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Vagha JD, Wazurkar A, Madke B, Lohiya S, Wandile S, Vagha K, Javvaji CK, Naseri S. Beyond Skin Deep: A Case Report of Infantile Systemic Hyalinosis in a Six-Month-Old Infant. Cureus 2024; 16:e59510. [PMID: 38826988 PMCID: PMC11143919 DOI: 10.7759/cureus.59510] [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: 04/24/2024] [Accepted: 05/02/2024] [Indexed: 06/04/2024] Open
Abstract
A rare autosomal recessive condition called infantile systemic hyalinosis (ISH) is characterized by early-onset skin lesions that progress to the formation of numerous contractures. The underlying disease is the progressive accumulation of hyaline substances in many tissues. We are presenting the case of a male infant who was referred for evaluation and management at the age of six months. The infant had a history of recurrent episodes of diarrhea and showed limited movement in all four limbs. Upon physical examination, hyperpigmented papulonodular lesions on bony prominences and perianal regions were found, coupled with contractures in the elbow and knee joints. Hyaline deposition in the mid-dermal region was confirmed by histopathological analysis of a skin biopsy sample. The baby also had acute otitis media, which needed to be treated with antibiotics. Parents were counseled regarding the disease's diagnosis, complications, prognosis, and inheritance pattern. This case highlights the clinical presentation, diagnostic process, and management strategies employed in the care of ISH, emphasizing the importance of early recognition and multidisciplinary management in mitigating its devastating effects.
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Affiliation(s)
- Jayant D Vagha
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Ajinkya Wazurkar
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Bhushan Madke
- Dermatology, Venereology and Leprosy, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Sham Lohiya
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Shailesh Wandile
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Keta Vagha
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Chaitanya Kumar Javvaji
- Pediatrics, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
| | - Suhit Naseri
- Pathology, Jawaharlal Nehru Medical College, Datta Meghe Institute of Higher Education and Research, Wardha, IND
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2
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Baroud S, Alawadhi A. A Severe Case of Infantile Systemic Hyalinosis in an Asian Child: A Product of Consanguinity. Cureus 2021; 13:e16433. [PMID: 34414050 PMCID: PMC8365122 DOI: 10.7759/cureus.16433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2021] [Indexed: 11/30/2022] Open
Abstract
Infantile systemic hyalinosis (ISH) is a rare, autosomal recessive disorder characterized by widespread abnormal growth of hyalinized fibrous tissue in skin and mucosae. The typical clinical picture consists of the development of joint contractures, skin lesions, and severe, chronic pain. We report the case of a 2-year-old Pakistani girl, who presented to our clinic with papulonodular lesions, gingival hyperplasia, hypotonia, and joint contractures. Skin biopsy revealed hyaline deposits, and genetic testing revealed a mutation in the protein Anthrax toxin receptor 2 (ANTXR2).
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Affiliation(s)
- Sumer Baroud
- Department of Dermatology, Medical University of Sharjah, Sharjah, ARE
| | - Ameen Alawadhi
- Department of Dermatology, Salmaniya Medical Complex, Manama, BHR
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3
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Pereira TDSF, Sales JFD, Travassos DV, Lanza CR, Castro WH, Gomes CC, Fonseca FP, Silva TA, Gomez RS. Hyaline fibromatosis syndrome: A case report. Oral Surg Oral Med Oral Pathol Oral Radiol 2020; 130:e328-e335. [PMID: 32771412 DOI: 10.1016/j.oooo.2020.06.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/11/2020] [Accepted: 06/26/2020] [Indexed: 11/18/2022]
Abstract
Hyaline fibromatosis syndrome (HFS) is a rare monogenic disease inherited in an autosomal recessive pattern and characterized by hyaline deposits on the skin, mucosa, and multiple organs; osteoporosis; and joint contractures. This progressive condition is caused by mutations in the gene encoding the anthrax toxin receptor 2 protein (ANTXR2). HFS is a disabling disease, and patients suffer from progressive pain and disfiguring symptoms. There are few published case reports detailing oral findings in patients with this condition. The present case report describes a 4-year-old female patient who showed severe manifestations of HFS, emphasizing the oral manifestations, the histopathologic aspects of HFS, the molecular pathogenesis, and the interdisciplinary management of patients affected by this condition.
