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The Great Rift Valley: a dividing continent Africa's Great Rift Valley is geologically active: gradually the continent is being split in two. In July and August 2007 one of the discrete rifting events contributing to this continental break-up was recorded in the form of a seismic crisis in the Lake Natron area, Tanzania. This provided an opportunity to examine the respective roles of faulting and magmatism in the rifting process. Data from the local seismic network, GPS stations and the Envisat satellite reveal that initial ground deformation was due to aseismic slip on a fault on the eastern side of the rift, and then to the emplacement of magma into the crust. This points to strain accommodation by magma intrusion as a major factor — in addition to slow slip along normal faults — during the early stages of continental rifting. Continental rifts initiate and develop through repeated episodes of faulting and magmatism, yet strain partitioning between faulting and magmatism during discrete rifting episodes remains poorly documented. It is shown that most of the strain during the July–August 2007 seismic crisis in the Natron rift, Tanzania, was released aseismically. This event provides evidence for strain accommodation by magma intrusion, in addition to slip along normal faults, during the initial stages of continental rifting, and before significant crustal thinning. Continental rifts begin and develop through repeated episodes of faulting and magmatism, but strain partitioning between faulting and magmatism during discrete rifting episodes remains poorly documented. In highly evolved rifts, tensile stresses from far-field plate motions accumulate over decades before being released during relatively short time intervals by faulting and magmatic intrusions 1 , 2 , 3 . These rifting crises are rarely observed in thick lithosphere during the initial stages of rifting. Here we show that most of the strain during the July–August 2007 seismic crisis in the weakly extended Natron rift, Tanzania, was released aseismically. Deformation was achieved by slow slip on a normal fault that promoted subsequent dyke intrusion by stress unclamping. This event provides compelling evidence for strain accommodation by magma intrusion, in addition to slip along normal faults, during the initial stages of continental rifting and before significant crustal thinning.

Renal and cardiovascular complications of prematurity are well established, notably the development of hypertension in adulthood. However, the underlying molecular mechanisms remain poorly understood. Our objective was to investigate the impact of prematurity on the ontogenesis of renal corticosteroid pathways, to evaluate its implication in perinatal renal complications and in the emergence of hypertension in adulthood. Swiss CD1 pregnant mice were injected with lipopolysaccharides at 18 days of gestation (E18) to induce prematurity at E18.5. Pups were sacrificed at birth, 7 days and 6 months of life. Second (F2) and third (F3) generations, established by mating prematurely born adult females with wild-type males, were also analyzed. Former preterm males developed hypertension at M6 (P < 0.0001). We found robust activation of renal corticosteroid target gene transcription at birth in preterm mice (αENaC (+45%), Gilz (+85%)), independent of any change in mineralocorticoid or glucocorticoid receptor expression. The offspring of the preterm group displayed increased blood pressure in F2 and F3, associated with increased renal Gilz mRNA expression, despite similar MR or GR expression and plasma corticosteroid levels measured by LC-MS/MS. Gilz promoter methylation measured by methylated DNA immunoprecipitation-qPCR was reduced with a negative correlation between methylation and expression (P = 0.0106). Our study demonstrates prematurity-related alterations in renal corticosteroid signaling pathways, with transgenerational inheritance of blood pressure dysregulation and epigenetic Gilz regulation up to the third generation. This study provides a better understanding of the molecular mechanisms involved in essential hypertension, which could partly be due to perinatal epigenetic programming from previous generations.High blood pressure: Exploring inheritanceA propensity towards high blood pressure may be passed down through several generations from adults who were born preterm. People who are born prematurely often suffer from kidney (renal) problems, high blood pressure and cardiovascular disease as they age. Recent research suggests adults born prematurely can pass dysregulated blood pressure to their children. Laetitia Martinerie at INSERM Unit 1185, Le Kremlin Bicêtre and Robert Debré Hospital in Paris, France, and co-workers studied generations of mice to explore how epigenetic alterations, DNA modifications that do not change the DNA code, affect blood pressure from birth through to adulthood. The team identified tissue-specific alterations in renal signaling pathways in premature mice. They also traced the associated overexpression of a gene called Gilz, known to play a role in blood pressure maintenance, through second and third generation mice born to the first generation preterms.

