Role of the ribosome biogenesis protein Rsl24d1 in mouse embryonic stem cells

Le contrôle de l'expression des programmes géniques orchestrant le développement précoce et l'homéostasie des cellules souches fait l'objet de recherches intenses. En effet, les cellules souches embryonnaires (CSE) sont caractérisées par des propriétés comme leur clonogénicité (la capacité à proliférer dans le même état indifférencié) et leur pluripotence (la capacité à se différencier et à former les tissus embryonnaires et adultes). Au niveau moléculaire, l'identité des CSE est orchestrée par le contrôle de l'expression génique aux niveaux épigénétique, transcriptionnel, post- transcriptionnel et traductionnel en réponse à l'activation de voies de signalisation spécifiques. Dans ce contexte, des données récentes suggèrent un rôle de la machinerie traductionnelle les ribosomes et de la régulation de leur biogenèse, dans le maintien de l'homéostasie de cellules souches de différentes espèces. À partir de l'analyse de données transcriptomiques à haut débit (RNAseq), mon équipe d'accueil a ainsi identifié un ensemble de protéines associées aux ribosomes (PaR) significativement enrichies dans les cellules souches embryonnaires murines (CSEm) en comparaison à des lignées cellulaires murines différenciées et à des tissus. Parmi ces candidats, mes travaux de thèse ont consisté à la caractérisation d'une PaR particulièrement enrichie : Rsl24d1. Rsl24d1 est une protéine de biogenèse des ribosomes décrites exclusivement chez la levure. Son profil d'expression dans différentes lignées de CSEm suggère une fonction spécifique: enrichissement au niveau transcriptionnel et protéique dans les CSE à l'état de pluripotence naïf et diminution importante au cours de la différenciation. En effet, des approches de perte d'expression de Rsl24d1 m'ont permis d'établir l'importance de cette PaR dans l'homéostasie des CSEm. Rsl24d1 contribue au maintien de la prolifération cellulaire des CSE, de leur clonogénicité et plus modérément à leur pluripotence. Rsl24d1 semble être une protéine majoritairement nucléaire mais également associée aux sous- unités 60S libres des ribosomes cytoplasmiques. D'autre part, la perte d'expression de Rsl24d1 affecte spécifiquement la biogenèse des particules ribosomiques 60S. Ainsi, comme chez la levure, dans les CSEm, Rsl24d1 est un facteur navette orchestrant la maturation des particules ribosomiques pré-60S. Par ailleurs, Rsl24d1 semble permettre le maintien d'un taux de synthèse protéique élevé permettant notamment le renouvellement des protéines ayant une demi-vie courte parmi lesquels on recense des facteurs de transcription de la pluripotence comme Oct4 (Oct3/4), Nanog et Esrrb. Mes travaux de thèse ont donc permis d'identifier et de caractériser un facteur de biogenèse de la sous-unité 60S, Rsl24d1, impliqué dans l'homéostasie des CSEmEmbryonic stem cells (ESC) possess clonogenic and pluripotency abilities i.e. they are able to self-renew indefinitely in the same developpemental state and to differentiate in all the cell types composing embryonic and adult tissues. ESC homeostasis is coordinated by complex networks which are regulated at different levels of gene expression regulation, including epigenetic, transcriptional and post-transcriptional levels. Furthermore, emerging evidences point out that the translational machinery, ribosomes, are directly implicated in the control of adult and embryonic stem cell homeostasis in different model organisms. Along this line, we have identified Rsl24d1, a ribosomal associated protein (RaP), which is strongly expressed in naïve murine ESCs compared to their differentiated progenies. We demonstrated that Rsl24d1 actively contributes to ESC homeostasis and its expression is essential for ESC proliferation and clonogenic capacities. Finally, we have also demonstrated that Rsl24d1, like Rlp24 its yeast ortholog, is associated to pre-ribosomes in ESCs from the nucleus to the cytoplasm and is required for the biogenesis of the large ribosomal subuni

Implication de la protéine de biogenèse des ribosomes Rsl24d1 dans l'homéostasie de cellules souches embryonnaires murines

