Východiska: Za poslední desetiletí přibyly stovky studií, jež souhlasně prokázaly, že krátké nekódující RNA jsou slibnými diagnostickými, prognostickými a prediktivními biomarkery nádorových onemocnění. Významnou podskupinu těchto molekul představují RNA interagující s PIWI proteiny, označované jako piRNA. Tyto krátké RNA se podílejí na regulaci genové exprese na transkripční nebo post-transkripční úrovni, jejich hlavní úlohou je však epigenetické umlčování transpozibilních elementů LINE a SINE, čímž významně přispívají k udržení genomové stability. Dále se účastní důležitých buněčných procesů, jakými jsou gametogeneze, segregace chromozomů či sebeobnova kmenových buněk. Přestože byly piRNA poprvé detekovány v zárodečných buňkách, bylo zjištěno, že se vyskytují ve vysokých hladinách také v jiných lidských tkáních, přičemž jejich exprese vykazuje tkáňovou specificitu. První studie rovněž prokázaly změněný expresní profil piRNA u pacientů s nádorovými onemocněními. Funkce těchto molekul v procesu kancerogeneze však zatím zůstávají neobjasněné. Do popředí zájmu se v poslední době též dostávají volné cirkulující piRNA v tělních tekutinách, které nabízejí široké využití pro včasný záchyt nádorových onemocnění, predikci léčebné odpovědi či stanovení prognózy pacientů. Cíl: Tento přehledový článek jako první v českém jazyce shrnuje dosavadní poznatky o biogenezi piRNA, o jejich strategii při umlčování transpozibilních elementů a dalších genů. Poskytuje rovněž ucelený přehled o piRNA s deregulovanou expresí u lidských nádorových onemocnění a klade důraz na jejich potenciální diagnostické a terapeutické využití.

Background: In the past few years, a number of studies have suggested that small non-coding RNAs could be promising diagnostic, prognostic and predictive biomarkers in oncology. Recently, small RNAs interacting with PIWI proteins (piRNAs) have been described. These small RNAs regulate gene expression at transcriptional and post-transcriptional levels; however, they appear to be specifically involved in silencing the transposable elements LINE and SINE and are thus considered to contribute to genomic stability. Furthermore, piRNAs participate also in other important biological processes, such as gametogenesis, chromosome segregation, and stem cell self-renewal. Although their expression was first noted in germ line cells, they are now known to be present in all tissue types and their expression is highly tissue-specific. In addition, piRNA expression is dysregulated in tumor tissues. Nevertheless, the exact function of these molecules in cancerogenesis is not known. Recently, free circulating piRNAs were reported to be stably present in body fluids, suggesting that they could serve as promising noninvasive biomarkers to enable early diagnosis, therapy response prediction, and accurate prognosis prediction of cancer patients. Aim: The aim of this review is to summarize current knowledge about piRNA biogenesis and their functions in the regulation of gene expression and transposons silencing. In addition, the review focuses on piRNAs that show dysregulated expression in different types of cancers and that could serve as potential diagnostic biomarkers and/or therapeutic targets.

• Keywords
• umlčování transpozonů,
• MeSH
• Organelle Biogenesis MeSH
• Carcinogenesis MeSH
• Humans MeSH
• RNA, Small Interfering * MeSH
• Biomarkers, Tumor genetics   MeSH
• Neoplasms * diagnosis   genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