The Mineralocorticoid Receptor (MR) mediates the sodium-retaining action of aldosterone in the distal nephron, but mechanisms regulating MR expression are still poorly understood. We previously showed that RNA Binding Proteins (RBPs) regulate MR expression at the post-transcriptional level in response to variations of extracellular tonicity. Herein, we highlight a novel regulatory mechanism involving the recruitment of microRNAs (miRNAs) under hypertonicity. RT-qPCR validated miRNAs candidates identified by high throughput screening approaches and transfection of a luciferase reporter construct together with miRNAs Mimics or Inhibitors demonstrated their functional interaction with target transcripts. Overexpression strategies using Mimics or lentivirus revealed the impact on MR expression and signaling in renal KC3AC1 cells. miR-324-5p and miR-30c-2-3p expression are increased under hypertonicity in KC3AC1 cells. These miRNAs directly affect Nr3c2 (MR) transcript stability, act with Tis11b to destabilize MR transcript but also repress Elavl1 (HuR) transcript, which enhances MR expression and signaling. Overexpression of miR-324-5p and miR-30c-2-3p alter MR expression and signaling in KC3AC1 cells with blunted responses in terms of aldosterone-regulated genes expression. We also confirm that their expression is increased by hypertonicity in vivo in the kidneys of mice treated with furosemide. These findings may have major implications for the pathogenesis of renal dysfunctions, sodium retention, and mineralocorticoid resistance.

Continental rifts and passive continental margins show fundamental along‐axis segmentation patterns that have been attributed to one or a number of different processes: extensional fault geometry, variable stretching along strike, preexisting lithospheric compositional and structural heterogeneities, oblique rifting, and the presence or absence of eruptive volcanic centers. The length and width scales of the rift stage fault‐bounded basin systems change during the late evolution of the new plate boundary, and the role of magmatism may increase as rifting progresses to continental rupture. Along obliquely spreading ridges, first‐order mid‐ocean ridge geometries originate during the synrift stage, indicating an intimate relationship between magma production and transform fault spacing and location. The Gulf of Aden rift is a young ocean basin in which the earliest synrift to breakup structures are well exposed onshore and covered by thin sediment layers offshore. This obliquely spreading rift is considered magma‐poor and has several large‐offset transforms that originated during late stage rifting and control the first‐order axial segmentation of the spreading ridge. Widely spaced geophysical transects of passive margins that produce only isolated 2‐D images of crust and uppermost mantle structure are inadequate for evaluation of competing rift evolution models. Using closely spaced new geophysical and geological observations from the Gulf of Aden we show that rift sectors between transforms have a large internal variability over short distances (∼10 km): the ocean‐continent transition (OCT) evolves from a narrow magmatic transition to wider zones where continental mantle is probably exhumed. We suggest that this small‐scale variability may be explained (1) by the distribution of volcanism and (2) by the along‐strike differences in time‐averaged extension rate of the oblique rift system. The volcanism may be associated with (1) the long‐offset Alula‐Fartak Fracture Zone, which may enhance magma production on its younger side, or (2) channeled flow from the Afar plume material along the newly formed OCT and the spreading ridge. Oblique extension and/or hot spot interactions may thereby have a significant control on the styles of rifting and continental breakup and on the evolution of many magma‐poor margins.

