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Towler OW, Shore EM, Kaplan FS. Molecular Developmental Biology of Fibrodysplasia Ossificans Progressiva: Measuring the Giant by Its Toe. Biomolecules 2024; 14:1009. [PMID: 39199396 PMCID: PMC11353020 DOI: 10.3390/biom14081009] [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: 06/25/2024] [Revised: 08/12/2024] [Accepted: 08/13/2024] [Indexed: 09/01/2024] Open
Abstract
When a genetic disease is characterized by the abnormal activation of normal molecular pathways and cellular events, it is illuminating to critically examine the places and times of these activities both in health and disease. Therefore, because heterotopic ossification (HO) in fibrodysplasia ossificans progressiva (FOP) is by far the disease's most prominent symptom, attention is also directed toward the pathways and processes of bone formation during skeletal development. FOP is recognizable by effects of the causative mutation on skeletal development even before HO manifests, specifically in the malformation of the great toes. This signature skeletal phenotype is the most highly penetrant, but is only one among several skeletal abnormalities associated with FOP. Patients may present clinically with joint malformation and ankylosis, particularly in the cervical spine and costovertebral joints, as well as characteristic facial features and a litany of less common, non-skeletal symptoms, all stemming from missense mutations in the ACVR1 gene. In the same way that studying the genetic cause of HO advanced our understanding of HO initiation and progression, insight into the roles of ACVR1 signaling during tissue development, particularly in the musculoskeletal system, can be gained from examining altered skeletal development in individuals with FOP. This review will detail what is known about the molecular mechanisms of developmental phenotypes in FOP and the early role of ACVR1 in skeletal patterning and growth, as well as highlight how better understanding these processes may serve to advance patient care, assessments of patient outcomes, and the fields of bone and joint biology.
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Affiliation(s)
- O. Will Towler
- Division of Plastic Surgery, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA;
| | - Eileen M. Shore
- Center for Research in FOP and Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA;
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Frederick S. Kaplan
- Center for Research in FOP and Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA;
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Kaliya-Perumal AK, Celik C, Carney TJ, Harris MP, Ingham PW. Genetic regulation of injury-induced heterotopic ossification in adult zebrafish. Dis Model Mech 2024; 17:dmm050724. [PMID: 38736327 DOI: 10.1242/dmm.050724] [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: 01/31/2024] [Accepted: 04/05/2024] [Indexed: 05/14/2024] Open
Abstract
Heterotopic ossification is the inappropriate formation of bone in soft tissues of the body. It can manifest spontaneously in rare genetic conditions or as a response to injury, known as acquired heterotopic ossification. There are several experimental models for studying acquired heterotopic ossification from different sources of damage. However, their tenuous mechanistic relevance to the human condition, invasive and laborious nature and/or lack of amenability to chemical and genetic screens, limit their utility. To address these limitations, we developed a simple zebrafish injury model that manifests heterotopic ossification with high penetrance in response to clinically emulating injuries, as observed in human myositis ossificans traumatica. Using this model, we defined the transcriptional response to trauma, identifying differentially regulated genes. Mutant analyses revealed that an increase in the activity of the potassium channel Kcnk5b potentiates injury response, whereas loss of function of the interleukin 11 receptor paralogue (Il11ra) resulted in a drastically reduced ossification response. Based on these findings, we postulate that enhanced ionic signalling, specifically through Kcnk5b, regulates the intensity of the skeletogenic injury response, which, in part, requires immune response regulated by Il11ra.
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Affiliation(s)
- Arun-Kumar Kaliya-Perumal
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive 636921, Singapore
| | - Cenk Celik
- Department of Genetics, Evolution and Environment, Genetics Institute, University College London, London WC1E 6BT, UK
| | - Tom J Carney
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive 636921, Singapore
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Proteos 138673, Singapore
| | - Matthew P Harris
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Department of Orthopedic Research, Boston Children's Hospital, Boston, MA 02115, USA
| | - Philip W Ingham
- Lee Kong Chian School of Medicine, Nanyang Technological University, 59 Nanyang Drive 636921, Singapore
- Department of Life Sciences, University of Bath, Bath BA2 7AY, UK
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Mejias Rivera L, Shore EM, Mourkioti F. Cellular and Molecular Mechanisms of Heterotopic Ossification in Fibrodysplasia Ossificans Progressiva. Biomedicines 2024; 12:779. [PMID: 38672135 PMCID: PMC11048698 DOI: 10.3390/biomedicines12040779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 03/22/2024] [Accepted: 03/26/2024] [Indexed: 04/28/2024] Open
Abstract
Fibrodysplasia ossificans progressiva (FOP) is a debilitating genetic disorder characterized by recurrent episodes of heterotopic ossification (HO) formation in muscles, tendons, and ligaments. FOP is caused by a missense mutation in the ACVR1 gene (activin A receptor type I), an important signaling receptor involved in endochondral ossification. The ACVR1R206H mutation induces increased downstream canonical SMAD-signaling and drives tissue-resident progenitor cells with osteogenic potential to participate in endochondral HO formation. In this article, we review aberrant ACVR1R206H signaling and the cells that give rise to HO in FOP. FOP mouse models and lineage tracing analyses have been used to provide strong evidence for tissue-resident mesenchymal cells as cellular contributors to HO. We assess how the underlying mutation in FOP disrupts muscle-specific dynamics during homeostasis and repair, with a focus on muscle-resident mesenchymal cells known as fibro-adipogenic progenitors (FAPs). Accumulating research points to FAPs as a prominent HO progenitor population, with ACVR1R206H FAPs not only aberrantly differentiating into chondro-osteogenic lineages but creating a permissive environment for bone formation at the expense of muscle regeneration. We will further discuss the emerging role of ACVR1R206H FAPs in muscle regeneration and therapeutic targeting of these cells to reduce HO formation in FOP.
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Affiliation(s)
- Loreilys Mejias Rivera
- Cell and Molecular Biology, Genetics and Epigenetics Graduate Program, University of Pennsylvania, Philadelphia, PA 19104, USA;
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, Philadelphia, PA 19104, USA
- Center for Research in FOP and Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Eileen M. Shore
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, Philadelphia, PA 19104, USA
- Center for Research in FOP and Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Foteini Mourkioti
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, Philadelphia, PA 19104, USA
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Musculoskeletal Program, Penn Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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4
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Lai B, Jiang H, Gao Y, Zhou X. Skeletal ciliopathy: pathogenesis and related signaling pathways. Mol Cell Biochem 2024; 479:811-823. [PMID: 37188988 DOI: 10.1007/s11010-023-04765-5] [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: 03/29/2023] [Accepted: 05/09/2023] [Indexed: 05/17/2023]
Abstract
Cilia are tiny organelles with conserved structures and components in eukaryotic cells. Ciliopathy is a set of diseases resulting from cilium dysfunction classified into first-order and second-order ciliopathy. With the advancement of clinical diagnosis and radiography, numerous skeletal phenotypes, including polydactyly, short limbs, short ribs, scoliosis, a narrow thorax, and numerous anomalies in bone and cartilage, have been discovered in ciliopathies. Mutation in genes encoding cilia core components or other cilia-related molecules have been found in skeletal ciliopathies. Meanwhile, various signaling pathways associated with cilia and skeleton development have been deemed to be significant for the occurrence and progression of diseases. Herein, we review the structure and key components of the cilium and summarize several skeletal ciliopathies with their presumable pathology. We also emphasize the signaling pathways involved in skeletal ciliopathies, which may assist in developing potential therapies for these diseases.
