Biology subjects

Saulnier, D.

Publications and source records attributed to Saulnier, D..

5 recordsLinked to original sources

bioRxiv2025

Metabolic Maturation Unveils Left Ventricular Identity in WNT ON/OFF Human Pluripotent Stem Cell-Derived Cardiomyocytes

Deriving high-purity mature left ventricular (LV) cardiomyocytes (CMs) from human pluripotent stem cells (hPSCs) is a priority for cardiovascular research and for future therapeutic applications. Small-molecule WNT modulation (WNT ON/OFF) is currently the predominant differentiation method; however, a critical discordance exists regarding its cardiac subtype outcome. While lineage tracing suggests a First Heart Field (FHF) bias, phenotypic characterizations report significant heterogeneity regarding definitive ventricular markers, leading to controversy about the cardiac subtypes generated by this method. Here, we demonstrate that this apparent heterogeneity is a result of CM immaturity. Using single-cell protein analysis, we first show that WNT ON/OFF generates an NKX2.5+ progenitor pool that robustly co-expresses HAND1, confirming uniform FHF specification regardless of differentiation efficiency. We then demonstrate that the CM population negative for the ventricular marker MYL2 observed at early differentiation timepoints mostly represents immature LV cardiomyocytes that have not yet acquired their definitive phenotype. By implementing a targeted metabolic maturation regime, we unlocked this identity, achieving 95% MYL2+/HAND1+/TBX5+ LV CMs by day 38, substantially earlier and with higher chamber-specific purity than previously reported. This phenotypic resolution was accompanied by advanced structural maturation, including sarcomeric protein isoform switching, multinucleation, and notably, the assembly of polarized XIRP2+ intercalated discs, a hallmark of postnatal CM maturation not previously described in 2D differentiations. Validated across three independent hPSC lines, these findings provide the field with a rapid, high-fidelity platform for generating pure mature LV cardiomyocytes for disease modeling and therapeutic research.

developmental biology↗

bioRxiv2023

The transcription factor OCT6 promotes the dissolution of the naive pluripotent state by repressing Nanog and activating a formative state gene regulatory network.

Animal development relies on complex gene regulatory networks (GRNs) that govern the nearly irreversible changes that occur during cell differentiation. In this work we aimed to determine key transcription factors (TFs) associated with the dissolution of the naive pluripotent state and the acquisition of a formative identity. We identified OCT6 as one of the earliest TFs induced during the onset of mouse embryonic stem cell (mESCs) differentiation. To investigate its role, we generated an Oct6 knockout mESC line, which failed to acquire the characteristic cell morphology associated with the formative state. Transcriptome analysis of differentiating cells revealed nearly 300 differentially expressed genes compared to wild-type cells, including pluripotency TFs Nanog, Klf2, Nr5a2, Prdm14, and Esrrb, that failed to correctly downregulate. Notably, premature expression of OCT6 in naive cells triggered a rapid morphological transformation mirroring differentiation, accompanied by self-induction of Oct6 and expression of TFs such as Sox3, Zic2/3, Foxp1, as well as the formative genes Dnmt3A and FGF5. Strikingly, the majority of OCT6 expressing cells did not express NANOG. Gene expression and single molecule RNA-FISH analysis confirmed that this regulation was at the transcriptional level. Collectively, our results establish OCT6 as a key TF in the dissolution of the naive pluripotent state and support a model where Oct6 and Nanog form a double negative feedback loop which could act as a toggle switch important for the transition to the formative state. HighlightsO_LIOct6 is rapidly induced as mESCs exit ground state pluripotency. C_LIO_LILoss of OCT6 negatively affects the transition to formative pluripotency. C_LIO_LIPremature expression of OCT6 in mESCs is sufficient to induce a formative-like phenotype. C_LIO_LIOCT6 and NANOG repress each other forming a double negative feedback loop. C_LI

developmental biology↗

bioRxiv2022

Experimental Diets Dictate the Metabolic Benefits of Lactobacillus Strains in Obesity