Central serous chorioretinopathy (CSCR) belongs to the pachychoroid spectrum, a pathological phenotype of the choroidal vasculature, in which blood flow is under the choroidal nervous system (ChNS) regulation. The pathogenesis of CSCR is multifactorial, with the most recognised risk factor being intake of glucocorticoids, which activate both the gluco- and the mineralocorticoid (MR) receptors. As MR over-activation is pathogenic in the retina and choroid, it could mediate the pathogenic effects of glucocorticoids in CSCR. But the role of MR signalling in pachychoroid is unknown and whether it affects the ChNS has not been explored. Using anatomo-neurochemical characterisation of the ChNS in rodents and humans, we discovered that beside innervation of arteries, choroidal veins and choriocapillaris are also innervated, suggesting that the entire choroidal vasculature is under neural control. The numerous synapses together with calcitonin gene-related peptide (CGRP) vesicles juxtaposed to choroidal macrophages indicate a neuro-immune crosstalk. Using ultrastructural approaches, we show that transgenic mice overexpressing human MR, display a pachychoroid-like phenotype, with signs of choroidal neuropathy including myelin abnormalities, accumulation and enlargement of mitochondria and nerves vacuolization. Transcriptomic analysis of the RPE/choroid complex in the transgenic mice reveals regulation of corticoids target genes, known to intervene in nerve pathophysiology, such as Lcn2 , rdas1/dexras1, S100a8 and S100a9 , rabphilin 3a ( Rph3a ), secretogranin ( Scg2 ) and Kinesin Family Member 5A ( Kif5a ). Genes belonging to pathways related to vasculature development, hypoxia, epithelial cell apoptosis, epithelial mesenchymal transition, and inflammation, support the pachychoroid phenotype and highlight downstream molecular targets. Hypotheses on the imaging phenotype of pachychoroid in humans are put forward in the light of these new data. Our results provide evidence that MR overactivation causes a choroidal neuropathy that could explain the pachychoroid phenotype found in transgenic mice overexpressing human MR. In patients with pachychoroid and CSCR in which systemic dysautonomia has been demonstrated, MR-induced choroidal neuropathy could be the missing link between corticoids and pachychoroid.

Abstract Disclosure: M. Laulhé: None. Y. Pelloux: None. S. Djellout: None. T. Rajkumar: None. J. Perrot: None. A. Arzel: None. P. Kamenicky: None. S. Viengchareun: None. L. Martinerie: None. Synthetic glucocorticoids are prescribed worldwide. Although they considerably improved the management of chronic inflammatory diseases, these treatments are also associated with numerous adverse effects, with a large inter-individual variability that remains poorly understood. Glucocorticoids exert their effects via an ubiquitous nuclear receptor, the glucocorticoid receptor (GR), encoded by the NR3C1 gene. Polymorphisms in the NR3C1 gene have been associated with variation in glucocorticoid sensitivity, ranging from resistance to increased sensitivity. While the polymorphisms associated with glucocorticoid resistance are well characterized, the molecular mechanisms involved in glucocorticoid sensitivity are not fully understood. The N363S variant, which encodes for a missense mutation within the N-terminal domain of the protein, has been associated with increased glucocorticoid sensitivity, but has never been thoroughly characterized. We performed in vitro studies demonstrating that maximal transactivation activity (GRWT 93,8% ± 5.1 vs GRN363S 142.6% ± 9,0, n=38, P<0.0001) and target gene expression were higher in response to dexamethasone in HEK 293T cells expressing the N363S variant. Next, we aim to assess the impact of the N363S variant using an innovative mouse model expressing the variant. Using the CRISPR/Cas9 system, we introduced a point mutation corresponding to the human variant into the coding sequence of the mouse Nr3c1 gene (c.1139 A>G), as the mutated amino acid is conserved across species. The genotype (Wild type: