Nicolas Goudin

PIK3CA-related overgrowth spectrum (PROS) comprises a group of rare genetic disorders caused by de novo, mosaic, postzygotic gain-of-function mutations in the PIK3CA gene. These mutations arise during embryogenesis, affect multiple organ systems, and result in heterogeneous clinical phenotypes. We previously showed that primary cells derived from a PROS mouse model exhibit a metabolic shift toward aerobic glycolysis (a Warburg-like effect), accompanied by altered secretion of metabolites. Here, we observed that this metabolic reprogramming was associated with the up-regulation of key transcription factors, including cellular myelocytomatosis and hypoxia-inducible factor 1 alpha. PIK3CA hyperactivation induces a distinct microenvironment marked by metabolic dysregulation, extracellular matrix remodeling, increased cellular proliferation, elevated phosphorylated form of the histone variant H2AX levels, and enhanced macrophage infiltration, hallmarks commonly associated with increased lactate production. To further examine immune infiltration dynamics, we used a mouse model expressing a constitutively active PIK3CA mutation selectively in adipose tissue (AdipoCreER), a tissue frequently affected in PROS. Single-cell transcriptomics and flow cytometry profiling revealed that macrophages adopt an immunomodulatory phenotype, with increased infiltration of TREM2+ and Lyve1hiMHCIIlo macrophages, along with myeloid-derived suppressor cells, and a concurrent reduction in T-cell populations. These immune alterations parallel those observed in tumor microenvironments and may contribute to tissue overgrowth and impaired immune surveillance. Multiplex immunofluorescence analysis of tissue samples from individuals with PROS confirmed these findings, underscoring the translational relevance of the mouse model. Together, our results demonstrate that PIK3CA mutations in PROS profoundly remodel the tissue microenvironment and reprogram macrophage function in a manner reminiscent of tumor biology.

The primary cilium is a microtubule-based sensory organelle projecting from the plasma membrane of most mammalian cells. Genetic defects in ciliary components cause chronic kidney disease (CKD) characterized by heightened production of inflammatory and fibrogenic mediators by tubular epithelial cells. Yet, whether this reflects a physiological role of the primary cilium remains unknown. Here, we show that primary cilia on kidney tubular cells bind uropathogenic Escherichia coli and, in response to bacterial components, initiate a fibro-inflammatory program reminiscent of CKD. Integrating single-cell transcriptomics with conditional mouse models, we observed that epithelial cilia orchestrate a similar fibro-inflammatory response in the absence of infection during CKD. This convergence reveals a shared cilia-dependent signalling axis governing both host–pathogen responses and CKD progression. Mechanistically, cilia ablation selectively impairs tubular responses to ADP-heptose, a pathogen-associated molecular pattern that activates NF-κB via the cytosolic innate immune receptor ALPK1. In human kidney organoids, ADP-heptose induces robust fibro-inflammation, and genetic or pharmacological inhibition of ALPK1 attenuates this response in a rodent CKD model. Together, these findings identify primary cilia as central orchestrators of a fibro-inflammatory program linking pathogen detection to kidney disease progression.

Once passed into the bloodstream, bacterial pathogens have a limited time to interact with permissive receptors at the surface of host cells. Neisseria meningitidis has developed an extremely effective strategy allowing it to find its receptors in a few seconds. Here, we report that N. meningitidis type IV pili exploit the physical properties of host cells' plasma membranes to promote the formation of early tubular membrane structures essential for initial bacterial adhesion. These tubular structures, which form before any signaling events in host cells, concentrate and trap multiple plasma membrane-associated proteins in the vicinity of bacteria, thereby facilitating the selection, interaction and activation of specific adhesion and signaling receptors by bacterial ligands present on type IV pili. Our results define an additional paradigm for the recruitment of specific receptors by pathogenic bacteria, which depends on the physical property of bacterial pili to induce the formation of tubular plasma membrane structures enriched in integral plasma membrane receptors.

