Biology subjects

Baron, S.

Publications and source records attributed to Baron, S..

7 recordsLinked to original sources

bioRxiv2026

Renal adaptation to primary aldosteronism requires GDF15 to control plasma potassium level in mice and human.

Background Primary aldosteronism (PA), the most common secondary cause of hypertension, results from autonomous aldosterone production, driving renal Na retention and K secretion. Paradoxically, only 9 to 37% of PA patients develop hypokalemia, suggesting adaptive mechanisms. Growth differentiation factor 15 (GDF15) promotes intercalated cell type A (ICA) proliferation and K reabsorption in the collecting duct, but its role in PA is unexplored. Methods We measured urinary and plasma GDF15 in 81 PA patients (two centers) and 41 controls. A murine model of chronic mineralocorticoid excess (DOCP treatment) was used in wild-type (WT) and GDF15 knockout (GDF15KO) mice to assess renal adaptation. Results PA patients exhibited 3-fold higher urinary GDF15 and 1.6-fold higher plasma GDF15 than controls, with normalization post-treatment. 24-hour urinary GDF15 correlated with urinary aldosterone (rho=0.35, p<0.01), age, and BMI (Body Mass Index), but not plasma K. WT mice developed hypokalemia following DOCP administration (plasma K 3.5{+/-}0.1 mM vs. 4.3{+/-}0.1 mM in controls, p<0.01). In GDF15KO mice DOCP-induced hypokalemia was more severe, indicating a protective role of GDF15. In WT mice, DOCP increased 24-hour urinary GDF15 (2-fold) and GDF15 expression in the collecting duct. Transcriptomic analysis revealed an inverted transcriptional response to chronic mineralocorticoid in ICA and PC according to the genotype. This could be related to the increase of ICA number in WT, an effect abolished in GDF15KO mice. Conclusions These results indicate that GDF15 is involved in the renal response to mineralocorticoid excess, likely through stimulation of ICA proliferation, which may promote potassium reabsorption in the collecting duct and help mitigate aldosterone-mediated K loss.

physiology↗

bioRxiv2026

Optimization of Agrobacterium-mediated transformation of commercial heirloom tomato cultivars to develop novel traits via CRISPR/Cas9 Genome Editing

Genetic improvement using new genome editing approaches rely on the efficient delivery of the CRISPR/Cas system in the vegetable crop tomato. Previous protocols for tomato transformation have primarily focused on a handful of cultivars (M82, Alisa Craig, Microtom, Sweet-100) with very little commercial relevance, and it is not clear if these protocols can be implemented directly in other commercially relevant varieties. Heirloom tomatoes are sought for their deep and diverse flavor but have not been subjected to systematic crop improvement via conventional breeding or biotechnology approaches such as transgenesis or genome editing. Therefore, we tested the transformation and regeneration capacity of six different heirloom cultivars known for their superior taste and market relevance in the US. Subsequently, we optimized rooting conditions and used the GRF4-GIF1 chimeric developmental regulator to successfully recover transgenic plants. Finally, we evaluated the efficiency of targeted genetic modification using the CRISPR/Cas9 genome editing system in several of these cultivars. We demonstrate that our optimizations led to successful transformation of several heirloom varieties, including the generation of edited plants for target genes modifying plant architecture and flowering time. Our results set the foundation for a biotechnology platform to deliver improved traits to local and regional heirloom varieties using genome editing.

plant biology↗

bioRxiv2025

Sexually dimorphic interzonal crosstalk reshapes the adrenal cortex in response to pathophysiological challenges