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Affiliation(s)
- Thaís Dos Santos Fontes Pereira
- Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Jéssica Félix de Sales
- Multiprofessional Integrated Residency in Health, Hospital das Clínicas, Universidade Federal de Minas Gerais
| | - Denise Vieira Travassos
- Department of Social and Preventive Dentistry, School of Dentistry, Universidade Federal de Minas Gerais
| | - Célia Regina Lanza
- Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Wagner Henriques Castro
- Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | | | - Felipe Paiva Fonseca
- Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Tarcília Aparecida Silva
- Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Ricardo Santiago Gomez
- Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
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Härter B, Benedicenti F, Karall D, Lausch E, Schweigmann G, Stanzial F, Superti‐Furga A, Scholl‐Bürgi S. Clinical aspects of Hyaline Fibromatosis Syndrome and identification of a novel mutation. Mol Genet Genomic Med 2020; 8:e1203. [PMID: 32196989 PMCID: PMC7284039 DOI: 10.1002/mgg3.1203] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 02/20/2020] [Accepted: 02/21/2020] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Hyaline fibromatosis syndrome is an autosomal recessive disease caused by mutations in ANTXR2 which leads to loss of function of the transmembrane protein anthrax toxin receptor 2. It is distinguished by characteristic skin lesions, gingival hyperplasia, joint and bone disease, and systemic involvement. METHODS Based on the case of an 11-year-old female patient with typical features of hyaline fibromatosis syndrome and the underlying pathogenic compound heterozygote variants in ANTXR2 we discuss the genetic and clinical aspects of hyaline fibromatosis syndrome. RESULTS The novel mutation in ANTXR2 (c.1223T>C, p.Leu408Pro variant) seems to allow for a protracted course of the disease. CONCLUSION Our findings add to the phenotypic, genetic, and biochemical spectrum of hyaline fibromatosis syndrome.
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Affiliation(s)
- Bettina Härter
- Division of Pediatric SurgeryDepartment of Visceral, Transplant and Thoracic SurgeryCenter of Operative MedicineInnsbruck Medical UniversityInnsbruckAustria
| | - Francesco Benedicenti
- Clinical Genetics Service and South Tyrol Coordination Center for Rare DiseasesDepartment of PediatricsRegional Hospital of BolzanoBolzanoItaly
| | - Daniela Karall
- Department of Pediatrics IInnsbruck Medical UniversityInnsbruckAustria
| | - Ekkehard Lausch
- Pediatric Genetics SectionDepartment of PediatricsUniversity of FreiburgFreiburgGermany
| | | | - Franco Stanzial
- Clinical Genetics Service and South Tyrol Coordination Center for Rare DiseasesDepartment of PediatricsRegional Hospital of BolzanoBolzanoItaly
| | - Andrea Superti‐Furga
- Division of Genetic MedicineLausanne University HospitalUniversity of LausanneLausanneSwitzerland
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5
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Bürgi J, Abrami L, Castanon I, Abriata LA, Kunz B, Yan SE, Lera M, Unger S, Superti-Furga A, Peraro MD, Gaitan MG, van der Goot FG. Ligand Binding to the Collagen VI Receptor Triggers a Talin-to-RhoA Switch that Regulates Receptor Endocytosis. Dev Cell 2020; 53:418-430.e4. [PMID: 32428455 DOI: 10.1016/j.devcel.2020.04.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 01/23/2020] [Accepted: 04/21/2020] [Indexed: 11/23/2022]
Abstract
Capillary morphogenesis gene 2 (CMG2/ANTXR2) is a cell surface receptor for both collagen VI and anthrax toxin. Biallelic loss-of-function mutations in CMG2 lead to a severe condition, hyaline fibromatosis syndrome (HFS). We have here dissected a network of dynamic interactions between CMG2 and various actin interactors and regulators, describing a different behavior from other extracellular matrix receptors. CMG2 binds talin, and thereby the actin cytoskeleton, only in its ligand-free state. Extracellular ligand binding leads to src-dependent talin release and recruitment of the actin cytoskeleton regulator RhoA and its effectors. These sequential interactions of CMG2 are necessary for the control of oriented cell division during fish development. Finally, we demonstrate that effective switching between talin and RhoA binding is required for the intracellular degradation of collagen VI in human fibroblasts, which explains why HFS mutations in the cytoskeleton-binding domain lead to dysregulation of extracellular matrix homeostasis.
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Affiliation(s)
- Jérôme Bürgi
- Faculty of Life Sciences, Global Health Institute, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland; EMBL Hamburg DESY, 22607 Hamburg, Germany
| | - Laurence Abrami
- Faculty of Life Sciences, Global Health Institute, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Irinka Castanon
- Departments of Biochemistry and of Molecular Biology, Sciences II, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Luciano Andres Abriata
- Faculty of Life Sciences, Institute of Bioengineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Beatrice Kunz
- Faculty of Life Sciences, Global Health Institute, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Shixu Emili Yan
- Faculty of Life Sciences, Global Health Institute, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Manuel Lera
- Departments of Biochemistry and of Molecular Biology, Sciences II, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Sheila Unger
- Division of Genetic Medicine, Centre Hospitalier Universitaire Vaudois, University of Lausanne, 1011 Lausanne, Switzerland
| | - Andrea Superti-Furga
- Division of Genetic Medicine, Centre Hospitalier Universitaire Vaudois, University of Lausanne, 1011 Lausanne, Switzerland
| | - Matteo Dal Peraro
- Faculty of Life Sciences, Institute of Bioengineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Marcos Gonzalez Gaitan
- Departments of Biochemistry and of Molecular Biology, Sciences II, 30 Quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Francoise Gisou van der Goot
- Faculty of Life Sciences, Global Health Institute, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
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6
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Cozma C, Hovakimyan M, Iurașcu MI, Makhseed N, Selim LA, Alhashem AM, Ben-Omran T, Mahmoud IG, Al Menabawy NM, Al-Mureikhi M, Martin M, Demuth L, Yüksel Z, Beetz C, Bauer P, Rolfs A. Genetic, clinical and biochemical characterization of a large cohort of patients with hyaline fibromatosis syndrome. Orphanet J Rare Dis 2019; 14:209. [PMID: 31455396 PMCID: PMC6712857 DOI: 10.1186/s13023-019-1183-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 08/16/2019] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Hyaline fibromatosis syndrome (HFS) is a rare clinical condition in which bi-allelic variants in ANTXR2 are associated with extracellular hyaline deposits. It manifests as multiple skin nodules, patchy hyperpigmentation, joint contractures and severe pain with movement. HFS shows some clinical overlap to Farber disease (FD), a recessive lysosomal storage disorder. RESULTS We here present the largest cohort of independent, genetically confirmed HFS cases reported to date: in 19 unrelated index patients, we identified ten distinct homozygous ANTXR2 mutations, three of which are novel frame-shift variants. The associated clinical data are consistent with the previous hypothesis of non-truncating variants in the terminal exons 13-17 to confer rather mild phenotypes. The novel observation of gender-dependent disease manifestation in our cohort received support from a meta-analysis of all previously published cases. Untargeted blood-based metabolomics revealed patient samples to be biochemically distinct from control samples. Numerous potential HFS biomarker metabolites could thus be identified. We also found metabolomics profiles of HFS patients to highly overlap with those from FD patients. CONCLUSIONS Our study extends the mutational spectrum for HFS, suggests gender-dependency of manifestation, and provides pilot metabolomics data for biomarker identification and a better pathomechanistic understanding of the disorder.
