@baptisterafanel.bsky.social
Transposons, Transcription, piRNA, Drosophila PhD Student in the Brennecke lab at IMBA
How are RNAs sorted for export vs. degradation in the nucleus? In collaboration with @heick.bsky.social’s lab we (@clemensplaschka.bsky.social and @juliusbrennecke.bsky.social labs) discovered a direct mechanistic link between the export and decay machineries: www.biorxiv.org/content/10.1... (1/x)
22.09.2025 23:23 — 👍 82 🔁 42 💬 2 📌 2My first first-author paper is out!🎉
Here we propose a model where a silencing complex, PIWI*, assembles on target RNAs to recruit effectors and shut down transposon activity.
Huge thanks to the Brennecke and Plaschka labs, especially Julius and Clemens, and all co-authors!
12/ This work is part of my PhD project at the @viennabiocenter.bsky.social. A big Thank You to @juliusbrennecke.bsky.social and Kirsten Senti for their supervision! To my co-authors Liudmila and @86dominik.bsky.social, and to the rest of the Brennecke lab!
14.08.2025 17:09 — 👍 4 🔁 0 💬 0 📌 011/ All in all, our work strongly suggests that the decision to process a transcript into piRNAs is not a feature of the genomic source locus but rather a decision that is taken in the cytoplasm after export of a TE antisense-containing transcript.
14.08.2025 17:09 — 👍 4 🔁 0 💬 1 📌 0
10/ And @astridhaase.bsky.social’s group uncovered compelling evidence that in mammals, including humans, antisense insertions of endogenous retroviruses downstream of genes also correlate with piRNA production suggesting that this mechanism is conserved. www.cell.com/cell-reports...
14.08.2025 17:09 — 👍 4 🔁 0 💬 1 📌 0
9/ Importantly, this is not restricted to flies, Bill Theurkauf and colleagues, showed that silencing of the invading KoRV-A retrovirus in wild koala populations strongly correlates with the presence of a single antisense insertion in a host gene 3′ UTR. www.sciencedirect.com/science/arti...
14.08.2025 17:09 — 👍 3 🔁 1 💬 1 📌 08/ Altogether, our data show that antisense insertions of TEs in host gene exons are sufficient to elicit a piRNA response, which expands the repertoire of piRNA source loci to host genes expressed in gonads in addition to “classical” piRNA clusters.
14.08.2025 17:09 — 👍 2 🔁 0 💬 1 📌 0
A GFP transgene containing an antisense tirant insertion in the 3'UTR can silence tirant expression. An insertion in the sense orientation does not affect the expression of tirant.
7/ To test this idea, we generated a synthetic construct in which we placed antisense tirant sequence into the 3′ UTR of a UAS-GFP transgene. When expressed in follicle cells, this transgene silenced tirant expression, confirming our model.
14.08.2025 17:09 — 👍 1 🔁 0 💬 1 📌 06/ This led us to propose a model in which antisense piRNAs can only be generated if a TE inserts itself into a host transcription unit (gene or piRNA cluster). This generates a cytoplasmic antisense RNA that is processed into piRNAs.
14.08.2025 17:09 — 👍 4 🔁 0 💬 1 📌 0
An insertion of tirant in the antisense orientation in the 3'UTR of the gene Fs(2)Ket leads to the production of piRNAs.
An ectopic copy of the gene Fs(2)Ket containing the tirant insertion is sufficient for the production of piRNAs and silencing of tirant. This requires the production of a chimeric transcript containing both the Fs(2)Ket and the tirant RNA.
5/ Surprisingly, we found that a single antisense insertion of tirant in the 3′ UTR of a host gene, Fs(2)Ket, is sufficient to trigger piRNA production and silence tirant. piRNA production from this insertion requires host gene transcription and a chimeric mRNA-TE transcript.
14.08.2025 17:09 — 👍 2 🔁 0 💬 1 📌 14/ Some strains lack tirant insertions in flamenco or in any other known piRNAs cluster. However, they are still able to produce piRNAs and silence tirant. So where are these piRNAs coming from?
14.08.2025 17:09 — 👍 3 🔁 0 💬 1 📌 0
The tirant-GFP:lacZ reporter is expressed in the somatic follicle cells of the Drosophila melanogaster ovary and is silenced by piRNAs.
3/ We first show that tirant is exclusively expressed in somatic cells of the ovary. Here, most strains also produce tirant piRNAs from tirant insertions in flamenco, the major piRNAs cluster active in that tissue. But this is not true in all strains …
14.08.2025 17:09 — 👍 3 🔁 0 💬 1 📌 02/ Over the past century, several TEs invaded Drosophila melanogaster (thanks to the work of @rokofler.bsky.social). We traced how natural strains acquired piRNA immunity against one of these TEs, tirant, an LTR retrotransposon.
14.08.2025 17:09 — 👍 4 🔁 0 💬 1 📌 01/ How do animals develop immunity against a newly encountered transposable element from scratch? Our study reveals that the mobility of TEs is their Achilles heel, allowing hosts to develop a powerful small RNA-mediated silencing response.
www.biorxiv.org/content/10.1...
