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Arunachalam AK, Aboobacker FN, Sampath E, Devasia AJ, Korula A, George B, Edison ES. Molecular Heterogeneity of Osteopetrosis in India: Report of 17 Novel Variants. Indian J Hematol Blood Transfus 2024; 40:494-503. [PMID: 39011244 PMCID: PMC11246401 DOI: 10.1007/s12288-023-01732-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 12/26/2023] [Indexed: 07/17/2024] Open
Abstract
Osteopetrosis is a clinically and genetically heterogeneous group of inherited bone disorders that is caused by defects in osteoclast formation or function. Treatment options vary with the disease severity and an accurate molecular diagnosis helps in prognostication and treatment decisions. We investigated the genetic causes of osteopetrosis in 31 unrelated patients of Indian origin. Screening for the genetic variants was done by Sanger sequencing or next generation sequencing in 48 samples that included 31 samples from index patients, 16 from parents' and 1 chorionic villus sample. A total of 30 variants, including 29 unique variants, were identified in 26 of the 31 patients in the study. TCIRG1 was the most involved gene (n = 14) followed by TNFRSF11A (n = 4) and CLCN7 (n = 3). A total of 17 novel variants were identified. Prenatal diagnosis was done in one family and the foetus showed homozygous c.807 + 2T > G variant in TCIRG1. Molecular diagnosis of osteopetrosis aids in therapeutic decisions including the need for a stem cell transplantation and gives a possible option of performing prenatal diagnosis in affected families. Further studies would help in understanding the genetic etiology in patients where no variants were identified. Supplementary Information The online version contains supplementary material available at 10.1007/s12288-023-01732-4.
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Affiliation(s)
| | - Fouzia N. Aboobacker
- Department of Haematology, Christian Medical College, Vellore, Tamil Nadu 632517 India
| | - Eswari Sampath
- Department of Haematology, Christian Medical College, Vellore, Tamil Nadu 632517 India
| | - Anup J. Devasia
- Department of Haematology, Christian Medical College, Vellore, Tamil Nadu 632517 India
| | - Anu Korula
- Department of Haematology, Christian Medical College, Vellore, Tamil Nadu 632517 India
| | - Biju George
- Department of Haematology, Christian Medical College, Vellore, Tamil Nadu 632517 India
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Jodeh W, Katz AJ, Hart M, Warden SJ, Niziolek P, Alam I, Ing S, Polgreen LE, Imel EA, Econs MJ. Autosomal Dominant Osteopetrosis (ADO) Caused by a Missense Variant in the TCIRG1 Gene. J Clin Endocrinol Metab 2024; 109:1726-1732. [PMID: 38261998 PMCID: PMC11180502 DOI: 10.1210/clinem/dgae040] [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: 08/04/2023] [Revised: 01/03/2024] [Accepted: 01/18/2024] [Indexed: 01/25/2024]
Abstract
CONTEXT Autosomal dominant osteopetrosis (ADO) is a rare genetic disorder resulting from impaired osteoclastic bone resorption. Clinical manifestations frequently include fractures, osteonecrosis (particularly of the jaw or maxilla), osteomyelitis, blindness, and/or bone marrow failure. ADO usually results from heterozygous missense variants in the Chloride Channel 7 gene (CLCN7) that cause disease by a dominant negative mechanism. Variants in the T-cell immune regulator 1 gene (TCIRG1) are commonly identified in autosomal recessive osteopetrosis but have only been reported in 1 patient with ADO. CASE DESCRIPTION Here, we report 3 family members with a single heterozygous missense variant (p.Gly579Arg) in TCIRG1 who have a phenotype consistent with ADO. Three of 5 protein prediction programs suggest this variant likely inhibits the function of TCIRG1. CONCLUSION This is the first description of adult presentation of ADO caused by a TCIRG1 variant. Similar to families with ADO from CLCN7 mutations, this variant in TCIRG1 results in marked phenotype variability, with 2 subjects having severe disease and the third having very mild disease. This family report implicates TCIRG1 missense mutations as a cause of ADO and demonstrates that the marked phenotypic variability in ADO may extend to disease caused by TCIRG1 missense mutations.
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Affiliation(s)
- Wade Jodeh
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Amy J Katz
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Marian Hart
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Stuart J Warden
- Department of Physical Therapy, Indiana University School of Health & Human Sciences, Indianapolis, IN 46202, USA
| | - Paul Niziolek
- Department of Radiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Imranul Alam
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Steven Ing
- Division of Endocrinology, Diabetes, and Metabolism, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Lynda E Polgreen
- The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA 90502, USA
| | - Erik A Imel
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Michael J Econs
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Chu A, Yao Y, Glibowicka M, Deber CM, Manolson MF. The Human Mutation K237_V238del in a Putative Lipid Binding Motif within the V-ATPase a2 Isoform Suggests a Molecular Mechanism Underlying Cutis Laxa. Int J Mol Sci 2024; 25:2170. [PMID: 38396846 PMCID: PMC10889665 DOI: 10.3390/ijms25042170] [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: 12/29/2023] [Revised: 01/19/2024] [Accepted: 02/01/2024] [Indexed: 02/25/2024] Open
Abstract
Vacuolar ATPases (V-ATPases), proton pumps composed of 16 subunits, are necessary for a variety of cellular functions. Subunit "a" has four isoforms, a1-a4, each with a distinct cellular location. We identified a phosphoinositide (PIP) interaction motif, KXnK(R)IK(R), conserved in all four isoforms, and hypothesize that a/PIP interactions regulate V-ATPase recruitment/retention to different organelles. Among the four isoforms, a2 is enriched on Golgi with a2 mutations in the PIP motif resulting in cutis laxa. We hypothesize that the hydrophilic N-terminal (NT) domain of a2 contains a lipid-binding domain, and mutations in this domain prevent interaction with Golgi-enriched PIPs, resulting in cutis laxa. We recreated the cutis laxa-causing mutation K237_V238del, and a double mutation in the PIP-binding motif, K237A/V238A. Circular dichroism confirmed that there were no protein structure alterations. Pull-down assays with PIP-enriched liposomes revealed that wildtype a2NT preferentially binds phosphatidylinositol 4-phosphate (PI(4)P), while mutants decreased binding to PI(4)P. In HEK293 cells, wildtype a2NT was localized to Golgi and co-purified with microsomal membranes. Mutants reduced Golgi localization and membrane association. Rapamycin depletion of PI(4)P diminished a2NT-Golgi localization. We conclude that a2NT is sufficient for Golgi retention, suggesting the lipid-binding motif is involved in V-ATPase targeting and/or retention. Mutational analyses suggest a molecular mechanism underlying how a2 mutations result in cutis laxa.
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Affiliation(s)
- Anh Chu
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
| | - Yeqi Yao
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
| | - Miroslawa Glibowicka
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, ON, Canada; (M.G.); (C.M.D.)
| | - Charles M. Deber
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, ON, Canada; (M.G.); (C.M.D.)
- Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto M5S 1A8, ON, Canada
| | - Morris F. Manolson
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
- Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto M5S 1A8, ON, Canada
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Tüysüz B, Usluer E, Uludağ Alkaya D, Ocak S, Saygılı S, Şeker A, Apak H. The molecular spectrum of Turkish osteopetrosis and related osteoclast disorders with natural history, including a candidate gene, CCDC120. Bone 2023; 177:116897. [PMID: 37704070 DOI: 10.1016/j.bone.2023.116897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/21/2023] [Accepted: 09/08/2023] [Indexed: 09/15/2023]
Abstract
BACKGROUND Osteopetrosis and related osteoclastic disorders are a heterogeneous group of inherited diseases characterized by increased bone density. The aim of this study is to investigate the molecular spectrum and natural history of the clinical and radiological features of these disorders. METHODS 28 patients from 20 families were enrolled in the study; 20 of them were followed for a period of 1-16 years. Targeted gene analysis and whole-exome sequencing (WES) were performed. RESULTS Biallelic mutations in CLCN7 and TCIRG1 were detected in three families each, in TNFRSF11A and CA2 in two families each, and in SNX10 in one family in the osteopetrosis group. A heterozygous variant in CLCN7 was also found in one family. In the osteopetrosis and related osteoclast disorders group, three different variants in CTSK were detected in five families with pycnodysostosis and a SLC29A3 variant causing dysosteosclerosis was detected in one family. In autosomal recessive osteopetrosis (ARO), a malignant infantile form, four patients died during follow-up, two of whom had undergone hematopoietic stem cell transplantation. Interestingly, all patients had osteopetrorickets of the long bone metaphyses in infancy, typical skeletal features such as Erlenmeyer flask deformity and bone-in-bone appearance that developed toward the end of early childhood. Two siblings with a biallelic missense mutation in CLCN7 and one patient with the compound heterozygous novel splicing variants in intron 15 and 17 in TCIRG1 corresponded to the intermediate form of ARO (IARO); there was intrafamilial clinical heterogeneity in the family with the CLCN7 variant. One of two patients with IARO and distal tubular acidosis was found to have a large deletion in CA2. In one family, two siblings with a heterozygous mutation in CLCN7 were affected, whereas the father with the same mutation was asymptomatic. In WES analysis of three brothers from a family without mutations in osteopetrosis genes, a hemizygous missense variant in CCDC120, a novel gene, was found to be associated with high bone mass. CONCLUSION This study extended the natural history of the different types of osteopetrosis and also introduced a candidate gene, CCDC120, potentially causing osteopetrosis.
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Affiliation(s)
- Beyhan Tüysüz
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Pediatric Genetics, Istanbul, Turkey.
| | - Esra Usluer
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Pediatric Genetics, Istanbul, Turkey
| | - Dilek Uludağ Alkaya
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Pediatric Genetics, Istanbul, Turkey
| | - Süheyla Ocak
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Pediatric Hematology, Istanbul, Turkey
| | - Seha Saygılı
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Pediatric Nephrology, Istanbul, Turkey
| | - Ali Şeker
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Orthopedics and Traumatology, Istanbul, Turkey
| | - Hilmi Apak
- Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Pediatric Hematology, Istanbul, Turkey
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El-Kamah GY, Mehrez MI, Taher MB, El-Bassyouni HT, Gaber KR, Amr KS. Outlining the Clinical Profile of TCIRG1 14 Variants including 5 Novels with Overview of ARO Phenotype and Ethnic Impact in 20 Egyptian Families. Genes (Basel) 2023; 14:genes14040900. [PMID: 37107657 PMCID: PMC10137576 DOI: 10.3390/genes14040900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 03/15/2023] [Accepted: 03/17/2023] [Indexed: 04/29/2023] Open
Abstract
TCIRG1 gene mutations underlie osteopetrosis, a rare genetic disorder impacting osteoclast function with consequent brittle bones prone to fracture, in spite of being characterized by increased bone density. The disorder is known to exhibit marked genetic heterogeneity, has no treatment, and is lethal in most instances. There are reports of ethnic variations affecting bone mineral density and variants' expression as diverse phenotypes even within individuals descending from the same pedigree. We herein focus on one of osteopetrosis's three types: the autosomal recessive malignant form (MIM 259700) (ARO) that is almost always associated with severe clinical symptoms. We reviewed the results of about 1800 Egyptian exomes and we did not detect similar variants within our Egyptian dataset and secondary neurological deficit. We studied twenty Egyptian families: sixteen ARO patients, ten carrier parents with at least one ARO affected sib, and two fetuses. They were all subjected to thorough evaluation and TCIRG1 gene sequencing. Our results of twenty-eight individuals descending from twenty Egyptian pedigrees with at least one ARO patient, expand the phenotype as well as genotype spectrum of recessive mutations in the TCIRG1 gene by five novel pathogenic variants. Identifying TCIRG1 gene mutations in Egyptian patients with ARO allowed the provision of proper genetic counseling, carrier detection, and prenatal diagnosis starting with two families included herein. It also could pave the way to modern genomic therapeutic approaches.
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Affiliation(s)
- Ghada Y El-Kamah
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Mennat I Mehrez
- Oro-Dental Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Mohamed B Taher
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Hala T El-Bassyouni
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Khaled R Gaber
- Prenatal Diagnosis and Fetal Medicine Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Khalda S Amr
- Medical Molecular Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
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Characterization of a PIP Binding Site in the N-Terminal Domain of V-ATPase a4 and Its Role in Plasma Membrane Association. Int J Mol Sci 2023; 24:ijms24054867. [PMID: 36902293 PMCID: PMC10002524 DOI: 10.3390/ijms24054867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/13/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
Vacuolar ATPases (V-ATPases) are multi-subunit ATP-dependent proton pumps necessary for cellular functions, including pH regulation and membrane fusion. The evidence suggests that the V-ATPase a-subunit's interaction with the membrane signaling lipid phosphatidylinositol (PIPs) regulates the recruitment of V-ATPase complexes to specific membranes. We generated a homology model of the N-terminal domain of the human a4 isoform (a4NT) using Phyre2.0 and propose a lipid binding domain within the distal lobe of the a4NT. We identified a basic motif, K234IKK237, critical for interaction with phosphoinositides (PIP), and found similar basic residue motifs in all four mammalian and both yeast a-isoforms. We tested PIP binding of wildtype and mutant a4NT in vitro. In protein lipid overlay assays, the double mutation K234A/K237A and the autosomal recessive distal renal tubular-causing mutation K237del reduced both PIP binding and association with liposomes enriched with PI(4,5)P2, a PIP enriched within plasma membranes. Circular dichroism spectra of the mutant protein were comparable to wildtype, indicating that mutations affected lipid binding, not protein structure. When expressed in HEK293, wildtype a4NT localized to the plasma membrane in fluorescence microscopy and co-purified with the microsomal membrane fraction in cellular fractionation experiments. a4NT mutants showed reduced membrane association and decreased plasma membrane localization. Depletion of PI(4,5)P2 by ionomycin caused reduced membrane association of the WT a4NT protein. Our data suggest that information contained within the soluble a4NT is sufficient for membrane association and that PI(4,5)P2 binding capacity is involved in a4 V-ATPase plasma membrane retention.
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Gong HP, Ren Y, Zha PP, Zhang WY, Zhang J, Zhang ZW, Wang C. Clinical and genetic diagnosis of autosomal dominant osteopetrosis type II in a Chinese family: A case report. World J Clin Cases 2023; 11:700-708. [PMID: 36793634 PMCID: PMC9923847 DOI: 10.12998/wjcc.v11.i3.700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/23/2022] [Accepted: 01/05/2023] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Osteopetrosis is a rare genetic disorder characterized by increased bone density due to defective bone resorption of osteoclasts. Approximately, 80% of autosomal dominant osteopetrosis type II (ADO-II) patients were usually affected by heterozygous dominant mutations in the chloride voltage-gated channel 7 (ClCN7) gene and present early-onset osteoarthritis or recurrent fractures. In this study, we report a case of persistent joint pain without bone injury or underlying history.
CASE SUMMARY We report a 53-year-old female with joint pain who was accidentally diagnosed with ADO-II. The clinical diagnosis was based on increased bone density and typical radiographic features. Two heterozygous mutations in the ClCN7 and T-cell immune regulator 1 (TCIRG1) genes by whole exome sequencing were identified in the patient and her daughter. The missense mutation (c.857G>A) occurred in the CLCN7 gene p. R286Q, which is highly conserved across species. The TCIRG1 gene point mutation (c.714-20G>A) in intron 7 (near the splicing site of exon 7) had no effect on subsequent transcription.