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Affiliation(s)
| | | | | | - Nawal Makhseed
- Department of Pediatrics, Jahra Hospital, Ministry of Health, Jahra City, Kuwait
| | - Laila A. Selim
- Division of Neurology and Metabolism, Kasr Al Ainy School of Medicine, Cairo University Children Hospital, Cairo, Egypt
| | - Amal M. Alhashem
- Prince Sultan Military Medical City, Pediatrics, Riyadh, Saudi Arabia
- Alfaisal University, Riyadh, Saudi Arabia
| | - Tawfeg Ben-Omran
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, Hamad Medical Corporation, Doha, Qatar
| | - Iman G. Mahmoud
- Division of Neurology and Metabolism, Kasr Al Ainy School of Medicine, Cairo University Children Hospital, Cairo, Egypt
| | - Nihal M. Al Menabawy
- Division of Neurology and Metabolism, Kasr Al Ainy School of Medicine, Cairo University Children Hospital, Cairo, Egypt
| | - Mariam Al-Mureikhi
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, Hamad Medical Corporation, Doha, Qatar
| | - Magi Martin
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, Hamad Medical Corporation, Doha, Qatar
| | - Laura Demuth
- Centogene AG, Am Strande 7, 18057 Rostock, Germany
| | - Zafer Yüksel
- Centogene AG, Am Strande 7, 18057 Rostock, Germany
| | | | - Peter Bauer
- Centogene AG, Am Strande 7, 18057 Rostock, Germany
| | - Arndt Rolfs
- Centogene AG, Am Strande 7, 18057 Rostock, Germany
- Rostock Medical University, Rostock, Germany
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7
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Needham PG, Guerriero CJ, Brodsky JL. Chaperoning Endoplasmic Reticulum-Associated Degradation (ERAD) and Protein Conformational Diseases. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033928. [PMID: 30670468 DOI: 10.1101/cshperspect.a033928] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Misfolded proteins compromise cellular homeostasis. This is especially problematic in the endoplasmic reticulum (ER), which is a high-capacity protein-folding compartment and whose function requires stringent protein quality-control systems. Multiprotein complexes in the ER are able to identify, remove, ubiquitinate, and deliver misfolded proteins to the 26S proteasome for degradation in the cytosol, and these events are collectively termed ER-associated degradation, or ERAD. Several steps in the ERAD pathway are facilitated by molecular chaperone networks, and the importance of ERAD is highlighted by the fact that this pathway is linked to numerous protein conformational diseases. In this review, we discuss the factors that constitute the ERAD machinery and detail how each step in the pathway occurs. We then highlight the underlying pathophysiology of protein conformational diseases associated with ERAD.
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Affiliation(s)
- Patrick G Needham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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8
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Greither T, Wedler A, Rot S, Keßler J, Kehlen A, Holzhausen HJ, Bache M, Würl P, Taubert H, Kappler M. CMG2 Expression Is an Independent Prognostic Factor for Soft Tissue Sarcoma Patients. Int J Mol Sci 2017; 18:ijms18122648. [PMID: 29215551 PMCID: PMC5751250 DOI: 10.3390/ijms18122648] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 11/29/2017] [Accepted: 11/30/2017] [Indexed: 12/14/2022] Open
Abstract
The capillary morphogenesis gene 2 (CMG2), also known as the anthrax toxin receptor 2 (ANTXR2), is a transmembrane protein putatively involved in extracellular matrix (ECM) adhesion and tissue remodeling. CMG2 promotes endothelial cell proliferation and exhibits angiogenic properties. Its downregulation is associated with a worsened survival of breast carcinoma patients. Aim of this study was to analyze the CMG2 mRNA and protein expression in soft tissue sarcoma and their association with patient outcome. CMG2 mRNA was measured in 121 tumor samples of soft tissue sarcoma patients using quantitative real-time PCR. CMG2 protein was evaluated in 52 tumor samples by ELISA. CMG2 mRNA was significantly correlated with the corresponding CMG2 protein expression (rs = 0.31; p = 0.027). CMG2 mRNA expression was associated with the mRNA expressions of several ECM and tissue remodeling enzymes, among them CD26 and components of the uPA system. Low CMG2 mRNA expression was correlated with a worsened patients’ disease-specific survival in Kaplan-Meier analyses (mean patient survival was 25 vs. 96 months; p = 0.013), especially in high-stage tumors. A decreased CMG2 expression is a negative prognostic factor for soft tissue sarcoma patients. CMG2 may be an interesting candidate gene for the further exploration of soft tissue sarcoma genesis and progression.
