Maternally-inherited anti-sense piRNAs antagonize transposon expression in teleost embryos

Transposable elements threaten genome stability, and the Piwi-piRNA system has evolved to silence transposons in the germline. However, it remains largely unknown what mechanisms are utilized in early vertebrate embryos prior to germline establishment and ping-pong piRNA production. To address this, we first characterized small RNAs in early zebrafish embryos and detected abundant maternally-deposited, Ziwi-associated, antisense piRNAs that map largely to evolutionarily young long terminal repeat (LTR) retrotransposons. Notably, the focal establishment of the repressive modification H3K9me2/3 coincides with these young LTR elements, is deposited independent of transcription, and is required for LTR silencing. We find piRNAs highly enriched and maintained in primordial germ cells (PGCs), which display lower LTR expression than somatic cells. To examine the consequences of piRNA loss, we used reciprocal zebrafish-medaka hybrids, which display selective activation of LTRs that lack maternally-contributed targeting piRNAs. Thus, the Piwi-piRNA system actively antagonizes transposons in the soma and PGCs during early vertebrate embryogenesis.

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Chicken blastoderms and primordial germ cells possess a higher expression of DNA repair genes and lower expression of apoptosis genes to preserve their genome stability

Scientific Reports ◽

10.1038/s41598-021-04417-y ◽

2022 ◽

Vol 12 (1) ◽

Author(s):

Deivendran Rengaraj ◽

Sohyoung Won ◽

Kyung Min Jung ◽

Seung Je Woo ◽

Haerang Lee ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Germ Cells ◽

Genome Stability ◽

Primordial Germ Cells ◽

Cell Types ◽

Repair Pathway ◽

Apoptosis Pathway ◽

Whole Transcriptome Sequencing ◽

Apoptosis Pathways

AbstractDNA is susceptible to damage by various sources. When the DNA is damaged, the cell repairs the damage through an appropriate DNA repair pathway. When the cell fails to repair DNA damage, apoptosis is initiated. Although several genes are involved in five major DNA repair pathways and two major apoptosis pathways, a comprehensive understanding of those gene expression is not well-understood in chicken tissues. We performed whole-transcriptome sequencing (WTS) analysis in the chicken embryonic fibroblasts (CEFs), stage X blastoderms, and primordial germ cells (PGCs) to uncover this deficiency. Stage X blastoderms mostly consist of undifferentiated progenitor (pluripotent) cells that have the potency to differentiate into all cell types. PGCs are also undifferentiated progenitor cells that later differentiate into male and female germ cells. CEFs are differentiated and abundant somatic cells. Through WTS analysis, we identified that the DNA repair pathway genes were expressed more highly in blastoderms and high in PGCs than CEFs. Besides, the apoptosis pathway genes were expressed low in blastoderms and PGCs than CEFs. We have also examined the WTS-based expression profiling of candidate pluripotency regulating genes due to the conserved properties of blastoderms and PGCs. In the results, a limited number of pluripotency genes, especially the core transcriptional network, were detected higher in both blastoderms and PGCs than CEFs. Next, we treated the CEFs, blastoderm cells, and PGCs with hydrogen peroxide (H2O2) for 1 h to induce DNA damage. Then, the H2O2 treated cells were incubated in fresh media for 3–12 h to observe DNA repair. Subsequent analyses in treated cells found that blastoderm cells and PGCs were more likely to undergo apoptosis along with the loss of pluripotency and less likely to undergo DNA repair, contrasting with CEFs. These properties of blastoderms and PGCs should be necessary to preserve genome stability during the development of early embryos and germ cells, respectively.

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A novel F‐box domain containing cyclin F like gene is required for maintaining the genome stability and survival of chicken primordial germ cells

The FASEB Journal ◽

10.1096/fj.201901294r ◽

2019 ◽

Vol 34 (1) ◽

pp. 1001-1017

Author(s):

Bo Ram Lee ◽

Deivendran Rengaraj ◽

Hee Jung Choi ◽

Jae Yong Han

Keyword(s):

Germ Cells ◽

Genome Stability ◽

Primordial Germ Cells ◽

Cyclin F

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P granules protect RNA interference genes from silencing by piRNAs

10.1101/707562 ◽

2019 ◽

Author(s):

John Paul T. Ouyang ◽

Andrew Folkmann ◽

Lauren Bernard ◽

Chih-Yung Lee ◽

Uri Seroussi ◽

...