WT; heterozygous: HET; homozygous: HOM) was assessed by PCR. We evaluated the impact of the variant in unstimulated mice, evaluating weight, glucose metabolism, and HPA axis activity. Next, we studied its impact on susceptibility to adverse effects after treatment with dexamethasone (1 mg/kg/d) for 28 days via osmotic pumps. Expression of the N363S variant did not affect the viability or fertility of the mice. In the absence of dexamethasone treatment, we observed no significant differences between groups in adrenal gland weight, corticosterone secretion levels after a single intraperitoneal administration of dexamethasone (WT 9.4 ng/ml [3.5 ;12.2] ; HET 4.4 ng/ml [2.6 ;6.2] ; HOM 9.6 ng/ml [4.8 ; 12.6], n=4), glucose metabolism (fasting glycemia, WT 117 mg/dL[ 90 ;145], HET 107 mg/dL [95 ;121], HOM 96 mg/dL [83 ;138], n=3) or behavioral outcomes. The impact of genotype on the development of adverse effects, such as glucocorticoid-induced adrenal insufficiency, impaired glucose metabolism and depressive features, is currently being investigated after prolonged dexamethasone treatment. Overall, we developed an innovative transgenic mouse model that will provide new insights into glucocorticoid sensitivity and could emphasize the N363S variant as a predictive tool for personalized medicine. Presentation: Monday, July 14, 2025

Disclosure: M. Laulhé: None. E. Kuhn: None. J. Bouligand: None. L. Amazit: None. J. Perrot: None. P. Kamenicky: None. M. Lombes: None. J. Fagart: None. S. Viengchareun: None. L. Martinerie: None. Introduction: Constitutive glucocorticoid resistance is associated with mutations in the NR3C1 gene, encoding the Glucocorticoid Receptor (GR). We identified a novel heterozygous point mutation causing fluctuating resistance to glucocorticoid depending on ligand concentrations. Initially, the propositus, a 45-year-old man, was diagnosed with a right adrenal incidentaloma and an ACTH-independent biological hypercortisolism. Shortly after adrenal surgery, plasma cortisol increased again (612 nmol/L) associated with inadequate ACTH levels (122 pg/mL) without any evidence of pituitary adenoma or ectopic ACTH-secreting tumor, suggesting a glucocorticoid resistance syndrome. Methods: We sequenced NR3C1 gene and performed in vitro analysis to assess contribution of this variant to the patient’s phenotype and how it affects biological activity of GR. Results: Exon sequencing of the NR3C1 gene identified a novel missense variant located on exon 5 (NM_000176.3, c.1706 G>A) resulting in substitution of arginine to glutamine at amino acid 569 (GR R569Q) in the Ligand-Binding Domain (LBD) of GR. We characterized transcriptional activity of GR R569Q in HEK 293T cells transiently co-transfected with either GR WT or GR R569Q, together with a luciferase reporter gene construct placed under control of a promoter containing two glucocorticoid responsive elements. We observed a decreased transcriptional activity of GR R569Q (EC50 4.55 nM [3.8;5.3]) compared to GR WT (EC50 0.19 nM [0.15; 0.24]), in response to dexamethasone. Interestingly, GR R569Q exerted a dominant negative effect on GR WT, with a decrease in transcriptional activity of 80% when stimulated with 1 nM dexamethasone (2-way ANOVA test, P<0.0001), which was blunted when stimulated with a 100-fold higher concentration of dexamethasone. As the variant is located within the second nuclear localization signal, we studied nuclear translocation in response to 1 nM cortisol for 1 h. As expected, nuclear-cytoplasmic ratio was lower in patients’ fibroblasts (2.3 ± 0.14 vs 3.0 ± 0.98, ANOVA 2-Way, P < 0.0001) compared with control fibroblasts, as quantified by automated high-throughput microscopy. Three-dimensional modeling revealed that arginine substitution leads to loss of a hydrogen bond stabilizing the LBD structure. This may result in a lower ligand affinity that can be bypassed by high concentrations of agonist. We are currently testing receptor affinity and reversibility of phenotype after hydrogen bond restoration by directed mutagenesis (c.1705 C>A, p.Q569K). Conclusion: Overall, we identified a novel variant of the NR3C1 gene associated with fluctuating GR sensitivity depending on ligand concentration. This finding may provide new insights into mechanisms involved in GR sensitivity. Presentation: Friday, June 16, 2023