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Affiliation(s)
- Bowen Lai
- Department of Orthopedics, Changzheng Hospital, Second Military Medical University, Fengyang Road 415, Shanghai, 200003, China
| | - Heng Jiang
- Department of Orthopedics, Changzheng Hospital, Second Military Medical University, Fengyang Road 415, Shanghai, 200003, China
| | - Yuan Gao
- Department of Orthopedics, Changzheng Hospital, Second Military Medical University, Fengyang Road 415, Shanghai, 200003, China
| | - Xuhui Zhou
- Department of Orthopedics, Changzheng Hospital, Second Military Medical University, Fengyang Road 415, Shanghai, 200003, China.
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Szilágyi SS, Burdzinski W, Jatzlau J, Ehrlich M, Knaus P, Henis YI. The Activation of the Fibrodysplasia Ossificans Progressiva-Inducing ALK2-R206H Mutant Depends on the Distinct Homo-Oligomerization Patterns of ACVR2B and ACVR2A. Cells 2024; 13:221. [PMID: 38334613 PMCID: PMC10854824 DOI: 10.3390/cells13030221] [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: 12/19/2023] [Revised: 01/18/2024] [Accepted: 01/23/2024] [Indexed: 02/10/2024] Open
Abstract
Mutations in activin-like kinase 2 (ALK2), e.g., ALK2-R206H, induce aberrant signaling to SMAD1/5/8, leading to Fibrodysplasia Ossificans Progressiva (FOP). In spite of extensive studies, the underlying mechanism is still unclear. Here, we quantified the homomeric and heteromeric interactions of ACVR2A, ACVR2B, ALK2-WT, and ALK2-R206H by combining IgG-mediated immobilization of one receptor with fluorescence recovery after photobleaching (FRAP) measurements on the lateral diffusion of a co-expressed receptor. ACVR2B formed stable homomeric complexes that were enhanced by Activin A (ActA), while ACVR2A required ActA for homodimerization. ALK2-WT, but not ALK2-R206H, exhibited homomeric complexes unaffected by ActA. ACVR2B formed ActA-enhanced heterocomplexes with ALK2-R206H or ALK2-WT, while ACVR2A interacted mainly with ALK2-WT. The extent of the homomeric complex formation of ACVR2A or ACVR2B was reflected in their ability to induce the oligomerization of ALK2-R206H and ALK2-WT. Thus, ACVR2B, which forms dimers without ligand, induced ActA-independent ALK2-R206H clustering but required ActA for enhancing the oligomerization of the largely dimeric ALK2-WT. In contrast, ACVR2A, which undergoes homodimerization in response to ActA, required ActA to induce ALK2-R206H oligomerization. To investigate whether these interactions are translated into signaling, we studied signaling by the FOP-inducing hyperactive ALK2-R206H mutant, with ALK2-WT signaling as control. The activation of SMAD1/5/8 signaling in cells expressing ALK2-R206H alone or together with ACVR2A or ACVR2B was measured by blotting for pSMAD1/5/8 and by transcriptional activation assays using BRE-Luc reporter. In line with the biophysical studies, ACVR2B activated ALK2-R206H without ligand, while activation by ACVR2A was weaker and required ActA. We propose that the homodimerization of ACVR2B or ACVR2A dictates their ability to recruit ALK2-R206H into higher complexes, enabling the homomeric interactions of ALK2-R206H receptors and, subsequently, their activation.
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Affiliation(s)
- Szabina Szófia Szilágyi
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel;
| | - Wiktor Burdzinski
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany (J.J.); (P.K.)
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Jerome Jatzlau
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany (J.J.); (P.K.)
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel;
| | - Petra Knaus
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany (J.J.); (P.K.)
| | - Yoav I. Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel;
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Allen RS, Jones WD, Hale M, Warder BN, Shore EM, Mullins MC. Reduced GS Domain Serine/Threonine Requirements of Fibrodysplasia Ossificans Progressiva Mutant Type I BMP Receptor ACVR1 in the Zebrafish. J Bone Miner Res 2023; 38:1364-1385. [PMID: 37329499 DOI: 10.1002/jbmr.4869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 04/29/2023] [Accepted: 06/14/2023] [Indexed: 06/19/2023]
Abstract
Fibrodysplasia ossificans progressiva (FOP) is a rare human genetic condition characterized by altered skeletal development and extraskeletal bone formation. All cases of FOP are caused by mutations in the type I bone morphogenetic protein (BMP) receptor gene ACVR1 that result in overactivation of the BMP signaling pathway. Activation of the wild-type ACVR1 kinase requires assembly of a tetrameric type I and II BMP receptor complex followed by phosphorylation of the ACVR1 GS domain by type II BMP receptors. Previous studies showed that the FOP-mutant ACVR1-R206H required type II BMP receptors and presumptive glycine/serine-rich (GS) domain phosphorylation for overactive signaling. Structural modeling of the ACVR1-R206H mutant kinase domain supports the idea that FOP mutations alter the conformation of the GS domain, but it is unclear how this leads to overactive signaling. Here we show, using a developing zebrafish embryo BMP signaling assay, that the FOP-mutant receptors ACVR1-R206H and -G328R have reduced requirements for GS domain phosphorylatable sites to signal compared to wild-type ACVR1. Further, ligand-independent and ligand-dependent signaling through the FOP-mutant ACVR1 receptors have distinct GS domain phosphorylatable site requirements. ACVR1-G328R showed increased GS domain serine/threonine requirements for ligand-independent signaling compared to ACVR1-R206H, whereas it exhibited reduced serine/threonine requirements for ligand-dependent signaling. Remarkably, while ACVR1-R206H does not require the type I BMP receptor partner, Bmpr1, to signal, a ligand-dependent GS domain mutant of ACVR1-R206H could signal independently of Bmpr1 only when Bmp7 ligand was overexpressed. Of note, unlike human ACVR1-R206H, the zebrafish paralog Acvr1l-R203H does not show increased signaling activity. However, in domain-swapping studies, the human kinase domain, but not the human GS domain, was sufficient to confer overactive signaling to the Acvr1l-R203H receptor. Together these results reflect the importance of GS domain activation and kinase domain functions in regulating ACVR1 signaling and identify mechanisms of reduced regulatory constraints conferred by FOP mutations. © 2023 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Robyn S Allen
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
- Department of Orthopaedic Surgery, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - William D Jones
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Maya Hale
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Bailey N Warder
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Eileen M Shore
- Department of Orthopaedic Surgery, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
- Department of Genetics, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Mary C Mullins
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
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Saeed S, Naveed H, Maktabijahromi N, Mohammed N, Rehman A. An Atypical Presentation of Fibrodysplasia Ossificans Progressiva and the Imperative for Multidisciplinary Care: A Case Report. Cureus 2023; 15:e43309. [PMID: 37700978 PMCID: PMC10493469 DOI: 10.7759/cureus.43309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2023] [Indexed: 09/14/2023] Open
Abstract
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by the gradual heterotopic ossification of soft tissues, leading to abnormal bone growth within muscles, tendons, and ligaments, due to a mutation in the ACVR1 gene. This specific case report highlights an unusual occurrence of FOP, emphasizing the diagnostic challenges and the importance of quick identification and appropriate intervention to mitigate its debilitating effects. The report also underscores the need for comprehensive genetic counseling and a multidisciplinary treatment approach, involving experts, such as orthopedic specialists, geneticists, and physical therapists, to improve the prognosis and overall well-being of those affected by FOP.