Embryonic stem cells (ESC) possess clonogenic and pluripotency abilities i.e. they are able to self-renew indefinitely in the same developpemental state and to differentiate in all the cell types composing embryonic and adult tissues. ESC homeostasis is coordinated by complex networks which are regulated at different levels of gene expression regulation, including epigenetic, transcriptional and post-transcriptional levels. Furthermore, emerging evidences point out that the translational machinery, ribosomes, are directly implicated in the control of adult and embryonic stem cell homeostasis in different model organisms. Along this line, we have identified Rsl24d1, a ribosomal associated protein (RaP), which is strongly expressed in naïve murine ESCs compared to their differentiated progenies. We demonstrated that Rsl24d1 actively contributes to ESC homeostasis and its expression is essential for ESC proliferation and clonogenic capacities. Finally, we have also demonstrated that Rsl24d1, like Rlp24 its yeast ortholog, is associated to pre-ribosomes in ESCs from the nucleus to the cytoplasm and is required for the biogenesis of the large ribosomal subunitLe contrôle de l'expression des programmes géniques orchestrant le développement précoce et l'homéostasie des cellules souches fait l'objet de recherches intenses. En effet, les cellules souches embryonnaires (CSE) sont caractérisées par des propriétés comme leur clonogénicité (la capacité à proliférer dans le même état indifférencié) et leur pluripotence (la capacité à se différencier et à former les tissus embryonnaires et adultes). Au niveau moléculaire, l'identité des CSE est orchestrée par le contrôle de l'expression génique aux niveaux épigénétique, transcriptionnel, post- transcriptionnel et traductionnel en réponse à l'activation de voies de signalisation spécifiques. Dans ce contexte, des données récentes suggèrent un rôle de la machinerie traductionnelle les ribosomes et de la régulation de leur biogenèse, dans le maintien de l'homéostasie de cellules souches de différentes espèces. À partir de l'analyse de données transcriptomiques à haut débit (RNAseq), mon équipe d'accueil a ainsi identifié un ensemble de protéines associées aux ribosomes (PaR) significativement enrichies dans les cellules souches embryonnaires murines (CSEm) en comparaison à des lignées cellulaires murines différenciées et à des tissus. Parmi ces candidats, mes travaux de thèse ont consisté à la caractérisation d'une PaR particulièrement enrichie : Rsl24d1. Rsl24d1 est une protéine de biogenèse des ribosomes décrites exclusivement chez la levure. Son profil d'expression dans différentes lignées de CSEm suggère une fonction spécifique: enrichissement au niveau transcriptionnel et protéique dans les CSE à l'état de pluripotence naïf et diminution importante au cours de la différenciation. En effet, des approches de perte d'expression de Rsl24d1 m'ont permis d'établir l'importance de cette PaR dans l'homéostasie des CSEm. Rsl24d1 contribue au maintien de la prolifération cellulaire des CSE, de leur clonogénicité et plus modérément à leur pluripotence. Rsl24d1 semble être une protéine majoritairement nucléaire mais également associée aux sous- unités 60S libres des ribosomes cytoplasmiques. D'autre part, la perte d'expression de Rsl24d1 affecte spécifiquement la biogenèse des particules ribosomiques 60S. Ainsi, comme chez la levure, dans les CSEm, Rsl24d1 est un facteur navette orchestrant la maturation des particules ribosomiques pré-60S. Par ailleurs, Rsl24d1 semble permettre le maintien d'un taux de synthèse protéique élevé permettant notamment le renouvellement des protéines ayant une demi-vie courte parmi lesquels on recense des facteurs de transcription de la pluripotence comme Oct4 (Oct3/4), Nanog et Esrrb. Mes travaux de thèse ont donc permis d'identifier et de caractériser un facteur de biogenèse de la sous-unité 60S, Rsl24d1, impliqué dans l'homéostasie des CSE

Cell-intrinsic and -extrinsic functions of the ESCRT-III component shrub in cytokinetic abscission of Drosophila sensory organ precursor

International audienceAlthough the molecular mechanisms governing abscission of isolated cells are largely decrypted, those of epithelial progenitors surrounded by epidermal cells (ECs) connected via cellular junctions remain largely unexplored. Here, we investigated the remodeling of the paracellular diffusion barrier ensured by septate junctions (SJs) during cytokinesis of Drosophila sensory organ precursor (SOP). We report that SOP cytokinesis involves the coordinated, polarized assembly and remodeling of SJs in the dividing cell and its neighbors, which remain connected to the former via membrane protrusions pointing towards the SOP midbody. SJs assembly and midbody basal displacement occur faster in SOPs than in ECs, leading to a quicker disentanglement of neighboring cells membrane protrusions prior to midbody release. As reported in isolated cells, the endosomal sorting complex required for transport-III component Shrub/CHMP4B is recruited at the midbody and cell-autonomously regulates abscission. In addition, Shrub is recruited to membrane protrusions, is required for SJ integrity, and alteration of SJ integrity leads to premature abscission. Our study uncovers cell- intrinsic and -extrinsic functions of Shrub in coordinating remodeling of the SJs and SOP abscission