Keyword(s):

Rna Interference ◽

Germ Cells ◽

Small Rnas ◽

Primordial Germ Cells ◽

Safe Harbor ◽

Wild Type ◽

P Granules ◽

C Elegans ◽

Rna Biogenesis ◽

Endogenous Genes

SUMMARYP granules are perinuclear condensates in C. elegans germ cells proposed to serve as hubs for self/non-self RNA discrimination by Argonautes. We report that a mutant (meg-3 meg-4) that does not assemble P granules in primordial germ cells loses competence for RNA-interference over several generations and accumulates silencing small RNAs against hundreds of endogenous genes, including the RNA-interference genes rde-11 and sid-1. In wild-type, rde-11 and sid-1 transcripts are heavily targeted by piRNAs, accumulate in P granules, but maintain expression. In the primordial germ cells of meg-3 meg-4 mutants, rde-11 and sid-1 transcripts disperse in the cytoplasm with the small RNA biogenesis machinery, become hyper-targeted by secondary sRNAs, and are eventually silenced. Silencing requires the PIWI-class Argonaute PRG-1 and the nuclear Argonaute HRDE-1 that maintains trans-generational silencing of piRNA targets. These observations support a “safe harbor” model for P granules in protecting germline transcripts from piRNA-initiated silencing.

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Transcription of nanos-1 in Zebrafish Embryos is not Affected by Bisphenol A: Evaluated Using Quantitative Real-Time PCR

American Journal of Undergraduate Research ◽

10.33697/ajur.2019.012 ◽

2019 ◽

Vol 16 (1) ◽

pp. 15-21

Author(s):

Bridget Babich ◽

George Roba ◽

Siti Sarah Safura ◽

Kevin Callahan ◽

Edward Freeman

Keyword(s):

Bisphenol A ◽

Real Time ◽

Germ Cells ◽

Real Time Pcr ◽

Target Gene ◽

Primordial Germ Cells ◽

Endocrine Disrupting Chemicals ◽

Zebrafish Embryos ◽

Quantitative Real Time Pcr ◽

Endocrine Disrupting

The presence of primordial germ cells (PGCs) is crucial for proper gonad formation in zebrafish (Danio rerio). The many aspects of PGC migration that allow these cells to reach the proper location at the gonadal ridge include receptors, ligands, germ plasm components, and internal maintenance of PGCs. Any one of these factors could be affected by endocrine-disrupting chemicals (EDCs), which have been shown to alter the directed migration of these cells during early embryonic development. Based on recent research wherein the EDC bisphenol A (BPA) inhibited normal PGC migration, we have used the same dose of BPA to determine the impact of BPA on a gene central to proper germ cell migration. Zebrafish embryos were exposed to BPA, and the levels of the target gene nanos-1 were analyzed using quantitative real-time PCR (q-PCR). The target gene nanos-1 is a critically important germplasm component that allows for survival and proper migration of PGCs. The q-PCR results showed that BPA did not affect the transcription level of nanos-1 in zebrafish embryos. KEYWORDS: Zebrafish; Zebrafish Embryos; nanos-1; Primordial Germ Cells; PGC Migration; Gonad Development; Endocrine-Disrupting Chemicals; Bisphenol A; Sex Determination

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Hexachlorobenzene toxicity in the rat ovary: II. Ultrastructure induced by medium (10 mg/kg) dose exposure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012374x ◽

1992 ◽

Vol 50 (1) ◽

pp. 668-669

Author(s):

Amreek Singh ◽

Warren G. Foster ◽

Anna Dykeman ◽

David C. Villeneuve

Keyword(s):

Germ Cells ◽

Primordial Germ Cells ◽

Surface Epithelium ◽

Morphological Parameters ◽

Comprehensive Investigation ◽

Ovary Surface Epithelium ◽

Rat Ovary ◽

High Doses

Hexachlorobenzene (HCB) is a known toxicant that is found in the environment as a by-product during manufacture of certain pesticides. This chlorinated chemical has been isolated from many tissues including ovary. When administered in high doses, HCB causes degeneration of primordial germ cells and ovary surface epithelium in sub-human primates. A purpose of this experiment was to determine a no-effect dose of the chemical on the rat ovary. The study is part of a comprehensive investigation on the effects of the compound on the biochemical, hematological, and morphological parameters in the monkey and rat.

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