Biology subjects

Liaudet, N.

Publications and source records attributed to Liaudet, N..

5 recordsLinked to original sources

bioRxiv2026

Low-salt diet induces claudin-3 expression and drives adaptive changes in collecting duct of claudin-3-deficient mice

BackgroundRenal sodium reabsorption occurs via both transcellular and paracellular pathways. Tight junction proteins play a key role in mediating paracellular transport. The collecting duct (CD) is critical for the fine-tuning of Na+ balance and is sensitive to changes in dietary salt intake. A low-sodium diet, which increases endogenous aldosterone secretion, stimulates transcellular sodium transport via epithelial Na+ channels (ENaC) and Na,K-ATPase. We hypothesized that a low-sodium diet also modulates paracellular Na+ permeability by regulating the expression or function of claudin-3, a major tight junction protein in the CD, in order to limit the back-leak of reabsorbed sodium and preserve sodium balance. MethodsWe used in vivo mouse models and cultured mouse CD principal cells (mCCDcl1) to assess aldosterones effects on tight junction proteins. In mCCDcl1 cells, aldosterone-induced changes in claudin-3 expression and localization were evaluated via Western blotting and immunofluorescence, and Ussing chamber assays were used to assess paracellular Na+ and Cl- permeability after modulating claudin-3 expression. Wild-type and claudin-3 knockout mice were fed low (0.01%) or normal (0.18%) sodium diets for seven days. In subsets of low sodium diet mice, spironolactone (a mineralocorticoid receptor antagonist) was administered. ResultsIn mice, a low-sodium diet upregulates renal claudin-3 expression. Concordantly, in vitro studies using mCCDcl1 cells showed that aldosterone treatment increased claudin-3 protein levels and promoted its localization to the lateral membrane. Functional analyses demonstrated that claudin-3 overexpression reduced paracellular permeability to both Na+ and Cl-, while claudin-3 silencing increased it. Claudin-3 knockout mice subjected to a low-sodium diet exhibited compensatory upregulation of the - and {gamma}-subunits of ENaC, alongside increased expression of claudin-4, claudin-8, and claudin-10. This highlights an adaptive response that maintains sodium homeostasis in the absence of claudin-3. Importantly, this compensatory mechanism persists even under spironolactone treatment, suggesting that the adaptation of claudin-3-deficient mice occurs independently of mineralocorticoid receptor activation. ConclusionsOur findings demonstrate that aldosterone enhances claudin-3 expression, reinforcing the paracellular barrier to Na+ and complementing its classical role in transcellular Na+ transport. Under low-sodium conditions, claudin-3-deficient mice adapt through complementary mechanisms aimed at increasing sodium reabsorption via ENaC activation and upregulation of claudin-4 and claudin-8, both barrier-forming claudins that restrict paracellular sodium leakage in the CD. This is associated with increased claudin-10 abundance in the thick ascending limb of Henle, a pore-forming claudin that facilitates paracellular sodium permeability. This study advances our understanding of the complex control of renal sodium handling, revealing adaptive mechanisms in response to low-salt diet and claudin-3 deficiency.

physiology↗

bioRxiv2025

CtBP1 coordinates synaptic, metabolic and contractile changes induced by denervation in skeletal muscle

Nerve injury triggers dramatic atrophy of skeletal muscle, accompanied with synaptic and metabolic changes. Regulation of denervation-induced muscle fiber remodeling involves several factors governing genetic reprogramming and proteostasis changes. Here, we demonstrate that the transcriptional co-repressor CtBP1 coordinates synaptic and metabolic changes in muscle fibers upon denervation. CtBP1 was present both in sub- and non-synaptic myonuclei in innervated muscle. Although CtBP1 levels remained unchanged in denervated muscle, CtBP1 accumulated transiently in myonuclei after 2 days of denervation. Ctbp1 knockdown perturbed the expression of a large set of activity-independent and -dependent genes in innervated and denervated skeletal muscles. CtBP1 loss had limited effect on the expression of most synaptic genes, but increased transcript levels of Chrne, encoding the adult {varepsilon} sub-unit of acetylcholine receptors (AChR). However, it did not affect AChR turnover or maintenance of the post-synaptic compartment upon denervation. Importantly, we uncovered that Ctbp1 knockdown promotes denervation-induced changes in metabolic gene expression, including most genes encoding proteins of the respiratory chain complexes. Consistently, it enhanced the switch towards slower, oxidative fibers in fast muscle after 2 weeks of denervation. Moreover, CtBP1 loss precipitated the profound ultrastructural remodeling of mitochondria network induced after denervation. Hence, our study unveils the role of CtBP1 in the integrated muscle response to denervation, with important implications for CtBP1-related muscle diseases. One-sentence summaryLoss of CtBP1 perturbs synaptic, metabolic and contractile changes induced by denervation in skeletal muscle

physiology↗

bioRxiv2025

Tissular glucocorticoid reactivating enzyme 11beta-HSD1 drives pathogenic myofibroblast differentiation in chronic kidney disease

