Biology subjects

Villet, M.

Publications and source records attributed to Villet, M..

4 recordsLinked to original sources

bioRxiv2025

Phylogenomics and Fossilized Birth-Death Dating Reveals Gondawanan Origin and Extensive Post-Cretaceous Diversification of Worldwide Cicadidae.

The Cretaceous-Paleogene (K-Pg) mass extinction resulted in a massive turnover in biodiversity. The oldest fossils of the globally-distributed insect family Cicadidae date to the Paleocene, suggesting that this family diversified after the K-Pg boundary. We analyzed 490 nuclear Anchored Hybrid Enrichment loci as well as mitochondrial genomes for the Cicadidae, sampling all five subfamilies and 82% of tribes, using concatenated maximum-likelihood and multi-species coalescent approaches to resolve the phylogenetic relationships of Cicadidae subfamilies. We estimated divergence times of Cicadidae lineages using a fossilized birth-death model augmented into the multispecies coalescent with 44 fossil taxa. We estimated a Cretaceous origin for Cicadidae with four of the five subfamilies diversifying shortly after the K-Pg extinction event. Our fossilized birth-death tip-dating approach improved the precision of age estimates for many cicada clades compared to dates based on node-calibration from previous studies. Our results augment insight into how the K-Pg mass extinction shaped present-day diversity.

evolutionary biology↗

bioRxiv2025

Cortico-striatal dynamics across working memory stages

Working memory depends on the temporary retention and manipulation of information, bridging the gap between short-term memory and information processing functions. However, when the same working memory task is repeated over several days, it raises the question of whether the rule or task set becomes automated (or proceduralized). The medial prefrontal cortex (mPFC) is crucial for working memory. Yet, the role of the dorsolateral striatum (DLS) in the automation (proceduralization) of rules or task sets remains to be clarified. Using a longitudinal approach of the "delay non-match to place" (DNMP) task in a T-maze combined to chemogenetic inhibition of the mPFC or DLS in mice, we show that the mPFC becomes less critical in the maintenance phase of the task as behaviour progressively shifts toward automation. During this phase, the DLS facilitates automated processing. Accordingly, silencing through chemogenetic inhibition of the DLS during maintenance triggers an adaptation in learning strategies, reactivating a goal-directed behaviour. Our findings strengthen memory traces as a dynamic reorganization of neural networks, challenging the classical view of information migration between brain structures. We here propose that the memory trace remains in a dormant state--less energy-consuming for the system--while still allowing for rapid flexibility in case of task modification.

neuroscience↗

bioRxiv2025

Combination of Cas9 and adeno-associated vectors (AAVs) enables efficient in vivo knockdown of precise miRNAs in the rodent brain

Although the advent of Cas9 technology has expanded our ability to precisely edit the genome, manipulating microRNAs in vivo has been shown to be particularly challenging, especially in the brain. Here, we sought to generate novel tools aiming at targeting and efficiently downregulating defined microRNAs species in a cell-specific manner so that their function in discrete neuronal networks could be investigated. Focusing on miR-124, a microRNA highly expressed in the mammalian brain and transcribed from three independent chromosomal loci, we designed and validated different guide RNAs directed against this miRNA. In vitro, our Cas9 designs show not only a significant reduction in miR-124 levels but also a functional effect on miR-124 silencing. Similarly, when packed into AAV vectors and injected into the mouse cortex, miR-124-Cas9 vectors strongly downregulate miR-124 levels without affecting the expression of other miRNAs. In parallel, levels of endogenous miR-124 targets exhibit a significant increase supporting the release of its silencing activity. To functionally validate our tools, we provide evidences that deletion of miR-124 in the subventricular zone altered migration of newly generated neurons into the olfactory bulb. Finally, we also showed that our vectors modified the Ca2+ permeability of AMPA receptors, a robust functional output downstream of miR-124. These tools are expected to help elucidating miRNA function in complex experimental settings such as brain networks in vivo.

neuroscience↗

bioRxiv2023

Coding dynamics of the striatal networks during learning

The rat dorsomedial (DMS) and dorsolateral striatum (DMS), equivalent to caudate nucleus and putamen in primates, are generally required for goal-directed and habit behaviour, respectively. However, it is still unclear whether and how this functional dychotomy emerges in the course of learning. In this study we investigated this issue by recording DMS and DLS single neuron activity in rats performing a continuous spatial alternation task, from the acquisition to optimized performance. We first applied a classical analytical approach to identify task-related activity based on the modifications of single neuron firing rate in relation to specific task events or maze trajectories. We then used an innovative approach based on Hawkes process to reconstruct a directed connectivity graph of simultaneously recorded neurons, that was used to decode animal behavior. This approach enabled us to better unravel the role of DMS and DLS neural networks across learning stages. We showed that DMS and DLS display different task-related activity throughout learning stages, and the proportion of coding neurons over time decreases in the DMS and increases in the DLS. Despite theses major differences, the decoding power of both networks increases during learning. These results suggest that DMS and DLS neural networks gradually reorganize in different ways in order to progressively increase their control over the behavioral performance.

neuroscience↗