Structured Abstract BackgroundPrimary aldosteronism is the most common form of secondary arterial hypertension, due to autonomous aldosterone production from the adrenal cortex. Genome wide association studies discovered genetic risk loci associated with the disease, which may affect adrenal cortex renewal, differentiation and lineage conversion. Genetic susceptibility may be modulated by environmental challenges. MethodHere we investigate how environmental cues affecting mineralocorticoid output modulate adrenal cortex homeostasis, cell lineage conversion and zone-specific transcriptional landscape. We have used a newly developed Cyp11b2Cremouse model and characterised its adaptation to a high or low salt diet (HSD, LSD), as well as dexamethasone (DEX) treatment. To explore underlying mechanisms, deep functional and morphological phenotyping, lineage tracing and spatial transcriptomics of the adrenal cortex were performed. ResultsCyp11b2 expression was detected in Cyp11b2Cre-mTmG mice as early as day P1 in different areas of the ZG, associated with high plasma aldosterone levels, with lineage conversion of zona glomerulosa (ZG) into zona fasciculata (ZF) cells progressing between 2 and 9 weeks of age and a progressive reduction of ZG size and evolution of cell components of the adrenal cortex over time. Transdifferentiation progressed into the X-zone (ZX) in females, revealing a previously unrecognized connection between ZF and ZX cells in adult mice. A sexually dimorphic, reciprocal interaction between the ZG and the ZF in adapting to salt diets or DEX treatment was observed, involving changes in cell composition and transcriptional reprogramming of the three zones. ConclusionHSD, LSD and DEX induce a sexually dimorphic cellular and transcriptional response, involving all layers of the adrenal cortex, and the reciprocal contribution of ZG and ZF cells, indicating functional interaction between adrenocortical zones in adapting to external cues.

physiology↗

bioRxiv2025

Blood-borne sphingosine 1-phosphate maintains vascular resistance and cardiac function.

G protein-coupled receptors (GPCRs) are key regulators of cardiovascular function that provide targets for the treatment of cardiovascular disease. Sphingosine 1-phosphate (S1P) is an erythrocyte- and platelet-derived lipid mediator with cognate GPCRs on endothelial cells (EC), vascular smooth muscle cells (VSMC) and cardiomyocytes. S1P circulates in plasma bound to apolipoprotein M (ApoM)-containing high-density lipoproteins (HDL) and to albumin. Circulating S1P levels correlate positively with systolic blood pressure in hypertension and negatively with severity in septic shock and with left ventricular (LV) function in coronary heart disease. In mice, impaired S1P binding to HDL or signaling to EC both trigger hypertension, supporting an essential role for HDL-S1P in supporting endothelial function. The roles of albumin-S1P and myocyte S1PRs in cardiovascular homeostasis remain incompletely defined. Contrasting isolated HDL-S1P deficiency, we report that non-selective depletion of circulating S1P pools in mice impairs LV contractile function and induces hypotension and resistance to the spontaneous increase in blood pressure with age. Cardiac output was preserved in naive S1P deficient mice by compensatory LV dilation, but cardiac reserve reduced in a dobutamine stress test. These phenotypes tracked with hematopoietic cell S1P production and were partially or fully reversed by erythrocyte transfusion. Hypotension was accompanied by reduced peripheral resistance, and S1P infusion dose-dependently increased vascular resistance in isolated perfused kidneys from wild-type mice but not mice with compound deficiency in S1PR2&3. Epistatic analysis supported a critical role for S1PR3 in S1P-dependent blood pressure regulation and pointed to a distinct origin of the cardiac phenotype. Although circulating S1P is elevated in hypertensive mice and humans, increasing circulating S1P was not sufficient to induce hypertension in naive mice. These observations suggests that albumin-S1P crosses the endothelium in resistance arteries to gain access to contractile VSMC S1P receptors, and that myocyte S1PR signaling is essential for vascular resistance and blood pressure maintenance in mice. They also highlight the role for plasma chaperones in specifying vascular responses to S1P and the relevance of S1P as a biomarker and potential therapeutic target for blood pressure regulation and heart failure.

physiology↗

bioRxiv2024

Identification of a mimotope of a complex gp41 Human Immunodeficiency VIrus epitope related to a non-structural protein of Hepacivirus previously implicated in Kawasaki disease