Poikiloderma with neutropenia is a genetic disorder characterized by skin abnormalities, nail dystrophy, bone anomalies, and neutropenia. USB1 encodes a phosphodiesterase essential for processing spliceosomal U6 RNA and some microRNAs, regulating their stability. This study describes a heterozygous de novo USB1 variant (p.P44L) identified in a patient with recurrent infections, hypogammaglobulinemia, and low neutrophil counts. Unlike previously reported mutations, p.P44L affects a conserved proline in the N-terminal domain, predicted to be critical for protein interactions and stability. Functional assays revealed that while U6 RNA processing remained intact, the variant altered protein interactions and subcellular localization, reducing nuclear presence and accumulation within nuclear speckles. In vitro, the variant did not prevent neutrophil differentiation but reduced clonal capacity. In zebrafish, it led to reduced neutrophils and pigmentation. These findings expand the spectrum of genetic traits associated with USB1 and suggest that a heterozygous variant affecting the N-terminal domain of USB1 impacts clinical phenotypes and that hypogammaglobulinemia may be associated with USB1 dysfunction.

Dendritic cells (DCs) are professional antigen (Ag)–presenting cells that excel in initiating adaptive immune responses by continuously scanning peripheral tissues for Ags. To facilitate efficient DC migration, constant cross-talk between actin and microtubules is required to coordinate cytoskeletal networks and actomyosin contractility, but the related mechanisms have not been extensively characterized. We show that mouse DCs lacking Kif5b (the heavy chain of kinesin-1) exhibit a major impairment in cell migration in vivo and in vitro. Mechanistically, kinesin-1 coordinates cytoskeletal cross-talk between actin and microtubules during DC migration by modulating negatively RhoA activity through its interaction with GEF-H1, thereby limiting GEF-H1’s availability in the cytosol. The same mechanism operates in human primary monocyte–derived DCs and regulates efficient migration in a confined environment. Thus, our results highlight kinesin-1 as a key regulator of DC migration, through its coordinated control of cytoskeletal dynamics.

Crescentic glomerulonephritis (cGN) is a severe kidney pathology characterized by the aberrant proliferation of epithelial cells, leading to crescent formation within the Bowman’s space. The molecular pathways involved in crescent formation remain poorly understood despite its clinical relevance. Given the mechanical stress experienced by podocytes, likely exacerbated in cGN, we hypothesized that activation of the mechanosensor yes-associated protein 1 (YAP), an effector of the Hippo pathway, may contribute to the development of cGN. Here, we demonstrate activation of YAP and its target genes in the nephrotoxic nephritis model, a murine model of cGN. Mechanistically, podocyte-specific hyperactivation of YAP (YAP ^5SA ) in transgenic mice led to cell-autonomous hypertrophy of podocytes and non–cell-autonomous activation and proliferation of parietal epithelial cells (PECs), culminating in crescents. Transcriptomic profiling in a human podocyte cell line expressing the same YAP ^5SA isoform revealed the reactivation of developmental programs within differentiated podocytes and identified the phosphoinositide 3-kinase–protein kinase B–mechanistic target of rapamycin (PI3K-Akt-mTOR) signaling pathway as a candidate involved in YAP-induced podocyte hypertrophy. Furthermore, this analysis identified connective tissue growth factor (CTGF) and heparin-binding epidermal growth factor–like growth factor (HB-EGF) as potential mediators in the cross-talk between YAP-activated podocytes and PECs, driving PEC hyperplasia. Collectively, these findings highlight the pivotal role of YAP in the pathogenesis of cGN and indicate that targeting YAP signaling could be a promising therapeutic strategy for this severe kidney disease.

Mutations in PIK3R1 have recently been identified in patients with overgrowth syndromes and complex vascular malformations. PIK3R1 encodes p85α which acts as the regulatory subunit of the lipid kinase PI3Kα. PIK3R1 mutations result in the excessive activation of the AKT/mTOR pathway. Currently, there are no approved treatments specifically dedicated to patients with PIK3R1 mutations, and medical care primarily focuses on managing symptoms. In this study, we identified three patients, including two children, who had mosaic somatic PIK3R1 mutations affecting the iSH2 domain, along with severe associated symptoms that were unsuccessfully treated with rapamycin. We conducted in vitro experiments to investigate the impact of these mutations, including a double PIK3R1 mutation in cis observed in one patient. Our findings revealed that p85α mutants in the iSH2 domain showed sensitivity to alpelisib, a pharmacological inhibitor of PI3Kα. Based on these findings, we received authorization to administer alpelisib to all three patients. Following drug introduction, patients rapidly demonstrated clinical improvement, pain, fatigue and inflammatory flares were attenuated. Magnetic Resonance Imaging showed a mean decrease of 22.67% in the volume of vascular malformations over twelve months of treatment with alpelisib. No drug-related adverse events were reported during the course of the study. In conclusion, this study provides support for the use of PI3Kα inhibition as a promising therapeutic approach for individuals with PIK3R1 -related anomalies.