CONCLUSION This ADO-II case had a pathogenic CLCN7 mutation and late onset without the usual clinical symptoms. For the diagnosis and assessment of the prognosis for osteopetrosis, genetic analysis is advised.
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Affiliation(s)
- Hong-Ping Gong
- International Medical Center Ward, General Practice Medical Center, Sichuan University West China Hospital, Chengdu 610041, Sichuan Province, China
- Department of Endocrinology and Metabolism, Sichuan University West China Hospital, Chengdu 610041, Sichuan Province, China
| | - Yan Ren
- Department of Endocrinology and Metabolism, Sichuan University West China Hospital, Chengdu 610041, Sichuan Province, China
| | - Pan-Pan Zha
- Department of Endocrinology and Metabolism, Sichuan University West China Hospital, Chengdu 610041, Sichuan Province, China
| | - Wen-Yan Zhang
- Department of Pathology, West China Hospital, Sichuan University, Chengdu 610041, Sichuan Province, China
| | - Jin Zhang
- Department of Endocrinology and Metabolism, The People’s Hospital of Leshan, Leshan 614003, Sichuan Province, China
| | - Zhi-Wen Zhang
- Department of Endocrinology and Metabolism, The People’s Hospital of Leshan, Leshan 614003, Sichuan Province, China
| | - Chun Wang
- Department of Endocrinology and Metabolism, Sichuan University West China Hospital, Chengdu 610041, Sichuan Province, China
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Pillai NR, Aggarwal A, Orchard P. Phenotype-autosomal recessive osteopetrosis. Bone 2022; 165:116577. [PMID: 36195244 DOI: 10.1016/j.bone.2022.116577] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Revised: 09/27/2022] [Accepted: 09/29/2022] [Indexed: 11/02/2022]
Abstract
Osteopetrosis (OPT) is a life-threatening disease characterized by increased bone mass caused by diminished osteoclast function/differentiation. The autosomal recessive forms, caused by biallelic variants in implicated genes, usually present in infancy. Without treatment, autosomal recessive OPTs are usually fatal within the first 10 years of life [1]. Here, we review the clinical features and associated pathophysiology of the autosomal recessive OPT. A greater understanding of these rare disorders will advance early diagnosis and optimal management.
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Affiliation(s)
- Nishitha R Pillai
- Division of Genetics and Metabolism, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA.
| | - Anjali Aggarwal
- Division of Genetics and Metabolism, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA
| | - Paul Orchard
- Division of Blood and Marrow Transplantation, Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA
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9
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Jaber A, Schwarze M, Steinle V, Götze M, Hagmann S. Pediatric patient with a bilateral Salter-Harris II fracture and slipped capital femoral epiphysis secondary to autosomal recessive osteopetrosis. ORTHOPADIE (HEIDELBERG, GERMANY) 2022; 51:1015-1021. [PMID: 35802155 PMCID: PMC9715516 DOI: 10.1007/s00132-022-04278-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 06/08/2022] [Indexed: 06/15/2023]
Abstract
Treatment of femoral neck fractures secondary to osteopetrosis is an uncertain and puzzled decision. Experience in the treatment, especially in the pediatric population, is scarcely reported. The duration of conservative treatment is prolonged and poses the risks of non-union and development of coxa vara deformity. The recommended treatment is closed reduction and internal fixation; however, surgery on osteopetrotic bone is challenging due to defective bone marrow function, delayed consolidation and higher risk of intraoperative fractures. Slipped capital femoral epiphysis secondary to osteopetrosis is very rarely reported. This article presents the case of a 5-year-old female patient with rapidly deteriorating physical function due to bilateral proximal femoral Salter-Harris type II fractures with associated slippage of the growth plates secondary to confirmed autosomal recessive osteopetrosis. Operative treatment was performed in a tertiary level orthopedic center with closed reduction and internal fixation with cannulated screws. A loss of fixation with coxa vara deformity was seen on the left side 7 months postoperatively with increasing pain. A revision surgery with reosteosynthesis and a valgus osteotomy was thus performed which showed good subjective and objective results 1 year postoperatively with complete bony union.
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Affiliation(s)
- Ayham Jaber
- Department of Orthopedics and Trauma Surgery, Center for Orthopedics, Trauma Surgery and Spinal Cord Injury, Heidelberg University Hospital, Schlierbacher Landstr. 200a, 69118, Heidelberg, Germany.
| | - Martin Schwarze
- Department of Orthopedics and Trauma Surgery, Center for Orthopedics, Trauma Surgery and Spinal Cord Injury, Heidelberg University Hospital, Schlierbacher Landstr. 200a, 69118, Heidelberg, Germany
| | - Verena Steinle
- Department of Diagnostic and interventional Radiology, Heidelberg University Hospital, Im Neuenheimer Feld 420, 69120, Heidelberg, Germany
| | - Marco Götze
- Department of Orthopedics and Trauma Surgery, Center for Orthopedics, Trauma Surgery and Spinal Cord Injury, Heidelberg University Hospital, Schlierbacher Landstr. 200a, 69118, Heidelberg, Germany
| | - Sébastien Hagmann
- Department of Orthopedics and Trauma Surgery, Center for Orthopedics, Trauma Surgery and Spinal Cord Injury, Heidelberg University Hospital, Schlierbacher Landstr. 200a, 69118, Heidelberg, Germany
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Capo V, Abinun M, Villa A. Osteoclast rich osteopetrosis due to defects in the TCIRG1 gene. Bone 2022; 165:116519. [PMID: 35981697 DOI: 10.1016/j.bone.2022.116519] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/10/2022] [Accepted: 08/11/2022] [Indexed: 11/28/2022]
Abstract
Discovery that mutations in TCIRG1 (also known as Atp6i) gene are responsible for most instances of autosomal recessive osteopetrosis (ARO) heralded a new era for comprehension and treatment of this phenotypically heterogeneous rare bone disease. TCIRG1 encodes the a3 subunit, an essential isoform of the vacuolar ATPase proton pump involved in acidification of the osteoclast resorption lacuna and in secretory lysosome trafficking. TCIRG1 defects lead to inefficient bone resorption by nonfunctional osteoclasts seen in abundance on bone marrow biopsy, delineating this ARO as 'osteoclast-rich'. Presentation is usually in early childhood and features of extramedullary haematopoiesis (hepatosplenomegaly, anaemia, thrombocytopenia) due to bone marrow fibrosis, and cranial nerve impingement (blindness in particular). Impaired dietary calcium uptake due to high pH causes the co-occurrence of rickets, described as "osteopetrorickets". Osteoclast dysfunction leads to early death if untreated, and allogeneic haematopoietic stem cell transplantation is currently the treatment of choice. Studies of patients as well as of mouse models carrying spontaneous (the oc/oc mouse) or targeted disruption of Atp6i (TCIRG1) gene have been instrumental providing insight into disease pathogenesis and development of novel cellular therapies that exploit gene correction.
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Affiliation(s)
- Valentina Capo
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy; Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Milan, Italy
| | - Mario Abinun
- Children's Haematopoietic Stem Cell Transplantation Unit, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Anna Villa
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy; Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Milan, Italy.