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Affiliation(s)
- Shahzeb Saeed
- Internal Medicine, Army Medical College, Rawalpindi, PAK
| | - Husnain Naveed
- Internal Medicine, Shifa Tameer-E-Millat University Shifa College of Medicine, Islamabad, PAK
| | | | - Norhan Mohammed
- Pediatrics, St. George's University School of Medicine, St. George, GRD
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Lalonde RL, Nicolas HA, Cutler RS, Pantekidis I, Zhang W, Yelick PC. Functional comparison of human ACVR1 and zebrafish Acvr1l FOP-associated variants in embryonic zebrafish. Dev Dyn 2023; 252:605-628. [PMID: 36606464 PMCID: PMC10311797 DOI: 10.1002/dvdy.566] [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: 07/13/2021] [Revised: 12/21/2022] [Accepted: 12/28/2022] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Fibrodysplasia ossificans progressiva (FOP), a rare disease characterized by progressive heterotopic ossification of muscle and connective tissues, is caused by autosomal dominant activating mutations in the type I receptor, ACVR1/ALK2. The classic human FOP variant, ACVR1R206H , shows increased bone morphogenetic protein (BMP) signaling and activation by activins. RESULTS Here, we performed in vivo functional characterization of human ACVR1R206H and orthologous zebrafish Acvr1lR203H using early embryonic zebrafish dorsoventral patterning as a phenotypic readout for receptor activity. Our results showed that human ACVR1R206H and zebrafish Acvr1lR203H exhibit functional differences in early embryonic zebrafish, and that human ACVR1R206H retained its signaling activity in the absence of a ligand-binding domain (LBD). We also showed, for the first time, that zebrafish Acvr2ba/Acvr2bb receptors are required for human ACVR1R206H signaling in early embryonic zebrafish. CONCLUSIONS Together, these data provide new insight into ACVR1R206H signaling pathways that may facilitate the design of new and effective therapies for FOP patients.
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Affiliation(s)
- Robert L. Lalonde
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, 136 Harrison Avenue, Boston, MA, USA 02111
| | - Hannah A. Nicolas
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, ON, Canada K1N 6N5
| | - Rowan S. Cutler
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, 136 Harrison Avenue, Boston, MA, USA 02111
| | - Irene Pantekidis
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, 136 Harrison Avenue, Boston, MA, USA 02111
| | - Weibo Zhang
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, 136 Harrison Avenue, Boston, MA, USA 02111
| | - Pamela C. Yelick
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, 136 Harrison Avenue, Boston, MA, USA 02111
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Zebrafish Models to Study Ectopic Calcification and Calcium-Associated Pathologies. Int J Mol Sci 2023; 24:ijms24043366. [PMID: 36834795 PMCID: PMC9967340 DOI: 10.3390/ijms24043366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/20/2023] [Accepted: 02/01/2023] [Indexed: 02/11/2023] Open
Abstract
Ectopic calcification refers to the pathological accumulation of calcium ions in soft tissues and is often the result of a dysregulated action or disrupted function of proteins involved in extracellular matrix mineralization. While the mouse has traditionally been the go-to model organism for the study of pathologies associated with abnormal calcium deposition, many mouse mutants often have exacerbated phenotypes and die prematurely, limiting the understanding of the disease and the development of effective therapies. Since the mechanisms underlying ectopic calcification share some analogy with those of bone formation, the zebrafish (Danio rerio)-a well-established model for studying osteogenesis and mineralogenesis-has recently gained momentum as a model to study ectopic calcification disorders. In this review, we outline the mechanisms of ectopic mineralization in zebrafish, provide insights into zebrafish mutants that share phenotypic similarities with human pathological mineralization disorders, list the compounds capable of rescuing mutant phenotypes, and describe current methods to induce and characterize ectopic calcification in zebrafish.