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Affiliation(s)
- Thomas Greither
- Center for Reproductive Medicine and Andrology, Martin Luther University, 06120 Halle (Saale), Germany.
| | - Alice Wedler
- Center for Reproductive Medicine and Andrology, Martin Luther University, 06120 Halle (Saale), Germany.
| | - Swetlana Rot
- Department of Oral and Maxillofacial Plastic Surgery, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Jacqueline Keßler
- Department of Radiotherapy, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Astrid Kehlen
- Institute of Medical Microbiology, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Hans-Jürgen Holzhausen
- Institute of Pathology, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Matthias Bache
- Department of Radiotherapy, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Peter Würl
- Department of General and Visceral Surgery, Hospital Dessau, 06847 Dessau-Roßlau, Germany.
| | - Helge Taubert
- Clinic of Urology, FA University Hospital Erlangen-Nuremberg, 91054 Erlangen, Germany.
| | - Matthias Kappler
- Department of Oral and Maxillofacial Plastic Surgery, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
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9
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Soni JP, Puri RD, Jetha K, Bhavani GSL, Chaudhary M, Kohli S, Verma IC. Infantile Systemic Hyalinosis: Novel Founder Mutation in the Initiation Codon among "Malis (Farmers)" in Jodhpur. Indian J Pediatr 2016; 83:1341-1345. [PMID: 27753005 DOI: 10.1007/s12098-016-2218-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 08/10/2016] [Indexed: 10/20/2022]
Abstract
Infantile systemic hyalinosis (OMIM 236490) is a progressive autosomal recessive disorder characterized by widespread deposition of hyaline material in many tissues leading to multiple subcutaneous skin nodules, gingival hypertrophy and joint contractures. The authors describe five children from four unrelated families, from the "mali (farmer)" community in Jodhpur, with the disorder. All of them had classical clinical features, and four died from severe infections between age of 7 mo to 3 y. Two affected children had the same, but novel mutation in the initiation codon, in homozygous form c.1 A > G; p. M1? in capillary morphogenesis protein-2 (CMG2), or ANTXR2 gene on chromosome 4q21.21. The other two parents had the same mutation in heterozygous form. It is likely that this is a founder mutation in this community.
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Affiliation(s)
- Jai Prakash Soni
- Genetic Clinic, Department of Pediatrics, Mother and Chlid Hospital, MDM Hospital, Shastri Nagar, Jodhpur, Rajasthan, India.
| | - Ratna D Puri
- Institute of Genetics and Genomics, Sir Ganga Ram Hospital, Rajender Nagar, New Delhi, 110060, India
| | - Kapil Jetha
- Genetic Clinic, Department of Pediatrics, Mother and Chlid Hospital, MDM Hospital, Shastri Nagar, Jodhpur, Rajasthan, India
| | - G S L Bhavani
- Genetic Clinic, Department of Pediatrics, Mother and Chlid Hospital, MDM Hospital, Shastri Nagar, Jodhpur, Rajasthan, India
| | - Monika Chaudhary
- Genetic Clinic, Department of Pediatrics, Mother and Chlid Hospital, MDM Hospital, Shastri Nagar, Jodhpur, Rajasthan, India
| | - Sudha Kohli
- Institute of Genetics and Genomics, Sir Ganga Ram Hospital, Rajender Nagar, New Delhi, 110060, India
| | - I C Verma
- Institute of Genetics and Genomics, Sir Ganga Ram Hospital, Rajender Nagar, New Delhi, 110060, India.
