Search results for "Piwi"

2019

PIWI proteins and their guiding Piwi-interacting (pi-) RNAs direct the silencing of target nucleic acids in the animal germline and soma. Although in mammal testes fetal piRNAs are involved in extensive silencing of transposons, pachytene piRNAs have additionally been shown to act in post-transcriptional gene regulation. The bulk of pachytene piRNAs is produced from large genomic loci, named piRNA clusters. Recently, the presence of reversed pseudogenes within piRNA clusters prompted the idea that piRNAs derived from such sequences might direct regulation of their parent genes. Here, we examine primate piRNA clusters and integrated pseudogenes in a comparative approach to gain a deeper unde…

Intrinsically disordered protein PID-2 modulates Z granules and is required for heritable piRNA-induced silencing in the Caenorhabditis elegans embryo

2020

Abstract In Caenorhabditis elegans, the piRNA (21U RNA) pathway is required to establish proper gene regulation and an immortal germline. To achieve this, PRG‐1‐bound 21U RNAs trigger silencing mechanisms mediated by RNA‐dependent RNA polymerase (RdRP)‐synthetized 22G RNAs. This silencing can become PRG‐1‐independent and heritable over many generations, a state termed RNA‐induced epigenetic gene silencing (RNAe). How and when RNAe is established, and how it is maintained, is not known. We show that maternally provided 21U RNAs can be sufficient for triggering RNAe in embryos. Additionally, we identify PID‐2, a protein containing intrinsically disordered regions (IDRs), as a factor required …

Piwi Proteins and piRNAs in Mammalian Oocytes and Early Embryos

2015

SummaryGerm cells of most animals critically depend on piRNAs and Piwi proteins. Surprisingly, piRNAs in mouse oocytes are relatively rare and dispensable. We present compelling evidence for strong Piwi and piRNA expression in oocytes of other mammals. Human fetal oocytes express PIWIL2 and transposon-enriched piRNAs. Oocytes in adult human ovary express PIWIL1 and PIWIL2, whereas those in bovine ovary only express PIWIL1. In human, macaque, and bovine ovaries, we find piRNAs that resemble testis-borne pachytene piRNAs. Isolated bovine follicular oocytes were shown to contain abundant, relatively short piRNAs that preferentially target transposable elements. Using label-free quantitative pr…

Extensive nuclear gyration and pervasive non-genic transcription during primordial germ cell development in zebrafish.

2020

ABSTRACT Primordial germ cells (PGCs) are the precursors of germ cells, which migrate to the genital ridge during early development. Relatively little is known about PGCs after their migration. We studied this post-migratory stage using microscopy and sequencing techniques, and found that many PGC-specific genes, including genes known to induce PGC fate in the mouse, are only activated several days after migration. At this same time point, PGC nuclei become extremely gyrated, displaying general broad opening of chromatin and high levels of intergenic transcription. This is accompanied by changes in nuage morphology, expression of large loci (PGC-expressed non-coding RNA loci, PERLs) that ar…

Function and Evolution of Nematode RNAi Pathways

2019

Selfish genetic elements, like transposable elements or viruses, are a threat to genomic stability. A variety of processes, including small RNA-based RNA interference (RNAi)-like pathways, has evolved to counteract these elements. Amongst these, endogenous small interfering RNA and Piwi-interacting RNA (piRNA) pathways were implicated in silencing selfish genetic elements in a variety of organisms. Nematodes have several incredibly specialized, rapidly evolving endogenous RNAi-like pathways serving such purposes. Here, we review recent research regarding the RNAi-like pathways of Caenorhabditis elegans as well as those of other nematodes, to provide an evolutionary perspective. We argue tha…

Tīmekļa vietnes analīzes rīki

2015

Bakalaura darba mērķis ir iepazīties ar tīmekļa vietnes analīzes rīku piedāvātajām iespējām, noteikt rīku pielietojumu dažādos gadījumos un izpētīt to popularitāti Latvijā un ārpus Latvijas teritorijas. Daudzi informācijas tehnoloģijas speciālisti, kas strādā reālajos projektos, ieskaitot darba autoru, sastopas ar tīmekļa vietnes analīzes nepieciešamību. Parasti šim nolūkam izmanto vienu no pieejamiem rīkiem. Piemēram, darba autors savā ikdienas darbā izmanto Google Analytics rīku, lai analizētu tīmekļa vietni. Pamatoties uz personīgo pieredzi, darba autors veica rīku salīdzinājumu un to pielietošanas sfēras identificēšanu. Par galveno bakalaura darba rezultātu var uzskatīt to, ka darba nos…

RNAs That Behave Like Prions

2020

The term “prion” was originally coined to describe the proteinaceous infectious agents involved in mammalian neurological disorders. More recently, a prion has been defined as a nonchromosomal, protein-based genetic element that is capable of converting the copies of its own benign variant into the prion form, with the new phenotypic effects that can be transmitted through the cytoplasm. Some prions are toxic to the cell, are able to aggregate and/or form amyloid structures, and may be infectious in the wild, but none of those traits are seen as an integral property of all prions. We propose that the definition of prion should be expanded, to include the inducible transmissible entities und…

Isolation of Zebrafish Gonads for RNA Isolation

2013

Piwi proteins and piRNAs are abundant in the gonads of various animal species. Gonads from different developmental stages provide us information regarding the function of piRNAs and the PIWI pathway during germline development. Here we describe methods for gonad and germ cell preparation from different developmental stages of zebrafish. We also describe how to use these gonads to purify and characterize piRNAs.

What the human sperm methylome tells us.

2017

Aim: To characterize the sperm methylome in semen samples from 19 donors with proven fertility. Materials & methods: Bisulfite-converted sperm DNA was hybridized on the HumanMethylation450 Infinium BeadChip platform. CpG fluorescence intensities were extracted and converted to β-values. Results: The sperm methylome is highly homogeneous and hypomethylated. Genes with hypomethylated promoters are ontologically associated to biological functions related to spermatogenesis and embryogenesis. Sex chromosomes are the most hypomethylated chromosomes, supporting data that indicated their essential role in spermatogenesis. A total of 94 genes are resistant to demethylation, being strong candid…

Temperature-responsive miRNAs in Drosophila orchestrate adaptation to different ambient temperatures

2017

The majority of Drosophila genes are expressed in a temperature-dependent manner, but the way in which small RNAs may contribute to this effect is completely unknown as we currently lack an idea of how small RNA transcriptomes change as a function of temperature. Applying high-throughput sequencing techniques complemented by quantitative real-time PCR experiments, we demonstrate that altered ambient temperature induces drastic but reversible changes in sequence composition and total abundance of both miRNA and piRNA populations. Further, mRNA sequencing reveals that the expression of miRNAs and their predicted target transcripts correlates inversely, suggesting that temperature-responsive m…