harmful, RLR signaling is strictly regulated. However, the regulatory mechanisms are not fully understood. By expression cloning, we identified Pumilio proteins, PUM1 and PUM2, as candidate positive regulators of RIG-I signaling. Overexpression of Pumilio proteins and their knockdown augmented and diminished IFN-β promoter activity induced by Newcastle disease virus (NDV), respectively. Both proteins showed a specific association with LGP2, but not with RIG-I or MDA5. Furthermore, all of these components were recruited to NDV-induced antiviral stress granules. Interestingly, biochemical analyses revealed that Pumilio increased double-stranded (ds) RNA binding affinity of LGP2; however, Pumilio was absent in the dsRNA-LGP2 complex, suggesting that Pumilio facilitates viral RNA recognition by LGP2 through its chaperon-like function. Collectively, our results demonstrate an unknown function of Pumilio in viral recognition by LGP2. Mammals utilize innate immune system to counteract viral infections. The host pattern-recognition receptors, such as RIG-I-like receptors (RLRs), sense invading pathogens and initiate innate immune responses. RLRs are composed of three RNA helicases, RIG-I, MDA5 and LGP2, and detect a series of RNA viruses, such as influenza or hepatitis C virus, in the cytoplasm. Upon RNA virus infection, RLRs transmit signals through mitochondrial adaptor protein, IPS-1, to activate transcription factor IRF-3/7, resulting in the production of type I interferon (IFN). Type I IFN plays a crucial role in innate immune system by inducing a hundreds of interferon-stimulated genes and its induction is tightly controlled at transcriptional and translational steps. Pumilio proteins are originally identified as translational repressor through direct binding to specific sequence motifs in the 3′ untranslated regions of specific mRNA, and regulate critical biological processes, such as development and differentiation. In this report, we identified human Pumilio proteins, PUM1 and PUM2, as candidate regulators of IFN signaling. Our results demonstrated an unknown function of Pumilio in viral recognition by LGP2.
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Affiliation(s)
- Ryo Narita
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Kiyohiro Takahasi
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Institute for Innovative NanoBio Drug Discovery and Development, Graduate School of Pharmaceutical Science, Kyoto University, Kyoto, Japan
| | - Etsu Murakami
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Emi Hirano
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Seiji P. Yamamoto
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Mitsutoshi Yoneyama
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba, Japan
| | - Hiroki Kato
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Takashi Fujita
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- * E-mail:
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117
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Datla US, Scovill NC, Brokamp AJ, Kim E, Asch AS, Lee MH. Role of PUF-8/PUF protein in stem cell control, sperm-oocyte decision and cell fate reprogramming. J Cell Physiol 2014; 229:1306-11. [PMID: 24638209 DOI: 10.1002/jcp.24618] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 03/14/2014] [Indexed: 01/18/2023]
Abstract
Pumilio and FBF (PUF) proteins are conserved stem cell regulators that maintain germline stem cells (GSCs) in worms and flies. Moreover, they are also present in vertebrate stem cells. The nematode Caenorhabditis elegans has multiple PUF proteins with specialized roles. Among them, PUF-8 protein controls multiple cellular processes, including proliferation, differentiation, sperm-oocyte decision, and cell fate reprogramming, depending on the genetic context in the C. elegans germline. In this review, we describe the possible mechanisms of how PUF-8 protein systematically controls multiple cellular processes in the C. elegans germline. Since PUF proteins are evolutionarily conserved, we suggest that a similar mechanism may be involved in controlling stem cell regulation and differentiation in other organisms, including humans.
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Affiliation(s)
- Udaya Sree Datla
- Program in Biomedical Sciences, Brody School of Medicine, East Carolina University, Greenville, North Carolina; Department of Oncology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
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118
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Weidmann CA, Raynard NA, Blewett NH, Van Etten J, Goldstrohm AC. The RNA binding domain of Pumilio antagonizes poly-adenosine binding protein and accelerates deadenylation. RNA (NEW YORK, N.Y.) 2014; 20:1298-319. [PMID: 24942623 PMCID: PMC4105754 DOI: 10.1261/rna.046029.114] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 05/20/2014] [Indexed: 05/24/2023]
Abstract
PUF proteins are potent repressors that serve important roles in stem cell maintenance, neurological processes, and embryonic development. These functions are driven by PUF protein recognition of specific binding sites within the 3' untranslated regions of target mRNAs. In this study, we investigated mechanisms of repression by the founding PUF, Drosophila Pumilio, and its human orthologs. Here, we evaluated a previously proposed model wherein the Pumilio RNA binding domain (RBD) binds Argonaute, which in turn blocks the translational activity of the eukaryotic elongation factor 1A. Surprisingly, we found that Argonautes are not necessary for repression elicited by Drosophila and human PUFs in vivo. A second model proposed that the RBD of Pumilio represses by recruiting deadenylases to shorten the mRNA's polyadenosine tail. Indeed, the RBD binds to the Pop2 deadenylase and accelerates deadenylation; however, this activity is not crucial for regulation. Rather, we determined that the poly(A) is necessary for repression by the RBD. Our results reveal that poly(A)-dependent repression by the RBD requires the poly(A) binding protein, pAbp. Furthermore, we show that repression by the human PUM2 RBD requires the pAbp ortholog, PABPC1. Pumilio associates with pAbp but does not disrupt binding of pAbp to the mRNA. Taken together, our data support a model wherein the Pumilio RBD antagonizes the ability of pAbp to promote translation. Thus, the conserved function of the PUF RBD is to bind specific mRNAs, antagonize pAbp function, and promote deadenylation.
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Affiliation(s)
- Chase A Weidmann
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA Genetics Training Program, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Nathan A Raynard
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA Genetics Training Program, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Nathan H Blewett
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA Program in Cellular and Molecular Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Jamie Van Etten
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Aaron C Goldstrohm
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA Genetics Training Program, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA Program in Cellular and Molecular Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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119
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He J, Xuan T, Xin T, An H, Wang J, Zhao G, Li M. Evidence for chromatin-remodeling complex PBAP-controlled maintenance of the Drosophila ovarian germline stem cells. PLoS One 2014; 9:e103473. [PMID: 25068272 PMCID: PMC4113433 DOI: 10.1371/journal.pone.0103473] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 06/30/2014] [Indexed: 11/19/2022] Open
Abstract
In the Drosophila oogenesis, germline stem cells (GSCs) continuously self-renew and differentiate into daughter cells for consecutive germline lineage commitment. This developmental process has become an in vivo working platform for studying adult stem cell fate regulation. An increasing number of studies have shown that while concerted actions of extrinsic signals from the niche and intrinsic regulatory machineries control GSC self-renewal and germline differentiation, epigenetic regulation is implicated in the process. Here, we report that Brahma (Brm), the ATPase subunit of the Drosophila SWI/SNF chromatin-remodeling complexes, is required for maintaining GSC fate. Removal or knockdown of Brm function in either germline or niche cells causes a GSC loss, but does not disrupt normal germline differentiation within the germarium evidenced at the molecular and morphological levels. There are two Drosophila SWI/SNF complexes: the Brm-associated protein (BAP) complex and the polybromo-containing BAP (PBAP) complex. More genetic studies reveal that mutations in polybromo/bap180, rather than gene encoding Osa, the BAP complex-specific subunit, elicit a defect in GSC maintenance reminiscent of the brm mutant phenotype. Further genetic interaction test suggests a functional association between brm and polybromo in controlling GSC self-renewal. Taken together, studies in this paper provide the first demonstration that Brm in the form of the PBAP complex functions in the GSC fate regulation.