Abstract Disclosure: L. Martinerie: None. I. Hani: None. L. Guyon: None. N. Cherradi: None. T. Vu: None. J. Perrot: None. T. Rajkumar: None. E. Pussard: None. P. Boileau: None. R. Brillet: None. J. Guegan: None. J. Bouligand: None. P. Kamenicky: None. M. Lombes: None. S. Viengchareun: None. Aldosterone regulates sodium homeostasis by binding to the Mineralocorticoid Receptor (MR). We previously identified a critical temporal window during renal development when MR expression is low, explaining the physiological sodium losses observed in newborns at birth. However, the molecular mechanisms governing MR expression remain unclear. Here, we report the involvement of two microRNAs (miRNAs), miR-409-3p and miR-431-5p, in regulating MR expression during early renal development. Using miRNA sequencing, we identified these miRNAs as upregulated on postnatal day 0 (D0) compared to day 8 (D8). RT-qPCR validated their differential expression, while luciferase reporter assays confirmed their functional interaction with MR transcripts. Functional studies using miRNA mimics and inhibitors revealed that miR-409-3p and miR-431-5p modulate MR expression and signaling in primary renal cell cultures. Specifically, their increased expression at D0 destabilizes MR transcripts and decreases MR expression and signaling, while their decreased expression at D8 leads to MR stabilization and enhanced mineralocorticoid signaling. Notably, digital droplet PCR (ddPCR) analysis of neonatal urine samples from the PREMALDO cohort demonstrated that these miRNAs are highly expressed at birth but decrease gradually postnatally. To explore the broader regulatory network, we performed RNA sequencing to identify differentially expressed genes (DEGs) between D0 and D8. Cross-referencing DEGs with the predicted targets of miR-409-3p and miR-431-5p yielded 83 differentially expressed target genes. Functional annotation of these genes highlighted significant enrichment in pathways related to kidney development, sodium transport and homeostasis. Our findings identify miR-409-3p and miR-431-5p as key regulators of MR expression and mineralocorticoid signaling during renal development. These miRNAs could serve as potential predictive and non-invasive biomarkers of renal maturity and mineralocorticoid signaling efficiency in premature infants. Presentation: Monday, July 14, 2025

Disclosure: L. Bessiene: None. J. Perrot: None. S. Hescot: None. A. Bourdin-Pintueles: None. G. Vitellius: None. L.M. Sachs: None. P. Kamenicky: None. M. Lombes: None. E. Pussard: None. S. Viengchareun: None. L. Martinerie: None. Glucocorticoid hormone metabolism is regulated by 11-beta hydroxysteroid dehydrogenase enzymes: 11βHSD2, mostly expressed in the distal nephron, converts corticosterone into 11-dehydrocorticosterone in rodents, while 11βHSD1 catalyzes the opposite reaction in liver. Glucocorticoid hormone metabolism may be altered under pathophysiological conditions of hypothyroidism. However, direct functional relationship between glucocorticoid and thyroid hormones (T3) signaling pathways remains elusive. Identification of putative Thyroid Response Elements (TRE) in the promoter regions of hsd11b2 and hsd11b1 genes suggested that T3 might directly regulate expression and/or activity of these enzymes.We used human translational studies, a mouse model of hyperthyroidism and murine renal and hepatic cell lines to investigate the role of thyroid hormones in glucocorticoid hormone metabolism.In hypothyroid patients, the urinary [E]/[F] ratio measured by LC-MS/MS technology, showed a 60% decrease (P<0.05), compared to age- and sex- matched euthyroid controls, suggesting a regulation of glucocorticoid metabolism by T3. Similarly, a significant positive correlation was observed between the urinary [E]/[F] ratio and serum T4L concentration in hyperthyroid patients before and after normalization of T4L levels.Administration of T3 in drinking water, mimicking a mouse model of hyperthyroidism, led to significant increase in renal 11βHSD2 mRNA (P<0.05) and decrease in liver 11βHSD1 mRNA and protein levels (P<0.01), compared to control mice.Finally, T3 induced an increase in 11βHSD2 transcript levels in renal KC3AC1 cells (P<0.01) and a decrease in 11βHSD1 mRNA levels in hepatic HepG2 cells (P<0.01). 