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Abstract
Osteopetrosis (OPT) is a rare inherited bone disease characterized by a bone resorption defect, due to osteoclast malfunction (in osteoclast-rich, oc-rich, OPT forms) or absence (in oc-poor OPT forms). This causes severe clinical abnormalities, including increased bone density, lack of bone marrow cavity, stunted growth, macrocephaly, progressive deafness, blindness, hepatosplenomegaly, and severe anemia. The oc-poor subtype of OPT is ultra-rare in humans. It is caused by mutations in either the tumor necrosis factor ligand superfamily member 11 (TNFSF11) gene, encoding RANKL (Receptor Activator of Nuclear factor-kappa B [NF-κB] Ligand) which is expressed on cells of mesenchymal origin and lymphocytes, or the TNFRSF member 11A (TNFRSF11A) gene, encoding the RANKL functional receptor RANK which is expressed on cells of myeloid lineage including osteoclasts. Clinical presentation is usually severe with onset in early infancy or in fetal life, although as more patients are reported, expressivity is variable. Phenotypic variability of RANK-deficient OPT sometimes includes hypogammaglobulinemia or radiological features of dysosteosclerosis. Disease progression is somewhat slower in RANKL-deficient OPT than in other 'malignant' subtypes of OPT. While both RANKL and RANK are essential for normal bone turnover, hematopoietic stem cell transplantation (HSCT) is the treatment of choice only for patients with the RANK-deficient form of oc-poor OPT. So far, there is no cure for RANKL-deficient OPT.
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Affiliation(s)
- Cristina Sobacchi
- CNR-IRGB, Milan Unit, via Fantoli 16/15, 20138 Milan, Italy; Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, MI, Italy.
| | - Mario Abinun
- Paediatric Haematopoietic Stem Cell Transplant Unit, Great North Children's Hospital, Royal Victoria Infirmary, Queen Victoria Road, Newcastle upon Tyne NE1 4LP, UK; Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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Nakanishi-Matsui M, Matsumoto N. V-ATPase a3 Subunit in Secretory Lysosome Trafficking in Osteoclasts. Biol Pharm Bull 2022; 45:1426-1431. [PMID: 36184499 DOI: 10.1248/bpb.b22-00371] [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] [Indexed: 11/22/2022]
Abstract
Vacuolar-type ATPase (V-ATPase) shares its structure and rotational catalysis with F-type ATPase (F-ATPase, ATP synthase). However, unlike subunits of F-ATPase, those of V-ATPase have tissue- and/or organelle-specific isoforms. Structural diversity of V-ATPase generated by different combinations of subunit isoforms enables it to play diverse physiological roles in mammalian cells. Among these various roles, this review focuses on the functions of lysosome-specific V-ATPase in bone resorption by osteoclasts. Lysosomes remain in the cytoplasm in most cell types, but in osteoclasts, secretory lysosomes move toward and fuse with the plasma membrane to secrete lysosomal enzymes, which is essential for bone resorption. Through this process, lysosomal V-ATPase harboring the a3 isoform of the a subunit is relocated to the plasma membrane, where it transports protons from the cytosol to the cell exterior to generate the acidic extracellular conditions required for secreted lysosomal enzymes. In addition to this role as a proton pump, we recently found that the lysosomal a3 subunit of V-ATPase is essential for anterograde trafficking of secretory lysosomes. Specifically, a3 interacts with Rab7, a member of the Rab guanosine 5'-triphosphatase (GTPase) family that regulates organelle trafficking, and recruits it to the lysosomal membrane. These findings revealed the multifunctionality of lysosomal V-ATPase in osteoclasts; V-ATPase is responsible not only for the formation of the acidic environment by transporting protons, but also for intracellular trafficking of secretory lysosomes by recruiting organelle trafficking factors. Herein, we summarize the molecular mechanism underlying secretory lysosome trafficking in osteoclasts, and discuss the possible regulatory role of V-ATPase in organelle trafficking.
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Affiliation(s)
| | - Naomi Matsumoto
- Division of Biochemistry, School of Pharmacy, Iwate Medical University
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Afshariyamchlou S, Ng M, Ferdjallah A, Warden SJ, Niziolek P, Alam I, Polgreen LE, Imel EA, Orchard P, Econs MJ. Unusual Cortical Phenotype After Hematopoietic Stem Cell Transplantation in a Patient With Osteopetrosis. JBMR Plus 2022; 6:e10616. [PMID: 35720663 PMCID: PMC9189909 DOI: 10.1002/jbm4.10616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 01/27/2022] [Accepted: 02/12/2022] [Indexed: 11/07/2022] Open
Abstract
The osteopetroses are a group of rare genetic diseases caused by osteoclast dysfunction or absence. The hallmark of osteopetrosis is generalized increased bone mineral density (BMD). However, the bone is fragile and fractures are common. Autosomal recessive osteopetrosis is usually a severe disorder and often life-threatening in childhood. We present male siblings with autosomal recessive osteopetrosis due to biallelic variants in TCIRG1 who survived childhood and underwent hematopoietic stem cell transplant (HSCT) in adulthood. One sibling died of posttransplant complications. After transplant, the other sibling had improvement of multiple clinical parameters, including some decline in BMD Z-scores by dual-energy X-ray absorptiometry (DXA) and cessation of fractures. However, spine quantitative computed tomography 11 years after transplant demonstrated an anvil pattern of sclerosis with BMD Z-score of +18.3. High-resolution peripheral quantitative computed tomography (HR-pQCT) of the tibia demonstrated near complete obliteration of the marrow space combined with an unusual cortical phenotype, suggesting extensive cortical porosity at the distal tibia. This case highlights that despite successful transplantation and subsequent improvement in clinical parameters, this patient continued to have significantly elevated bone density and decreased marrow space. Transplant-associated increased cortical porosity is multifactorial and occurs in two-thirds of non-osteopetrotic patients undergoing HSCT. This finding after transplant in osteopetrosis may suggest particular sensitivity of the cortical bone to resorptive activity of transplanted osteoclasts. The case also suggests HR-pQCT may be a useful modality for imaging and assessing the therapeutic effects on bone in individuals with osteopetrosis. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
| | - Michelle Ng
- Department of PediatricsUniversity of Minnesota Medical SchoolMinneapolisMNUSA
| | - Asmaa Ferdjallah
- Department of PediatricsUniversity of Minnesota Medical SchoolMinneapolisMNUSA
| | - Stuart J. Warden
- Department of Physical TherapyIndiana University School of Health and Human SciencesIndianapolisINUSA
| | - Paul Niziolek
- Department of RadiologyIndiana University School of MedicineIndianapolisINUSA
| | - Imranul Alam
- Department of MedicineIndiana University School of MedicineIndianapolisINUSA
| | | | - Erik A. Imel
- Department of MedicineIndiana University School of MedicineIndianapolisINUSA
| | - Paul Orchard
- Department of PediatricsUniversity of Minnesota Medical SchoolMinneapolisMNUSA
| | - Michael J. Econs
- Department of MedicineIndiana University School of MedicineIndianapolisINUSA
- Department of Medical and Molecular GeneticsIndiana University School of MedicineIndianapolisINUSA
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14
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Liu C, Ajmal M, Akram Z, Ghafoor T, Farhan M, Shafique S, Wahid S, Bano S, Xiao J, Satti HS, Zhang F, Khan TN. Genetic analysis of osteopetrosis in Pakistani families identifies novel and known sequence variants. BMC Med Genomics 2021; 14:264. [PMID: 34753502 PMCID: PMC8576874 DOI: 10.1186/s12920-021-01117-4] [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] [Received: 06/08/2021] [Accepted: 10/26/2021] [Indexed: 11/28/2022] Open
Abstract
Osteopetrosis is a genetically heterogenous, fatal bone disorder characterized by increased bone density. Globally, various genetic causes are reported for osteopetrosis with all forms of inheritance patterns. A precise molecular diagnosis is necessary for prognosis and for prescribing treatment paradigms in osteopetrosis. Here we report on thirteen individuals diagnosed with infantile malignant osteopetrosis coming from ten unrelated Pakistani families; nine of whom are consanguineous. We performed whole exome sequencing and Sanger sequencing in all families and identified homozygous variants in genes previously reported for autosomal recessive inheritance of osteopetrosis. All the identified variants are expected to affect the stability or length of gene products except one nonsynonymous missense variant. TCIRG1 was found as a candidate causal gene in majority of the families. We report six novel variants; four in TCIRG1 and one each in CLCN7 and OSTM1. Our combined findings will be helpful in molecular diagnosis and genetic counselling of patients with osteopetrosis particularly in populations with high consanguinity.