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Affiliation(s)
- Jie He
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Tao Xuan
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, P R China
- * E-mail: (TX); (ML)
| | - Tianchi Xin
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Hongbo An
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Jinye Wang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, P R China
| | - Gengchun Zhao
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
| | - Mingfa Li
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, P R China
- * E-mail: (TX); (ML)
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120
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Choi JY, Aquadro CF. The coevolutionary period of Wolbachia pipientis infecting Drosophila ananassae and its impact on the evolution of the host germline stem cell regulating genes. Mol Biol Evol 2014; 31:2457-71. [PMID: 24974378 DOI: 10.1093/molbev/msu204] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The endosymbiotic bacteria Wolbachia pipientis is known to infect a wide range of arthropod species yet less is known about the coevolutionary history it has with its hosts. Evidence of highly identical W. pipientis strains in evolutionary divergent hosts suggests horizontal transfer between hosts. For example, Drosophila ananassae is infected with a W. pipientis strain that is nearly identical in sequence to a strain that infects both D. simulans and D. suzukii, suggesting recent horizontal transfer among these three species. However, it is unknown whether the W. pipientis strain had recently invaded all three species or a more complex infectious dynamic underlies the horizontal transfers. Here, we have examined the coevolutionary history of D. ananassae and its resident W. pipientis to infer its period of infection. Phylogenetic analysis of D. ananassae mitochondrial DNA and W. pipientis DNA sequence diversity revealed the current W. pipientis infection is not recent. In addition, we examined the population genetics and molecular evolution of several germline stem cell (GSC) regulating genes of D. ananassae. These studies reveal significant evidence of recent and long-term positive selection at stonewall in D. ananassae, whereas pumillio showed patterns of variation consistent with only recent positive selection. Previous studies had found evidence for adaptive evolution of two key germline differentiation genes, bag of marbles (bam) and benign gonial cell neoplasm (bgcn), in D. melanogaster and D. simulans and proposed that the adaptive evolution at these two genes was driven by arms race between the host GSC and W. pipientis. However, we did not find any statistical departures from a neutral model of evolution for bam and bgcn in D. ananassae despite our new evidence that this species has been infected with W. pipientis for a period longer than the most recent infection in D. melanogaster. In the end, analyzing the GSC regulating genes individually showed two of the seven genes to have evidence of selection. However, combining the data set and fitting a specific population genetic model significant proportion of the nonsynonymous sites across the GSC regulating genes were driven to fixation by positive selection. Clearly the GSC system is under rapid evolution and potentially multiple drivers are causing the rapid evolution.
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Affiliation(s)
- Jae Young Choi
- Department of Molecular Biology and Genetics, Cornell University
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121
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Homozygous inactivating mutation in NANOS3 in two sisters with primary ovarian insufficiency. BIOMED RESEARCH INTERNATIONAL 2014; 2014:787465. [PMID: 25054146 PMCID: PMC4098983 DOI: 10.1155/2014/787465] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/30/2014] [Accepted: 06/03/2014] [Indexed: 12/27/2022]
Abstract
Despite the increasing understanding of female reproduction, the molecular diagnosis of primary ovarian insufficiency (POI) is seldom obtained. The RNA-binding protein NANOS3 poses as an interesting candidate gene for POI since members of the Nanos family have an evolutionarily conserved function in germ cell development and maintenance by repressing apoptosis. We performed mutational analysis of NANOS3 in a cohort of 85 Brazilian women with familial or isolated POI, presenting with primary or secondary amenorrhea, and in ethnically-matched control women. A homozygous p.Glu120Lys mutation in NANOS3 was identified in two sisters with primary amenorrhea. The substituted amino acid is located within the second C2HC motif in the conserved zinc finger domain of NANOS3 and in silico molecular modelling suggests destabilization of protein-RNA interaction. In vitro analyses of apoptosis through flow cytometry and confocal microscopy show that NANOS3 capacity to prevent apoptosis was impaired by this mutation. The identification of an inactivating missense mutation in NANOS3 suggests a mechanism for POI involving increased primordial germ cells (PGCs) apoptosis during embryonic cell migration and highlights the importance of NANOS proteins in human ovarian biology.
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122
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Functional analysis of the Drosophila embryonic germ cell transcriptome by RNA interference. PLoS One 2014; 9:e98579. [PMID: 24896584 PMCID: PMC4045815 DOI: 10.1371/journal.pone.0098579] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 05/05/2014] [Indexed: 11/19/2022] Open
Abstract
In Drosophila melanogaster, primordial germ cells are specified at the posterior pole of the very early embryo. This process is regulated by the posterior localized germ plasm that contains a large number of RNAs of maternal origin. Transcription in the primordial germ cells is actively down-regulated until germ cell fate is established. Bulk expression of the zygotic genes commences concomitantly with the degradation of the maternal transcripts. Thus, during embryogenesis, maternally provided and zygotically transcribed mRNAs determine germ cell development collectively. In an effort to identify novel genes involved in the regulation of germ cell behavior, we carried out a large-scale RNAi screen targeting both maternal and zygotic components of the embryonic germ line transcriptome. We identified 48 genes necessary for distinct stages in germ cell development. We found pebble and fascetto to be essential for germ cell migration and germ cell division, respectively. Our data uncover a previously unanticipated role of mei-P26 in maintenance of embryonic germ cell fate. We also performed systematic co-RNAi experiments, through which we found a low rate of functional redundancy among homologous gene pairs. As our data indicate a high degree of evolutionary conservation in genetic regulation of germ cell development, they are likely to provide valuable insights into the biology of the germ line in general.
