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Alfeghaly C, Castel G, Cazottes E, Moscatelli M, Moinard E, Casanova M, Boni J, Mahadik K, Lammers J, Freour T, Chauviere L, Piqueras C, Boers R, Boers J, Gribnau J, David L, Ouimette JF, Rougeulle C. XIST dampens X chromosome activity in a SPEN-dependent manner during early human development. Nat Struct Mol Biol 2024; 31:1589-1600. [PMID: 38834912 PMCID: PMC11479943 DOI: 10.1038/s41594-024-01325-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 04/25/2024] [Indexed: 06/06/2024]
Abstract
XIST (X-inactive specific transcript) long noncoding RNA (lncRNA) is responsible for X chromosome inactivation (XCI) in placental mammals, yet it accumulates on both X chromosomes in human female preimplantation embryos without triggering X chromosome silencing. The XACT (X-active coating transcript) lncRNA coaccumulates with XIST on active X chromosomes and may antagonize XIST function. Here, we used human embryonic stem cells in a naive state of pluripotency to assess the function of XIST and XACT in shaping the X chromosome chromatin and transcriptional landscapes during preimplantation development. We show that XIST triggers the deposition of polycomb-mediated repressive histone modifications and dampens the transcription of most X-linked genes in a SPEN-dependent manner, while XACT deficiency does not significantly affect XIST activity or X-linked gene expression. Our study demonstrates that XIST is functional before XCI, confirms the existence of a transient process of X chromosome dosage compensation and reveals that XCI and dampening rely on the same set of factors.
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Affiliation(s)
- Charbel Alfeghaly
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Gaël Castel
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Emmanuel Cazottes
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | | | - Eva Moinard
- Center for Research in Transplantation and Translational Immunology (CR2TI), CHU Nantes, Inserm, Nantes Université, Nantes, France
| | - Miguel Casanova
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Juliette Boni
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Kasturi Mahadik
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Jenna Lammers
- Service de Biologie de la Reproduction, CHU Nantes, Nantes Université, Nantes, France
| | - Thomas Freour
- Service de Biologie de la Reproduction, CHU Nantes, Nantes Université, Nantes, France
| | - Louis Chauviere
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Carla Piqueras
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France
| | - Ruben Boers
- Department of Developmental Biology, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Joachim Boers
- Department of Developmental Biology, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Joost Gribnau
- Department of Developmental Biology, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Laurent David
- Center for Research in Transplantation and Translational Immunology (CR2TI), CHU Nantes, Inserm, Nantes Université, Nantes, France
- BioCore, CNRS, CHU Nantes, Inserm, Nantes Université, Nantes, France
| | | | - Claire Rougeulle
- Epigenetics and Cell Fate, CNRS, Université Paris Cité, Paris, France.
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Kang MJ, Ioannou S, Lougheide Q, Dittmar M, Hsu Y, Pastor-Soler NM. The study of intercalated cells using ex vivo techniques: primary cell culture, cell lines, kidney slices, and organoids. Am J Physiol Cell Physiol 2024; 326:C229-C251. [PMID: 37899748 DOI: 10.1152/ajpcell.00479.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 10/23/2023] [Accepted: 10/24/2023] [Indexed: 10/31/2023]
Abstract
This review summarizes methods to study kidney intercalated cell (IC) function ex vivo. While important for acid-base homeostasis, IC dysfunction is often not recognized clinically until it becomes severe. The advantage of using ex vivo techniques is that they allow for the differential evaluation of IC function in controlled environments. Although in vitro kidney tubular perfusion is a classical ex vivo technique to study IC, here we concentrate on primary cell cultures, immortalized cell lines, and ex vivo kidney slices. Ex vivo techniques are useful in evaluating IC signaling pathways that allow rapid responses to extracellular changes in pH, CO2, and bicarbonate (HCO3-). However, these methods for IC work can also be challenging, as cell lines that recapitulate IC do not proliferate easily in culture. Moreover, a "pure" IC population in culture does not necessarily replicate its collecting duct (CD) environment, where ICs are surrounded by the more abundant principal cells (PCs). It is reassuring that many findings obtained in ex vivo IC systems signaling have been largely confirmed in vivo. Some of these newly identified signaling pathways reveal that ICs are important for regulating NaCl reabsorption, thus suggesting new frontiers to target antihypertensive treatments. Moreover, recent single-cell characterization studies of kidney epithelial cells revealed a dual developmental origin of IC, as well as the presence of novel CD cell types with certain IC characteristics. These exciting findings present new opportunities for the study of IC ex vivo and will likely rediscover the importance of available tools in this field.NEW & NOTEWORTHY The study of kidney intercalated cells has been limited by current cell culture and kidney tissue isolation techniques. This review is to be used as a reference to select ex vivo techniques to study intercalated cells. We focused on the use of cell lines and kidney slices as potential useful models to study membrane transport proteins. We also review how novel collecting duct organoids may help better elucidate the role of these intriguing cells.