Chronic kidney disease (CKD) is a growing public health crisis, affecting over 10% of the global population and significantly increasing mortality and morbidity. Irrespective of its underlying cause, tubulointerstitial fibrosis (TIF) is a hallmark of CKD progression, with myofibroblasts being the primary effectors of renal fibrosis. Here, we show that 11beta-hydroxysteroid dehydrogenase type 1 (11{beta}-HSD1) is a critical driver of pathogenic myofibroblast differentiation and fibrosis in CKD. Using genetic deletion and pharmacological inhibition of 11{beta}-HSD1 in mouse models, we demonstrate a marked reduction in TIF severity and improved renal function, linked to the suppression of a regulatory myofibroblast (Reg-MF) subpopulation. Single-cell and spatial transcriptomics data reveal that 11{beta}-HSD1 is essential for the activation and expansion of Reg-MFs, which is conserved across species and predicts worse outcomes in CKD patients and kidney allograft recipients. These findings establish a direct link between 11{beta}-HSD1 activity and renal fibrogenesis, highlighting its role during the transition from pericytes to pathogenic Reg-MFs. Our results support 11{beta}-HSD1 inhibition as a promising therapeutic strategy to mitigate CKD progression, offering both mechanistic insights and translational potential for improving patient outcomes.

physiology↗

bioRxiv2020

Spatial transcriptomics of tumor microenvironment in formalin-fixed paraffin-embedded breast cancer

Tumor samples are conserved in clinical practice in formalin-fixed paraffin-embedded (FFPE) blocks. Formalin fixation chemically alters nucleic acids, rendering transcriptomic analysis challenging. RNA-sequencing is usually performed on tumor bulk, without distinction of cell subtypes or location. Here we describe the development of a robust method for RNA extraction and exome-capture RNA-sequencing of laser-capture microdissected tumor cells (TC) and stromal immune cells (TIL) based on their morphology. We applied this method on 7 tumor samples (surgical or core needle biopsy) of triple-negative breast cancer (TNBC) stored in FFPE blocks over 3-10 years. Unsupervised clustering and principal component analysis showed a clear separation between gene-expression profile of TIL and TC. TIL were enriched in markers of B cells (CD79B, PAX5 and BLNK) and T cells (CD2, CD3D and CD8B) whereas tumor cells expressed epithelial markers (EPCAM, MUC1 and KRT8). Microenvironment cell populations-counter (MCP)-counter deconvolution showed an enrichment in adaptive immune cell signatures in microdissected TIL. Transcripts of immune checkpoints were differentially expressed in TIL and TC. We further validated our results by qRT-PCR and multispectral immunohistochemistry. In conclusion, we showed that combining laser-capture microdissection and RNA-sequencing on archived FFPE blocks is feasible and allows spatial transcriptional characterization of tumor microenvironment.

cancer biology↗

bioRxiv2019

Centrosomes control kinetochore-fiber plus-end dynamics via HURP to ensure symmetric divisions

During mitosis centrosomes can affect the length of kinetochore-fibers (k-fibers) and the stability of kinetochore-microtubule attachments, implying that they regulate k-fiber dynamics. The exact cellular and molecular mechanisms by which centrosomes regulate k-fibers remain, however, unknown. Here, we created human non-cancerous cells with only one centrosome to investigate these mechanisms. Such cells formed highly asymmetric bipolar spindles that resulted in asymmetric cell divisions. K-fibers in acentrosomal spindles were shorter, more stable, had a reduced poleward microtubule flux at minus-ends, and more frequent pausing events at their plus-ends. This indicates that centrosomes regulate k-fiber dynamics both locally at minus-ends and far away at plus-ends. At the molecular level we find that the microtubule-stabilizing protein HURP is enriched on the k-fiber plus-ends in the acentrosomal spindles of cells with only one centrosome. HURP depletion rebalance k-fiber stability and dynamics in such cells, and improved spindle and cell division symmetry. Our data further indicate that HURP accumulates on k-fibers inversely proportionally to half-spindle length. We propose that centrosomes regulate k-fiber plus-ends indirectly via length-dependent accumulation of HURP. Thus by ensuring equal k-fiber length, centrosomes promote HURP symmetry, reinforcing the symmetry of the mitotic spindle and of cell division.

cell biology↗