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123
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Maternal syntabulin is required for dorsal axis formation and is a germ plasm component in Xenopus. Differentiation 2014; 88:17-26. [PMID: 24798204 DOI: 10.1016/j.diff.2014.03.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/20/2014] [Accepted: 03/20/2014] [Indexed: 11/23/2022]
Abstract
In amphibians and teleosts, early embryonic axial development is driven by maternally deposited mRNAs and proteins, called dorsal determinants, which migrate to the presumptive dorsal side of the embryo in a microtubule-dependent manner after fertilization. Syntabulin is an adapter protein that binds to kinesin KIF5B and to the transmembrane protein Syntaxin1. In zebrafish, a mutation in Syntabulin causes complete embryo ventralization. It is unknown whether Syntabulin plays an analogous role during early development of other species, a question addressed here in Xenopus laevis. in situ hybridization of syntabulin mRNA was carried out at different stages of Xenopus development. In oocytes, syntabulin transcripts were localized to the vegetal cortex of large oocytes and the mitochondrial cloud of very young oocytes. We extended the zebrafish data by finding that during cleavage Xenopus syntabulin mRNA localized to the germ plasm and was later expressed in primordial germ cells (PGCs). This new finding suggested a role for Syntabulin during germ cell differentiation. The functional role of maternal syntabulin mRNA was investigated by knock-down with phosphorothioate DNA antisense oligos followed by oocyte transfer. The results showed that syntabulin mRNA depletion caused the complete loss of dorso-anterior axis formation in frog embryos. Consistent with the ventralized phenotype, syntabulin-depleted embryos displayed severe reduction of dorsal markers and ubiquitous transcription of the ventral marker sizzled. Syntabulin was required for the maternal Wnt/β-Catenin signal, since ventralization could be completely rescued by injection of β-catenin (or syntabulin) mRNA. The data suggest an evolutionarily conserved role for Syntabulin, a protein that bridges microtubule motors and membrane vesicles, during dorso-ventral axis formation in the vertebrates.
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124
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A regulatory network of Drosophila germline stem cell self-renewal. Dev Cell 2014; 28:459-73. [PMID: 24576427 DOI: 10.1016/j.devcel.2014.01.020] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 11/24/2013] [Accepted: 01/22/2014] [Indexed: 12/24/2022]
Abstract
Stem cells possess the capacity to generate two cells of distinct fate upon division: one cell retaining stem cell identity and the other cell destined to differentiate. These cell fates are established by cell-type-specific genetic networks. To comprehensively identify components of these networks, we performed a large-scale RNAi screen in Drosophila female germline stem cells (GSCs) covering ∼25% of the genome. The screen identified 366 genes that affect GSC maintenance, differentiation, or other processes involved in oogenesis. Comparison of GSC regulators with neural stem cell self-renewal factors identifies common and cell-type-specific self-renewal genes. Importantly, we identify the histone methyltransferase Set1 as a GSC-specific self-renewal factor. Loss of Set1 in neural stem cells does not affect cell fate decisions, suggesting a differential requirement of H3K4me3 in different stem cell lineages. Altogether, our study provides a resource that will help to further dissect the networks underlying stem cell self-renewal.
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125
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Desjarlais M, Pratt J, Lounis A, Mounier C, Haidara K, Annabi B. Tetracycline derivative minocycline inhibits autophagy and inflammation in concanavalin-a-activated human hepatoma cells. GENE REGULATION AND SYSTEMS BIOLOGY 2014; 8:63-73. [PMID: 24634581 PMCID: PMC3948715 DOI: 10.4137/grsb.s13946] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 01/15/2014] [Accepted: 01/29/2014] [Indexed: 12/16/2022]
Abstract
Inhibition of soluble matrix metalloproteinase (MMP) activity is among the non-antibiotic cellular effects exerted by the anti-inflammatory tetracycline derivative minocycline. The impact of minocycline on the signal transduction functions of membrane-bound MMPs is however unknown. We assessed minocycline in a concanavalin-A (ConA)-activated human HepG2 hepatoma cell model, a condition known to increase the expression of membrane type-1 MMP (MT-MMP) and to trigger inflammatory and autophagy processes. We found that minocycline inhibited ConA-induced formation of autophagic acidic vacuoles, green fluorescent microtubule-associated protein 1 light chain 3 (GFP-LC3) puncta formation, gene and protein expression of autophagy biomarker BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3), invasion biomarker MT1-MMP, and inflammation biomarker cyclooxygenase (COX)-2. Gene silencing of MT1-MMP abrogated ConA-induced formation of autophagic acidic vacuoles and ConA-induced expressions of BNIP3 and COX-2. Minocycline was also shown to inhibit ConA-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation as well as gene expression of NANOS1, a biomarker believed to colocalize with MT1-MMP and the specific silencing of which further inhibited ConA-induced STAT3 phosphorylation. Collectively, our data demonstrate that part of minocycline’s effects on autophagy could be exerted through the inhibition of MT1-MMP signaling functions, which contribute to the autophagy and inflammatory phenotype of ConA-activated HepG2 cells.
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Affiliation(s)
- Michel Desjarlais
- Laboratoire d'Oncologie Moléculaire, Département de Chimie, Université du Québec à Montréal, Québec, Canada
| | - Jonathan Pratt
- Laboratoire d'Oncologie Moléculaire, Département de Chimie, Université du Québec à Montréal, Québec, Canada
| | - Amine Lounis
- Département des Sciences Biologiques, Centre de Recherche BioMed, Université du Québec à Montréal, Quebec, Canada
| | - Catherine Mounier
- Département des Sciences Biologiques, Centre de Recherche BioMed, Université du Québec à Montréal, Quebec, Canada
| | - Khadidja Haidara
- Laboratoire d'Oncologie Moléculaire, Département de Chimie, Université du Québec à Montréal, Québec, Canada
| | - Borhane Annabi
- Laboratoire d'Oncologie Moléculaire, Département de Chimie, Université du Québec à Montréal, Québec, Canada
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Huang T, Kerstetter RA, Irish VF. APUM23, a PUF family protein, functions in leaf development and organ polarity in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:1181-91. [PMID: 24449383 PMCID: PMC3935572 DOI: 10.1093/jxb/ert478] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The normal biological function of leaves, such as intercepting light and exchanging gases, relies on proper differentiation of adaxial and abaxial polarity. KANADI (KAN) genes, members of the GARP family, are key regulators of abaxial identity in leaf morphogenesis. This study identified a mutant allele (apum23-3) of APUM23, which encodes a Pumilio/PUF domain protein and acts as an enhancer of the kan mutant. Arabidopsis APUM23 has been shown to function in pre-rRNA processing and play pleiotropic roles in plant development. The apum23-3 mutant also synergistically interacts with other leaf polarity mutants, affects proliferation of division-competent cells, and alters the expression of important leaf polarity genes. These phenotypes show that APUM23 has critical functions in plant development, particularly in polarity formation. The PUF gene family is conserved across kingdoms yet it has not been well characterized in plants. These results illuminating the functions of APUM23 suggest a novel role for PUF genes in Arabidopsis leaf development.
