Biology subjects

Loubalova, Z.

Publications and source records attributed to Loubalova, Z..

4 recordsLinked to original sources

bioRxiv2025

Pachytene piRNAs define a conserved program of meiotic gene regulation

PIWI-interacting RNAs (piRNAs) safeguard genome integrity and fertility across animals and in humans1-3. In mammals, pre-pachytene piRNAs execute the ancestral program of transposon silencing, whereas a second, mammalian-specific class functions during meiosis4. These pachytene piRNAs are indispensable for spermatogenesis3, yet their sequence diversity, rapid evolution, and lack of obvious complementarity have long obscured their primary targets and mode of action5. Here, we show that groups of pachytene piRNAs converge on single mRNAs with near-perfect complementarity, evoking the specificity and efficacy of classical RNA interference6. These mRNA-targeting piRNAs originate from pseudogene fragments within discrete piRNA clusters, establishing an unexpected one-to-one relationship: a given cluster encodes thousands of piRNAs that collectively silence a single gene. Deleting such piRNA clusters or their embedded pseudogene fragments, eliminates the gene-targeting piRNAs, derepresses the target mRNA, and causes spermatogenic defects. Comparative genomics reveals a simple, unifying logic, whereby rapidly evolving cluster-target pairs coexist with a conserved, primate-specific regulon maintained over tens of millions of years. These findings provide a mechanistic framework for pachytene piRNA action, repositioning them as precise gene regulators during meiosis and highlighting a uniquely preserved piRNA-target pair in primates.

developmental 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↗

bioRxiv2021

Golden hamster piRNAs are necessary for early embryonic development and establishment of spermatogonia

PIWI-associated RNAs (piRNAs) support the germline by suppressing retrotransposons and genes. In mice, piRNAs are essential for spermatogenesis but not oogenesis. To test how this applies to other mammals, we deleted Mov10l1 helicase in golden hamster, whose piRNA pathway is configured more similarly to that of other mammals. Mov10l1-/- male hamsters showed impaired establishment of spermatogonia accompanied by transcriptome dysregulation and a surge in MYSERV retrotransposon expression. The rare viable spermatogenic cells showed a meiotic failure phenotype like Mov10l1-/- mice. Female Mov10l1-/- hamsters were sterile due to post-meiotic loss of developmental competence in zygotes. Unique phenotypes of Mov10l1-/- hamsters demonstrate the adaptive nature of piRNA-mediated control of genes and retrotransposons in order to confront emerging genomic threats or acquire new physiological roles.

molecular biology↗