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10
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Perrody E, Abrami L, Feldman M, Kunz B, Urbé S, van der Goot FG. Ubiquitin-dependent folding of the Wnt signaling coreceptor LRP6. eLife 2016; 5. [PMID: 27751231 PMCID: PMC5102578 DOI: 10.7554/elife.19083] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 10/17/2016] [Indexed: 12/28/2022] Open
Abstract
Many membrane proteins fold inefficiently and require the help of enzymes and chaperones. Here we reveal a novel folding assistance system that operates on membrane proteins from the cytosolic side of the endoplasmic reticulum (ER). We show that folding of the Wnt signaling coreceptor LRP6 is promoted by ubiquitination of a specific lysine, retaining it in the ER while avoiding degradation. Subsequent ER exit requires removal of ubiquitin from this lysine by the deubiquitinating enzyme USP19. This ubiquitination-deubiquitination is conceptually reminiscent of the glucosylation-deglucosylation occurring in the ER lumen during the calnexin/calreticulin folding cycle. To avoid infinite futile cycles, folded LRP6 molecules undergo palmitoylation and ER export, while unsuccessfully folded proteins are, with time, polyubiquitinated on other lysines and targeted to degradation. This ubiquitin-dependent folding system also controls the proteostasis of other membrane proteins as CFTR and anthrax toxin receptor 2, two poor folders involved in severe human diseases. DOI:http://dx.doi.org/10.7554/eLife.19083.001 Proteins carry out almost every process that happens inside a cell. Like all machines, their ability to work properly depends on their three-dimensional shape and structure. To make proteins, building blocks called amino acids are first assembled into a string that, like wool in a sweater, needs to be knitted into the final three-dimensional structure. How proteins reach their 3D structure is called “folding”, and when protein folding fails, or is not so efficient, it can cause very severe diseases. Protein folding is not as nicely progressive as knitting a sweater: it is more like putting all the wool into a big messy blob that then suddenly turns into a protein with the right three-dimensional structure. Cells have machinery that can detect messy-looking molecules and destroy them. Therefore, new proteins need to be hidden from this machinery until they have finished folding. A human protein called LRP6 is found on the surface of cells and it plays an important role in allowing cells to communicate with each other. Like many other proteins, LRP6 is produced inside the cell in a compartment called the endoplasmic reticulum and is then exported to the cell surface. In 2008, a team of researchers found that LRP6 is modified in a particular way known as S-palmitoylation before it leaves the endoplasmic reticulum. This suggested that there is a system that helps this protein to fold correctly. Here Perrody, Abrami et al. – including some of the researchers from the previous work – used biochemical techniques to investigate how LRP6 folds. The experiments show that another type of protein modification that involves attaching a molecule called ubiquitin to LRP6 promotes this protein’s folding. Once the protein is folded, the ubiquitin is removed from LRP6 by an enzyme called USP19. Further experiments show that this system also helps to ensure that two other important proteins fold correctly. The next steps following on from this work are to identify the other molecules involved in this protein folding system. A future challenge is to find out how this system protects new proteins from being degraded while they are still folding. DOI:http://dx.doi.org/10.7554/eLife.19083.002
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Affiliation(s)
- Elsa Perrody
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Laurence Abrami
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Michal Feldman
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Beatrice Kunz
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Sylvie Urbé
- Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - F Gisou van der Goot
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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11
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Friebe S, Deuquet J, van der Goot FG. Differential dependence on N-glycosylation of anthrax toxin receptors CMG2 and TEM8. PLoS One 2015; 10:e0119864. [PMID: 25781883 PMCID: PMC4363784 DOI: 10.1371/journal.pone.0119864] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/16/2015] [Indexed: 11/29/2022] Open
Abstract
ANTXR 1 and 2, also known as TEM8 and CMG2, are two type I membrane proteins, which have been extensively studied for their role as anthrax toxin receptors, but with a still elusive physiological function. Here we have analyzed the importance of N-glycosylation on folding, trafficking and ligand binding of these closely related proteins. We find that TEM8 has a stringent dependence on N-glycosylation. The presence of at least one glycan on each of its two extracellular domains, the vWA and Ig-like domains, is indeed necessary for efficient trafficking to the cell surface. In the absence of any N-linked glycans, TEM8 fails to fold correctly and is recognized by the ER quality control machinery. Expression of N-glycosylation mutants reveals that CMG2 is less vulnerable to sugar loss. The absence of N-linked glycans in one of the extracellular domains indeed has little impact on folding, trafficking or receptor function of the wild type protein expressed in tissue culture cells. N-glycans do, however, seem required in primary fibroblasts from human patients. Here, the presence of N-linked sugars increases the tolerance to mutations in cmg2 causing the rare genetic disease Hyaline Fibromatosis Syndrome. It thus appears that CMG2 glycosylation provides a buffer towards genetic variation by promoting folding of the protein in the ER lumen.
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Affiliation(s)
- Sarah Friebe
- Faculty of Life Sciences, Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Julie Deuquet
- Faculty of Life Sciences, Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - F. Gisou van der Goot
- Faculty of Life Sciences, Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- * E-mail:
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12
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Yan SE, Lemmin T, Salvi S, Lausch E, Superti-Furga A, Rokicki D, Dal Peraro M, van der Goot FG. In-depth analysis of hyaline fibromatosis syndrome frameshift mutations at the same site reveal the necessity of personalized therapy. Hum Mutat 2013; 34:1005-17. [PMID: 23554269 DOI: 10.1002/humu.22324] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 03/20/2013] [Indexed: 11/07/2022]
Abstract
Hyaline fibromatosis syndrome is an autosomal recessive disease caused by mutations in ANTXR2, a gene involved in extracellular matrix homeostasis. Sixty percent of patients carry frameshift mutations at a mutational hotspot in exon 13. We show in patient cells that these mutations lead to low ANTXR2 mRNA and undetectable protein levels. Ectopic expression of the proteins encoded by the mutated genes reveals that a two base insertion leads to the synthesis of a protein that is rapidly targeted to the ER-associated degradation pathway due to the modified structure of the cytosolic tail, which instead of being hydrophilic and highly disordered as in wild type ANTXR2, is folded and exposes hydrophobic patches. In contrast, one base insertion leads to a truncated protein that properly localizes to the plasma membrane and retains partial function. We next show that targeting the nonsense mediated mRNA decay pathway in patient cells leads to a rescue of ANTXR2 protein in patients carrying one base insertion but not in those carrying two base insertions. This study highlights the importance of in-depth analysis of the molecular consequences of specific patient mutations, which even when they occur at the same site can have drastically different consequences.