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Yamamoto M, Stoessel SJ, Yamamoto S, Goldhamer DJ. Overexpression of Wild-Type ACVR1 in Fibrodysplasia Ossificans Progressiva Mice Rescues Perinatal Lethality and Inhibits Heterotopic Ossification. J Bone Miner Res 2022; 37:2077-2093. [PMID: 35637634 PMCID: PMC9708949 DOI: 10.1002/jbmr.4617] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 04/22/2022] [Accepted: 05/28/2022] [Indexed: 11/07/2022]
Abstract
Fibrodysplasia ossificans progressiva (FOP) is a devastating disease of progressive heterotopic bone formation for which effective treatments are currently unavailable. FOP is caused by dominant gain-of-function mutations in the receptor ACVR1 (also known as ALK2), which render the receptor inappropriately responsive to activin ligands. In previous studies, we developed a genetic mouse model of FOP that recapitulates most clinical aspects of the disease. In this model, genetic loss of the wild-type Acvr1 allele profoundly exacerbated heterotopic ossification, suggesting the hypothesis that the stoichiometry of wild-type and mutant receptors dictates disease severity. Here, we tested this model by producing FOP mice that conditionally overexpress human wild-type ACVR1. Injury-induced heterotopic ossification (HO) was completely blocked in FOP mice when expression of both the mutant and wild-type receptor were targeted to Tie2-positive cells, which includes fibro/adipogenic progenitors (FAPs). Perinatal lethality of Acvr1R206H/+ mice was rescued by constitutive ACVR1 overexpression, and these mice survived to adulthood at predicted Mendelian frequencies. Constitutive overexpression of ACVR1 also provided protection from spontaneous abnormal skeletogenesis, and the incidence and severity of injury-induced HO in these mice was dramatically reduced. Analysis of pSMAD1/5/8 signaling both in cultured cells and in vivo indicates that ACVR1 overexpression functions cell-autonomously by reducing osteogenic signaling in response to activin A. We propose that ACVR1 overexpression inhibits HO by decreasing the abundance of ACVR1(R206H)-containing signaling complexes at the cell surface while increasing the representation of activin-A-bound non-signaling complexes comprised of wild-type ACVR1. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Masakazu Yamamoto
- Department of Molecular and Cell BiologyUniversity of Connecticut Stem Cell Institute, University of ConnecticutStorrsCTUSA
| | - Sean J Stoessel
- Department of Molecular and Cell BiologyUniversity of Connecticut Stem Cell Institute, University of ConnecticutStorrsCTUSA
| | - Shoko Yamamoto
- Department of Molecular and Cell BiologyUniversity of Connecticut Stem Cell Institute, University of ConnecticutStorrsCTUSA
| | - David J Goldhamer
- Department of Molecular and Cell BiologyUniversity of Connecticut Stem Cell Institute, University of ConnecticutStorrsCTUSA
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Wentworth KL, Lalonde RL, Groppe JC, Brewer N, Moody T, Hansberry S, Taylor KE, Shore EM, Kaplan FS, Pignolo RJ, Yelick PC, Hsiao EC. Functional Testing of Bone Morphogenetic Protein (BMP) Pathway Variants Identified on Whole-Exome Sequencing in a Patient with Delayed-Onset Fibrodysplasia Ossificans Progressiva (FOP) Using ACVR1 R206H -Specific Human Cellular and Zebrafish Models. J Bone Miner Res 2022; 37:2058-2076. [PMID: 36153796 PMCID: PMC9950781 DOI: 10.1002/jbmr.4711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 07/28/2022] [Accepted: 08/07/2022] [Indexed: 11/06/2022]
Abstract
Bone morphogenetic protein (BMP) signaling is critical in skeletal development. Overactivation can trigger heterotopic ossification (HO) as in fibrodysplasia ossificans progressiva (FOP), a rare, progressive disease of massive HO formation. A small subset of FOP patients harboring the causative ACVR1R206H mutation show strikingly mild or delayed-onset HO, suggesting that genetic variants in the BMP pathway could act as disease modifiers. Whole-exome sequencing of one such patient identified BMPR1AR443C and ACVR2AV173I as candidate modifiers. Molecular modeling predicted significant structural perturbations. Neither variant decreased BMP signaling in ACVR1R206H HEK 293T cells at baseline or after stimulation with BMP4 or activin A (AA), ligands that activate ACVR1R206H signaling. Overexpression of BMPR1AR443C in a Tg(ACVR1-R206Ha) embryonic zebrafish model, in which overactive BMP signaling yields ventralized embryos, did not alter ventralization severity, while ACVR2AV173I exacerbated ventralization. Co-expression of both variants did not affect dorsoventral patterning. In contrast, BMPR1A knockdown in ACVR1R206H HEK cells decreased ligand-stimulated BMP signaling but did not affect dorsoventral patterning in Tg(ACVR1-R206Ha) zebrafish. ACVR2A knockdown decreased only AA-stimulated signaling in ACVR1R206H HEK cells and had no effect in Tg(ACVR1-R206Ha) zebrafish. Co-knockdown in ACVR1R206H HEK cells decreased basal and ligand-stimulated signaling, and co-knockdown/knockout (bmpr1aa/ab; acvr2aa/ab) decreased Tg(ACVR1-R206Ha) zebrafish ventralization phenotypes. Our functional studies showed that knockdown of wild-type BMPR1A and ACVR2A could attenuate ACVR1R206H signaling, particularly in response to AA, and that ACVR2AV173I unexpectedly increased ACVR1R206H -mediated signaling in zebrafish. These studies describe a useful strategy and platform for functionally interrogating potential genes and genetic variants that may impact the BMP signaling pathway. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Kelly L Wentworth
- Department of Medicine, Division of Endocrinology and Metabolism, Zuckerberg San Francisco General Hospital, San Francisco, CA, USA
| | - Robert L Lalonde
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, Boston, MA, USA
| | - Jay C Groppe
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX, USA
| | - Niambi Brewer
- Department of Orthopedic Surgery and The Center of Research for FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Tania Moody
- Institute for Human Genetics, the Program in Craniofacial Biology, the UCSF Eli and Edythe Broad Institute for Regeneration Medicine, and the Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Francisco, CA, USA
| | - Steven Hansberry
- San Francisco State University, California Institute of Regenerative Medicine Bridges to Stem Cell Research Program, San Francisco, CA, USA
| | - Kimberly E Taylor
- Russell/Engleman Rheumatology Research Center, University of California, San Francisco, CA, USA
| | - Eileen M Shore
- Department of Orthopedic Surgery and The Center of Research for FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Frederick S Kaplan
- Department of Orthopedic Surgery and The Center of Research for FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Pamela C Yelick
- Tufts University School of Dental Medicine, Division of Craniofacial and Molecular Genetics, Boston, MA, USA
| | - Edward C Hsiao
- Institute for Human Genetics, the Program in Craniofacial Biology, the UCSF Eli and Edythe Broad Institute for Regeneration Medicine, and the Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Francisco, CA, USA
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12
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Szilágyi SS, Amsalem-Zafran AR, Shapira KE, Ehrlich M, Henis YI. Competition between type I activin and BMP receptors for binding to ACVR2A regulates signaling to distinct Smad pathways. BMC Biol 2022; 20:50. [PMID: 35177083 PMCID: PMC8855587 DOI: 10.1186/s12915-022-01252-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 02/10/2022] [Indexed: 11/17/2022] Open
Abstract
Background Activins and bone morphogenetic proteins (BMPs) play critical, sometimes opposing roles, in multiple physiological and pathological processes and diseases. They signal to distinct Smad branches; activins signal mainly to Smad2/3, while BMPs activate mainly Smad1/5/8. This gives rise to the possibility that competition between the different type I receptors through which activin and BMP signal for common type II receptors can provide a mechanism for fine-tuning the cellular response to activin/BMP stimuli. Among the transforming growth factor-β superfamily type II receptors, ACVR2A/B are highly promiscuous, due to their ability to interact with different type I receptors (e.g., ALK4 vs. ALK2/3/6) and with their respective ligands [activin A (ActA) vs. BMP9/2]. However, studies on complex formation between these full-length receptors situated at the plasma membrane, and especially on the potential competition between the different activin and BMP type I receptors for a common activin type II receptor, were lacking. Results We employed a combination of IgG-mediated patching-immobilization of several type I receptors in the absence or presence of ligands with fluorescence recovery after photobleaching (FRAP) measurements on the lateral diffusion of an activin type II receptor, ACVR2A, to demonstrate the principle of competition between type I receptors for ACVR2. Our results show that ACVR2A can form stable heteromeric complexes with ALK4 (an activin type I receptor), as well as with several BMP type I receptors (ALK2/3/6). Of note, ALK4 and the BMP type I receptors competed for binding ACVR2A. To assess the implications of this competition for signaling output, we first validated that in our cell model system (U2OS cells), ACVR2/ALK4 transduce ActA signaling to Smad2/3, while BMP9 signaling to Smad1/5/8 employ ACVR2/ALK2 or ACVR2/ALK3. By combining ligand stimulation with overexpression of a competing type I receptor, we showed that differential complex formation of distinct type I receptors with a common type II receptor balances the signaling to the two Smad branches. Conclusions Different type I receptors that signal to distinct Smad pathways (Smad2/3 vs. Smad1/5/8) compete for binding to common activin type II receptors. This provides a novel mechanism to balance signaling between Smad2/3 and Smad1/5/8. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01252-z.