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Affiliation(s)
- Chunyu Liu
- Obstetrics and Gynecology Hospital, NHC Key Laboratory of Reproduction Regulation (Shanghai Institute for Biomedical and Pharmaceutical Technologies), School of Life Sciences, Fudan University, Shanghai, 200011, China
| | - Muhammad Ajmal
- Institute of Biomedical and Genetic Engineering, Islamabad, 44000, Pakistan
| | - Zaineb Akram
- Armed Forces Bone Marrow Transplant Centre, CMH Medical Complex, Rawalpindi, 46000, Pakistan
| | - Tariq Ghafoor
- Armed Forces Bone Marrow Transplant Centre, CMH Medical Complex, Rawalpindi, 46000, Pakistan
| | - Muhammad Farhan
- Armed Forces Bone Marrow Transplant Centre, CMH Medical Complex, Rawalpindi, 46000, Pakistan
| | - Sobia Shafique
- Institute of Biomedical and Genetic Engineering, Islamabad, 44000, Pakistan
| | - Sughra Wahid
- KRL General Hospital, Islamabad, 44000, Pakistan
| | - Shahar Bano
- KRL General Hospital, Islamabad, 44000, Pakistan
| | - Jianqiu Xiao
- Division of Bone and Mineral Diseases, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Humayoon Shafique Satti
- Department of Biological Sciences, National University of Medical Sciences, Rawalpindi, 46000, Pakistan
| | - Feng Zhang
- Obstetrics and Gynecology Hospital, NHC Key Laboratory of Reproduction Regulation (Shanghai Institute for Biomedical and Pharmaceutical Technologies), School of Life Sciences, Fudan University, Shanghai, 200011, China.
| | - Tahir Naeem Khan
- Department of Biological Sciences, National University of Medical Sciences, Rawalpindi, 46000, Pakistan. .,National Institute of Advance Studies and Research, National University of Medical Sciences, Rawalpindi, 46000, Pakistan.
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15
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Liang H, Li N, Yao RE, Yu T, Ding L, Chen J, Wang J. Clinical and molecular characterization of five Chinese patients with autosomal recessive osteopetrosis. Mol Genet Genomic Med 2021; 9:e1815. [PMID: 34545712 PMCID: PMC8606217 DOI: 10.1002/mgg3.1815] [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] [Received: 02/06/2021] [Revised: 04/27/2021] [Accepted: 09/07/2021] [Indexed: 11/08/2022] Open
Abstract
Background Osteopetrosis is characterized by increased bone density and bone marrow cavity stenosis due to a decrease in the number of osteoclasts or the dysfunction of their differentiation and absorption properties usually caused by biallelic variants of the TCIRG1 and CLCN7 genes. Methods In this study, we describe five Chinese children who presented with anemia, thrombocytopenia, hepatosplenomegaly, repeated infections, and increased bone density. Whole‐exome sequencing identified five compound heterozygous variants of the CLCN7 and TCIRG1 genes in these patients. Results Patient 1 had a novel variant c.1555C>T (p.L519F) and a previously reported pathogenic variant c.2299C>T (p.R767W) in CLCN7. Patient 2 harbored a novel missense variant (c.1025T>C; p.L342P) and a novel splicing variant (c.286‐9G>A) in CLCN7. Patients 3A and 3B from one family displayed the same compound heterozygous TCIRG1 variant, including a novel frameshift variant (c.1370del; p.T457Tfs*71) and a novel splicing variant (c.1554+2T>C). In Patient 4, two novel variants were identified in the TCIRG1 gene: c.676G>T; p.E226* and c.1191del; p.P398Sfs*5. Patient 5 harbored two known pathogenic variants, c.909C>A (p.Y303*) and c.2008C>T (p.R670*), in TCIRG1. Analysis of the products obtained from the reverse transcription‐polymerase chain reaction revealed that the c.286‐9G>A variant in CLCN7 of patient 2 leads to intron 3 retention, resulting in the formation of a premature termination codon (p.E95Vfs*8). These five patients were eventually diagnosed with autosomal recessive osteopetrosis, and the three children with TCIRG1 variants received hematopoietic stem cell transplantation. Conclusions Our results expand the spectrum of variation of genes related to osteopetrosis and deepen the understanding of the relationship between the genotype and clinical characteristics of osteopetrosis.
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Affiliation(s)
- Huanhuan Liang
- Key Laboratory of Pediatric Hematology and Oncology, Ministry of Health, Department of Hematology and Oncology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Niu Li
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Clinical Molecular Diagnostics for Pediatrics, Shanghai, China
| | - Ru-En Yao
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Clinical Molecular Diagnostics for Pediatrics, Shanghai, China
| | - Tingting Yu
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Clinical Molecular Diagnostics for Pediatrics, Shanghai, China
| | - Lixia Ding
- Key Laboratory of Pediatric Hematology and Oncology, Ministry of Health, Department of Hematology and Oncology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jing Chen
- Key Laboratory of Pediatric Hematology and Oncology, Ministry of Health, Department of Hematology and Oncology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian Wang
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Clinical Molecular Diagnostics for Pediatrics, Shanghai, China
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16
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Oh YK, Choi KE, Shin YJ, Kim ER, Kim JY, Kim MS, Cho SY, Jin DK. Autosomal Recessive Malignant Infantile Osteopetrosis Associated with a TCIRG1 Mutation: A Case Report of a Neonate Presenting with Hypocalcemia in South Korea. NEONATAL MEDICINE 2021. [DOI: 10.5385/nm.2021.28.3.133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Osteopetrosis refers to a group of genetic skeletal disorders characterized by osteosclerosis and fragile bones. Osteopetrosis can be classified into autosomal dominant, autosomal recessive, or X-linked forms, which might differ in clinical characteristics and disease severity. Autosomal recessive osteopetrosis, also known as malignant osteopetrosis, has an earlier onset, more serious clinical symptoms, and is usually fatal. We encountered a 1-day-old girl who was born full-term via vaginal delivery, which was complicated by meconium-stained amniotic fluid, cephalo-pelvic disproportion, and nuchal cord. Routine neonatal care was provided, in addition to blood tests and chest radiography to screen for sepsis, as well as skull radiography to rule out head injuries. Initial blood tests revealed hypocalcemia, which persisted on follow-up tests the next day. Radiographic examinations revealed diffusely increased bone density and a "space alien" appearance of the skull. Based on radiographic and laboratory findings, the infantile form of osteopetrosis was suspected and genetic testing for identification of the responsible gene. Eventually, a heterozygous mutation of the T cell immune regulator 1, ATPase H+ transporting V0 subunit a3 (TCIRG1) gene (c.292C>T) was identified, making this the first reported case of neonatal-onset malignant osteopetrosis with TCIRG1 mutation in South Korea. Early-onset hypocalcemia is common and usually results from prematurity, fetal growth restriction, maternal diabetes, perinatal asphyxia, and physiologic hypoparathyroidism. However, if hypocalcemia persists, we recommend considering 'infantile of osteopetrosis' as a rare cause of neonatal hypocalcemia and performing radiographic examinations to establish the diagnosis.