RSL24D1 sustains steady-state ribosome biogenesis and pluripotency translational programs in embryonic stem cells

Abstract Embryonic stem cell (ESC) fate decisions are regulated by a complex circuitry that coordinates gene expression at multiple levels from chromatin to mRNA processing. Recently, ribosome biogenesis and translation have emerged as key pathways that efficiently control stem cell homeostasis, yet the underlying molecular mechanisms remain largely unknown. Here, we identified RSL24D1 as highly expressed in both mouse and human pluripotent stem cells. RSL24D1 is associated with nuclear pre-ribosomes and is required for the biogenesis of 60S subunits in mouse ESCs. Interestingly, RSL24D1 depletion significantly impairs global translation, particularly of key pluripotency factors and of components from the Polycomb Repressive Complex 2 (PRC2). While having a moderate impact on differentiation, RSL24D1 depletion significantly alters ESC self-renewal and lineage commitment choices. Altogether, these results demonstrate that RSL24D1-dependant ribosome biogenesis is both required to sustain the expression of pluripotent transcriptional programs and to silence PRC2-regulated developmental programs, which concertedly dictate ESC homeostasis

RSL24D1 sustains steady-state ribosome biogenesis and pluripotency translational programs in embryonic stem cells

Abstract Embryonic stem cell (ESC) fate decisions are regulated by a complex circuitry that coordinates gene expression at multiple levels from chromatin to mRNA processing. Recently, ribosome biogenesis and translation have emerged as key pathways that efficiently control stem cell homeostasis, yet the underlying molecular mechanisms remain largely unknown. Here, we identified RSL24D1 as highly expressed in both mouse and human pluripotent stem cells. RSL24D1 is associated with nuclear pre-ribosomes and is required for the biogenesis of 60S subunits in mouse ESCs. Interestingly, RSL24D1 depletion significantly impairs global translation, particularly of key pluripotency factors and of components from the Polycomb Repressive Complex 2 (PRC2). While having a moderate impact on differentiation, RSL24D1 depletion significantly alters ESC self-renewal and lineage commitment choices. Altogether, these results demonstrate that RSL24D1-dependant ribosome biogenesis is both required to sustain the expression of pluripotent transcriptional programs and to silence PRC2-regulated developmental programs, which concertedly dictate ESC homeostasis

RSL24D1 sustains steady-state ribosome biogenesis and pluripotency translational programs in embryonic stem cells

Abstract Embryonic stem cell (ESC) fate decisions are regulated by a complex circuitry that coordinates gene expression at multiple levels from chromatin to mRNA processing. Recently, ribosome biogenesis and translation have emerged as key pathways that efficiently control stem cell homeostasis, yet the underlying molecular mechanisms remain largely unknown. Here, we identified RSL24D1 as highly expressed in both mouse and human pluripotent stem cells. RSL24D1 is associated with nuclear pre-ribosomes and is required for the biogenesis of 60S subunits in mouse ESCs. Interestingly, RSL24D1 depletion significantly impairs global translation, particularly of key pluripotency factors and of components from the Polycomb Repressive Complex 2 (PRC2). While having a moderate impact on differentiation, RSL24D1 depletion significantly alters ESC self-renewal and lineage commitment choices. Altogether, these results demonstrate that RSL24D1-dependant ribosome biogenesis is both required to sustain the expression of pluripotent transcriptional programs and to silence PRC2-regulated developmental programs, which concertedly dictate ESC homeostasis

Pooled Fecal Allogenic Microbiotherapy for Refractory Gastrointestinal Acute Graft-Versus-Host Disease: Results from the Early Access Program in France

International audienceIntroduction Acute graft-versus-host disease (aGvHD) is a major source of mortality following allogeneic hematopoietic cell transplantation (allo-HCT). Standard 1st line therapy for the treatment of aGvHD involves corticosteroids (CS). However, more than 50% of patients are refractory to CS (SR-aGvHD) and the associated mortality rate is of up to 80%. Recently, Ruxolitinib has been approved as 2nd line treatment for SR-aGvHD. However, patients with severe gastrointestinal (GI) aGvHD seem less likely to respond to Ruxolitinib and have poor outcomes with limited therapeutic options.In this context, fecal microbiotherapy has shown promising results in several pilot studies in patients with refractory GI-aGvHD. Here we report clinical outcomes from 81 patients diagnosed with SR or dependent (SD) GI-aGvHD treated with the pooled allogeneic microbiotherapy MaaT013 as part of the Early Access Program (EAP) in France.Methods 81 patients with SR/SD GI-aGvHD (Classical n=62, late onset n=12, overlap syndrome n=7) were treated with MaaT013 as part of an EAP in France. These patients had failed 1 to 6 prior systemic GvHD treatment lines (median 2; 66/81 received Ruxolitinib). Most patients had grade III-IV aGvHD (11% grade II, 51% grade III, 38% grade IV).For each patient, a total of 3 MaaT013 administrations were planned every 7 +/- 2 days. Each dose comprised 30g of feces in 150 mL of diluent, from 4 to 8 healthy donors, administered by enema (except for 1 patient by nasogastric tube).Treatment response was calculated among all treated patients based on aGvHD staging and grading at day 28 (D28) at the time of the EAP request.Results At D28, the GI-overall response rate (ORR) was 56%: 30 complete response (CR, 37%), 11 very good response rate (VGPR, 14%), 4 partial response (PR, 5%). The GI-ORR was higher in patients with lower grade aGvHD (89% in grade II, 66% in grade III, 32% in grade IV) and higher in SD versus SR patients (92% versus 49%). Including skin and liver symptoms (n=78), response rate was 49%, including 24 CR, 11 VGPR and 3 PR and inversely correlated with aGvHD initial grade (88% in grade II, 55% in grade III, 30% in grade IV).Overall survival (OS) was 51% at 6 months (M6) and 39% at M12. The median follow-up among surviving patients was 355 days (range, 53-731). OS was significantly higher in patients achieving at least GI-PR at D28 (Responder, R; n=45) compared to patients in treatment failure (Non-responder, NR; n=35): 69% versus 28% at M6, 59% versus 14% at M12, respectively. Median survival duration in R was 451 days versus 32 days in NR.Interestingly, aGvHD response was improved in the subgroup of 31 patients previously treated with Ruxolitinib as 2nd line and MaaT013 as 3rd line (65% D28 GI-ORR, OS M6 55% and 49% M12 and 74% versus 15% at M6 and 74% versus 0% at M12 for R and NR respectively).MaaT013 displayed a good overall safety profile in the EAP population: 20 pharmacovigilance cases were reported in 18 patients: sepsis in 11 patients, C. difficile colitis in 2, E. coli osteoarthritis in 1, G. silvicola in stools from 1, P. aeruginosa sinusitis in 1, appearance of air bubbles in the mesorectum in 1, respiratory distress in 1. No pathogen transmission was reported. In 2 patients, non-pathogenic commensal bacteria isolated following infectious events were detected in the administered MaaT013 batch. Causality could not be formally excluded in these cases.The overall incidence of bacteremia (14%) remains low, compared to an incidence of 31% to 74% in bloodstream infections reported in patients with GI-aGvHD. This suggests that fecal microbiotherapy may have a protective effect on bacterial translocation, but this needs to be confirmed in further clinical trials.47 deaths have been reported; the cause of which was GvHD in 21 patients, severe infection in 13, relapse of underlying malignancy in 6, COVID-19 in 3, hemorrhage during surgery in 1, neurological complications post allo-HCT in 1, and cardiac arrest in 2 patients. No causality link with MaaT013 administration has been identified.Conclusion Overall, EAP clinical data showed that MaaT013 was safe and effective for the treatment of SR/SD-GI-aGvHD especially in patients having previously received ruxolitinib. Interestingly, GI-response to aGvHD correlates with increased OS, suggesting a strong favorable benefit-risk profile for MaaT013. A Phase 3 trial is currently ongoing to confirm these results in ruxolitinib-refractory patients (NCT04769895)

Pooled Fecal Allogenic Microbiotherapy for Refractory Gastrointestinal Acute Graft-Versus-Host Disease : Results from Early Access Program in Europe