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Affiliation(s)
- Szabina Szófia Szilágyi
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Ayelet R Amsalem-Zafran
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Keren E Shapira
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
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13
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Towler OW, Shore EM. BMP signaling and skeletal development in fibrodysplasia ossificans progressiva (FOP). Dev Dyn 2022; 251:164-177. [PMID: 34133058 PMCID: PMC9068236 DOI: 10.1002/dvdy.387] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 05/07/2021] [Accepted: 05/20/2021] [Indexed: 01/03/2023] Open
Abstract
Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disease caused by increased BMP pathway signaling due to mutation of ACVR1, a bone morphogenetic protein (BMP) type 1 receptor. The primary clinical manifestation of FOP is extra-skeletal bone formation (heterotopic ossification) within soft connective tissues. However, the underlying ACVR1 mutation additionally alters skeletal bone development and nearly all people born with FOP have bilateral malformation of the great toes as well as other skeletal malformations at diverse anatomic sites. The specific mechanisms through which ACVR1 mutations and altered BMP pathway signaling in FOP influence skeletal bone formation during development remain to be elucidated; however, recent investigations are providing a clearer understanding of the molecular and developmental processes associated with ACVR1-regulated skeletal formation.
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Affiliation(s)
- Oscar Will Towler
- The Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA,Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Eileen M. Shore
- The Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA,Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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14
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Kaplan FS, Groppe JC, Xu M, Towler OW, Grunvald E, Kalunian K, Kallish S, Al Mukaddam M, Pignolo RJ, Shore EM. An ACVR1 R375P pathogenic variant in two families with mild fibrodysplasia ossificans progressiva. Am J Med Genet A 2021; 188:806-817. [PMID: 34854557 DOI: 10.1002/ajmg.a.62585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/06/2021] [Accepted: 11/02/2021] [Indexed: 11/11/2022]
Abstract
Genetic variants are vital in informing clinical phenotypes, aiding physical diagnosis, guiding genetic counseling, understanding the molecular basis of disease, and potentially stimulating drug development. Here we describe two families with an ultrarare ACVR1 gain-of-function pathogenic variant (codon 375, Arginine > Proline; ACVR1R375P ) responsible for a mild nonclassic fibrodysplasia ossificans progressiva (FOP) phenotype. Both families include people with the ultrarare ACVR1R375P variant who exhibit features of FOP while other individuals currently do not express any clinical signs of FOP. Thus, the mild ACVR1R375P variant greatly expands the scope and understanding of this rare disorder.
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Affiliation(s)
- Frederick S Kaplan
- Department of Orthopaedic Surgery, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Medicine, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,The Center for Research in FOP & Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jay C Groppe
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas, USA
| | - Meiqi Xu
- Department of Orthopaedic Surgery, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,The Center for Research in FOP & Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - O Will Towler
- Department of Orthopaedic Surgery, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,The Center for Research in FOP & Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Eduardo Grunvald
- Division of General Internal Medicine, The Department of Medicine, The University of California San Diego, San Diego, California, USA
| | - Kenneth Kalunian
- Division of Rheumatology, Allergy and Immunology, The Department of Medicine, UC San Diego School of Medicine, La Jolla, California, USA
| | - Staci Kallish
- The Center for Research in FOP & Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Division of Translational Medicine and Human Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Mona Al Mukaddam
- Department of Orthopaedic Surgery, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Medicine, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,The Center for Research in FOP & Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Robert J Pignolo
- The Department of Medicine, The Mayo Clinic, Rochester, Minnesota, USA
| | - Eileen M Shore
- Department of Orthopaedic Surgery, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,The Center for Research in FOP & Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
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15
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Prados B, Del Toro R, MacGrogan D, Gómez-Apiñániz P, Papoutsi T, Muñoz-Cánoves P, Méndez-Ferrer S, de la Pompa JL. Heterotopic ossification in mice overexpressing Bmp2 in Tie2+ lineages. Cell Death Dis 2021; 12:729. [PMID: 34294700 PMCID: PMC8298441 DOI: 10.1038/s41419-021-04003-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 07/06/2021] [Accepted: 07/07/2021] [Indexed: 12/29/2022]
Abstract
Bone morphogenetic protein (Bmp) signaling is critical for organismal development and homeostasis. To elucidate Bmp2 function in the vascular/hematopoietic lineages we generated a new transgenic mouse line in which ectopic Bmp2 expression is controlled by the Tie2 promoter. Tie2CRE/+;Bmp2tg/tg mice develop aortic valve dysfunction postnatally, accompanied by pre-calcific lesion formation in valve leaflets. Remarkably, Tie2CRE/+;Bmp2tg/tg mice develop extensive soft tissue bone formation typical of acquired forms of heterotopic ossification (HO) and genetic bone disorders, such as Fibrodysplasia Ossificans Progressiva (FOP). Ectopic ossification in Tie2CRE/+;Bmp2tg/tg transgenic animals is accompanied by increased bone marrow hematopoietic, fibroblast and osteoblast precursors and circulating pro-inflammatory cells. Transplanting wild-type bone marrow hematopoietic stem cells into lethally irradiated Tie2CRE/+;Bmp2tg/tg mice significantly delays HO onset but does not prevent it. Moreover, transplanting Bmp2-transgenic bone marrow into wild-type recipients does not result in HO, but hematopoietic progenitors contribute to inflammation and ectopic bone marrow colonization rather than to endochondral ossification. Conversely, aberrant Bmp2 signaling activity is associated with fibroblast accumulation, skeletal muscle fiber damage, and expansion of a Tie2+ fibro-adipogenic precursor cell population, suggesting that ectopic bone derives from a skeletal muscle resident osteoprogenitor cell origin. Thus, Tie2CRE/+;Bmp2tg/tg mice recapitulate HO pathophysiology, and might represent a useful model to investigate therapies seeking to mitigate disorders associated with aberrant extra-skeletal bone formation.