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17
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Wu P, Cai Z, Jiang WH, Lu G, Wu PQ, Xie ZW, Peng JZ, Chen C, Qi JY, Xu LZ, Shen KL, Zeng HS, Yin GQ. Two novel mutations in TCIRG1 induced infantile malignant osteopetrosis: a case report. BMC Pediatr 2021; 21:297. [PMID: 34210262 PMCID: PMC8246672 DOI: 10.1186/s12887-021-02774-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/14/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Infantile malignant osteopetrosis (IMO) is a rare autosomal recessive disease characterized by a higher bone density in bone marrow caused by the dysfunction of bone resorption. Clinically, IMO can be diagnosed with medical examination, bone mineral density test and whole genome sequencing. CASE PRESENTATION We present the case of a 4-month-old male infant with abnormal skull development, hypocalcemia and premature closure of the cranial sutures. Due to the hyper bone density showed by his radiographic examination, which are characteristic patterns of IMO, we speculated that he might be an IMO patient. In order to confirm this diagnosis, a high-precision whole exome sequencing of the infant and his parents was performed. The analysis of high-precision whole exome sequencing results lead to the identification of two novel heterozygous mutations c.504-1G > C (a splicing site mutation) and c.1371delC (p.G458Afs*70, a frameshift mutation) in gene TCIRG1 derived from his parents. Therefore, we propose that there is a close association between these two mutations and the onset of IMO. CONCLUSIONS To date, these two novel mutations in gene TCIRG1 have not been reported in the reference gene database of Chinese population. These variants have likewise not been reported outside of China in the Genome Aggregation Database (gnomAD). Our case suggests that the use of whole exome sequencing to detect these two mutations will improve the identification and early diagnosis of IMO, and more specifically, the identification of homozygous individuals with TCIRG1 gene mutation. We propose that these mutations in gene TCIRG1 could be a novel therapeutic target for the IMO in the future.
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Affiliation(s)
- Ping Wu
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
- Department of Respirology, Beijing Children's Hospital, Capital Medical University, Beijing, 100045, China
- Department of Allergy, Immunology and Rheumatology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Zhe Cai
- Department of Allergy, Immunology and Rheumatology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
- Guangzhou Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou, 510623, China
- Institute Pasteur of Shanghai, Chinese Academy of Science, Shanghai, 200031, China
- Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China
| | - Wen-Hui Jiang
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Gen Lu
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Pei-Qiong Wu
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Zhi-Wei Xie
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Jun-Zheng Peng
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Chen Chen
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Jun-Ye Qi
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Li-Zhen Xu
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Kun-Ling Shen
- Department of Respirology, Beijing Children's Hospital, Capital Medical University, Beijing, 100045, China
| | - Hua-Song Zeng
- Department of Allergy, Immunology and Rheumatology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China
| | - Gen-Quan Yin
- Department of Respirology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, 510120, Guangdong, China.
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Chu A, Zirngibl RA, Manolson MF. The V-ATPase a3 Subunit: Structure, Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption. Int J Mol Sci 2021; 22:ijms22136934. [PMID: 34203247 PMCID: PMC8269383 DOI: 10.3390/ijms22136934] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 12/29/2022] Open
Abstract
This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.
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Roy M, Roux S. Rab GTPases in Osteoclastic Bone Resorption and Autophagy. Int J Mol Sci 2020; 21:ijms21207655. [PMID: 33081155 PMCID: PMC7589333 DOI: 10.3390/ijms21207655] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/11/2020] [Accepted: 10/13/2020] [Indexed: 12/17/2022] Open
Abstract
Small guanosine triphosphate hydrolases (GTPases) of the Rab family are involved in plasma membrane delivery, fusion events, and lysosomal and autophagic degradation pathways, thereby regulating signaling pathways and cell differentiation and function. Osteoclasts are bone-resorbing cells that maintain bone homeostasis. Polarized vesicular trafficking pathways result in the formation of the ruffled border, the osteoclast’s resorptive organelle, which also assists in transcytosis. Here, we reviewed the different roles of Rab GTPases in the endomembrane machinery of osteoclasts and in bone diseases caused by the dysfunction of these proteins, with a particular focus on autophagy and bone resorption. Understanding the molecular mechanisms underlying osteoclast-related bone disease development is critical for developing and improving therapies.
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20
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V-ATPase a3 isoform mutations identified in osteopetrosis patients abolish its expression and disrupt osteoclast function. Exp Cell Res 2020; 389:111901. [PMID: 32045577 DOI: 10.1016/j.yexcr.2020.111901] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 02/05/2020] [Accepted: 02/07/2020] [Indexed: 12/19/2022]
Abstract
The a3 isoform of vacuolar-type proton-pumping ATPase (V-ATPase) is essential for bone resorption by osteoclasts. Although more than 90 mutations of the human a3 gene have been identified in patients with infantile malignant osteopetrosis, it is unclear whether they lead to osteoclast dysfunction. We have established an in vitro assay to induce osteoclasts from spleen macrophages derived from a3-knockout mice. Here, we examined the effects of these mutations in a3-knockout osteoclasts. We were interested in four mutations, two short deletions and two missense mutations, previously identified in the a3 cytosolic domain. a3 harboring either of the two short deletions was hardly expressed in osteoclasts and calcium phosphate resorption was impaired. On the other hand, osteoclasts expressing a3 with either of the two missense mutations exhibited no defects. Specifically, expression levels of the mutant proteins, V-ATPase assembly, and calcium phosphate resorption activity were similar to those of the wild type. Moreover, these missense mutants interacted with Rab7, a small GTPase that regulates lysosomal trafficking. These results suggest that the short deletions impair a3 expression and thus disrupt V-ATPase subunit assembly essential for bone resorption, while the missense mutations do not cause osteoclast dysfunction without an additional mutation(s) or impair resorption of bone, but not of calcium phosphate.
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21
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Lanzi G, Ferraro RM, Masneri S, Piovani G, Barisani C, Sobacchi C, Villa A, Vezzoni P, Giliani S. Generation of 3 clones of induced pluripotent stem cells (iPSCs) from a patient affected by Autosomal Recessive Osteopetrosis due to mutations in TCIRG1 gene. Stem Cell Res 2019; 42:101660. [PMID: 31794943 DOI: 10.1016/j.scr.2019.101660] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/12/2019] [Accepted: 11/14/2019] [Indexed: 01/15/2023] Open
Abstract
Autosomal recessive osteopetrosis (ARO) is a rare inherited disorder leading to increased bone density with impairment in bone resorption. Among the genes responsible for ARO, the TCIRG1 gene, coding for the a3 subunit of the osteoclast proton pump, is mutated in more than 50% of the cases, increasing the importance of TCIRG1-iPSCs as disease model. We generated 3 iPSC clones derived from Peripheral Blood Mononuclear Cells (PBMCs) of a patient carrying the heterozygous mutations p.Y512X and c.2236 + 1G > A. A Sendai virus-based vector was used and the iPSCs were characterized for genetic identity to parental cells, genomic integrity, pluripotency, and differentiation ability.
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Affiliation(s)
- Gaetana Lanzi
- A. Nocivelli Institute for Molecular Medicine, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy.
