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Bloom JC, Schimenti JC. Sexually dimorphic DNA damage responses and mutation avoidance in the mouse germline. Genes Dev 2020; 34:1637-1649. [PMID: 33184219 PMCID: PMC7706705 DOI: 10.1101/gad.341602.120] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 10/07/2020] [Indexed: 12/20/2022]
Abstract
In this study, Bloom and Schimenti examine the response of primordial germ cells to DNA damage. Using both environmental and genetic stresses, the authors reveal the importance of the G1 checkpoint in preventing accumulation of complex mutations in the germline, and the differentiation of the DNA damage response during germ cell development. Germ cells specified during fetal development form the foundation of the mammalian germline. These primordial germ cells (PGCs) undergo rapid proliferation, yet the germline is highly refractory to mutation accumulation compared with somatic cells. Importantly, while the presence of endogenous or exogenous DNA damage has the potential to impact PGCs, there is little known about how these cells respond to stressors. To better understand the DNA damage response (DDR) in these cells, we exposed pregnant mice to ionizing radiation (IR) at specific gestational time points and assessed the DDR in PGCs. Our results show that PGCs prior to sex determination lack a G1 cell cycle checkpoint. Additionally, the response to IR-induced DNA damage differs between female and male PGCs post-sex determination. IR of female PGCs caused uncoupling of germ cell differentiation and meiotic initiation, while male PGCs exhibited repression of piRNA metabolism and transposon derepression. We also used whole-genome single-cell DNA sequencing to reveal that genetic rescue of DNA repair-deficient germ cells (Fancm−/−) leads to increased mutation incidence and biases. Importantly, our work uncovers novel insights into how PGCs exposed to DNA damage can become developmentally defective, leaving only those genetically fit cells to establish the adult germline.
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Affiliation(s)
- Jordana C Bloom
- Department of Biomedical Sciences,, Cornell University, Ithaca, New York 14853, USA.,Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - John C Schimenti
- Department of Biomedical Sciences,, Cornell University, Ithaca, New York 14853, USA.,Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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Bloom JC, Schimenti JC. A reporter mouse for in vivo detection of DNA damage in embryonic germ cells. Genesis 2020; 58:e23368. [PMID: 32343484 PMCID: PMC7897368 DOI: 10.1002/dvg.23368] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/08/2020] [Accepted: 04/08/2020] [Indexed: 12/28/2022]
Abstract
Maintaining genome integrity in the germline is essential for survival and propagation of a species. In both mouse and human, germ cells originate during fetal development and are hypersensitive to both endogenous and exogenous DNA damaging agents. Currently, mechanistic understanding of how primordial germ cells respond to DNA damage is limited in part by the tools available to study these cells. We developed a mouse transgenic reporter strain expressing a 53BP1-mCherry fusion protein under the control of the Oct4ΔPE embryonic germ cell-specific promoter. This reporter binds sites of DNA double strand breaks (DSBs) on chromatin, forming foci. Using ionizing radiation as a DNA DSB-inducing agent, we show that the transgenic reporter expresses specifically in the embryonic germ cells of both sexes and forms DNA damage induced foci in both a dose- and time-dependent manner. The dynamic time-sensitive and dose-sensitive DNA damage detection ability of this transgenic reporter, in combination with its specific expression in embryonic germ cells, makes it a versatile and valuable tool for increasing our understanding of DNA damage responses in these unique cells.
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Affiliation(s)
- Jordana C. Bloom
- Department of Biomedical Sciences and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
| | - John C. Schimenti
- Department of Biomedical Sciences and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
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Bloom JC, Loehr AR, Schimenti JC, Weiss RS. Germline genome protection: implications for gamete quality and germ cell tumorigenesis. Andrology 2019; 7:516-526. [PMID: 31119900 DOI: 10.1111/andr.12651] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/25/2019] [Accepted: 04/26/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Germ cells have a unique and critical role as the conduit for hereditary information and therefore employ multiple strategies to protect genomic integrity and avoid mutations. Unlike somatic cells, which often respond to DNA damage by arresting the cell cycle and conducting DNA repair, germ cells as well as long-lived pluripotent stem cells typically avoid the use of error-prone repair mechanisms and favor apoptosis, reducing the risk of genetic alterations. Testicular germ cell tumors, the most common cancers of young men, arise from pre-natal germ cells. OBJECTIVES To summarize the current understanding of DNA damage response mechanisms in pre-meiotic germ cells and to discuss how they impact both the origins of testicular germ cell tumors and their remarkable responsiveness to genotoxic chemotherapy. MATERIALS AND METHODS We conducted a review of literature gathered from PubMed regarding the DNA damage response properties of testicular germ cell tumors and the germ cells from which they arise, as well as the influence of these mechanisms on therapeutic responses by testicular germ cell tumors. RESULTS AND DISCUSSION This review provides a comprehensive evaluation of how the developmental origins of male germ cells and their inherent germ cell-like DNA damage response directly impact the development and therapeutic sensitivity of testicular germ cell tumors. CONCLUSIONS The DNA damage response of germ cells directly impacts the development and therapeutic sensitivity of testicular germ cell tumors. Recent advances in the study of primordial germ cells, post-natal mitotically dividing germ cells, and pluripotent stem cells will allow for new investigations into the initiation, progression, and treatment of testicular germ cell tumors.