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Affiliation(s)
- Tengbo Huang
- Department of Plant Biology and Pathology, Waksman Institute, Rutgers, State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8104, USA
- * To whom correspondence should be addressed. E-mail:
| | - Randall A. Kerstetter
- Department of Plant Biology and Pathology, Waksman Institute, Rutgers, State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Vivian F. Irish
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8104, USA
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520-8106, USA
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127
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Oulhen N, Wessel GM. Every which way--nanos gene regulation in echinoderms. Genesis 2014; 52:279-86. [PMID: 24376110 DOI: 10.1002/dvg.22737] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 12/16/2013] [Indexed: 12/12/2022]
Abstract
Nanos is an essential factor of germ line success in all animals tested. This gene encodes a Zn-finger RNA-binding protein that in complex with its partner pumilio binds to and changes the fate of several known transcripts. We summarize here the documented functions of Nanos in several key organisms, and then emphasize echinoderms as a working model for how nanos expression is regulated. Nanos presence outside of the target cells is often detrimental to the animal, and in sea urchins, nanos expression appears to be regulated at every step of transcription, and post-transcriptional activity, making this gene product exciting, every which way.
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Affiliation(s)
- Nathalie Oulhen
- Department of Molecular and Cell Biology and Biochemistry, Brown University, Providence, Rhode Island
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128
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Xin T, Xuan T, Tan J, Li M, Zhao G, Li M. The Drosophila putative histone acetyltransferase Enok maintains female germline stem cells through regulating Bruno and the niche. Dev Biol 2013; 384:1-12. [PMID: 24120347 DOI: 10.1016/j.ydbio.2013.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/29/2013] [Accepted: 10/02/2013] [Indexed: 12/16/2022]
Abstract
Maintenance of adult stem cells is largely dependent on the balance between their self-renewal and differentiation. The Drosophila ovarian germline stem cells (GSCs) provide a powerful in vivo system for studying stem cell fate regulation. It has been shown that maintaining the GSC population involves both genetic and epigenetic mechanisms. Although the role of epigenetic regulation in this process is evident, the underlying mechanisms remain to be further explored. In this study, we find that Enoki mushroom (Enok), a Drosophila putative MYST family histone acetyltransferase controls GSC maintenance in the ovary at multiple levels. Removal or knockdown of Enok in the germline causes a GSC maintenance defect. Further studies show that the cell-autonomous role of Enok in maintaining GSCs is not dependent on the BMP/Bam pathway. Interestingly, molecular studies reveal an ectopic expression of Bruno, an RNA binding protein, in the GSCs and their differentiating daughter cells elicited by the germline Enok deficiency. Misexpression of Bruno in GSCs and their immediate descendants results in a GSC loss that can be exacerbated by incorporating one copy of enok mutant allele. These data suggest a role for Bruno in Enok-controlled GSC maintenance. In addition, we observe that Enok is required for maintaining GSCs non-autonomously. Compromised expression of enok in the niche cells impairs the niche maintenance and BMP signal output, thereby causing defective GSC maintenance. This is the first demonstration that the niche size control requires an epigenetic mechanism. Taken together, studies in this paper provide new insights into the GSC fate regulation.
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Affiliation(s)
- Tianchi Xin
- MoE Key Laboratory of Developmental Genetics and Neuropsychiatric Diseases, Bio-X Institutes, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240 Shanghai, PR China
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129
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Pushpa K, Kumar GA, Subramaniam K. PUF-8 and TCER-1 are essential for normal levels of multiple mRNAs in the C. elegans germline. Development 2013; 140:1312-20. [PMID: 23444359 PMCID: PMC3585663 DOI: 10.1242/dev.087833] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PUF family proteins are well-conserved regulators of cell proliferation in different developmental processes. They regulate target mRNAs by promoting degradation or by influencing translation through interaction with the translation initiation machinery. Here we show that Caenorhabditis elegans PUF-8 functions redundantly with the nuclear protein TCER-1 in the post-transcriptional maintenance of at least six germline mRNAs. The levels of spliced mRNAs in the puf-8(-) tcer-1(-) double mutant are only 10-30% of the wild type, whereas the unspliced forms increase by ∼2- to 3-fold compared with the wild type. These two proteins colocalise at the inner nuclear periphery, and their absence leads to reduced germ cell proliferation and to sterility. A yeast two-hybrid screen of 31 components of the nuclear pore complex and mRNA processing machineries identified seven proteins involved in mRNA export as potential partners of PUF-8. One of these, the nuclear cap-binding protein NCBP-2, colocalises with PUF-8 in the nucleus. A 50 amino acid N-terminal domain of PUF-8 is essential for interaction with NCBP-2 and for PUF-8 to function redundantly with TCER-1. These results reveal two important unexpected aspects of PUF proteins: that, in addition to the C-terminal PUF domain, the N-terminal domain is crucial for PUF function, and that PUF proteins have a novel role in mRNA maintenance. We propose that PUF proteins, in addition to their known cytoplasmic roles, participate in nuclear processing and/or export of mRNAs.
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Affiliation(s)
- Kumari Pushpa
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
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130
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Li Y, Zhang Q, Carreira-Rosario A, Maines JZ, McKearin DM, Buszczak M. Mei-p26 cooperates with Bam, Bgcn and Sxl to promote early germline development in the Drosophila ovary. PLoS One 2013; 8:e58301. [PMID: 23526974 PMCID: PMC3603962 DOI: 10.1371/journal.pone.0058301] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 02/01/2013] [Indexed: 01/17/2023] Open
Abstract
In the Drosophila female germline, spatially and temporally specific translation of mRNAs governs both stem cell maintenance and the differentiation of their progeny. However, the mechanisms that control and coordinate different modes of translational repression within this lineage remain incompletely understood. Here we present data showing that Mei-P26 associates with Bam, Bgcn and Sxl and nanos mRNA during early cyst development, suggesting that this protein helps to repress the translation of nanos mRNA. Together with recently published studies, these data suggest that Mei-P26 mediates both GSC self-renewal and germline differentiation through distinct modes of translational repression depending on the presence of Bam.