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Affiliation(s)
- Shixu E Yan
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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13
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Al Sinani S, Al Murshedy F, Abdwani R. Infantile systemic hyalinosis: a case report with a novel mutation. Oman Med J 2013; 28:53-5. [PMID: 23386947 DOI: 10.5001/omj.2013.12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Accepted: 11/12/2012] [Indexed: 11/03/2022] Open
Abstract
Infantile Systemic Hyalinosis (ISH) (OMIM 236490) is a rare, progressive and fatal autosomal recessive disorder characterized by multiple subcutaneous skin nodules, gingival hypertrophy, osteopenia, joint contractures, failure to thrive, diarrhea with protein losing enteropathy, and frequent infections. There is diffuse deposition of hyaline material in the skin, gastrointestinal tract, muscle and endocrine glands. It is caused by mutations in the ANTXR2 (also known as CMG2) gene, which encodes a trans-membranous protein involved in endothelial development and basement membrane-extracellular matrix assembly. We describe a child with classical features of ISH presenting in infancy with severe chronic debilitating pain and progressive joint contractures. The diagnosis was confirmed by molecular DNA sequencing of ANTXR2 gene which revealed a novel homozygous mutation not previously reported; 79 bp deletion of the entire exon 11 (c.867_945del, p.E289DfsX22). Although this is the first reported case of ISH in Oman, we believe that the disease is under-diagnosed since children affected with this lethal disease pass away early in infancy prior to establishing a final diagnosis.
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Affiliation(s)
- Siham Al Sinani
- Department of Child Health, Sultan Qaboos University Hospital, Al Khoud, Sultanate of Oman
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14
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Fong K, Rama Devi AR, Lai-Cheong JE, Chirla D, Panda SK, Liu L, Tosi I, McGrath JA. Infantile systemic hyalinosis associated with a putative splice-site mutation in the ANTXR2 gene. Clin Exp Dermatol 2012; 37:635-8. [PMID: 22300424 DOI: 10.1111/j.1365-2230.2011.04287.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Infantile systemic hyalinosis (ISH) is a rare autosomal recessive genetic disorder characterized by dermal and subcutaneous fibromatosis, joint contractures and bone deformities. The condition usually presents at birth, resulting in death in infancy. ISH is caused by mutations in the anthrax toxin receptor 2 gene, ANTXR2, also known as CMG2. We report an Indian child with ISH in whom we identified a homozygous acceptor splice site mutation, IVS2-4G>A. In silico analysis of this sequence showed that it changed predicted cryptic splicing, leading to out-of-frame transcripts and little, if any, functional protein. Mutations in the ANTXR2 gene can also cause juvenile hyaline fibromatosis (JHF). Although there are currently no effective treatments for ISH or JHF, identification of pathogenetic mutations in the ANTXR2 gene makes DNA-based prenatal diagnosis feasible for subsequent pregnancies.
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Affiliation(s)
- K Fong
- St John's Institute of Dermatology, King's College London (Guy's Campus), London, UK
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15
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Alreheili K, AlMehaidib A, Alsaleem K, Banemi M, Aldekhail W, Al-Mayouf SM. Intestinal lymphangiectasia in a patient with infantile systemic hyalinosis syndrome: a rare cause of protein-losing enteropathy. Ann Saudi Med 2012; 32:206-8. [PMID: 22366835 PMCID: PMC6086646 DOI: 10.5144/0256-4947.2012.206] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/01/2010] [Indexed: 11/22/2022] Open
Abstract
Infantile systemic hyalinosis (ISH) is a rare autosomal recessive disease. Typically, ISH patients present with progressive painful joint contractures, intractable diarrhea, hyperpigmented skin lesions, and peri-anal fleshy nodules. We report a case of a 19-month-old male child with atypical ISH presentation. His main clinical finding was protein-losing enteropathy due to intestinal lymphangectasia. This report is intended to enhance awareness about the gastrointestinal tract presentation of ISH.