Once passed into the bloodstream, bacterial pathogens have a limited time to interact with permissive receptors at the surface of host cells. Neisseria meningitidis has developed an extremely effective strategy allowing it to find its receptors in a few seconds. Here, we report that N. meningitidis type IV pili exploit the physical properties of host cells plasma membranes to promote the formation of early tubular membrane structures essential for initial bacterial adhesion. These tubular structures, which form before any signaling events in host cells, concentrate and trap multiple plasma membrane-associated proteins in the vicinity of bacteria, thereby facilitating the selection, interaction and activation of specific adhesion and signaling receptors by bacterial ligands bound to type IV pili. Our results define an additional paradigm for the recruitment of specific receptors by pathogenic bacteria, which depends on the physical property of bacterial pili to induce the formation of tubular plasma membrane structures enriched in integral membrane receptor.

Background: Primary cilia are sensory antennas that are present on the majority of quiescent vertebrate cells where they mediate key signaling during development and in response to environmental stimuli. Defects in primary cilia result in a group of heterogeneous inherited disorders with overlapping phenotypes, called ciliopathies. Nephronophthisis is an autosomal recessive tubulo-interstitial kidney ciliopathy with more than 25 identified genes called NPHP . Presently, no treatment exists beyond supportive care and kidney transplant, underscoring the need for novel therapies. Methods: Using a phenotypic screening approach in cultured cell lines, we previously identified prostaglandin analogues as candidate therapeutic molecules based on their ability to rescue ciliogenesis defects in kidney tubular cells from NPHP1 patients. Here, we have investigated the potential beneficial effects of ROCK inhibitors and Eupatilin, similarly identified by other groups in different NPHP contexts, in kidney cells from NPHP1 and IQCB1/NPHP5 patients as well as in a zebrafish NPHP mutant line ( traf3ip1/ift54 ). Results: Eupatilin partially rescued NPHP1 -associated ciliogenesis defects. Transcriptomic analyses pointed out that cell cycle progression was inhibited by Eupatilin, likely explaining its broad effects on cilia assembly. Interestingly, while ciliary defects also observed in NPHP5 patient cells were rescued by both prostaglandins and Eupatilin, only prostaglandin analogues were able to reduce pronephric cysts size in the used nphp zebrafish model. Conclusion: Our study indicates that these molecules can show beneficial effects across genetic contexts and shed light on their potential as therapeutic interventions for nephronophthisis.

Here we conduct a study involving 12 individuals with retinal dystrophy, neurological impairment, and skeletal abnormalities, with special focus on GPATCH11, a lesser-known G-patch domain-containing protein, regulator of RNA metabolism. To elucidate its role, we study fibroblasts from unaffected individuals and patients carrying the recurring c.328+1 G > T mutation, which specifically removes the main part of the G-patch domain while preserving the other domains. Additionally, we generate a mouse model replicating the patients’ phenotypic defects, including retinal dystrophy and behavioral abnormalities. Our results reveal a subcellular localization of GPATCH11 characterized by a diffuse presence in the nucleoplasm, as well as centrosomal localization, suggesting potential functions in RNA and cilia metabolism. Transcriptomic analysis performed on mouse retina detect dysregulation in both gene expression and splicing activity, impacting key processes such as photoreceptor light responses, RNA regulation, and primary cilia-associated metabolism. Proteomic analysis of mouse retina confirms the roles GPATCH11 plays in RNA processing, splicing, and transcription regulation, while also suggesting additional functions in synaptic plasticity and nuclear stress response. Our research provides insights into the diverse roles of GPATCH11 and identifies that the mutations affecting this protein are responsible for a recently characterized described syndrome.