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Affiliation(s)
- Belén Prados
- Intercellular Signaling in Cardiovascular Development & Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029, Madrid, Spain
- CIBER de Enfermedades Cardiovasculares, Madrid, Spain
| | - Raquel Del Toro
- CIBER de Enfermedades Cardiovasculares, Madrid, Spain
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Cardiovascular Physiophatology group, Instituto de Biomedicina de Sevilla-IBIS, (Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla). Manuel Siurot, s/n, 41013, Sevilla, Spain
| | - Donal MacGrogan
- Intercellular Signaling in Cardiovascular Development & Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029, Madrid, Spain
- CIBER de Enfermedades Cardiovasculares, Madrid, Spain
| | - Paula Gómez-Apiñániz
- Intercellular Signaling in Cardiovascular Development & Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029, Madrid, Spain
- CIBER de Enfermedades Cardiovasculares, Madrid, Spain
| | - Tania Papoutsi
- Intercellular Signaling in Cardiovascular Development & Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029, Madrid, Spain
- CIBER de Enfermedades Cardiovasculares, Madrid, Spain
| | - Pura Muñoz-Cánoves
- Tissue Regeneration Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Department of Experimental & Health Sciences, Universidad Pompeu Fabra (UPF), ICREA and CIBERNED, Dr. Aiguader 88, Barcelona, Spain
| | - Simón Méndez-Ferrer
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute and Department of Haematology, University of Cambridge, and National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge, CB2 0AW, UK
- National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge, CB2 0PT, UK
| | - José Luis de la Pompa
- Intercellular Signaling in Cardiovascular Development & Disease Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029, Madrid, Spain.
- CIBER de Enfermedades Cardiovasculares, Madrid, Spain.
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16
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Abstract
TGF-β family heterodimeric ligands show increased or exclusive signaling compared to homodimeric ligands in both vertebrate and insect development as well as in therapeutically relevant processes, like osteogenesis. However, the mechanisms that differentiate heterodimer and homodimer signaling remain uncharacterized. We show that BMP antagonists do not account for the exclusive signaling of Bmp2/7 heterodimers in zebrafish development. We found that overexpressed homodimers can signal but surprisingly require two distinct type I receptors, like heterodimers, indicating a required activity of the heteromeric type I receptor complex. We further demonstrate that a canonical type I receptor function has been delegated to only one of these receptors, Acvr1. Our findings should inform both basic and translational research in multiple TGF-β family signaling contexts. Heterodimeric TGF-β ligands outperform homodimers in a variety of developmental, cell culture, and therapeutic contexts; however, the mechanisms underlying this increased potency remain uncharacterized. Here, we use dorsal–ventral axial patterning of the zebrafish embryo to interrogate the BMP2/7 heterodimer signaling mechanism. We demonstrate that differential interactions with BMP antagonists do not account for the reduced signaling ability of homodimers. Instead, we find that while overexpressed BMP2 homodimers can signal, they require two nonredundant type I receptors, one from the Acvr1 subfamily and one from the Bmpr1 subfamily. This implies that all BMP signaling within the zebrafish gastrula, even BMP2 homodimer signaling, requires Acvr1. This is particularly surprising as BMP2 homodimers do not bind Acvr1 in vitro. Furthermore, we find that the roles of the two type I receptors are subfunctionalized within the heterodimer signaling complex, with the kinase activity of Acvr1 being essential, while that of Bmpr1 is not. These results suggest that the potency of the Bmp2/7 heterodimer arises from the ability to recruit both Acvr1 and Bmpr1 into the same signaling complex.
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17
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Ventura F, Williams E, Ikeya M, Bullock AN, ten Dijke P, Goumans MJ, Sanchez-Duffhues G. Challenges and Opportunities for Drug Repositioning in Fibrodysplasia Ossificans Progressiva. Biomedicines 2021; 9:biomedicines9020213. [PMID: 33669809 PMCID: PMC7922784 DOI: 10.3390/biomedicines9020213] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/08/2021] [Accepted: 02/15/2021] [Indexed: 01/05/2023] Open
Abstract
Fibrodysplasia ossificans progressiva (FOP) is an ultrarare congenital disease that progresses through intermittent episodes of bone formation at ectopic sites. FOP patients carry heterozygous gene point mutations in activin A receptor type I ACVR1, encoding the bone morphogenetic protein (BMP) type I serine/threonine kinase receptor ALK2, termed activin receptor-like kinase (ALK)2. The mutant ALK2 displays neofunctional responses to activin, a closely related BMP cytokine that normally inhibits regular bone formation. Moreover, the mutant ALK2 becomes hypersensitive to BMPs. Both these activities contribute to enhanced ALK2 signalling and endochondral bone formation in connective tissue. Being a receptor with an extracellular ligand-binding domain and intrinsic intracellular kinase activity, the mutant ALK2 is a druggable target. Although there is no approved cure for FOP yet, a number of clinical trials have been recently initiated, aiming to identify a safe and effective treatment for FOP. Among other targeted approaches, several repurposed drugs have shown promising results. In this review, we describe the molecular mechanisms underlying ALK2 mutation-induced aberrant signalling and ectopic bone formation. In addition, we recapitulate existing in vitro models to screen for novel compounds with a potential application in FOP. We summarize existing therapeutic alternatives and focus on repositioned drugs in FOP, at preclinical and clinical stages.
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Affiliation(s)
- Francesc Ventura
- Department de Ciències Fisiològiques, Universitat de Barcelona, IDIBELL, L’Hospitalet de Llobregat, 08907 Barcelona, Spain;
| | - Eleanor Williams
- Centre for Medicines Discovery, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK; (E.W.); (A.N.B.)
| | - Makoto Ikeya
- Department of Clinical Application, Center for iPS Cell Research and Application, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan;
| | - Alex N. Bullock
- Centre for Medicines Discovery, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK; (E.W.); (A.N.B.)
| | - Peter ten Dijke
- Oncode Institute and Department of Cell and Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands;
| | - Marie-José Goumans
- Department of Cell and Chemical Biology, Cardiovascular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands;
| | - Gonzalo Sanchez-Duffhues
- Department of Cell and Chemical Biology, Cardiovascular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands;
- Correspondence:
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18
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Cardiopulmonary and Neurologic Dysfunctions in Fibrodysplasia Ossificans Progressiva. Biomedicines 2021; 9:biomedicines9020155. [PMID: 33562570 PMCID: PMC7915901 DOI: 10.3390/biomedicines9020155] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 01/20/2021] [Accepted: 01/28/2021] [Indexed: 12/28/2022] Open
Abstract
Fibrodysplasia Ossificans Progressiva (FOP) is an ultra-rare but debilitating disorder characterized by spontaneous, progressive, and irreversible heterotopic ossifications (HO) at extraskeletal sites. FOP is caused by gain-of-function mutations in the Activin receptor Ia/Activin-like kinase 2 gene (Acvr1/Alk2), with increased receptor sensitivity to bone morphogenetic proteins (BMPs) and a neoceptor response to Activin A. There is extensive literature on the skeletal phenotypes in FOP, but a much more limited understanding of non-skeletal manifestations of this disease. Emerging evidence reveals important cardiopulmonary and neurologic dysfunctions in FOP including thoracic insufficiency syndrome, pulmonary hypertension, conduction abnormalities, neuropathic pain, and demyelination of the central nervous system (CNS). Here, we review the recent research and discuss unanswered questions regarding the cardiopulmonary and neurologic phenotypes in FOP.