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Affiliation(s)
- Khalid Alreheili
- Department of Pediatrics, Section of Gastroenterology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Ali AlMehaidib
- Department of Pediatrics, Section of Gastroenterology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Khalid Alsaleem
- Department of Pediatrics, Section of Gastroenterology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Mohammad Banemi
- Department of Pediatrics, Section of Gastroenterology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Wajeeh Aldekhail
- Department of Pediatrics, Section of Gastroenterology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Sulaiman M. Al-Mayouf
- Department of Pediatrics, Section of Rheumatology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
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16
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Abstract
The outcome of exposure to infectious microbes or their toxins is influenced by both microbial and host genes. Some host genes encode defense mechanisms, whereas others assist pathogen functions. Genomic analyses have associated host gene mutations with altered infectious disease susceptibility, but evidence for causality is limited. Here we demonstrate that human genetic variation affecting capillary morphogenesis gene 2 (CMG2), which encodes a host membrane protein exploited by anthrax toxin as a principal receptor, dramatically alters toxin sensitivity. Lymphoblastoid cells derived from a HapMap Project cohort of 234 persons of African, European, or Asian ancestry differed in sensitivity mediated by the protective antigen (PA) moiety of anthrax toxin by more than four orders of magnitude, with 99% of the cohort showing a 250-fold range of sensitivity. We find that relative sensitivity is an inherited trait that correlates strongly with CMG2 mRNA abundance in cells of each ethnic/geographical group and in the combined population pool (P = 4 × 10(-11)). The extent of CMG2 expression in transfected murine macrophages and human lymphoblastoid cells affected anthrax toxin binding, internalization, and sensitivity. A CMG2 single-nucleotide polymorphism (SNP) occurring frequently in African and European populations independently altered toxin uptake, but was not statistically associated with altered sensitivity in HapMap cell populations. Our results reveal extensive human diversity in cell lethality dependent on PA-mediated toxin binding and uptake, and identify individual differences in CMG2 expression level as a determinant of this diversity. Testing of genomically characterized human cell populations may offer a broadly useful strategy for elucidating effects of genetic variation on infectious disease susceptibility.
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17
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Deuquet J, Lausch E, Superti-Furga A, van der Goot FG. The dark sides of capillary morphogenesis gene 2. EMBO J 2012; 31:3-13. [PMID: 22215446 PMCID: PMC3252584 DOI: 10.1038/emboj.2011.442] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 11/07/2011] [Indexed: 11/08/2022] Open
Abstract
Capillary morphogenesis gene 2 (CMG2) is a type I membrane protein involved in the homeostasis of the extracellular matrix. While it shares interesting similarities with integrins, its exact molecular role is unknown. The interest and knowledge about CMG2 largely stems from the fact that it is involved in two diseases, one infectious and one genetic. CMG2 is the main receptor of the anthrax toxin, and knocking out this gene in mice renders them insensitive to infection with Bacillus anthracis spores. On the other hand, mutations in CMG2 lead to a rare but severe autosomal recessive disorder in humans called Hyaline Fibromatosis Syndrome (HFS). We will here review what is known about the structure of CMG2 and its ability to mediate anthrax toxin entry into cell. We will then describe the limited knowledge available concerning the physiological role of CMG2. Finally, we will describe HFS and the consequences of HFS-associated mutations in CMG2 at the molecular and cellular level.
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Affiliation(s)
- Julie Deuquet
- Ecole Polytechnique Fédérale de Lausanne, Institute of Global Health, Lausanne, Switzerland
| | - Ekkehart Lausch
- Department of Pediatrics, University of Freiburg, Freiburg, Germany
| | - Andrea Superti-Furga
- Division of Molecular Pediatrics, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - F Gisou van der Goot
- Ecole Polytechnique Fédérale de Lausanne, Institute of Global Health, Lausanne, Switzerland
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18
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Wang YY, Wen CQ, Wei Z, Jin X. A novel splice site mutation in ANTXR2 (CMG2) gene results in systemic hyalinosis. J Pediatr Hematol Oncol 2011; 33:e355-7. [PMID: 22042284 DOI: 10.1097/mph.0b013e318223d0dc] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Systemic hyalinosis is a rare autosomal recessive inheritance disease characterized by accumulation of amorphous, unidentified hyaline material in skin and other organs, which leads to papulonodular skin lesions, gingival hypertrophy, flexion contractures of the joints, and large subcutaneous tumors. It is composed of 2 allelic syndromes, infantile systemic hyalinosis and juvenile hyaline fibromatosis. Here we describe a patient with juvenile hyaline fibromatosis confirmed by clinical and histopathologic findings, and genetic analysis, which revealed a novel homozygous splice site mutation IVS14+1G→T on exon 14 in anthrax toxin receptor 2 gene.
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Affiliation(s)
- Yun-Ying Wang
- Department of Medical Genetics, Affiliated Qingdao Municipal Hospital of Qingdao University Medical College, Qingdao, Shandong, China
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19
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Deuquet J, Lausch E, Guex N, Abrami L, Salvi S, Lakkaraju A, Ramirez MCM, Martignetti JA, Rokicki D, Bonafe L, Superti-Furga A, van der Goot FG. Hyaline fibromatosis syndrome inducing mutations in the ectodomain of anthrax toxin receptor 2 can be rescued by proteasome inhibitors. EMBO Mol Med 2011; 3:208-21. [PMID: 21328543 PMCID: PMC3377065 DOI: 10.1002/emmm.201100124] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 01/14/2011] [Accepted: 01/18/2011] [Indexed: 11/25/2022] Open
Abstract
Hyaline Fibromatosis Syndrome (HFS) is a human genetic disease caused by mutations in the anthrax toxin receptor 2 (or cmg2) gene, which encodes a membrane protein thought to be involved in the homeostasis of the extracellular matrix. Little is known about the structure and function of the protein or the genotype–phenotype relationship of the disease. Through the analysis of four patients, we identify three novel mutants and determine their effects at the cellular level. Altogether, we show that missense mutations that map to the extracellular von Willebrand domain or the here characterized Ig-like domain of CMG2 lead to folding defects and thereby to retention of the mutated protein in the endoplasmic reticulum (ER). Mutations in the Ig-like domain prevent proper disulphide bond formation and are more efficiently targeted to ER-associated degradation. Finally, we show that mutant CMG2 can be rescued in fibroblasts of some patients by treatment with proteasome inhibitors and that CMG2 is then properly transported to the plasma membrane and signalling competent, identifying the ER folding and degradation pathway components as promising drug targets for HFS.
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Affiliation(s)
- Julie Deuquet
- Ecole Polytechnique Fédérale de Lausanne, Global Health InstituteLausanne, Switzerland
| | - Ekkehart Lausch
- Department of Pediatrics, University of FreiburgFreiburg, Germany
| | - Nicolas Guex
- Vital-IT Group, Swiss Institute of BioinformaticsLausanne Switzerland
| | - Laurence Abrami
- Ecole Polytechnique Fédérale de Lausanne, Global Health InstituteLausanne, Switzerland
| | - Suzanne Salvi
- Ecole Polytechnique Fédérale de Lausanne, Global Health InstituteLausanne, Switzerland
| | - Asvin Lakkaraju
- Ecole Polytechnique Fédérale de Lausanne, Global Health InstituteLausanne, Switzerland
| | - Maria Celeste M Ramirez
- Department of Genetics and Genomic Sciences, Mount Sinai School of MedicineNew York, NY, USA
| | - John A Martignetti
- Department of Genetics and Genomic Sciences, Mount Sinai School of MedicineNew York, NY, USA
- Department of Pediatrics, Mount Sinai School of MedicineNew York, NY, USA
- Department of Oncological Sciences, Mount Sinai School of MedicineNew York, NY, USA
| | - Dariusz Rokicki
- Division of Inborn Errors of Metabolism, Children's Memorial Health InstituteWarsaw, Poland
| | - Luisa Bonafe
- Division of Molecular Pediatrics, Centre Hospitalier Universitaire Vaudois, University of LausanneSwitzerland
| | - Andrea Superti-Furga
- Department of Pediatrics, University of FreiburgFreiburg, Germany
- Division of Molecular Pediatrics, Centre Hospitalier Universitaire Vaudois, University of LausanneSwitzerland
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20
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El-Maaytah M, Jerjes W, Shah P, Upile T, Murphy C, Ayliffe P. Gingival hyperplasia associated with juvenile hyaline fibromatosis: a case report and review of the literature. J Oral Maxillofac Surg 2010; 68:2604-8. [PMID: 20863945 DOI: 10.1016/j.joms.2009.09.060] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 09/15/2009] [Indexed: 11/30/2022]
Affiliation(s)
- Mohammed El-Maaytah
- Department of Oral and Maxillofacial Surgery, Eastman Dental Hospital, London, UK
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21
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El-Kamah GY, Fong K, El-Ruby M, Afifi HH, Clements SE, Lai-Cheong JE, Amr K, El-Darouti M, McGrath JA. Spectrum of mutations in the ANTXR2 (CMG2) gene in infantile systemic hyalinosis and juvenile hyaline fibromatosis. Br J Dermatol 2010; 163:213-5. [PMID: 20331448 DOI: 10.1111/j.1365-2133.2010.09769.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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22
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Abrami L, Kunz B, Deuquet J, Bafico A, Davidson G, van der Goot FG. Functional interactions between anthrax toxin receptors and the WNT signalling protein LRP6. Cell Microbiol 2008; 10:2509-19. [PMID: 18717822 DOI: 10.1111/j.1462-5822.2008.01226.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
To exert its activity, anthrax toxin must be endocytosed and its enzymatic toxic subunits delivered to the cytoplasm. It has been proposed that, in addition to the anthrax toxin receptors (ATRs), lipoprotein-receptor-related protein 6 (LRP6), known for its role in Wnt signalling, is also required for toxin endocytosis. These findings have however been challenged. We show that LRP6 can indeed form a complex with ATRs, and that this interaction plays a role both in Wnt signalling and in anthrax toxin endocytosis. We found that ATRs control the levels of LRP6 in cells, and thus the Wnt signalling capacity. RNAi against ATRs indeed led to a drastic decrease in LRP6 levels and a subsequent drop in Wnt signalling. Conversely, LRP6 plays a role in anthrax toxin endocytosis, but is not essential. We indeed found that toxin binding triggered tyrosine phosphorylation of LRP6, induced its redistribution into detergent-resistant domains, and its subsequent endocytosis. RNAis against LRP6 strongly delayed toxin endocytosis. As the physiological role of ATRs is probably to interact with the extracellular matrix, our findings raise the interesting possibility that, through the ATR-LRP6 interaction, adhesion to the extracellular matrix could locally control Wnt signalling.
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Affiliation(s)
- Laurence Abrami
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Station 15, CH 1015 Lausanne, Switzerland
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