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Affiliation(s)
- J C Bloom
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - A R Loehr
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - J C Schimenti
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - R S Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
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Gata4 is required for formation of the genital ridge in mice. PLoS Genet 2013; 9:e1003629. [PMID: 23874227 PMCID: PMC3708810 DOI: 10.1371/journal.pgen.1003629] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Accepted: 05/29/2013] [Indexed: 12/20/2022] Open
Abstract
In mammals, both testis and ovary arise from a sexually undifferentiated precursor, the genital ridge, which first appears during mid-gestation as a thickening of the coelomic epithelium on the ventromedial surface of the mesonephros. At least four genes (Lhx9, Sf1, Wt1, and Emx2) have been demonstrated to be required for subsequent growth and maintenance of the genital ridge. However, no gene has been shown to be required for the initial thickening of the coelomic epithelium during genital ridge formation. We report that the transcription factor GATA4 is expressed in the coelomic epithelium of the genital ridge, progressing in an anterior-to-posterior (A-P) direction, immediately preceding an A-P wave of epithelial thickening. Mouse embryos conditionally deficient in Gata4 show no signs of gonadal initiation, as their coelomic epithelium remains a morphologically undifferentiated monolayer. The failure of genital ridge formation in Gata4-deficient embryos is corroborated by the absence of the early gonadal markers LHX9 and SF1. Our data indicate that GATA4 is required to initiate formation of the genital ridge in both XX and XY fetuses, prior to its previously reported role in testicular differentiation of the XY gonad. During mammalian fetal development, the precursor of the testis or ovary first appears as a simple thickening, in a specific region, of the epithelial cell layer that lines the body cavity. The resulting structure is called the genital ridge, which then differentiates into either testis or ovary, depending on whether the sex chromosome constitution is XY or XX. A handful of genes, including Lhx9, Sf1, Wt1, and Emx2, are required to sustain the growth of the genital ridge. However, mice with mutations in any of these genes still undergo the initial step of epithelial thickening, suggesting that an additional step (or factor) is required to initiate genital ridge formation. We found that the evolutionarily conserved transcription factor GATA4 is expressed in the epithelium of the genital ridge before initial thickening. We produced a mouse with a Gata4 mutation in this tissue and demonstrated that the initial thickening does not take place; the mutant embryos fail to initiate gonad development. In support of this observation, the Gata4 mutant does not express the early gonadal markers LHX9 and SF1. These findings indicate that a genetically discrete, Gata4-dependent initiation step precedes the previously known processes that result in formation of testes and ovaries.
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Mark-Kappeler CJ, Hoyer PB, Devine PJ. Xenobiotic effects on ovarian preantral follicles. Biol Reprod 2011; 85:871-83. [PMID: 21697514 PMCID: PMC3197911 DOI: 10.1095/biolreprod.111.091173] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Revised: 02/16/2011] [Accepted: 05/17/2011] [Indexed: 01/30/2023] Open
Abstract
Women are born with a finite population of ovarian follicles, which are slowly depleted during their reproductive years until reproductive failure (menopause) occurs. The rate of loss of primordial follicles is determined by genetic and environmental influences, but certain toxic exposures can accelerate this process. Ionizing radiation reduces preantral follicle numbers in rodents and humans in a dose-dependent manner. Cigarette smoking is linked to menopause occurring 1-4 yr earlier than with nonsmokers, and components of smoke, polycyclic aromatic hydrocarbons, can cause follicle depletion in rodents or in ovaries in vitro. Chemotherapeutic agents, such as alkylating drugs and cisplatin, also cause loss of preantral ovarian follicles. Effects depend on dose, type, and reactivity of the drug, and the age of the individual. Evidence suggests DNA damage may underlie follicle loss induced by one common alkylating drug, cyclophosphamide. Occupational exposures have also been linked to ovarian damage. In an industrial setting, 2-bromopropane caused infertility in men and women, and it can induce ovarian follicle depletion in rats. Solvents, such as butadiene, 4-vinylcyclohexene, and their diepoxides, can also cause specific preantral follicle depletion. The mechanism(s) underlying effects of the latter compound may involve alterations in apoptosis, survival factors such as KIT/Kit Ligand, and/or the cellular signaling that maintains primordial follicle dormancy. Estrogenic endocrine disruptors may alter follicle formation/development and impair fertility or normal development of offspring. Thus, specific exposures are known or suspected of detrimentally impacting preantral ovarian follicles, leading to early ovarian failure.