International audienceIntroduction Acute Graft-versus-host disease (aGvHD) is a major source of mortality following allogeneic hematopoietic cell transplantation (allo-HCT). Fecal microbiotherapy has shown promising results in several pilot studies in patients with refractory gastrointestinal (GI)-aGvHD. Here we report clinical outcomes from 111 patients diagnosed with steroid-refractory (SR) or dependent (SD) GI-aGvHD treated with the pooled allogeneic microbiotherapy MaaT013 as part of the Early Access Program (EAP) in Europe. Patients and methods One hundred and eleven patients (including 1 pediatric patient aged 15 years) with SR/SD GI-aGvHD (Classical n=70, late onset n=12, overlap syndrome n=16, hyper-acute n=13) were treated with MaaT013 therapy as part of Early Access Program in Europe (France and Germany). These patients had previously failed 1 to 6 systemic GvHD treatment lines (median 3; 94/111 received ruxolitinib). Most patients had grade III to IV aGvHD (9% grade II, 49% grade III aGvHD, 42% grade IV). For each patient, a total of 3 MaaT013 administrations were planned every 7 +/- 2 days (median dose administered 3). Each dose is composed of 30 g of feces in 150 mL of suspension from 4 to 8 healthy donors administered by enema (except for 1 patient by nasogastric tube). Treatment response was calculated among all treated patients based on aGvHD staging and grading at day 28 (D28) at the time of the EAP request. Results At D28, the GI-ORR was 53%: 39 CR (35%), 15 VGPR (14%), 5 PR (5%). GI-ORR was higher in patients with lower grade aGvHD (100% in grade II, 63% in grade III, 32% in grade IV) and higher in SD versus SR (88% versus 47%). Overall response considering all organs (n=108 with 3 missing data) was 50%, including 34 CR, 16 VGPR and 4 PR. Administration of MaaT013 in the pediatric patient was well tolerated and led to complete response of GI and skin symptoms (the patient had stage 3 skin and stage 4 GI aGvHD) up to 12 months. Symptoms of the liver were not resolved at D28 (stage 2 liver, stable disease) but improved from month 6 without additional therapy. Overall survival (OS) was 56% at 6 months (M6) and 47% at M12 . The median follow-up among surviving patients was 355 days (range, 27-731).OS was significantly higher in patients achieving at least GI-PR at D28 (Responder, R; n=59) compared to patients in treatment failure (Non-responder, NR; n=52): 74% versus 36% at M6, 67% versus 24% at M12 (p<0.0001 log-rank test) . Median survival duration in R was 293 days versus 56 days in NR. Interestingly, in the subgroup of 38 patients previously treated with ruxolitinib as 2 nd line and MaaT013 as 3 rd line GI-ORR was improved being 61% D28, with 58% CR. OS at M6 was 55% and 52% at M12. OS was significantly higher in R patients, when compared to NR patients (81% versus 16% at M6 and 81% versus 8% at M12 for R and NR respectively, p<0.0001 log-rank test). MaaT013 displays a good overall safety profile in EAP population: 29 pharmacovigilance cases were reported in 27 patients, including 18 cases that could be possibly considered related to MaaT013 either by the physician or the company: sepsis in 5 patients, bacteremia in 7 patients, rectal bleeding/ anorectal disorder in 3, C. difficile colitis in 1, E. coli osteoarthritis in 1, detection of G. silvicola in stools in 1. No pathogen transmission has been reported. In 2 patients, non-pathogenic commensal bacteria isolated following infectious events were detected in the administered MaaT013 batch. Causality could not be formally excluded in these cases. 56 deaths have been reported. The cause of death was GvHD in 23 patients, severe infection in 15, relapse of underlying malignancy in 9, COVID-19 in 5, hemorrhage during surgery in 1, neurological complications post allo-HCT in 1, and cardiac arrest in 2 patients. No causality link with MaaT013 administration has been identified. Conclusion Overall, EAP clinical data showed that MaaT013 was safe and effective for the treatment of SR/SD-GI-aGvHD especially in patients having previously received ruxolitinib. Interestingly, response of GI-aGvHD correlates with increased overall survival, suggesting a strong favorable benefit-risk profile for MaaT013. A Phase 3 trial is currently ongoing to confirm these results in ruxolitinib-refractory patients (NCT04769895)