| | - Rosalba Monica Ferraro
- A. Nocivelli Institute for Molecular Medicine, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Stefania Masneri
- A. Nocivelli Institute for Molecular Medicine, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Giovanna Piovani
- Biology and Genetics Division, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Chiara Barisani
- A. Nocivelli Institute for Molecular Medicine, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Cristina Sobacchi
- Humanitas Clinical and Research Institute, Rozzano, Italy; National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Anna Villa
- Humanitas Clinical and Research Institute, Rozzano, Italy; National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Paolo Vezzoni
- Humanitas Clinical and Research Institute, Rozzano, Italy; National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Silvia Giliani
- A. Nocivelli Institute for Molecular Medicine, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
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22
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Zirngibl RA, Wang A, Yao Y, Manolson MF, Krueger J, Dupuis L, Mendoza-Londono R, Voronov I. Novel c.G630A TCIRG1 mutation causes aberrant splicing resulting in an unusually mild form of autosomal recessive osteopetrosis. J Cell Biochem 2019; 120:17180-17193. [PMID: 31111556 DOI: 10.1002/jcb.28979] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Revised: 03/19/2019] [Accepted: 03/22/2019] [Indexed: 12/22/2022]
Abstract
Autosomal recessive osteopetrosis (ARO) is a severe genetic bone disease characterized by high bone density due to mutations that affect formation or function of osteoclasts. Mutations in the a3 subunit of the vacuolar-type H+ -ATPase (encoded by T-cell immune regulator 1 [TCIRG1]) are responsible for ~50% of all ARO cases. We identified a novel TCIRG1 (c.G630A) mutation responsible for an unusually mild form of the disease. To characterize this mutation, osteoclasts were differentiated using peripheral blood monocytes from the patient (c.G630A/c.G630A), male sibling (+/+), unaffected female sibling (+/c.G630A), and unaffected parent (+/c.G630A). Osteoclast formation, bone-resorbing function, TCIRG1 protein, and mRNA expression levels were assessed. The c.G630A mutation did not affect osteoclast differentiation; however, bone-resorbing function was decreased. Both TCIRG1 protein and full-length TCIRG1 mRNA expression levels were also diminished in the affected patient's sample. The c.G630A mutation replaces the last nucleotide of exon 6 and may cause splicing defects. We analyzed the TCIRG1 splicing pattern between exons 4 to 8 and detected deletions of exons 5, 6, 7, and 5-6 (ΔE56). These deletions were only observed in c.G630A/c.G630A and +/c.G630A samples, but not in +/+ controls. Among these deletions, only ΔE56 maintained the reading frame and was predicted to generate an 85 kDa protein. Exons 5-6 encode an uncharacterized portion of the cytoplasmic N-terminal domain of a3, a domain not involved in proton translocation. To investigate the effect of ΔE56 on V-ATPase function, we transformed yeast with plasmids carrying full-length or truncated Vph1p, the yeast ortholog of a3. Both proteins were expressed; however, ΔE56-Vph1p transformed yeast failed to grow on Zn2+ -containing plates, a growth assay dependent on V-ATPase-mediated vacuolar acidification. In conclusion, our results show that the ΔE56 truncated protein is not functional, suggesting that the mild ARO phenotype observed in the patient is likely due to the residual full-length protein expression.
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Affiliation(s)
- Ralph A Zirngibl
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Andrew Wang
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Yeqi Yao
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Morris F Manolson
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Joerg Krueger
- Division of Hematology/Oncology and Blood and Marrow Transplant, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Lucie Dupuis
- Division of Clinical and Metabolic Genetics, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Roberto Mendoza-Londono
- Division of Clinical and Metabolic Genetics, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Irina Voronov
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
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TCIRG1 and SNX10 gene mutations in the patients with autosomal recessive osteopetrosis. Gene 2019; 702:83-88. [PMID: 30898715 DOI: 10.1016/j.gene.2019.02.088] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 02/08/2019] [Accepted: 02/25/2019] [Indexed: 11/21/2022]
Abstract
Autosomal recessive osteopetrosis (ARO) is a rare genetic bone disease characterized by dense and fragile bone, caused by a defect in osteoclasts responsible for the bone destruction. In this study, we aimed to investigate the mutations in TCIRG1 and SNX10 that are responsible for 50% and 4% of the cases, respectively. All amplicons were sequenced by Sanger sequencing following PCR amplification. As a result, six different mutations of the TCIRG1 gene were found in five of the twelve unrelated cases. These include two novel mutations, namely c.630 + 1G > T mutation and c.1778_1779delTG mutation of the gene which are identified as homozygous. A compound heterozygosity of known mutations c.649_674del26 and c.1372G > A and homozygous presence of the known c.2235 + 1G > A mutation were also observed in different patients. In addition, as a result of the prenatal testing in a family with osteopetrosis infant, the c.1674-1G > A mutation was detected as homozygous for the fetus. In TCIRG1, c.166C > T change, which is indicated as likely benign according to ClinVar database, was heterozygous. Several known polymorphisms; c.117 + 83 T > C, c.417 + 11A > G and c.714-19C > A in TCIRG1 gene; c.24 + 36 T > A and c.112-84G > A in SNX10 gene were also detected. In conclusion, our study revealed that five of the twelve cases carry at least one mutation of TCIRG1 gene. Further studies with more patients and other genes would help better understanding of genetic etiology of the disease.
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Cao WH, Wei WB, Yu G, Li L, Wu Q. Complex Heterozygous Mutation in the T-cell Immune Regulator 1 Gene Associated with Severe Ocular Characteristics of Osteopetrosis in an Infant. Chin Med J (Engl) 2018; 131:354-356. [PMID: 29363653 PMCID: PMC5798059 DOI: 10.4103/0366-6999.223844] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Affiliation(s)
- Wen-Hong Cao
- Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University; Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Key Laboratory of Intraocular Tumor Diagnosis and Treatment, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Wen-Bin Wei
- Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Key Laboratory of Intraocular Tumor Diagnosis and Treatment, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Gang Yu
- Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University, Beijing 100045, China
| | - Li Li
- Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University, Beijing 100045, China
| | - Qian Wu
- Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University, Beijing 100045, China
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Cao W, Wei W, Wu Q. Ophthalmic phenotype of TCIRG1 gene mutations in Chinese infantile malignant osteopetrosis. BMJ Open Ophthalmol 2018; 3:e000180. [PMID: 30539151 PMCID: PMC6257380 DOI: 10.1136/bmjophth-2018-000180] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/25/2018] [Accepted: 09/26/2018] [Indexed: 12/17/2022] Open
Abstract
Objective To evaluate the ophthalmic phenotypes associated with T-cell immune regulator 1 (TCIRG1) mutations in Chinese patients with infantile malignant osteopetrosis (IMO). Methods and analysis 27 Chinese TCIRG1-related osteoporosis infants were enrolled using direct DNA sequencing of PCR-amplified exons. 12 cases had frameshift mutation (the frameshift mutation group, group F), and 15 cases had point mutation (the point mutation group, group P). The clinical features of the two groups were compared, including age at onset, gaze qualities, optic atrophy, optic canal stenosis and waveforms of Flash visual-evoked potential (FVEP). Results The clinical signs, except age at onset and FVEP, showed statistically significant differences between the two groups. The mean age at onset was 1.8 months in group F and 4.3 months in group P; 22 eyes (92%) with frameshift mutation and 16 (53%) with point mutation had poor gaze qualities, such as nystagmus and/or strabismus; optic atrophy was found in 16 eyes (67%) in group F and 6 (20%) in group P; the average optic canal diameter was 1.45 mm in the frameshift mutation cases, 1.87 mm in other cases; FVEP indicated that the waveforms in 10 eyes (42%) were not elicited in group F, yet five eyes (17%) in group P. Conclusion In Chinese TCIRG1-related patients of IMO, the optic canal stenosis and optic atrophy were more serious in cases with frameshift mutations. However, no differences in the conduction block of optic nerve were found between the two groups.
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Affiliation(s)
- Wenhong Cao
- Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University, Beijing, China.,Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Key Laboratory of Intraocular Tumor Diagnosis and Treatment, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Wenbin Wei
- Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Key Laboratory of Intraocular Tumor Diagnosis and Treatment, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Qian Wu
- Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University, Beijing, China
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26
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Abstract
PURPOSE OF REVIEW The term osteopetrosis refers to a group of rare skeletal diseases sharing the hallmark of a generalized increase in bone density owing to a defect in bone resorption. Osteopetrosis is clinically and genetically heterogeneous, and a precise molecular classification is relevant for prognosis and treatment. Here, we review recent data on the pathogenesis of this disorder. RECENT FINDINGS Novel mutations in known genes as well as defects in new genes have been recently reported, further expanding the spectrum of molecular defects leading to osteopetrosis. Exploitation of next-generation sequencing tools is ever spreading, facilitating differential diagnosis. Some complex phenotypes in which osteopetrosis is accompanied by additional clinical features have received a molecular classification, also involving new genes. Moreover, novel types of mutations have been recognized, which for their nature or genomic location are at high risk being neglected. Yet, the causative mutation is unknown in some patients, indicating that the genetics of osteopetrosis still deserves intense research efforts.