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Affiliation(s)
- Yun Li
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Qiao Zhang
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Arnaldo Carreira-Rosario
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Jean Z. Maines
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Dennis M. McKearin
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Michael Buszczak
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- * E-mail:
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131
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Seervai RNH, Wessel GM. Lessons for inductive germline determination. Mol Reprod Dev 2013; 80:590-609. [PMID: 23450642 DOI: 10.1002/mrd.22151] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 01/03/2013] [Indexed: 12/25/2022]
Abstract
Formation of the germline in an embryo marks a fresh round of reproductive potential, yet the developmental stage and location within the embryo where the primordial germ cells (PGCs) form differs wildly among species. In most animals, the germline is formed either by an inherited mechanism, in which maternal provisions within the oocyte drive localized germ-cell fate once acquired in the embryo, or an inductive mechanism that involves signaling between cells that directs germ-cell fate. The inherited mechanism has been widely studied in model organisms such as Drosophila melanogaster, Caenorhabditis elegans, Xenopus laevis, and Danio rerio. Given the rapid generation time and the effective adaptation for laboratory research of these organisms, it is not coincidental that research on these organisms has led the field in elucidating mechanisms for germline specification. The inductive mechanism, however, is less well understood and is studied primarily in the mouse (Mus musculus). In this review, we compare and contrast these two fundamental mechanisms for germline determination, beginning with the key molecular determinants that play a role in the formation of germ cells across all animal taxa. We next explore the current understanding of the inductive mechanism of germ-cell determination in mice, and evaluate the hypotheses for selective pressures on these contrasting mechanisms. We then discuss the hypothesis that the transition between these determination mechanisms, which has happened many times in phylogeny, is more of a continuum than a binary change. Finally, we propose an analogy between germline determination and sex determination in vertebrates-two of the milestones of reproduction and development-in which animals use contrasting strategies to activate similar pathways.
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Affiliation(s)
- Riyad N H Seervai
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, 02192, USA
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132
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Menon KP, Carrillo RA, Zinn K. Development and plasticity of the Drosophila larval neuromuscular junction. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 2:647-70. [PMID: 24014452 DOI: 10.1002/wdev.108] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Drosophila larval neuromuscular system is relatively simple, containing only 32 motor neurons in each abdominal hemisegment, and its neuromuscular junctions (NMJs) have been studied extensively. NMJ synapses exhibit developmental and functional plasticity while displaying stereotyped connectivity. Drosophila Type I NMJ synapses are glutamatergic, while the vertebrate NMJ uses acetylcholine as its primary neurotransmitter. The larval NMJ synapses use ionotropic glutamate receptors (GluRs) that are homologous to AMPA-type GluRs in the mammalian brain, and they have postsynaptic scaffolds that resemble those found in mammalian postsynaptic densities. These features make the Drosophila neuromuscular system an excellent genetic model for the study of excitatory synapses in the mammalian central nervous system. The first section of the review presents an overview of NMJ development. The second section describes genes that regulate NMJ development, including: (1) genes that positively and negatively regulate growth of the NMJ, (2) genes required for maintenance of NMJ bouton structure, (3) genes that modulate neuronal activity and alter NMJ growth, (4) genes involved in transsynaptic signaling at the NMJ. The third section describes genes that regulate acute plasticity, focusing on translational regulatory mechanisms. As this review is intended for a developmental biology audience, it does not cover NMJ electrophysiology in detail, and does not review genes for which mutations produce only electrophysiological but no structural phenotypes.
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Affiliation(s)
- Kaushiki P Menon
- Broad Center, Division of Biology, California Institute of Technology, Pasadena, CA, USA
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133
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Beer RL, Draper BW. nanos3 maintains germline stem cells and expression of the conserved germline stem cell gene nanos2 in the zebrafish ovary. Dev Biol 2013; 374:308-18. [DOI: 10.1016/j.ydbio.2012.12.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 11/30/2012] [Accepted: 12/04/2012] [Indexed: 01/17/2023]
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134
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Oulhen N, Yoshida T, Yajima M, Song JL, Sakuma T, Sakamoto N, Yamamoto T, Wessel GM. The 3'UTR of nanos2 directs enrichment in the germ cell lineage of the sea urchin. Dev Biol 2013; 377:275-83. [PMID: 23357540 DOI: 10.1016/j.ydbio.2013.01.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 01/15/2013] [Accepted: 01/18/2013] [Indexed: 12/30/2022]
Abstract
Nanos is a translational regulator required for the survival and maintenance of primordial germ cells during embryogenesis. Three nanos homologs are present in the genome of the sea urchin Strongylocentrotus purpuratus (Sp), and each nanos mRNA accumulates specifically in the small micromere (sMic) lineage. We found that a highly conserved element in the 3' UTR of nanos2 is sufficient for reporter expression selectively in the sMic lineage: microinjection into a Sp fertilized egg of an RNA that contains the GFP open reading frame followed by Sp nanos2 3'UTR leads to selective reporter enrichment in the small micromeres in blastulae. The same result was seen with nanos2 from the sea urchin Hemicentrotus pulcherrimus (Hp). In both species, the 5'UTR alone is not sufficient for the sMic localization but it always increased the sMic reporter enrichment when present with the 3'UTR. We defined an element conserved between Hp and Sp in the nanos2 3'UTR which is necessary and sufficient for protein enrichment in the sMic, and refer to it as GNARLE (Global Nanos Associated RNA Lability Element). We also found that the nanos2 3'UTR is essential for the selective RNA retention in the small micromeres; GNARLE is required but not sufficient for this process. These results show that a combination of selective RNA retention and translational control mechanisms instills nanos accumulation uniquely in the sMic lineage.
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Affiliation(s)
- Nathalie Oulhen
- Department of Molecular and Cell Biology and Biochemistry, Brown University, 185 Meeting Street, Providence, RI 02912, USA
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135
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Abstract
One of the most important and evolutionarily conserved strategies to control gene expression in higher metazoa is posttranscriptional regulation via small regulatory RNAs such as microRNAs (miRNAs), endogenous small interfering RNAs (endo-siRNAs), and piwi-interacting RNAs (piRNAs). Primordial germ cells, which are defined by their totipotent potential and noted for their dependence on posttranscriptional regulation by RNA-binding proteins, rely on these small regulatory RNAs for virtually every aspect of their development, including specification, migration, and differentiation into competent gametes. Here, we review current knowledge of the roles miRNAs, endo-siRNAs, and piRNAs play at all stages of germline development in various organisms, focusing on studies in the mouse.
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Affiliation(s)
- Matthew S Cook
- Department of Urology, University of California, San Francisco, California, USA.