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19
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Genomic Context and Mechanisms of the ACVR1 Mutation in Fibrodysplasia Ossificans Progressiva. Biomedicines 2021; 9:biomedicines9020154. [PMID: 33562470 PMCID: PMC7914827 DOI: 10.3390/biomedicines9020154] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 01/30/2021] [Accepted: 02/02/2021] [Indexed: 11/20/2022] Open
Abstract
Basic research in Fibrodysplasia Ossificans Progressiva (FOP) was carried out in the various fields involved in the disease pathophysiology and was important for designing therapeutic approaches, some of which were already developed as ongoing or planned clinical trials. Genetic research was fundamental in identifying the FOP causative mutation, and the astonishing progress in technologies for genomic analysis, coupled to related computational methods, now make possible further research in this field. We present here a review of molecular and cellular factors which could explain why a single mutation, the R206H in the ACVR1 gene, is absolutely prevalent in FOP patients. We also address the mechanisms by which FOP expressivity could be modulated by cis-acting variants in the ACVR1 genomic region in human chromosome 2q. Finally, we also discuss the general issue of genetic modifiers in FOP.
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20
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de Ruiter RD, Smilde BJ, Pals G, Bravenboer N, Knaus P, Schoenmaker T, Botman E, Sánchez-Duffhues G, Pacifici M, Pignolo RJ, Shore EM, van Egmond M, Van Oosterwyck H, Kaplan FS, Hsiao EC, Yu PB, Bocciardi R, De Cunto CL, Longo Ribeiro Delai P, de Vries TJ, Hilderbrandt S, Jaspers RT, Keen R, Koolwijk P, Morhart R, Netelenbos JC, Rustemeyer T, Scott C, Stockklausner C, ten Dijke P, Triffit J, Ventura F, Ravazzolo R, Micha D, Eekhoff EMW. Fibrodysplasia Ossificans Progressiva: What Have We Achieved and Where Are We Now? Follow-up to the 2015 Lorentz Workshop. Front Endocrinol (Lausanne) 2021; 12:732728. [PMID: 34858325 PMCID: PMC8631510 DOI: 10.3389/fendo.2021.732728] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/22/2021] [Indexed: 11/20/2022] Open
Abstract
Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare progressive genetic disease effecting one in a million individuals. During their life, patients with FOP progressively develop bone in the soft tissues resulting in increasing immobility and early death. A mutation in the ACVR1 gene was identified as the causative mutation of FOP in 2006. After this, the pathophysiology of FOP has been further elucidated through the efforts of research groups worldwide. In 2015, a workshop was held to gather these groups and discuss the new challenges in FOP research. Here we present an overview and update on these topics.
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Affiliation(s)
- Ruben D. de Ruiter
- Department of Internal Medicine, Section Endocrinology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
- *Correspondence: Ruben D. de Ruiter, ; Elisabeth M. W. Eekhoff,
| | - Bernard J. Smilde
- Department of Internal Medicine, Section Endocrinology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
| | - Gerard Pals
- Department of Clinical Genetics and Bone Histomorphology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Nathalie Bravenboer
- Department of Clinical Chemistry, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
| | - Petra Knaus
- Freie Universität Berlin, Institute for Chemistry and Biochemistry, Berlin, Germany
| | - Ton Schoenmaker
- Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit, Amsterdam, Netherlands
| | - Esmée Botman
- Department of Internal Medicine, Section Endocrinology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
| | | | - Maurizio Pacifici
- Translational Research Program in Pediatric Orthopaedics, Abramson Research Center, Division of Orthopaedic Surgery, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | | | - Eileen M. Shore
- Department of Orthopaedic Surgery and Genetics, and the Center for Research in FOP and Related Disorders, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
| | - Marjolein van Egmond
- Department of Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Hans Van Oosterwyck
- Division of Biomechanics, Department of Mechanical Engineering, Katholieke Universiteit (KU) Leuven, Leuven, Belgium
- Prometheus division of skeletal tissue engineering, Katholieke Universiteit (KU) Leuven, Leuven, Belgium
| | - Frederick S. Kaplan
- Department of Orthopaedic Surgery and Medicine, Center for Research in FOP and Related Disorders, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
| | - Edward C. Hsiao
- Department of Endocrinology and Metabolism, and the Institute for Human Genetics, Department of Medicine, University of California, San Francisco, CA, United States
| | - Paul B. Yu
- Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Renata Bocciardi
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), Università degli Studi di Genova, Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, Genova, Italy
| | - Carmen Laura De Cunto
- Rheumatology Section, Department of Pediatrics, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina
| | | | - Teun J. de Vries
- Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit, Amsterdam, Netherlands
| | - Susanne Hilderbrandt
- Freie Universität Berlin, Institute for Chemistry and Biochemistry, Berlin, Germany
- Berlin-Brandenburg Center for Regenerative Therapies, Charité Medical University of Berlin, Berlin, Germany
| | - Richard T. Jaspers
- Laboratory for Myology, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
| | - Richard Keen
- Centre for Metabolic Bone Disease, Royal National Orthopaedic Hospital, Stanmore, United Kingdom
| | - Peter Koolwijk
- Department of Physiology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Rolf Morhart
- Department of Pediatrics, Garmisch-Partenkichen Medical Center, Garmisch-Partenkirchen, Germany
| | - Jan C. Netelenbos
- Department of Internal Medicine, Section Endocrinology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
| | - Thomas Rustemeyer
- Department of Dermatology, Amsterdam University Medical Center (AmsterdamUMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Christiaan Scott
- Division of Paediatric Rheumatology, Departmet of Paediatrics and Child Heath, Red Cross War Memorial Children’s Hospital, University of Cape Town, Cape Town, South Africa
| | - Clemens Stockklausner
- Laboratory for Myology, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
| | - Peter ten Dijke
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - James Triffit
- Botnar Research Centre, University of Oxford, Oxford, United Kingdom
| | - Francesc Ventura
- Departamento de Cièncias Fisiológicas, Facultad de Medicina y Ciencias de la Salud, Universitat de Barcelona, Barcelona, Spain
| | - Roberto Ravazzolo
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), Università degli Studi di Genova, Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, Genova, Italy
| | - Dimitra Micha
- Department of Clinical Genetics and Bone Histomorphology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Elisabeth M. W. Eekhoff
- Department of Internal Medicine, Section Endocrinology, Amsterdam University Medical Center (Amsterdam UMC), Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands
- *Correspondence: Ruben D. de Ruiter, ; Elisabeth M. W. Eekhoff,
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21
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Lin CY, Lu MYJ, Yue JX, Li KL, Le Pétillon Y, Yong LW, Chen YH, Tsai FY, Lyu YF, Chen CY, Hwang SPL, Su YH, Yu JK. Molecular asymmetry in the cephalochordate embryo revealed by single-blastomere transcriptome profiling. PLoS Genet 2021; 16:e1009294. [PMID: 33382716 PMCID: PMC7806126 DOI: 10.1371/journal.pgen.1009294] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 01/13/2021] [Accepted: 11/24/2020] [Indexed: 12/13/2022] Open
Abstract
Studies in various animals have shown that asymmetrically localized maternal transcripts play important roles in axial patterning and cell fate specification in early embryos. However, comprehensive analyses of the maternal transcriptomes with spatial information are scarce and limited to a handful of model organisms. In cephalochordates (amphioxus), an early branching chordate group, maternal transcripts of germline determinants form a compact granule that is inherited by a single blastomere during cleavage stages. Further blastomere separation experiments suggest that other transcripts associated with the granule are likely responsible for organizing the posterior structure in amphioxus; however, the identities of these determinants remain unknown. In this study, we used high-throughput RNA sequencing of separated blastomeres to examine asymmetrically localized transcripts in two-cell and eight-cell stage embryos of the amphioxus Branchiostoma floridae. We identified 111 and 391 differentially enriched transcripts at the 2-cell stage and the 8-cell stage, respectively, and used in situ hybridization to validate the spatial distribution patterns for a subset of these transcripts. The identified transcripts could be categorized into two major groups: (1) vegetal tier/germ granule-enriched and (2) animal tier/anterior-enriched transcripts. Using zebrafish as a surrogate model system, we showed that overexpression of one animal tier/anterior-localized amphioxus transcript, zfp665, causes a dorsalization/anteriorization phenotype in zebrafish embryos by downregulating the expression of the ventral gene, eve1, suggesting a potential function of zfp665 in early axial patterning. Our results provide a global transcriptomic blueprint for early-stage amphioxus embryos. This dataset represents a rich platform to guide future characterization of molecular players in early amphioxus development and to elucidate conservation and divergence of developmental programs during chordate evolution.