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Peeters M, Ottersbach K, Bollerot K, Orelio C, de Bruijn M, Wijgerde M, Dzierzak E. Ventral embryonic tissues and Hedgehog proteins induce early AGM hematopoietic stem cell development. Development 2009; 136:2613-21. [PMID: 19570846 DOI: 10.1242/dev.034728] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Hematopoiesis is initiated in several distinct tissues in the mouse conceptus. The aorta-gonad-mesonephros (AGM) region is of particular interest, as it autonomously generates the first adult type hematopoietic stem cells (HSCs). The ventral position of hematopoietic clusters closely associated with the aorta of most vertebrate embryos suggests a polarity in the specification of AGM HSCs. Since positional information plays an important role in the embryonic development of several tissue systems, we tested whether AGM HSC induction is influenced by the surrounding dorsal and ventral tissues. Our explant culture results at early and late embryonic day 10 show that ventral tissues induce and increase AGM HSC activity, whereas dorsal tissues decrease it. Chimeric explant cultures with genetically distinguishable AGM and ventral tissues show that the increase in HSC activity is not from ventral tissue-derived HSCs, precursors or primordial germ cells (as was previously suggested). Rather, it is due to instructive signaling from ventral tissues. Furthermore, we identify Hedgehog protein(s) as an HSC inducing signal.
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Affiliation(s)
- Marian Peeters
- Erasmus Stem Cell Institute, Department of Cell Biology, Erasmus Medical Center, Rotterdam, The Netherlands
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Miqueloto CA, Zorn TM. Characterization and distribution of hyaluronan and the proteoglycans decorin, biglycan and perlecan in the developing embryonic mouse gonad. J Anat 2007; 211:16-25. [PMID: 17543016 PMCID: PMC2375803 DOI: 10.1111/j.1469-7580.2007.00741.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The morphogenesis of tissues and organs requires dynamic changes in cells and in extracellular matrix components. It is known that various extracellular matrix molecules are of fundamental importance for gonad differentiation and growth. In the adult testis, the extracellular matrix represents an important component of the interstitium, participating in the transport of biologically active substances needed for the communication between different cellular components, as well as for the regulation of spermatogenesis and hormone production. The present study was designed in order to identify the proteoglycans biglycan, decorin and perlecan, as well as the glycosaminoglycan hyaluronan, during testis development in mouse embryos. Our data profile the chronology of testis differentiation, as well as the distribution of these extracellular matrix components during testis development in mice. We show that these extracellular matrix molecules are present early in the development of the gonads, suggesting that they play a role in gonad development. In addition, we found no decorin in the testicular cords. Furthermore, of the proteoglycans analysed, only biglycan was seen surrounding immature Sertoli cells and Leydig cell precursors in the testicular cords. This indicates that specific sets of extracellular matrix molecules are required in the various compartments of the developing gonad.
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Affiliation(s)
- C A Miqueloto
- Laboratory of Reproductive and Extracellular Matrix Biology, Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, Brazil
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Sun L, Lee J, Fine HA. Neuronally expressed stem cell factor induces neural stem cell migration to areas of brain injury. J Clin Invest 2004; 113:1364-74. [PMID: 15124028 PMCID: PMC398428 DOI: 10.1172/jci20001] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Accepted: 02/17/2004] [Indexed: 12/11/2022] Open
Abstract
Neural stem/progenitor cell (NSPC) migration toward sites of damaged central nervous system (CNS) tissue may represent an adaptive response for the purpose of limiting and/or repairing damage. Little is known of the mechanisms responsible for this migratory response. We constructed a cDNA library of injured mouse forebrain using subtractive suppression hybridization (SSH) to identify genes that were selectively upregulated in the injured hemisphere. We demonstrate that stem cell factor (SCF) mRNA and protein are highly induced in neurons within the zone of injured brain. Additionally, the SCF receptor c-kit is expressed on NSPCs in vitro and in vivo. Finally, we demonstrate that recombinant SCF induces potent NSPC migration in vitro and in vivo through the activation of c-kit on NSPCs. These data suggest that the SCF/c-kit pathway is involved in the migration of NSPCs to sites of brain injury and that SCF may prove useful for inducing progenitor cell recruitment to specific areas of the CNS for cell-based therapeutic strategies.