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136
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Kershner A, Crittenden SL, Friend K, Sorensen EB, Porter DF, Kimble J. Germline stem cells and their regulation in the nematode Caenorhabditis elegans. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 786:29-46. [PMID: 23696350 DOI: 10.1007/978-94-007-6621-1_3] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
C. elegans germline stem cells exist within a stem cell pool that is maintained by a single-celled mesenchymal niche and Notch signaling. Downstream of Notch signaling, a regulatory network governs stem cells and differentiation. Central to that network is the FBF RNA-binding protein, a member of the widely conserved PUF family that functions by either of two broadly conserved mechanisms to repress its target mRNAs. Without FBF, germline stem cells do not proliferate and they do not maintain their naïve, undifferentiated state. Therefore, FBF is a pivotal regulator of germline self-renewal. Validated FBF targets include several key differentiation regulators as well as a major cell cycle regulator. A genomic analysis identifies many other developmental and cell cycle regulators as likely FBF targets and suggests that FBF is a broad-spectrum regulator of the genome with >1,000 targets. A comparison of the FBF target list with similar lists for human PUF proteins, PUM1 and PUM2, reveals ∼200 shared targets. The FBF hub works within a network controlling self-renewal vs. differentiation. This network consists of classical developmental cell fate regulators and classical cell cycle regulators. Recent results have begun to integrate developmental and cell cycle regulation within the network. The molecular dynamics of the network remain a challenge for the future, but models are proposed. We suggest that molecular controls of C. elegans germline stem cells provide an important model for controls of stem cells more broadly.
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Affiliation(s)
- Aaron Kershner
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706, USA
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137
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Abstract
The Drosophila Sex-lethal (Sxl) gene encodes a female-specific RNA binding protein that in somatic cells globally regulates all aspects of female-specific development and behavior. Sxl also has a critical, but less well understood, role in female germ cells. Germ cells without Sxl protein can adopt a stem cell fate when housed in a normal ovary, but fail to successfully execute the self-renewal differentiation fate switch. The failure to differentiate is accompanied by the inappropriate expression of a set of male specific markers, continued proliferation, and formation of a tumor. The findings in Chau et al., (2012) identify the germline stem cell maintenance factor nanos as one of its target genes, and suggest that Sxl enables the switch from germline stem cell to committed daughter cell by posttranscriptional downregulation of nanos expression. These studies provide the basis for a new model in which Sxl directly couples sexual identity with the self-renewal differentiation decision and raises several interesting questions about the genesis of the tumor phenotype.
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Affiliation(s)
- Helen K Salz
- Department of Genetics and Genome Sciences, Case Western Reserve University, School of Medicine, Cleveland, OH, USA.
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138
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Abstract
Germline stem cells are key to genome transmission to future generations. Over recent years, there have been numerous insights into the regulatory mechanisms that govern both germ cell specification and the maintenance of the germline in adults. Complex regulatory interactions with both the niche and the environment modulate germline stem cell function. This perspective highlights some examples of this regulation to illustrate the diversity and complexity of the mechanisms involved.
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Affiliation(s)
- Ruth Lehmann
- Howard Hughes Medical Institute; Skirball Institute, The Helen L. and Martin S. Kimmel Center for Stem Cell Biology, Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.
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139
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PUF-8, a Pumilio homolog, inhibits the proliferative fate in the Caenorhabditis elegans germline. G3-GENES GENOMES GENETICS 2012; 2:1197-205. [PMID: 23050230 PMCID: PMC3464112 DOI: 10.1534/g3.112.003350] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 08/06/2012] [Indexed: 01/10/2023]
Abstract
Stem cell populations are maintained by keeping a balance between self-renewal (proliferation) and differentiation of dividing stem cells. Within the Caenorhabditis elegans germline, the key regulator maintaining this balance is the canonical Notch signaling pathway, with GLP-1/Notch activity promoting the proliferative fate. We identified the Pumilio homolog, PUF-8, as an inhibitor of the proliferative fate of stem cells in the C. elegans germline. puf-8(0) strongly enhances overproliferation of glp-1(gf) mutants and partially suppresses underproliferation of a weak glp-1(lf) mutant. The germline tumor that is formed in a puf-8(0); glp-1(gf) double mutant is due to a failure of germ cells to enter meiotic prophase. puf-8 likely inhibits the proliferative fate through negatively regulating GLP-1/Notch signaling or by functioning parallel to it.
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140
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A eukaryotic translation initiation factor 4E-binding protein promotes mRNA decapping and is required for PUF repression. Mol Cell Biol 2012; 32:4181-94. [PMID: 22890846 DOI: 10.1128/mcb.00483-12] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
PUF proteins are eukaryotic RNA-binding proteins that repress specific mRNAs. The mechanisms and corepressors involved in PUF repression remain to be fully identified. Here, we investigated the mode of repression by Saccharomyces cerevisiae Puf5p and Puf4p and found that Puf5p specifically requires Eap1p to repress mRNAs, whereas Puf4p does not. Surprisingly, we observed that Eap1p, which is a member of the eukaryotic translation initiation factor 4E (eIF4E)-binding protein (4E-BP) class of translational inhibitors, does not inhibit the efficient polyribosome association of a Puf5p target mRNA. Rather, we found that Eap1p accelerates mRNA degradation by promoting decapping, and the ability of Eap1p to interact with eIF4E facilitates this activity. Deletion of EAP1 dramatically reduces decapping, resulting in accumulation of deadenylated, capped mRNA. In support of this phenotype, Eap1p associates both with Puf5p and the Dhh1p decapping factor. Furthermore, recruitment of Eap1p to downregulated mRNA is mediated by Puf5p. On the basis of these results, we propose that Puf5p promotes decapping by recruiting Eap1p and associated decapping factors to mRNAs. The implication of these findings is that a 4E-BP can repress protein expression by promoting specific mRNA degradation steps in addition to or in lieu of inhibiting translation initiation.
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141
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Cha DS, Datla US, Hollis SE, Kimble J, Lee MH. The Ras-ERK MAPK regulatory network controls dedifferentiation in Caenorhabditis elegans germline. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1847-55. [PMID: 22820175 DOI: 10.1016/j.bbamcr.2012.07.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 07/10/2012] [Accepted: 07/11/2012] [Indexed: 11/19/2022]
Abstract
How a committed cell can be reverted to an undifferentiated state is a central question in stem cell biology. This process, called dedifferentiation, is likely to be important for replacing stem cells as they age or get damaged. Tremendous progress has been made in understanding this fundamental process, but its mechanisms are poorly understood. Here we demonstrate that the aberrant activation of Ras-ERK MAPK signaling promotes cellular dedifferentiation in the Caenorhabditis elegans germline. To activate signaling, we removed two negative regulators, the PUF-8 RNA-binding protein and LIP-1 dual specificity phosphatase. The removal of both of these two regulators caused secondary spermatocytes to dedifferentiate and begin mitotic divisions. Interestingly, reduction of Ras-ERK MAPK signaling, either by mutation or chemical inhibition, blocked the initiation of dedifferentiation. By RNAi screening, we identified RSKN-1/P90(RSK) as a downstream effector of MPK-1/ERK that is critical for dedifferentiation: rskn-1 RNAi suppressed spermatocyte dedifferentiation and instead induced meiotic divisions. These regulators are broadly conserved, suggesting that similar molecular circuitry may control cellular dedifferentiation in other organisms, including humans.