BackgroundGrowing evidence supports the use of probiotics to prevent or mitigate obesity-related dysmetabolism and non-alcoholic fatty liver disease (NAFLD). However, frequent reports of responders versus non-responders to probiotic treatment warrant a better understanding of key modifiers of host-microbe interactions. The influence of host diet on probiotic efficacy, in particular against metabolic diseases, remains elusive. MethodWe fed C57BL6/J mice a low fat reference diet or one of two energy-matched high fat and high sucrose diets for 12 weeks; a classical high fat diet (HFD) and a customized fast food-mimicking diet (FFMD). During the studies, mice fed either obesogenic diet were gavaged daily with one of two probiotic lactic acid bacteria (LAB) strains previously classified as Lactobaccillus, namely Limosilactobacillus reuteri (L. reuteri) or Lacticaseibacillus paracasei subsp. paracasei (L. paracasei), or vehicle. ResultsThe tested probiotics exhibited a reproducible efficacy but dichotomous response according to the obesogenic diets used. Indeed, L. paracasei prevented weight gain, improved insulin sensitivity, and protected against NAFLD development in mice fed HFD, but not FFMD. Conversely, L. reuteri improved glucoregulatory capacity, reduced NAFLD development, and increased distal gut bile acid levels associated with changes in predicted functions of the gut microbiota exclusively in the context of FFMD-feeding. ConclusionWe found that the probiotic efficacy of two LAB strains is highly dependent on experimental obesogenic diets. These findings highlight the need to carefully consider the confounding impact of diet in order to improve both the reproducibility of preclinical probiotic studies and their clinical research translatability. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

microbiology↗

bioRxiv2021

First isolation of virulent Tenacibaculum maritimum strains from diseased orbicular batfish (Platax orbicularis) farmed in Tahiti Island

The orbicular batfish (Platax orbicularis), also called Paraha peue in Tahitian, is the most important marine fish species reared in French Polynesia. Sudden and widespread outbreaks of severe white-patch disease have occurred since 2011 in batfish farms one to three weeks after the transfer of juveniles from bio-secured hatcheries to lagoon cages. With cumulative mortality ranging from 20 to 90%, the sustainability of aquaculture of this species is severely threatened. In this study, we describe for the first time the isolation from diseased batfish of several strains belonging to the species Tenacibaculum maritimum, a major pathogen of many marine fish species. Histopathological analysis, an experimental bath challenge and a field monitoring study showed that T. maritimum is associated with white-patch disease. Moreover, molecular and serological analyses performed on representative strains revealed some degree of genetic diversity among the isolates, a finding of primary importance for epidemiological studies and for the development of management and control strategies such as vaccination.

pathology↗

bioRxiv2020

Dual RNAseq highlights the kinetics of skin microbiome and fish host responsiveness to bacterial infection

a) BackgroundTenacibaculum maritimum is a worldwide-distributed fish pathogen known for causing dramatic damages on a broad range of wild and farmed marine fish populations. Recently sequenced genome of T. maritimum strain NCIMB 2154T provided unprecedented information on the possible molecular mechanisms involved in virulence for this species. However, little is known on the dynamic on the infection in vivo, and information are lacking on both the intrinsic host response (gene expression) and its associated microbiome community. Here, we applied complementary omic approaches, including dual RNAseq and 16S rRNA gene metabarcoding sequencing using Nanopore and short-reads Illumina technologies to unravel the host-pathogens interplay in experimental infection system using the tropical fish Platax orbicularis as model. b) ResultsWe show that T. maritimum transcriptomic landscape during infection is characterized by an enhancement of antibiotic catalytic and glucan catalytic functions while decreasing specific sulphate assimilation process, compared to in vitro cultures. Simultaneously, fish host display a large palette of immune effectors, notably involving innate response and triggering acute inflammatory response. In addition, results suggest that fish activate adaptive immune response visible through stimulation of T-helper cells, Th17, with congruent reduction of Th2 and T-regulatory cells. Fish were however largely sensitive to infection, and less than 25% of them survived after 96hpi. These surviving fish showed no evidence of stress (cortisol levels) as well as no significant difference in microbiome diversity compared to control at the same sampling time. The presence of Tenacibaculum in resistant fish skin and the total absence of any skin lesion suggest that these fish did not escape contact with the pathogen but rather prevent the pathogen entry. In these individuals we detected the up-regulation of specific immune-related genes differentiating resistant from control at 96hpi, which suggests a possible genomic basis of resistance while no genetic variations in coding regions was reported. c) ConclusionHere we refine the interplay between common fish pathogens and host immune response during experimental infection. We further highlight key actors of defense response, pathogenicity and possible genomic bases of resistance to T. maritimum.

genomics↗