Glioblastom (GBM) je nejčastěji se vyskytující primární nádor mozku astrocytárního původu. Navzdory pokrokům v oblasti molekulární patologie a onkologie stále neexistují klinicky využitelné přístupy umožňující jednak klasifikovat pacienty dle jejich prognózy, ani překonat rezistenci GBM vůči konvenční terapii. To vede k časným relapsům a krátkému přežívání pacientů s GBM. Biologické chování GBM je dáváno do souvislosti s přítomností glioblastomových kmenových buněk (GSC), subpopulace vyznačující se vlastnostmi pluripotentních kmenových buněk, mezi které patří i schopnost udržovat genomovou stabilitu neustále narušovanou transponovatelnými elementy (TE). U kmenových buněk je regulace TE zprostředkovávána především PIWI-interagujícími RNA (piRNA). Deregulované hladiny těchto krátkých RNA byly pozorovány u mnoha nádorových onemocnění, včetně nádorových kmenových buněk, což naznačuje jejich významnou úlohu v kancerogenezi. Hlubší pochopení role piRNA u GSC by tak mohlo vést jak k vývoji nových terapeutických cílů, tak k objevení nových prognostických biomarkerů u pacientů s GBM.; Glioblastoma (GBM) is the most frequent primary brain tumor of astrocytic origin. Despite great advances in molecular pathology and oncology, there is still no clinically applicable ways to classify patients according their prognosis and to overcome GBM resistance to the conventional therapy, respectively. This results in an early tumor recurrence and dismal survival of GBM patients. Biological behavior of GBM is largely linked to the presence of glioblastoma stem cells (GSCs), a cell subpopulation displaying features of pluripotent stem cells among which belongs also the ability to maintain genomic stability constantly disturbed by transposable elements (TEs). Regulation of TEs in stem cells is managed mainly by PIWI-interacting RNAs (piRNAs). Deregulated levels of these small RNAs have been also observed in many cancers including cancer stem cells suggesting their important role in cancerogenesis. Deeper understanding of piRNA roles in GSCs could led to the first step to both development of new therapeutic targets and discovery new prognostic biomarkers in GBM patients.

• Keywords
• prognóza, prognosis, léčba, therapy, glioblastoma, glioblastom, PIWI-interagující RNA, glioblastomové kmenové buňky, PIWI-interacting RNA, glioblastoma stem cells,

• NML Publication type
• závěrečné zprávy o řešení grantu AZV MZ ČR

OBJECTIVE: The PIWIL (P-element induced wimpy testis like protein) subfamily of argonaute proteins is essential for Piwi-interacting RNA (piRNA) biogenesis and their function to silence transposons during germ-line development. Here we explored their presence and regulation in rheumatoid arthritis (RA). METHODS: The expression of PIWIL genes in RA and osteoarthritis (OA) synovial tissues and synovial fibroblasts (SF) was analysed by Real-time PCR, immunofluorescence and Western blot. The expression of piRNAs was quantified by next generation small RNA sequencing (NGS). The regulation of PIWI/piRNAs, proliferation and methylation of LINE-1 after silencing of PIWIL genes were studied. RESULTS: PIWIL2 and 4 mRNA were similarly expressed in synovial tissues and SF from RA and OA patients. However, on the protein level only PIWIL4 was strongly expressed in SF. Using NGS up to 300 piRNAs were identified in all SF without significant differences in expression levels between RA and OASF. Of interest, the analysis of the co-expression of the detected piRNAs revealed a less tightly regulated pattern of piRNA-823, -4153 and -16659 expression in RASF. In RASF and OASF, stimulation with TNFα+IL1β/TLR-ligands further significantly increased the expression levels of PIWIL2 and 4 mRNA and piRNA-16659 was significantly (4-fold) induced upon Poly(I:C) stimulation. Silencing of PIWIL2/4 neither affect LINE-1 methylation/expression nor proliferation of RASF. CONCLUSION: We detected a new class of small regulatory RNAs (piRNAs) and their specific binding partners (PIWIL2/4) in synovial fibroblasts. The differential regulation of co-expression of piRNAs in RASF and the induction of piRNA/Piwi-proteins by innate immune stimulators suggest a role in inflammatory processes.