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Affiliation(s)
- Dong Seok Cha
- Division of Hematology/Oncology, Department of Medicine, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
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142
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Sex-lethal enables germline stem cell differentiation by down-regulating Nanos protein levels during Drosophila oogenesis. Proc Natl Acad Sci U S A 2012; 109:9465-70. [PMID: 22645327 DOI: 10.1073/pnas.1120473109] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Drosophila ovarian germ cells require Sex-lethal (Sxl) to exit from the stem cell state and to enter the differentiation pathway. Sxl encodes a female-specific RNA binding protein and in somatic cells serves as the developmental switch gene for somatic sex determination and X-chromosome dosage compensation. None of the known Sxl target genes are required for germline differentiation, leaving open the question of how Sxl promotes the transition from stem cell to committed daughter cell. We address the mechanism by which Sxl regulates this transition through the identification of nanos as one of its target genes. Previous studies have shown that Nanos protein is necessary for GSC self-renewal and is rapidly down-regulated in the daughter cells fated to differentiate in the adult ovary. We find that this dynamic expression pattern is limited to female germ cells and is under Sxl control. In the absence of Sxl, or in male germ cells, Nanos protein is continuously expressed. Furthermore, this female-specific expression pattern is dependent on the presence of canonical Sxl binding sites located in the nanos 3' untranslated region. These results, combined with the observation that nanos RNA associates with the Sxl protein in ovarian extracts and loss and gain of function studies, suggest that Sxl enables the switch from germline stem cell to committed daughter cell by posttranscriptional down-regulation of nanos expression. These findings connect sexual identity to the stem cell self-renewal/differentiation decision and highlight the importance of posttranscriptional gene regulatory networks in controlling stem cell behavior.
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143
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Xie T. Control of germline stem cell self-renewal and differentiation in the Drosophila ovary: concerted actions of niche signals and intrinsic factors. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:261-73. [PMID: 24009036 DOI: 10.1002/wdev.60] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the Drosophila ovary, germline stem cells (GSCs) physically interact with their niche composed of terminal filament cells, cap cells, and possibly GSC-contacting escort cells (ECs). A GSC divides to generate a self-renewing stem cell that remains in the niche and a differentiating daughter that moves away from the niche. The GSC niche provides a bone morphogenetic protein (BMP) signal that maintains GSC self-renewal by preventing stem cell differentiation via repression of the differentiation-promoting gene bag of marbles (bam). In addition, it expresses E-cadherin, which mediates cell adhesion for anchoring GSCs in the niche, enabling continuous self-renewal. GSCs themselves also express different classes of intrinsic factors, including signal transducers, transcription factors, chromatin remodeling factors, translation regulators, and miRNAs, which control self-renewal by strengthening interactions with the niche and repressing various differentiation pathways. Differentiated GSC daughters, known as cystoblasts (CBs), also express distinct classes of intrinsic factors to inhibit self-renewal and promote germ cell differentiation. Surprisingly, GSC progeny are also dependent on their surrounding ECs for proper differentiation at least partly by preventing BMP from diffusing to the differentiated germ cell zone and by repressing ectopic BMP expression. Therefore, both GSC self-renewal and CB differentiation are controlled by collaborative actions of extrinsic signals and intrinsic factors.
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Affiliation(s)
- Ting Xie
- Stowers Institute for Medical Research, Kansas City, MO, USA; Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, USA.
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144
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Kim SY, Kim JY, Malik S, Son W, Kwon KS, Kim C. Negative regulation of EGFR/MAPK pathway by Pumilio in Drosophila melanogaster. PLoS One 2012; 7:e34016. [PMID: 22514614 PMCID: PMC3326002 DOI: 10.1371/journal.pone.0034016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Accepted: 02/21/2012] [Indexed: 12/19/2022] Open
Abstract
In Drosophila melanogaster, specification of wing vein cells and sensory organ precursor (SOP) cells, which later give rise to a bristle, requires EGFR signaling. Here, we show that Pumilio (Pum), an RNA-binding translational repressor, negatively regulates EGFR signaling in wing vein and bristle development. We observed that loss of Pum function yielded extra wing veins and additional bristles. Conversely, overexpression of Pum eliminated wing veins and bristles. Heterozygotes for Pum produced no phenotype on their own, but greatly enhanced phenotypes caused by the enhancement of EGFR signaling. Conversely, over-expression of Pum suppressed the effects of ectopic EGFR signaling. Components of the EGFR signaling pathway are encoded by mRNAs that have Nanos Response Element (NRE)–like sequences in their 3’UTRs; NREs are known to bind Pum to confer regulation in other mRNAs. We show that these NRE-like sequences bind Pum and confer repression on a luciferase reporter in heterologous cells. Taken together, our evidence suggests that Pum functions as a negative regulator of EGFR signaling by directly targeting components of the pathway in Drosophila.
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Affiliation(s)
- Sung Yun Kim
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
| | - Ji Young Kim
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Yuseong-gu, Daejeon, South Korea
| | - Sumira Malik
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
| | - Wonseok Son
- Department of Biological Science, KAIST (Korea Advanced Institute of Science and Technology), Daejeon, South Korea
| | - Ki-Sun Kwon
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Yuseong-gu, Daejeon, South Korea
| | - Changsoo Kim
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
- * E-mail:
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145
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Kobayashi K, Maezawa T, Nakagawa H, Hoshi M. Existence of Two Sexual Races in the Planarian Species Switching between Asexual and Sexual Reproduction. Zoolog Sci 2012; 29:265-72. [DOI: 10.2108/zsj.29.265] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Kazuya Kobayashi
- Center for Integrated Medical Research, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160–8582, Japan
| | - Takanobu Maezawa
- Center for Integrated Medical Research, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160–8582, Japan
| | - Haruka Nakagawa
- Center for Integrated Medical Research, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160–8582, Japan
| | - Motonori Hoshi
- The Open University of Japan, 2–11 Wakaba, Mihama-ku, Chiba 261–8586, Japan
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146
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Li Y, Maines JZ, Tastan OY, McKearin DM, Buszczak M. Mei-P26 regulates the maintenance of ovarian germline stem cells by promoting BMP signaling. Development 2012; 139:1547-56. [PMID: 22438571 DOI: 10.1242/dev.077412] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the Drosophila ovary, bone morphogenetic protein (BMP) ligands maintain germline stem cells (GSCs) in an undifferentiated state. The activation of the BMP pathway within GSCs results in the transcriptional repression of the differentiation factor bag of marbles (bam). The Nanos-Pumilio translational repressor complex and the miRNA pathway also help to promote GSC self-renewal. How the activities of different transcriptional and translational regulators are coordinated to keep the GSC in an undifferentiated state remains uncertain. Data presented here show that Mei-P26 cell-autonomously regulates GSC maintenance in addition to its previously described role of promoting germline cyst development. Within undifferentiated germ cells, Mei-P26 associates with miRNA pathway components and represses the translation of a shared target mRNA, suggesting that Mei-P26 can enhance miRNA-mediated silencing in specific contexts. In addition, disruption of mei-P26 compromises BMP signaling, resulting in the inappropriate expression of bam in germ cells immediately adjacent to the cap cell niche. Loss of mei-P26 results in premature translation of the BMP antagonist Brat in germline stem cells. These data suggest that Mei-P26 has distinct functions in the ovary and participates in regulating the fates of both GSCs and their differentiating daughters.