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Affiliation(s)
- Che-Yi Lin
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Mei-Yeh Jade Lu
- Biodiversity Research Center, Academia Sinica, Taipei, Taiwan
| | - Jia-Xing Yue
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Kun-Lung Li
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Yann Le Pétillon
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Luok Wen Yong
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Yi-Hua Chen
- Biodiversity Research Center, Academia Sinica, Taipei, Taiwan
| | - Fu-Yu Tsai
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Yu-Feng Lyu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Cheng-Yi Chen
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Sheng-Ping L. Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Yi-Hsien Su
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
- * E-mail: (Y-HS); (J-KY)
| | - Jr-Kai Yu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
- Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, Yilan, Taiwan
- * E-mail: (Y-HS); (J-KY)
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22
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Towler OW, Kaplan FS, Shore EM. The Developmental Phenotype of the Great Toe in Fibrodysplasia Ossificans Progressiva. Front Cell Dev Biol 2020; 8:612853. [PMID: 33364240 PMCID: PMC7753048 DOI: 10.3389/fcell.2020.612853] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/16/2020] [Indexed: 12/30/2022] Open
Abstract
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder in which extensive heterotopic ossification (HO) begins to form during early childhood and progresses throughout life. Although HO does not occur during embryonic development, children who carry the ACVR1R206H mutation that causes most cases of FOP characteristically exhibit malformation of their great toes at birth, indicating that the mutation acts during embryonic development to alter skeletal formation. Despite the high prevalence of the great toe malformation in the FOP population, it has received relatively little attention due to its clinically benign nature. In this study, we examined radiographs from a cohort of 41 FOP patients ranging from 2 months to 48 years of age to provide a detailed analysis of the developmental features, progression, and variability of the great toe malformation of FOP, which include absent skeletal structures, malformed epiphyses, ectopic ossification centers, malformed first metatarsals and phalangeal fusion.
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Affiliation(s)
- O Will Towler
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, United States.,The Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Pennsylvania, PA, United States
| | - Frederick S Kaplan
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, United States.,The Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Pennsylvania, PA, United States.,Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Eileen M Shore
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, United States.,The Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, Pennsylvania, PA, United States.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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23
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Towler OW, Peck SH, Kaplan FS, Shore EM. Dysregulated BMP signaling through ACVR1 impairs digit joint development in fibrodysplasia ossificans progressiva (FOP). Dev Biol 2020; 470:136-146. [PMID: 33217406 DOI: 10.1016/j.ydbio.2020.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/01/2020] [Accepted: 11/10/2020] [Indexed: 12/30/2022]
Abstract
The development of joints in the mammalian skeleton depends on the precise regulation of multiple interacting signaling pathways including the bone morphogenetic protein (BMP) pathway, a key regulator of joint development, digit patterning, skeletal growth, and chondrogenesis. Mutations in the BMP receptor ACVR1 cause the rare genetic disease fibrodysplasia ossificans progressiva (FOP) in which extensive and progressive extra-skeletal bone forms in soft connective tissues after birth. These mutations, which enhance BMP-pSmad1/5 pathway activity to induce ectopic bone, also affect skeletal development. FOP can be diagnosed at birth by symmetric, characteristic malformations of the great toes (first digits) that are associated with decreased joint mobility, shortened digit length, and absent, fused, and/or malformed phalanges. To elucidate the role of ACVR1-mediated BMP signaling in digit skeletal development, we used an Acvr1R206H/+;Prrx1-Cre knock-in mouse model that mimics the first digit phenotype of human FOP. We have determined that the effects of increased Acvr1-mediated signaling by the Acvr1R206H mutation are not limited to the first digit but alter BMP signaling, Gdf5+ joint progenitor cell localization, and joint development in a manner that differently affects individual digits during embryogenesis. The Acvr1R206H mutation leads to delayed and disrupted joint specification and cleavage in the digits and alters the development of cartilage and endochondral ossification at sites of joint morphogenesis. These findings demonstrate an important role for ACVR1-mediated BMP signaling in the regulation of joint and skeletal formation, show a direct link between failure to restrict BMP signaling in the digit joint interzone and failure of joint cleavage at the presumptive interzone, and implicate impaired, digit-specific joint development as the proximal cause of digit malformation in FOP.
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Affiliation(s)
- O Will Towler
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States; Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States
| | - Sun H Peck
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States; Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States
| | - Frederick S Kaplan
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States; Department of Medicine, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Perelman Center for Advanced Medicine, Philadelphia, PA 19104, United States; Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States
| | - Eileen M Shore
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States; Department of Genetics, Perelman School of Medicine, University of Pennsylvania, 415 Curie Boulevard, Clinical Research Building, Philadelphia, PA 19104, United States; Center for Research in FOP & Related Disorders, Perelman School of Medicine, University of Pennsylvania, 3450 Hamilton Walk, 309A Stemmler Hall, Philadelphia, PA 19104, United States.
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