• MeSH
• Argonaute Proteins genetics   metabolism   MeSH
• Cytokines metabolism   MeSH
• Long Interspersed Nucleotide Elements MeSH
• Fibroblasts pathology   MeSH
• Middle Aged MeSH
• Humans MeSH
• RNA, Small Interfering metabolism   MeSH
• Osteoarthritis genetics   metabolism   pathology   MeSH
• Proteins genetics   metabolism   MeSH
• Gene Expression Regulation MeSH
• Arthritis, Rheumatoid genetics   metabolism   pathology   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Synovial Membrane pathology   MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH

Osteoarthritis (OA) is a frequent musculoskeletal disorder affecting millions of people worldwide. Despite advances in understanding the pathogenesis of OA, prognostic biomarkers or effective targeted treatment are not currently available. Research on epigenetic factors has yielded some new insights as new technologies for their detection continue to emerge. In this context, non-coding RNAs, including microRNAs, long non-coding RNAs, circular RNAs, piwi-interacting RNAs, and small nucleolar RNAs, regulate intracellular signaling pathways and biological processes that have a crucial role in the development of several diseases. In this review, we present current knowledge on the role of epigenetic factors with a focus on non-coding RNAs in the development, prediction and treatment of OA. This article is categorized under: RNA in Disease and Development > RNA in Disease.

• MeSH
• RNA, Circular MeSH
• Humans MeSH
• MicroRNAs * genetics   MeSH
• Osteoarthritis * genetics   MeSH
• Piwi-Interacting RNA MeSH
• RNA, Long Noncoding * genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

PIWI-interacting RNAs (piRNAs) play a crucial role in safeguarding genome integrity by silencing mobile genetic elements. From flies to humans, piRNAs originate from long single-stranded precursors encoded by genomic piRNA clusters. How piRNA clusters form to adapt to genomic invaders and evolve to maintain protection remain key outstanding questions. Here, we generate a roadmap of piRNA clusters across seven species that highlights both similarities and variations. In mammals, we identify transcriptional readthrough as a mechanism to generate piRNAs from transposon insertions (piCs) downstream of genes (DoG). Together with the well-known stress-dependent DoG transcripts, our findings suggest a molecular mechanism for the formation of piRNA clusters in response to retroviral invasion. Finally, we identify a class of dynamic piRNA clusters in humans, underscoring unique features of human germ cell biology. Our results advance the understanding of conserved principles and species-specific variations in piRNA biology and provide tools for future studies.

• MeSH
• Species Specificity MeSH
• Humans MeSH
• RNA, Small Interfering * metabolism   genetics   MeSH
• Mice MeSH
• Piwi-Interacting RNA MeSH
• Dogs MeSH
• Mammals * genetics   MeSH
• DNA Transposable Elements genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Dogs MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH

• Publication type
• Meeting Abstract MeSH

Glioblastoma (GBM) is the most frequently occurring primary malignant brain tumor of astrocytic origin. To change poor prognosis, it is necessary to deeply understand the molecular mechanisms of gliomagenesis and identify new potential biomarkers and therapeutic targets. PIWI-interacting RNAs (piRNAs) help in maintaining genome stability, and their deregulation has already been observed in many tumors. Recent studies suggest that these molecules could also play an important role in the glioma biology. To determine GBM-associated piRNAs, we performed small RNA sequencing analysis in the discovery set of 19 GBM and 11 non-tumor brain samples followed by TaqMan qRT-PCR analyses in the independent set of 77 GBM and 23 non-tumor patients. Obtained data were subsequently bioinformatically analyzed. Small RNA sequencing revealed 58 significantly deregulated piRNA molecules in GBM samples in comparison with non-tumor brain tissues. Deregulation of piR-1849, piR-9491, piR-12487, and piR-12488 was successfully confirmed in the independent groups of patients and controls (all p < 0.0001), and piR-9491 and piR-12488 reduced GBM cells' ability to form colonies in vitro. In addition, piR-23231 was significantly associated with the overall survival of the GBM patients treated with Stupp regimen (p = 0.007). Our results suggest that piRNAs could be a novel promising diagnostic and prognostic biomarker in GBM potentially playing important roles in gliomagenesis.

