Biology subjects

Briand, N.

Publications and source records attributed to Briand, N..

4 recordsLinked to original sources

bioRxiv2025

Mitochondrial redox homeostasis links organellar stress surveillance to germline and somatic integrity in Caenorhabditis elegans

Mitochondrial redox homeostasis is essential for cellular metabolism and organismal development. To investigate the consequences of disrupting redox homeostasis in this organelle in a metazoan organism, we generated a double mutant lacking mitochondrial glutathione reductase (gsr-1a) and thioredoxin reductase (trxr-2) genes in Caenorhabditis elegans. While gsr-1a or trxr-2 single mutants are phenotypically normal, double gsr-1a trxr-2 mutants displayed small body size, gonadal migration defects, reduced brood size, and prolonged egg-laying period, without developmental delay or lethality. Transcriptomic analysis revealed strong induction of ATFS-1-dependent stress and detoxification genes. Consistent with this, gsr-1a trxr-2 worms exhibited constitutive ATFS-1 nuclear localization and robust Phsp-6::gfp expression. Triple gsr-1a trxr-2; atfs-1 mutants were nonviable, demonstrating that unfolded protein response (UPRmt) activation is essential under mitochondrial redox stress. Despite the induction of a stress response at the transcriptional level, gsr-1a trxr-2 double mutants were not more resistant to oxidative or pathogen stressors. Moreover, these mutants maintained normal respiration, ATP and ROS production while displaying altered mitochondrial morphology in a tissue-specific manner, independent of mitophagy genes but dependent on mitochondrial fission or fusion machinery. Functionally, gsr-1a trxr-2 mutants showed impaired motility, reduced calcium uptake upon carbachol stimulation, enhanced hypodermal wound repair, and decreased fertilization efficiency associated with lower muscle exopher production. Overall, our data show that simultaneous loss of mitochondrial GSR-1a and TRXR-2 compromises growth, fertility and muscle performance and triggers a constitutive ATFS-1-dependent UPRmt that sustains viability revealing mitochondrial redox control as a core determinant of organismal proteostasis. HighlightsO_LIgsr-1a or trxr-2 single mutants have no overt phenotypes. C_LIO_LIgsr-1a trxr-2 double mutants are viable but show small size, gonad migration defects and reduced progeny. C_LIO_LILoss of both reductases in mitochondria triggers a constitutive ATFS-1-dependent UPRmt. C_LIO_LIATFS-1 is essential for gsr-1a trxr-2 worms survival. C_LIO_LIgsr-1a trxr-2 animals remodel mitochondrial morphology in a tissue-specific manner. C_LIO_LIgsr-1a trxr-2 double mutants exhibit impaired muscle and sperm function but enhanced wound healing. C_LI Graphical abstract (to be incorporated)

genetics↗

bioRxiv2025

Mechanisms of sexually dimorphic adipose tissue remodelling upon prolonged breastfeeding

Early developmental cues exert lasting influence on the adipose tissue function and the metabolic health throughout adulthood. In mice, adipose tissue remodelling during the weaning transition programs long-term tissue plasticity, setting its capacity for expansion and thermogenesis in response to environmental stimuli. However, the mechanisms driving this remodelling, and the role of weaning-associated dietary changes in this process, are unknown. Here, we characterise the emergence of sexually dimorphic patterns of adipose tissue distribution and function during the post-weaning period. As subcutaneous adipocytes acquire a white phenotype, the tissue microenvironment undergoes a coordinated remodelling, including reduced innervation and an increase in immune cell content. Using a model of prolonged breastfeeding, we show that it promotes adipose tissue expansion through sex-dependent mechanisms, stimulating progenitor proliferation in males and adipocyte hypertrophy in females. In males, this is accompanied by accelerated tissue whitening, which we link to enhanced clearance of extracellular noradrenaline by mature adipocytes. Our findings reveal sex- and diet-dependent mechanisms governing adipose tissue maturation and highlight how early life nutritional cues shape the microenvironment and function of mature adipocytes. Highlights- The peri-weaning period associates with sexually dimorphic remodelling of the adipose tissue - Whitening of the adipose tissue associates with immune infiltration and decrease innervation in both sexes - Prolonged breastfeeding prevents drop in proliferation in males - Whitening is accelerated in males during prolonged breastfeeding

physiology↗

bioRxiv2025

SUMOylation Restricts Adaptive Thermogenesis by Suppressing Beiging Gene Networks

SUMOylation regulates chromatin states and transcriptional programs that preserve cellular identity, yet how transient perturbation of the SUMO pathway impacts adipocyte plasticity remains unclear. Here we show that brief pharmacologic inhibition of SUMO conjugation in human pre-adipocytes using TAK-981 primes stable de novo beige differentiation in the presence of the PPARG agonist rosiglitazone. Transient TAK-981 exposure before adipogenic induction produces long-lasting changes in the transcriptome and metabolism of mature adipocytes, including robust induction of canonical beiging markers like UCP1 and increased mitochondrial respiration. Mechanistically, ATAC-seq and transcription factor footprinting revealed immediate and durable chromatin remodeling and early mobilization of CEBP family members, followed by stable activation of CEBPA and PPARG regulatory networks. ChIP experiments demonstrated loss of H3K27me3 and gain of H3K27ac at PPAR response elements within key thermogenic enhancers, with increased PPARG occupancy across the UCP1 regulatory unit. This mechanism is enforced by enhanced cAMP-PKA-p38 signaling, and stabilization of beiging transcriptional activators. Our data support a model in which transient relief of SUMO-mediated repression unlocks dominant regulatory units, notably the UCP1 enhancer cluster, producing a monomorphic, cell type specific reprogramming toward adaptive thermogenesis. These findings identify SUMOylation as a reversible epigenetic barrier to adipocyte beiging and suggest that temporally controlled SUMO pathway inhibition combined with PPARG activation could be exploited to modulate adipose tissue thermogenic capacity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/642034v3_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@9efd29org.highwire.dtl.DTLVardef@1fecda3org.highwire.dtl.DTLVardef@16eb784org.highwire.dtl.DTLVardef@1d25683_HPS_FORMAT_FIGEXP M_FIG C_FIG SUMOylation restricts de novo differentiation of pre-adipocytes into beige adipocytes by repressing cAMP signaling and preventing epigenetic and transcriptional reprogramming of white adipocytes.

molecular biology↗

bioRxiv2022

De novo annotation of lncRNA HOTAIR transcripts by long-read RNA capture-seq reveals a differentiation-driven isoform switch

BackgroundLncRNAs are tissue-specific and emerge as important regulators of various biological processes and as disease biomarkers. HOTAIR is a well-established pro-oncogenic lncRNA which has been attributed a variety of functions in cancer and native contexts. However, a lack of an exhaustive, cell type-specific annotation questions whether HOTAIR functions are supported by the expression of multiple isoforms. ResultsUsing a capture long-read sequencing approach, we characterize HOTAIR isoforms expressed in human primary adipose stem cells. We identify a highly cell type-specific HOTAIR isoform and uncover a shift in the HOTAIR isoform balance at differentiation onset. Composition of the HOTAIR isoform pool is regulated by distinct promoter usage and is under control of hormonal and nutrient-sensing pathways. ConclusionOur results highlight the complexity and cell type-specificity of HOTAIR isoforms and open perspectives on functional implications of these variants and their balance to key cellular processes.

genomics↗