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Affiliation(s)
- Min Ju Kang
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Silvia Ioannou
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Quinn Lougheide
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Michael Dittmar
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Young Hsu
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
| | - Nuria M Pastor-Soler
- Division of Nephrology and Hypertension, Department of Medicine, Keck School of Medicine of USC, Los Angeles, California, United States
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Jung HJ, Dixon EE, Coleman R, Watnick T, Reiter JF, Outeda P, Cebotaru V, Woodward OM, Welling PA. Polycystin-2-dependent transcriptome reveals early response of autosomal dominant polycystic kidney disease. Physiol Genomics 2023; 55:565-577. [PMID: 37720991 PMCID: PMC11178268 DOI: 10.1152/physiolgenomics.00040.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/19/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in polycystin genes, Pkd1 and Pkd2, but the underlying pathogenic mechanisms are poorly understood. To identify genes and pathways that operate downstream of polycystin-2 (PC2), a comprehensive gene expression database was created, cataloging changes in the transcriptome immediately following PC2 protein depletion. To explore cyst initiation processes, an immortalized mouse inner medullary collecting duct line was developed with the ability to knock out the Pkd2 gene conditionally. Genome-wide transcriptome profiling was performed using RNA sequencing in the cells immediately after PC2 was depleted and compared with isogenic control cells. Differentially expressed genes were identified, and a bioinformatic analysis pipeline was implemented. Altered expression of candidate cystogenic genes was validated in Pkd2 knockout mice. The expression of nearly 900 genes changed upon PC2 depletion. Differentially expressed genes were enriched for genes encoding components of the primary cilia, the canonical Wnt pathway, and MAPK signaling. Among the PC2-dependent ciliary genes, the transcription factor Glis3 was significantly downregulated. MAPK signaling formed a key node at the epicenter of PC2-dependent signaling networks. Activation of Wnt and MAPK signaling, concomitant with the downregulation of Glis3, was corroborated in Pkd2 knockout mice. The data identify a PC2 cilia-to-nucleus signaling axis and dysregulation of the Gli-similar subfamily of transcription factors as a potential initiator of cyst formation in ADPKD. The catalog of PC2-regulated genes should provide a valuable resource for future ADPKD research and new opportunities for drug development.NEW & NOTEWORTHY Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease. Mutations in polycystin genes cause the disease, but the underlying mechanisms of cystogenesis are unknown. To help fill this knowledge gap, we created an inducible cell model of ADPKD and assembled a catalog of genes that respond in immediate proximity to polycystin-2 depletion using transcriptomic profiling. The catalog unveils a ciliary signaling-to-nucleus axis proximal to polycystin-2 dysfunction, highlighting Glis, Wnt, and MAPK signaling.