• Publication type
• Journal Article MeSH

The PIWI-interacting RNA (piRNA) pathway is a conserved defense mechanism that protects the genetic information of animal germ cells from the deleterious effects of molecular parasites, such as transposons. Discovered nearly a decade ago, this small RNA silencing system comprises PIWI-clade Argonaute proteins and their associated RNA-binding partners, the piRNAs. In this review, we highlight recent work that has advanced our understanding of how piRNAs preserve genome integrity across generations. We discuss the mechanism of piRNA biogenesis, give an overview of common themes as well as differences in piRNA-mediated silencing between species, and end by highlighting known and emerging functions of piRNAs.

• MeSH
• Argonaute Proteins genetics   metabolism   MeSH
• Chromosomal Proteins, Non-Histone genetics   metabolism   MeSH
• Drosophila melanogaster genetics   metabolism   MeSH
• Transcription, Genetic MeSH
• Histones genetics   metabolism   MeSH
• Humans MeSH
• RNA, Small Interfering genetics   metabolism   MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Microtubule-Associated Proteins genetics   metabolism   MeSH
• Drosophila Proteins genetics   metabolism   MeSH
• RNA-Binding Proteins genetics   metabolism   MeSH
• Gene Silencing * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

PIWI-interacting RNAs (piRNAs) and their associated PIWI clade Argonaute proteins constitute the core of the piRNA pathway. In gonadal cells, this conserved pathway is crucial for genome defense, and its main function is to silence transposable elements. This is achieved through posttranscriptional and transcriptional gene silencing. Precursors that give rise to piRNAs require specialized transcription and transport machineries because piRNA biogenesis is a cytoplasmic process. The ping-pong cycle, a posttranscriptional silencing mechanism, combines the cleavage-dependent silencing of transposon RNAs with piRNA production. PIWI proteins also function in the nucleus, where they scan for nascent target transcripts with sequence complementarity, instructing transcriptional silencing and deposition of repressive chromatin marks at transposon loci. Although studies have revealed numerous factors that participate in each branch of the piRNA pathway, the precise molecular roles of these factors often remain unclear. In this review, we summarize our current understanding of the mechanisms involved in piRNA biogenesis and function.

• MeSH
• Argonaute Proteins genetics   MeSH
• Drosophila melanogaster genetics   MeSH
• Transcription, Genetic * MeSH
• Gonads growth & development   MeSH
• RNA, Small Interfering biosynthesis   genetics   MeSH
• DNA Transposable Elements genetics   MeSH
• Gene Silencing MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

Germline genome defense evolves to recognize and suppress retrotransposons. One of defensive mechanisms is the PIWI-associated RNA (piRNA) pathway, which employs small RNAs for sequence-specific repression. The loss of the piRNA pathway in mice causes male sterility while females remain fertile. Unlike spermatogenic cells, mouse oocytes posses also RNA interference (RNAi), another small RNA pathway capable of retrotransposon suppression. To examine whether RNAi compensates the loss of the piRNA pathway, we produced a new RNAi pathway mutant DicerSOM and crossed it with a catalytically-dead mutant of Mili, an essential piRNA gene. Normal follicular and oocyte development in double mutants showed that RNAi does not suppress a strong ovarian piRNA knock-out phenotype. However, we observed redundant and non-redundant targeting of specific retrotransposon families illustrating stochasticity of recognition and targeting of invading retrotransposons. Intracisternal A Particle retrotransposon was mainly targeted by the piRNA pathway, MaLR and RLTR10 retrotransposons were targeted mainly by RNAi. Double mutants showed accumulations of LINE-1 retrotransposon transcripts. However, we did not find strong evidence for transcriptional activation and mobilization of retrotransposition competent LINE-1 elements suggesting that while both defense pathways are simultaneously expendable for ovarian oocyte development, yet another transcriptional silencing mechanism prevents mobilization of LINE-1 elements.

• MeSH
• Argonaute Proteins genetics   MeSH
• DEAD-box RNA Helicases genetics   MeSH
• RNA, Small Interfering genetics   MeSH
• Mutation MeSH
• Mice MeSH
• Oocytes chemistry   growth & development   MeSH
• Retroelements * MeSH
• Ribonuclease III genetics   MeSH
• RNA Interference * MeSH
• Signal Transduction MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH