Biology subjects

Percharde, M.

Publications and source records attributed to Percharde, M..

5 recordsLinked to original sources

bioRxiv2025

Inhibition of cytosolic DNA sensing and transposon activity safeguards pluripotency

Transposable elements (TEs) are mobile DNA sequences that make up a sizeable fraction of mammalian genomes yet are often tightly repressed by transcriptional and epigenetic mechanisms. During early development, epigenetic reprogramming selectively loosens TE repression, and TE transcription actively contributes to embryogenesis. This raises the question: how can embryos and embryonic stem cells (ESCs) tolerate TE expression without incurring widespread inflammation or DNA damage? Here, we reveal multiple mechanisms that prevent innate immune activation by TE-derived cytosolic DNA, including reduced cGAS/STING expression and signalling, dampening of Type I interferon responses by pluripotency factors, and post-transcriptional restriction of retrotransposition. These layers of protection are essential, as experimental perturbation triggers loss of ESC self-renewal and pluripotency. Our data explain how early development can be permissive to TE expression while safeguarding against harmful effects of TE activity.

developmental biology↗

bioRxiv2024

CRISPRa-mediated disentanglement of the Dux-MERVL axis in the 2C-like state, totipotency and cell death

Transposable elements (TEs) provide sequences that are powerful cis-regulatory drivers of gene expression programmes. This is particularly apparent during early development when many TEs become de-repressed. MERVL elements are highly yet transiently upregulated in mouse totipotent 2-cell (2C) embryos during major zygotic genome activation (ZGA), and in 2C-like cells in vitro. One of the most powerful activators of MERVL is the pioneer transcription factor, Dux. However, apparent differences lie in the requirement for Dux versus MERVL activation in embryos, for unclear reasons. Moreover, sustained Dux activation causes cell toxicity in multiple cell types, which may or may not be linked to MERVL activation. Using a CRISPR-activation, 2C-GFP reporter system, we have unpicked the relative role of Dux and MERVL in ZGA, totipotent-like characteristics and cell toxicity. We find that direct MERVL activation comprises only a portion of the Dux-dependent transcriptome, and which is sufficient for expanded fate potential, but not other totipotency features. Conversely, Dux-induced pathology is independent of MERVL activation and involves induction of the pro-apoptotic factor, Noxa. Our study highlights the complexity of the Dux-MERVL transcriptional network and uncovers a new player in Dux-driven pathology.

developmental biology↗

bioRxiv2024

The exit of naïve pluripotency contains a lipid metabolism-induced checkpoint for genome integrity.

Pluripotent progenitors undergo dramatic cellular and biochemical transformations during peri-implantation development. These large-scale reprogramming events are fundamental for subsequent differentiation, but how they are integrated and co-ordinated with the preservation of genome integrity remain unknown. Here, we uncover a metabolism-induced telomere checkpoint that takes place in pluripotent progenitors as they form rosette-like epithelial structures. We show that the glycolytic switch at the exit of naive pluripotency is preceded by an acceleration of mitochondrial respiration and de novo lipogenesis, fuelling the accumulation of lipid droplets required for morphogenesis. We find that downstream of these CIDEA-promoted metabolic events is the induction of ZSCAN4, a key pluripotency-associated regulator of telomere stability. Surprisingly, the build-up of lipid droplets corresponds to a transient shortening of telomeres, which triggers the activation of an elongation mechanism via ZSCAN4. Thus, telomere homeostasis can be safeguarded as essential lipid metabolic reprogramming unfolds to drive developmental progression.

developmental biology↗

bioRxiv2021

Nucleolar-based Dux repression is essential for 2-cell stage exit

Upon fertilisation, the mammalian embryo must switch from dependence on maternal transcripts to transcribing its own genome, and in mice involves the transient upregulation of MERVL transposons and MERVL-driven genes at the 2-cell stage. The mechanisms and requirement for MERVL and 2-cell (2C) gene upregulation are poorly understood. Moreover, this MERVL-driven transcriptional program must be rapidly shut off to allow 2C exit and developmental progression. Here, we report that robust ribosomal RNA (rRNA) synthesis and nucleolar maturation are essential for exit from the 2C state. 2C-like cells and 2C embryos show similar immature nucleoli with altered structure and reduced rRNA output. We reveal that nucleolar disruption via blocking Pol I activity or preventing nucleolar phase separation enhances conversion to a 2C-like state in embryonic stem cells (ESCs) by detachment of the MERVL activator Dux from the nucleolar surface. In embryos, nucleolar disruption prevents proper Dux silencing and leads to 2-4 cell arrest. Our findings reveal an intriguing link between rRNA synthesis, nucleolar maturation and gene repression during early development.

developmental biology↗

bioRxiv2017

The transcriptionally permissive chromatin state of ES cells is acutely tuned totranslational output

A permissive chromatin environment coupled to hypertranscription is critical to drive the rapid proliferation of Embryonic Stem (ES) cells and peri-implantation embryos. We carried out a genome-wide screen to systematically dissect the regulation of the euchromatic state of ES cells. The results reveal that activity of cellular growth pathways, prominently protein synthesis, perpetuates the euchromatic state and hypertranscription of ES cells. Acute, mild inhibition of translation results in rapid depletion of euchromatic marks in ES cells and blastocysts, concurrent with delocalization of RNA polymerase II and reduction in nascent transcription. Remarkably, reduced translational output leads to rewiring of open chromatin within 3 hours, including decreased accessibility at a subset of active developmental enhancers and increased accessibility at histone genes and transposable elements. Using a proteome-scale analysis, we show that several euchromatin regulators are unstable proteins and thus continuously depend on a high translational output. We propose that this mechanistic interdependence of euchromatin, transcription and translation sets the pace of proliferation at peri-implantation and may be employed generally by stem/progenitor cells.

molecular biology↗