BackgroundWe have previously isolated a highly mutated VH1-02 antibody termed group C 76-Q13-6F5 (6F5) that targets a conformational epitope on gp41. 6F5 has the capacity to mediate Ab dependent cell cytotoxicity (ADCC). When the VH1-02 group C 76 antibodies variable chain sequence was reverted to germline (76Canc), this still retained ADCC activity. Due to this ability for the 76Canc germline antibody to functionally target this epitope, we sought to identify a protein target for vaccine development. MethodsInitially, we interrogated peptide targeting by screening a microarray containing 29,127 linear peptides. Western blot and ELISAs were used to confirm binding and explore human serum targeting. Autoimmune targeting was further interrogated on a yeast-displayed human protein microarray. Results76Canc specifically recognized a number of acidic peptides. Meme analysis identified a peptide sequence similar to a non-structural protein of Hepacivirus previously implicated in Kawasaki disease (KD). Binding was confirmed to top peptides, including the Hepacivirus-related and KD-related peptide. On serum competitions studies using samples from children with KD compared to controls, targeting of this epitope showed no specific correlation to having KD. Human protein autoantigen screening was also reassuring. ConclusionsThis study identifies a peptide that can mimic the gp41 epitope targeted by 76C group antibodies (i.e. a mimotope). We show little risk of autoimmune targeting including any inflammation similar to KD, implying non-specific targeting of this peptide during KD. Development of such peptides as the basis for vaccination should proceed cautiously.

immunology↗

bioRxiv2024

Modulation of calcium signaling on demand to decipher the molecular mechanisms of primary aldosteronism

Primary aldosteronism (PA) is the most common form of secondary hypertension. Major advances have been made in our understanding of PA with the identification of germline and somatic mutations in ion pumps and channels. These mutations lead to the activation of calcium signalling, the major trigger of aldosterone biosynthesis. To elucidate the molecular mechanisms underlying the development of PA, we established an adrenocortical cell model in which we can modulate sodium entry into the cells "on demand" leading to calcium signalling activation. These cells recapitulated the major features of KCNJ5 mutations, the most frequent genetic alteration identified in Aldosterone-Producing-Adenoma. Activation of calcium signalling was associated with increased aldosterone biosynthesis and decreased cell proliferation. RNA sequencing and steroidome analyses revealed unique profiles associated with Na+ entry. Altogether, this work offers valuable insights into the role of sodium-induced calcium signalling in PA development and paves the way for developing new therapeutic strategies.

physiology↗

bioRxiv2018

Expression of a recombinant, 4’-Phosphopantetheinylated, active M. tuberculosis Fatty acid Synthase I in E. coli

Fatty acid synthase 1 (FAS I) from Mycobacterium. tuberculosis (Mtb) is an essential protein and a promising drug target. FAS I is a multi-functional, multi-domain protein that is organized as a large (1.9 MDa) homohexameric complex. Acyl intermediates produced during fatty acid elongation are attached covalently to an acyl carrier protein (ACP) domain. This domain is activated by the transfer of a 4-Phosphopantetheine (4-PP, also termed P-pant) group from CoA to ACP catalyzed by a 4-PP transferase, termed acyl carrier protein synthase (AcpS). In order to obtain an activated FAS I in E. coli, we transformed E. coli with tagged Mtb fas1 and acpS genes encoded by a separate plasmid.\n\nWe induced the expression of Mtb FAS I following induction of AcpS expression. FAS I was purified by Strep-Tactin affinity chromatography. Activation of Mtb FAS I was confirmed by the identification of a bound P-pant group on serine at position 1808 by mass spectrometry. The purified FAS I displayed biochemical activity shown by spectrophotometric analysis of NADPH oxidation and by CoA production, using the Ellman reaction. The purified Mtb FAS I forms a hexameric complex shown by negative staining and cryo-EM. Purified hexameric and active Mtb FAS I is required for binding and drug inhibition studies and for structurefunction analysis of this enzyme. This relatively simple and short procedure for Mtb FAS I production should facilitate studies of this enzyme.

microbiology↗