Biology subjects

Queguiner, I.

Publications and source records attributed to Queguiner, I..

4 recordsLinked to original sources

bioRxiv2023

Plasticity state-dependent changes in visual cortex parvalbumin interneuron mRNA translation and chromatin

The juvenile brain is shaped by critical periods (CPs) of plasticity regulated in part by parvalbumin (PV) interneurons. The "reopening" of CPs has been explored in brain disorders, yet it remains unclear whether adult enhanced plasticity recapitulates developmental mechanisms. We profiled visual cortex PV-specific ribosome-associated mRNAs at the CP peak and in two adult plasticity paradigms, chondroitinase ABC (ChABC) injection and extracellular OTX2 blockade. No shared translatomic signature emerged between the three conditions. Nonetheless, CP and ChABC-induced plasticity shared genes coding for synaptic components and extracellular matrix. Condition-specific pathways highlighted mechano-transduction and cytoskeletal remodeling for ChABC plasticity and DNA repair and heterochromatin for CP plasticity. These juvenile pathways were supported by elevated {gamma}H2AX, H3K9me3, and DAPI foci in PV cells uniquely during the CP. Thus, adult plasticity does not simply reinstate juvenile mechanisms, but instead may recruit partially overlapping, condition-specific molecular pathways revealing candidate targets for enhancing adult plasticity.

neuroscience↗

bioRxiv2021

Reciprocal regulation of Shh trafficking and H2O2 levels via a noncanonical BOC-Rac1 pathway

Among molecules that bridge environment, cell metabolism, and cell signaling, H2O2 recently appeared as an emerging but central player. Its level depends on cell metabolism and environment and was recently shown to play key roles during embryogenesis, contrasting with its long-established role in disease progression. We decided to explore whether the secreted morphogen Sonic hedgehog (Shh), known to be essential in a variety of biological processes ranging from embryonic development to adult tissue homeostasis and cancers, was part of these interactions. Here, we report that H2O2 levels control key steps of Shh delivery and that physiological in vivo modulation of H2O2 levels changes Shh distribution and tissue patterning. A feedback loop exists in which Shh trafficking controls H2O2 synthesis via a non-canonical BOC-Rac1 pathway, leading to cytoneme growth. Our findings reveal that Shh directly impacts its own distribution, thus providing a molecular explanation for the robustness of morphogenesis to both environmental insults and individual variability.

cell biology↗

bioRxiv2020

Bidirectional transfer of Engrailed homeoprotein across the plasma membrane requires PIP2

1.Homeoproteins are a class of transcription factors sharing the unexpected property of intercellular trafficking. It confers to homeoproteins a paracrine mode of action, shown to exert a wide range of physiological functions, during development and in the adult. Internalization and secretion, the two steps of intercellular transfer, rely on unconventional mechanisms but the cellular mechanisms at stake still need to be fully characterized. Thanks to the design of new quantitative and sensitive assays dedicated to the study of homeoprotein transfer in cell culture, we demonstrate a core role of the phosphoinositides PIP2 together with cholesterol in the translocation of Engrailed2 (EN2) homeoprotein across the plasma membrane. Both secretion and internalization are regulated according to PIP2 levels, challenged by drug or enzymatic treatments. In addition, EN2 specifically interacts with PIP2 and the reduced affinity of a paracrine deficient mutant of EN2 supports a role of PIP2 in homeoprotein physiological function. We propose that the two ways plasma membrane translocation steps accounting for homeoprotein secretion and internalization respectively are parts of a common process. Summary StatementDeciphering the mechanism of homeoprotein intercellular trafficking

cell biology↗

bioRxiv2018

Active fluctuations modulate gene expression in mouse oocytes

In mammals, the nucleus is central in oocytes, not defining the future embryo axis. Nucleus centring depends on an F-actin mediated pressure gradient. In Fmn2-/- oocytes, lacking the F-actin nucleator Formin 2, the nucleus is off-centre and can be centred by re-expressing Formin 2. Here, we addressed the biological significance of nucleus positioning in mammalian oocytes. Using a dedicated computational 3D imaging approach, we observed nuclear architecture alterations in mouse Fmn2-/- oocytes. RNA sequencing of control versus Fmn2-/- oocytes detected 2285 mis-regulated genes. Rescue experiments showed that the process of nuclear positioning impacts nuclear architecture and gene expression. Using signal processing methods coupled to biophysical modelling allowing the extraction of in vivo mechanical properties of the nuclear envelope, we showed that F-actin-mediated activity promotes nuclear envelope shape fluctuations and chromatin motion. We thus propose a mechano-transduction model whereby nucleus positioning via microfilaments modulates oocyte transcriptome, essential for further embryo development.

cell biology↗