Biology subjects

Robil, N.

Publications and source records attributed to Robil, N..

5 recordsLinked to original sources

bioRxiv2025

HnRNP C binding to inverted Alu elements protects the transcriptome from pre-mRNA circularization

Back-splicing is a non-canonical splicing event that drives the biogenesis of circular RNAs (circRNAs). Although the molecular mechanisms underlying circRNA biogenesis have been partially elucidated, how this process is globally regulated in tumors, has not been fully investigated. Herein, we uncover a hnRNP C-dependent mechanism that represses a broad repertoire of circRNAs in Group 3 medulloblastoma (MB). HnRNP C binds Alu elements and prevents the circularization of pre-mRNA transcripts. Expression of hnRNP C modulates the balance between linear and circular splicing and guarantees efficient expression of genes that sustain the oncogenic phenotype of Group 3 MB cells. Remarkably, in the absence of hnRNP C, the introns flanking the circularizing exons generate cytoplasmic dsRNAs through base-pairing of inverted Alu elements and trigger an interferon-induced antiviral response. These findings unveil the role of hnRNP C as guardian of transcriptome integrity by repressing circRNA biogenesis. Lastly, targeting hnRNP C in Group 3 MB may trigger an inflammatory immune response, thereby boosting cancer surveillance.

cancer biology↗

bioRxiv2024

Intestinal fibroblast heterogeneity: unifying RNA-seq studies and introducing consensus-driven nomenclature

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/627573v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1ca5bfborg.highwire.dtl.DTLVardef@5cf61aorg.highwire.dtl.DTLVardef@1213382org.highwire.dtl.DTLVardef@bca9b8_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG In the colon, single-layered epithelium lines the crypts, which descend into the underlying mucosa. Colonic crypts are surrounded by a network of fibroblasts essential for various functions, including the production and remodeling of the extracellular matrix (ECM), supporting the epithelial stem cell niche, and promoting the differentiation of epithelial cells. Recent studies indicate that fibroblasts are not a homogeneous cell population. However, differences in nomenclature and a lack of exact markers hindered their classification and functional understanding. Here, we used single-cell RNA-sequencing (scRNA-seq) to identify six distinct fibroblast subpopulations in mouse colonic mucosa, each with unique molecular signatures and functional specialization. Our analysis reveals that some fibroblasts are primarily involved in ECM production and remodeling, while others exhibit high contractility. Additionally, a subset of fibroblasts produces cytokines that promote epithelial cell differentiation, whereas another group secrete cytokines essential for maintaining the epithelial stem cell niche. We also map the spatial distribution of these fibroblast subpopulations within the colonic mucosa. Differentiation trajectory analysis suggests distinct pathways for fibroblast differentiation, while cell cycle scoring reveals that fibroblasts do not proliferate under homeostatic conditions. Furthermore, we integrated our scRNA-seq data with previously published datasets to identify common fibroblast populations and propose a standardized nomenclature for intestinal fibroblasts. This unified framework aims to improve communication within the research community and enhance understanding of fibroblast roles in gut homeostasis and gastrointestinal diseases.

cell biology↗

bioRxiv2021

In mice and humans, the brain's blood vessels mature postnatally to acquire barrier and contractile properties

The brain dense vascular network is essential for distributing oxygen and nutrients to neural cells. The network develops during embryogenesis and leads to the formation of the endothelial blood-brain barrier (BBB). This barrier is surrounded by mural cells (pericytes and vascular smooth muscle cells (VSMCs)) and fibroblasts. Here, we compared the molecular and functional properties of brain vascular cells on postnatal day (P)5 vs. P15, via a transcriptomic analysis of purified mouse cortical microvessels (MVs) and the identification of vascular-cell-type-specific or -preferentially expressed transcripts. We found that endothelial cells (ECs), VSMCs and fibroblasts follow specific molecular maturation programs over this time period. In particular, ECs acquire P-glycoprotein (P-gP)-mediated efflux capacities. The arterial VSMC network expands, acquires contractile proteins (such as smooth muscle actin (SMA) and myosin heavy chain 11 (Myh11)) and becomes contractile. We also analyzed samples of human brain cortex from the early prenatal stage through to adulthood: the expression of endothelial P-gP increased at birth and Myh11 in VSMCs acts as a developmental switch (as in the mouse) at birth and up to the age of 2 of 5 years. Thus, in both mice and humans, the early postnatal phase is a critical period during which the essential properties of cerebral blood vessels (i.e. the endothelial efflux of xenobiotics and other molecules, and the VSMC contractility required for vessel tone and brain perfusion) are acquired and mature.

neuroscience↗

bioRxiv2021

The JAK2-STAT3 pathway controls a beneficial proteostasis response of reactive astrocytes in Huntington disease

Huntingtons disease is a fatal neurodegenerative disease characterized by striatal neurodegeneration, aggregation of mutant Huntingtin and the presence of reactive astrocytes. Astrocytes are important partners for neurons and engage in a specific reactive response in Huntingtons disease that involves morphological, molecular and functional changes. How reactive astrocytes contribute to Huntingtons disease is still an open question, especially because their reactive state is poorly reproduced in experimental mouse models. Here, we show that the JAK2-STAT3 pathway, a central cascade controlling astrocyte reactive response, is activated in the putamen of Huntingtons disease patients. Selective activation of this cascade in astrocytes through viral gene transfer reduces the number and size of mutant Huntingtin aggregates in neurons and improves neuronal defects in two complementary mouse models of Huntingtons disease. It also reduces striatal atrophy and increases glutamate levels, two central clinical outcomes measured by non-invasive magnetic resonance imaging. Moreover, astrocyte-specific transcriptomic analysis shows that activation of the JAK2-STAT3 pathway in astrocytes coordinates a transcriptional program that increases their intrinsic proteolytic capacity, through the lysosomal and ubiquitin-proteasome degradation systems. This pathway also enhances their production and exosomal release of the co-chaperone DNAJB1, which contributes to mutant Huntingtin clearance in neurons. Together, our results show that the JAK2-STAT3 pathway controls a beneficial proteostasis response in reactive astrocytes in Huntingtons disease, which involves bi-directional signalling with neurons to reduce mutant Huntingtin aggregation, eventually improving disease outcomes.

neuroscience↗

bioRxiv2020

Oligodendrocyte secreted factors shape hippocampal GABAergic neuron transcriptome and physiology

Oligodendrocytes form myelin for central nervous system axons and release factors which signal to neurons during myelination. Here, we ask how oligodendroglial factors influence hippocampal GABAergic neuron physiology. In mixed hippocampal cultures GABAergic neurons fired action potentials of short duration and received high frequencies of excitatory synaptic events. In purified neuronal cultures without glial cells, GABAergic neuron excitability increased and the frequency of synaptic events decreased. These effects were largely reversed by adding oligodendrocyte conditioned medium. We compared the transcriptomic signature with the electrophysiological phenotype of single neurons in these three culture conditions. Genes expressed by single pyramidal or GABAergic neurons largely conformed to expected cell-type specific patterns. Multiple genes of GABAergic neurons were significantly downregulated by the transition from mixed cultures containing glial cells to purified neuronal cultures. Levels of these genes were restored by the addition of oligodendrocyte conditioned medium to purified cultures. Clustering genes with similar changes in expression between different culture conditions revealed processes affected by oligodendroglial factors. Enriched genes are linked to roles in synapse assembly, action potential generation and transmembrane ion transport, including of zinc. These results provide new insight into the molecular targets by which oligodendrocytes influence neuron excitability and synaptic function.

neuroscience↗