Biology subjects

Taborska, E.

Publications and source records attributed to Taborska, E..

4 recordsLinked to original sources

bioRxiv2024

Enhanced RNAi does not provide efficient innate antiviral immunity in mice in vivo.

In RNA interference (RNAi), long double-stranded RNA (dsRNA) is cleaved by Dicer endonuclease into small RNA interfering RNAs (siRNAs), which guide degradation of complementary RNAs. While RNAi mediates antiviral innate immunity in plants and many invertebrates, vertebrates adopted sequence-independent response and their Dicer produces siRNAs inefficiently because it is adapted to process small hairpin microRNA precursors in the gene-regulating microRNA pathway. Mammalian RNAi is thus a rudimentary pathway of unclear significance. To investigate its antiviral potential, we modified mouse Dicer locus to express a truncated variant (Dicer{Delta}HEL1) known to stimulate RNAi. Next, we analyzed how Dicer{Delta}HEL1/wt mice respond to four RNA viruses: Coxsackievirus B3 (CVB3) and encephalomyocarditis virus (ECMV) from Picornaviridae; tick-borne encephalitis virus (TBEV) from Flaviviridae; and lymphocytic choriomeningitis virus (LCMV) from Arenaviridae. Increased Dicer activity in Dicer{Delta}HEL1/wt mice did not elicit any antiviral effect. supporting insignificant antiviral function of endogenous mammalian RNAi in vivo. However, we also report that sufficiently high expression of Dicer{Delta}HEL1 suppressed LCMV in embryonic stem cells and in a transgenic mouse model. Altogether, mice with increased Dicer activity offer a new benchmark for identifying and studying viruses susceptible to mammalian RNAi in vivo.

molecular biology↗

bioRxiv2024

Activated RNAi does not rescue piRNA pathway deficiency in testes

RNA interference (RNAi) and PIWI-associated RNAs (piRNA) pathways use small RNAs as sequence-specific guides to repress transposable elements. In mice, the loss of Mili, an essential piRNA pathway factor, causes male sterility associated with mobilization of LINE L1 retrotransposons while female mutants remain fertile. At the same time, mouse oocytes have exceptionally active RNAi thanks to an oocyte-specific variant of RNase III Dicer, which efficiently makes small RNAs from long dsRNA substrates. In oocytes of mice lacking functional MILI and the oocyte-specific Dicer variant, we previously observed that L1 retrotransposons are redundantly targeted by both, RNAi and piRNA pathways. To test whether enhanced RNAi may reduce the Mili mutant phenotype in testes, we used transgenic mice ectopically expressing the oocyte-specific Dicer variant during spermatogenesis. We report here that this genetic modification increases siRNA biogenesis and supports RNAi but is not sufficient to reduce spermatogenic defects caused by the loss of Mili.

molecular biology↗

bioRxiv2023

Genetic activation of canonical RNA interference in mice

Canonical RNA interference (RNAi) is sequence-specific mRNA degradation guided by small interfering RNAs (siRNAs) made from double-stranded RNA (dsRNA) by RNase III Dicer. RNAi has different roles including gene regulation, antiviral immunity or defense against transposable elements. In mammals, RNAi is constrained by Dicer, which is adapted to produce microRNAs, another class of small RNAs. However, RNAi exists in mouse oocytes, which employs a truncated Dicer variant. A homozygous mutation to express only the truncated variant ({Delta}HEL1) causes dysregulation of microRNAs and perinatal lethality in mice. Here, we report the phenotype and RNAi activity in Dicer{Delta}HEL1/wtmice, which are viable, show minimal miRNome changes but their endogenous siRNA levels are increased by an order of magnitude. We show that siRNA abundance is limited by available dsRNA but not by PKR, a dsRNA sensor of innate immunity. Expressing dsRNA from a transgene, functional RNAi in vivo was induced in heart. Dicer{Delta}HEL1/wt mice thus represent a new model for researching mammalian canonical RNAi in vivo and offer an unprecedented platform for addressing claims about its biological roles.

molecular biology↗

bioRxiv2019

Restricted and non-essential redundancy of RNAi and piRNA pathways in mouse oocytes

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 post-transcriptional and transcriptional repression. The loss of the piRNA pathway in mice causes male sterility while females remain fertile. Unlike spermatogenic cells, mouse oocytes have also RNA interference (RNAi), another small RNA pathway capable of retrotransposon suppression. To examine whether RNAi compensates the loss of the piRNA pathway in mouse oocytes, 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 in double mutants showed that RNAi does not suppress a strong piRNA knock-out phenotype. However, we observed redundant and non-redundant targeting of specific retrotransposons. Intracisternal A Particle retrotransposon was mainly targeted by the piRNA pathway, MT and RLTR10 retrotransposons were targeted mainly by RNAi. Importantly, only double mutants showed increased background levels of transcripts potentially originating from intact LINE-1 elements. Our results thus show that while both small RNA pathways are simultaneously expendable defense pathways for ovarian oocyte development, yet another transcriptional silencing mechanism must mediate LINE-1 repression in female germ cells.\n\nAuthor summaryRetrotransposons are mobile genomic parasites causing mutations. Germ cells need protection against retrotransposons to prevent heritable transmission of their new insertions. The piRNA pathway is an ancient germline defense system analogous to acquired immunity: once a retrotransposons jumps into a specific \"genomic checkpoint\", it is recognized and suppressed. Remarkably, the murine piRNA pathway is essential for spermatogenesis but not oocyte development. In contrast, zebrafish lacking the piRNA pathway do not develop any germ cells. It was hypothesized that RNA interference pathway could rescue oocyte development in mice lacking the piRNA pathway. RNA interference also targets retrotransposons and is particularly enhanced in mouse oocytes. To test this hypothesis, we engineered mice lacking both pathways and observed that oocytes in these mice develop normally, which argues against the hypothesis. Furthermore, analysis of individual retrotransposon groups revealed that in specific cases the two pathways can mutually compensate each other. However, this ability is restricted to specific retrotransposon groups and seems to evolve stochastically. Finally, our results also indicate that there must be yet another layer of retrotransposon silencing in mouse oocytes, which prevents high retrotransposon activity in the absence of piRNA and RNA interference pathways.

molecular biology↗