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Affiliation(s)
- Lixin Sun
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Neurological Disorder and Stroke, NIH, Bethesda, Maryland 20892-8200, USA
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Alonso E, Sáez FJ, Madrid JF, Hernández F. Galactosides and sialylgalactosides in O-linked oligosaccharides of the primordial germ cells in Xenopus embryos. Glycoconj J 2001; 18:225-30. [PMID: 11602806 DOI: 10.1023/a:1012400623096] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The primordial germ cells (PGCs) are covered by surface glycoconjugates; some of them, like galactose residues recognized by peanut agglutinin (PNA), have been reported to be implicated in the PGC migration process. The aim of this work was the characterization of galactosides and sialylgalactosides in N- and O-linked oligosaccharides of Xenopus PGCs. Galactose(Gal)- and sialic acid(Neu5Ac)-binding lectin cytochemistry, in combination with chemical and enzymatic deglycosylation methods, were used. PGCs were slightly labeled with PNA, RCA-I and BSI-B4, which suggests the presence of the sequences Gal(beta1,4)GlcNAc and Gal(alpha1,3)Gal. Moreover, there was no labeling when beta-elimination pre-treatment was performed, suggesting that galactosides were in O-linked oligosaccharides. The strong staining with DSA was probably due to GlcNAc. Furthermore, sialylgalactosides with the sequence Neu5Ac(alpha2,3)Gal(beta1,4)GlcNAc in O-linked oligosaccharides have been shown by means of MAA, PNA and RCA-I.
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Affiliation(s)
- E Alonso
- Department of Cell Biology and Morphological Sciences, University of the Basque Country, Leioa, Vizcaya, Spain
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Abstract
In mammals the male sex determination switch is controlled by a single gene on the Y chromosome, SRY. SRY encodes a protein with an HMG-like DNA-binding domain, which probably acts as a local organizer of chromatin structure. It is believed to regulate downstream genes in the sex determination cascade, although no direct targets of SRY are clearly known. More genes in the pathway have been isolated through mutation approaches in mouse and human. At least three genes, SRY itself, SOX9, and DAX1, are dosage sensitive, providing molecular evidence that the sex determination step operates at a critical threshold. SRY initiates development of a testis from the bipotential cells of the early gonad. The dimorphic male and female pathways present a rare opportunity to link a pivotal gene in development with morphogenetic mechanisms that operate to pattern an organ and the differentiation of its cells. Mechanisms of testis organogenesis triggered downstream of SRY include pathways of cell signaling controlling cell reorganization, cell proliferation, cell migration, and vascularization.
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Affiliation(s)
- B Capel
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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García-Castro MI, Anderson R, Heasman J, Wylie C. Interactions between germ cells and extracellular matrix glycoproteins during migration and gonad assembly in the mouse embryo. J Cell Biol 1997; 138:471-80. [PMID: 9230086 PMCID: PMC2138185 DOI: 10.1083/jcb.138.2.471] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/1997] [Revised: 04/21/1997] [Indexed: 02/04/2023] Open
Abstract
Cells are known to bind to individual extracellular matrix glycoproteins in a complex and poorly understood way. Overall strength of adhesion is thought to be mediated by a combinatorial mechanism, involving adhesion of a cell to a variety of binding sites on the target glycoproteins. During migration in embryos, cells must alter their overall adhesiveness to the substrate to allow locomotion. The mechanism by which this is accomplished is not well understood. During early development, the cells destined to form the gametes, the primordial germ cells (PGCs), migrate from the developing hind gut to the site where the gonad will form. We have used whole-mount immunocytochemistry to study the changing distribution of three extracellular matrix glycoproteins, collagen IV, fibronectin, and laminin, during PGC migration and correlated this with quantitative assays of adhesiveness of PGCs to each of these. We show that PGCs change their strength of adhesion to each glycoprotein differentially during these stages. Furthermore, we show that PGCs interact with a discrete tract of laminin at the end of migration. Closer analysis of the adhesion of PGCs to laminin revealed that PGCs adhere particularly strongly to the E3 domain of laminin, and blocking experiments in vitro suggest that they adhere to this domain using a cell surface proteoglycan.
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Affiliation(s)
- M I García-Castro
- Wellcome/CRC Institute for Developmental Biology and Cancer, Cambridge CB2 1QR, England
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Abstract
More than 100 years have passed since Weismann first recognized the role of germ cells in the continuity of a species. Today, it remains unclear how a germ cell is initially set aside from somatic cells and how it chooses its unique developmental path. In this review, we address various aspects of germ cell development in Drosophila, such as germ cell determination, germ cell migration, gonad formation, sex determination, and gametogenesis. Many aspects of germ cell development, including the morphology of germ cells, their migratory behavior, as well as the processes of gonad formation and gametogenesis, show striking similarities among organisms. Considering the conservation of factors that regulate somatic development, it is likely that some aspects of germ cell development are shared not only on a morphological but also on the molecular level between Drosophila and other organisms.
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Affiliation(s)
- A Williamson
- Skirball Institute, New York University Medical Center Developmental Genetics Program, NY 10016, USA
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