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Affiliation(s)
- Hyun Jun Jung
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Eryn E Dixon
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Richard Coleman
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Terry Watnick
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States
- Chan Zuckerberg Biohub, San Francisco, California, United States
| | - Patricia Outeda
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Valeriu Cebotaru
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Owen M Woodward
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - Paul A Welling
- Division of Nephrology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
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Leroux AE, Biondi RM. The choreography of protein kinase PDK1 and its diverse substrate dance partners. Biochem J 2023; 480:1503-1532. [PMID: 37792325 DOI: 10.1042/bcj20220396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/24/2023] [Accepted: 08/31/2023] [Indexed: 10/05/2023]
Abstract
The protein kinase PDK1 phosphorylates at least 24 distinct substrates, all of which belong to the AGC protein kinase group. Some substrates, such as conventional PKCs, undergo phosphorylation by PDK1 during their synthesis and subsequently get activated by DAG and Calcium. On the other hand, other substrates, including members of the Akt/PKB, S6K, SGK, and RSK families, undergo phosphorylation and activation downstream of PI3-kinase signaling. This review presents two accepted molecular mechanisms that determine the precise and timely phosphorylation of different substrates by PDK1. The first mechanism involves the colocalization of PDK1 with Akt/PKB in the presence of PIP3. The second mechanism involves the regulated docking interaction between the hydrophobic motif (HM) of substrates and the PIF-pocket of PDK1. This interaction, in trans, is equivalent to the molecular mechanism that governs the activity of AGC kinases through their HMs intramolecularly. PDK1 has been instrumental in illustrating the bi-directional allosteric communication between the PIF-pocket and the ATP-binding site and the potential of the system for drug discovery. PDK1's interaction with substrates is not solely regulated by the substrates themselves. Recent research indicates that full-length PDK1 can adopt various conformations based on the positioning of the PH domain relative to the catalytic domain. These distinct conformations of full-length PDK1 can influence the interaction and phosphorylation of substrates. Finally, we critically discuss recent findings proposing that PIP3 can directly regulate the activity of PDK1, which contradicts extensive in vitro and in vivo studies conducted over the years.
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Affiliation(s)
- Alejandro E Leroux
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina
| | - Ricardo M Biondi
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina
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Woods LM, Ali FR, Gomez R, Chernukhin I, Marcos D, Parkinson LM, Tayoun ANA, Carroll JS, Philpott A. Elevated ASCL1 activity creates de novo regulatory elements associated with neuronal differentiation. BMC Genomics 2022; 23:255. [PMID: 35366798 PMCID: PMC8977041 DOI: 10.1186/s12864-022-08495-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 03/23/2022] [Indexed: 12/14/2022] Open
Abstract
Background The pro-neural transcription factor ASCL1 is a master regulator of neurogenesis and a key factor necessary for the reprogramming of permissive cell types to neurons. Endogenously, ASCL1 expression is often associated with neuroblast stem-ness. Moreover, ASCL1-mediated reprogramming of fibroblasts to differentiated neurons is commonly achieved using artificially high levels of ASCL1 protein, where ASCL1 acts as an “on-target” pioneer factor. However, the genome-wide effects of enhancing ASCL1 activity in a permissive neurogenic environment has not been thoroughly investigated. Here, we overexpressed ASCL1 in the neuronally-permissive context of neuroblastoma (NB) cells where modest endogenous ASCL1 supports the neuroblast programme. Results Increasing ASCL1 in neuroblastoma cells both enhances binding at existing ASCL1 sites and also leads to creation of numerous additional, lower affinity binding sites. These extensive genome-wide changes in ASCL1 binding result in significant reprogramming of the NB transcriptome, redirecting it from a proliferative neuroblastic state towards one favouring neuronal differentiation. Mechanistically, ASCL1-mediated cell cycle exit and differentiation can be increased further by preventing its multi-site phosphorylation, which is associated with additional changes in genome-wide binding and gene activation profiles. Conclusions Our findings show that enhancing ASCL1 activity in a neurogenic environment both increases binding at endogenous ASCL1 sites and also results in additional binding to new low affinity sites that favours neuronal differentiation over the proliferating neuroblast programme supported by the endogenous protein. These findings have important implications for controlling processes of neurogenesis in cancer and cellular reprogramming. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08495-8.
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