11βHSD2 activity increased by 20% (P<0.05). In HEK 293T cells, T3 transactivated hsd11b2 promoter via the Thyroid Receptor α1 (TRα1). ChIP experiments further demonstrated a T3-dependent specific recruitment of TRα1 onto hsd11b2 promoter. Altogether, these findings demonstrate that T3 directly regulate expression and activity of 11βHSD enzymes, thereby controlling glucocorticoid hormone metabolism and action. Presentation: Saturday, June 17, 2023

Disclosure: I. Hani: None. T. Vu: None. R. Brillet: None. J. Perrot: None. J. Bouligand: None. J. Guegan: None. N. Cherradi: None. P. Kamenicky: None. M. Lombes: None. L. Martinerie: None. S. Viengchareun: None. In tight epithelia, aldosterone controls sodium and water homeostasis by binding to the Mineralocorticoid Receptor (MR), a steroid nuclear receptor. We have identified a specific temporal window during renal development in which the mineralocorticoid signaling pathway is ineffective due to downregulation of MR expression, explaining physiological sodium wasting observed in human newborns during first days of life. However, underlying molecular mechanisms controlling MR expression remain unknown. Recently, we demonstrated in adult renal KC3AC1 cell line that MR expression is controlled by microRNAs (miR-30c-2-3p and miR-324-5p) in response to variations of tonicity. These regulators bind to 3'-untranslated region (3'-UTR) of MR transcripts to modulate their stability and translation. Therefore, we hypothesized that these miRNAs may be responsible for low expression level of MR at birth, where variations in tonicity are observed due to the transition from intra-amniotic to extra-uterine life. Using primary cultures of renal epithelial cells from neonatal mouse kidneys, harvested at birth (D0) and at Day 8 postnatal (D8), we showed that only miR-30c-2-3p regulates MR expression at D8. For this reason, we performed a complete transcriptomic analysis (miRNA-Seq and RNA-Seq) of kidneys collected at D0 and D8 to identify other miRNAs specifically involved in regulation of MR expression in perinatal period. Bioinformatics analysis allowed us to identify deregulated miRNAs and transcripts between D0 and D8 and to specify their involvement in biological processes and/or signaling pathways. We mainly focused on deregulated miRNAs that may modulate MR expression and affect mineralocorticoid signaling. miR-Seq identified 221 differentially expressed miRNAs. First, we selected 3 over- (miR-431-5p, miR-409-3p, and miR-92a-1-5p) and 3 under-expressed (miR-30a-5p, miR-30e-5p, and miR-802-5p) candidate miRNAs (FDR<0.05 and log2FC>1) having putative binding sites in MR 3'-UTR. Paradoxically, we showed in primary kidney cultures that overexpression of miR-30a-5p, miR-30e-5p, or miR-802-5p increased MR expression (from 50 to 100%, P<0.05) at D0, suggesting that these miRNAs may either positively modulate MR expression or may involve an intermediate regulator. On the opposite, over-expression of miR-92a-1-5p, miR-431-5p, and miR-409-3p at D8 led to a decrease (from 30-40%, P<0.05) in MR expression, suggesting that these miRNAs may modulate MR expression in postnatal period. Currently, we are evaluating whether they could be used as prognostic or severity biomarkers of water loss in neonates by quantifying these candidate miRNAs in urine exosomes of preterm and term infants. A better understanding of mechanisms regulating MR expression in the perinatal period will undoubtedly have a major impact on the management of premature infants with sodium balance maladjustment at birth. Presentation Date: Friday, June 16, 2023