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Affiliation(s)
- Yun Li
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9148, USA
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147
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Lai F, Singh A, King ML. Xenopus Nanos1 is required to prevent endoderm gene expression and apoptosis in primordial germ cells. Development 2012; 139:1476-86. [PMID: 22399685 DOI: 10.1242/dev.079608] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Nanos is expressed in multipotent cells, stem cells and primordial germ cells (PGCs) of organisms as diverse as jellyfish and humans. It functions together with Pumilio to translationally repress targeted mRNAs. Here we show by loss-of-function experiments that Xenopus Nanos1 is required to preserve PGC fate. Morpholino knockdown of maternal Nanos1 resulted in a striking decrease in PGCs and a loss of germ cells from the gonads. Lineage tracing and TUNEL staining reveal that Nanos1-deficient PGCs fail to migrate out of the endoderm. They appear to undergo apoptosis rather than convert to normal endoderm. Whereas normal PGCs do not become transcriptionally active until neurula, Nanos1-depleted PGCs prematurely exhibit a hyperphosphorylated RNA polymerase II C-terminal domain at the midblastula transition. Furthermore, they inappropriately express somatic genes characteristic of endoderm regulated by maternal VegT, including Xsox17α, Bix4, Mixer, GATA4 and Edd. We further demonstrate that Pumilio specifically binds VegT RNA in vitro and represses, along with Nanos1, VegT translation within PGCs. Repressed VegT RNA in wild-type PGCs is significantly less stable than VegT in Nanos1-depleted PGCs. Our data indicate that maternal VegT RNA is an authentic target of Nanos1/Pumilio translational repression. We propose that Nanos1 functions to translationally repress RNAs that normally specify endoderm and promote apoptosis, thus preserving the germline.
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Affiliation(s)
- Fangfang Lai
- Department of Cell Biology, University of Miami School of Medicine, 1011 NW 15th St, Miami, FL 33136, USA
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148
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Olesnicky EC, Bhogal B, Gavis ER. Combinatorial use of translational co-factors for cell type-specific regulation during neuronal morphogenesis in Drosophila. Dev Biol 2012; 365:208-18. [PMID: 22391052 DOI: 10.1016/j.ydbio.2012.02.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 02/15/2012] [Accepted: 02/20/2012] [Indexed: 11/26/2022]
Abstract
The translational regulators Nanos (Nos) and Pumilio (Pum) work together to regulate the morphogenesis of dendritic arborization (da) neurons of the Drosophila larval peripheral nervous system. In contrast, Nos and Pum function in opposition to one another in the neuromuscular junction to regulate the morphogenesis and the electrophysiological properties of synaptic boutons. Neither the cellular functions of Nos and Pum nor their regulatory targets in neuronal morphogenesis are known. Here we show that Nos and Pum are required to maintain the dendritic complexity of da neurons during larval growth by promoting the outgrowth of new dendritic branches and the stabilization of existing dendritic branches, in part by regulating the expression of cut and head involution defective. Through an RNA interference screen we uncover a role for the translational co-factor Brain Tumor (Brat) in dendrite morphogenesis of da neurons and demonstrate that Nos, Pum, and Brat interact genetically to regulate dendrite morphogenesis. In the neuromuscular junction, Brat function is most likely specific for Pum in the presynaptic regulation of bouton morphogenesis. Our results reveal how the combinatorial use of co-regulators like Nos, Pum and Brat can diversify their roles in post-transcriptional regulation of gene expression for neuronal morphogenesis.
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Affiliation(s)
- Eugenia C Olesnicky
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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149
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Chen D, Zheng W, Lin A, Uyhazi K, Zhao H, Lin H. Pumilio 1 suppresses multiple activators of p53 to safeguard spermatogenesis. Curr Biol 2012; 22:420-5. [PMID: 22342750 DOI: 10.1016/j.cub.2012.01.039] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 12/14/2011] [Accepted: 01/17/2012] [Indexed: 10/28/2022]
Abstract
During spermatogenesis, germ cells initially expand exponentially through mitoses. A majority of these cells are then eliminated through p53-mediated apoptosis to maintain germline homeostasis. However, the activity of p53 must be precisely modulated, especially suppressed in postmitotic spermatogenic cells, to guarantee robustness of spermatogenesis. Currently, how the suppression is achieved is not understood. Here, we show that Pumilio 1, a posttranscriptional regulator, binds to mRNAs representing 1,527 genes, with significant enrichment for mRNAs involved in pathways regulating p53, cell cycle, and MAPK signaling. In particular, eight mRNAs encoding activators of p53 are repressed by Pumilio 1. Deleting Pumilio 1 results in strong activation of p53 and apoptosis mostly in spermatocytes, which disrupts sperm production and fertility. Removing p53 reduces apoptosis and rescues testicular hypotrophy in Pumilio 1 null mice. These results indicate that key components of the p53 pathway are coordinately regulated by Pumilio 1 at the posttranscriptional level, which may exemplify an RNA operon.
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Affiliation(s)
- Dong Chen
- Yale Stem Cell Center and Department of Cell Biology, Yale School of Medicine, New Haven, CT 06519, USA
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150
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King ML, Messitt TJ, Mowry KL. Putting RNAs in the right place at the right time: RNA localization in the frog oocyte. Biol Cell 2012; 97:19-33. [PMID: 15601255 DOI: 10.1042/bc20040067] [Citation(s) in RCA: 243] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Localization of maternal mRNAs in many developing organisms provides the basis for both initial polarity during oogenesis and patterning during embryogenesis. Prominent examples of this phenomenon are found in Xenopus laevis, where localized maternal mRNAs generate developmental polarity along the animal/vegetal axis. Targeting of mRNA molecules to specific subcellular regions is a fundamental mechanism for spatial regulation of gene expression, and considerable progress has been made in defining the underlying molecular pathways.
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Affiliation(s)
- Mary Lou King
- Department of Cell Biology and Anatomy, University of Miami School of Medicine, 1011 NW 15th St., Miami, FL 33136, USA.
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