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Affiliation(s)
- Eleonora Palagano
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy
- Department of Medical Biotechnologies and Translational Medicine, University of Milan, Milan, Italy
| | - Ciro Menale
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy
- Milan Unit, CNR-IRGB, Milan, Italy
| | - Cristina Sobacchi
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy.
- Milan Unit, CNR-IRGB, Milan, Italy.
| | - Anna Villa
- Humanitas Clinical and Research Institute, via Manzoni 113, 20089, Rozzano, MI, Italy
- Milan Unit, CNR-IRGB, Milan, Italy
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Ahmadpour A, Goodarzi A, Lee DJ, Panchal RR, Kim KD. Cervical spine fractures in osteopetrosis: a case report and review of the literature. J Biomed Res 2018; 32:68-76. [PMID: 29353820 PMCID: PMC5956260 DOI: 10.7555/jbr.32.20170055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
While management of appendicular fractures has been well described in the setting of osteopetrosis, there is limited information on managing fractures of the axial spine. Here we present an osteopetrotic patient with multiple traumatic multiple, comminuted, unstable cervical spinal fractures managed with non-operative stabilization, and provide a review of the pathophysiology, genetic characteristics, and special considerations that must be explored when determining operative versus non-operative management of spinal injury in osteopetrosis. A PubMed query was performed for English articles in the literature published up to June 2016, and used the following search terms alone and in combination: "osteopetrosis", "spine", "fractures", "osteoclasts", and "operative management". Within four months after initial injury, treatment with halo vest allowed for adequate healing. The patient was asymptomatic with cervical spine dynamic radiographs confirming stability at four months. On four-year follow up examination, the patient remained without neck pain, and CT scan demonstrated partially sclerotic fracture lines with appropriate anatomical alignment. In conclusion, external halo stabilization may be an effective option for treatment of multiple unstable acute traumatic cervical spine fractures in patients with osteopetrosis. Given the challenge of surgical stabilization in osteopetrosis, further research is necessary to elucidate the optimal form of treatment in this select patient population.
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Affiliation(s)
- Arjang Ahmadpour
- Department of Neurological Surgery, University of California-Davis Medical Center, Sacramento, CA 95817, USA
| | - Amir Goodarzi
- Department of Neurological Surgery, University of California-Davis Medical Center, Sacramento, CA 95817, USA
| | - Darrin J Lee
- Department of Neurological Surgery, University of California-Davis Medical Center, Sacramento, CA 95817, USA
| | - Ripul R Panchal
- Department of Neurological Surgery, University of California-Davis Medical Center, Sacramento, CA 95817, USA
| | - Kee D Kim
- Department of Neurological Surgery, University of California-Davis Medical Center, Sacramento, CA 95817, USA
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28
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Palagano E, Susani L, Menale C, Ramenghi U, Berger M, Uva P, Oppo M, Vezzoni P, Villa A, Sobacchi C. Synonymous Mutations Add a Layer of Complexity in the Diagnosis of Human Osteopetrosis. J Bone Miner Res 2017; 32:99-105. [PMID: 27468155 DOI: 10.1002/jbmr.2929] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 07/25/2016] [Accepted: 07/27/2016] [Indexed: 11/08/2022]
Abstract
Autosomal recessive osteopetroses (AROs) are rare, genetically heterogeneous skeletal diseases with increased bone density that are often lethal if left untreated. A precise molecular classification is relevant for the patient's management, because in some subgroups hematopoietic stem cell transplantation (HSCT), which is the only curative therapy, is contraindicated. In two unrelated ARO patients, the molecular analysis revealed the presence of a synonymous variant in known ARO genes, namely in the TCIRG1 gene in one patient and in the CLCN7 in the other patient, predicted to impact on the splicing process. In the latter case, sequencing of the transcript confirmed the splicing defect, whereas in the former, for whom an RNA sample was not available, the defect was reconstructed in vitro by the minigene technology. These results strongly suggest that these synonymous changes were responsible for the disease in our patients. Our findings are novel with respect to ARO and add to the few reports in literature dealing with different diseases, underlining the importance of cDNA analysis for the correct assessment of exonic changes, even when exome sequencing is performed. In particular, we highlight the possibility that at least in some cases ARO is due to synonymous changes, erroneously considered clinically silent, in the genes already described in literature, and suggest carefully reevaluating the sequencing results of these genes when mutations are not found at a first analysis. In addition, with respect to the CLCN7 gene, we suggest that synonymous variants might also contribute to the large spectrum of severity typical of CLCN7-dependent osteopetrosis through more subtle, but not negligible, effects on protein availability and functionality. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Eleonora Palagano
- Humanitas Clinical and Research Institute, Rozzano, Italy.,Department of Medical Biotechnologies and Translational Medicine, University of Milan, Milan, Italy
| | - Lucia Susani
- Humanitas Clinical and Research Institute, Rozzano, Italy.,National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Ciro Menale
- Humanitas Clinical and Research Institute, Rozzano, Italy.,National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Ugo Ramenghi
- Department of Public Health and Pediatric Sciences, University of Turin, Turin, Italy
| | - Massimo Berger
- Pediatric Onco-Hematology and Stem Cell Transplant Division, Regina Margherita Children Hospital, City of Health and Science, Turin, Italy
| | - Paolo Uva
- CRS4, Science and Technology Park Polaris, Pula, Italy
| | - Manuela Oppo
- CRS4, Science and Technology Park Polaris, Pula, Italy.,Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Paolo Vezzoni
- Humanitas Clinical and Research Institute, Rozzano, Italy.,National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Anna Villa
- Humanitas Clinical and Research Institute, Rozzano, Italy.,National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
| | - Cristina Sobacchi
- Humanitas Clinical and Research Institute, Rozzano, Italy.,National Research Council-Institute of Genetics and Biomedical Research (CNR-IRGB), Milan Unit, Milan, Italy
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29
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Hoyoux C, Dresse MF, Forget P, Piette C, Rausin L, Villa A, Gothot A, Florkin B. Osteopetrosis mimicking juvenile myelomonocytic leukemia. Pediatr Int 2014; 56:779-82. [PMID: 25335998 DOI: 10.1111/ped.12342] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 01/06/2014] [Accepted: 02/05/2014] [Indexed: 01/15/2023]
Abstract
A 5-month-old boy developed splenomegaly, anemia, thrombocytopenia with elevated white cells, monocytosis and immature granulocytes in the peripheral blood. Bone marrow showed dysplasia without blastosis. Increased colony-forming unit-granulocyte-macrophage was found in the peripheral blood, mimicking granulocyte-macrophage colony-stimulating factor hypersensitivity. These findings fulfilled the diagnosis criteria for juvenile myelomonocytic leukemia (JMML), but no mutations in the CBL, NRAS, KRAS, or PTPN11 genes were detected. In addition to these findings severe hypogammaglobulinemia and elevated alkaline phosphatase were present. Bone X-ray showed dense and radiopaque bones with a bone-in-bone appearance characteristic of infantile malignant osteopetrosis (IMO). Genetic mutation in T-cell, immune regulator 1 (TCIRG1) was identified, confirming the diagnosis of IMO. Careful differential diagnosis including osteopetrosis, is therefore recommended in patients with clinical features and hematologic findings consistent with JMML.
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Affiliation(s)
- Claire Hoyoux
- Pediatric Hemato-oncology, CHR Citadelle, Liège, Belgium
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30
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Anderson SL, Jalas C, Fedick A, Reid KF, Carpenter TO, Chirnomas D, Treff NR, Ekstein J, Rubin BY. A founder mutation in the TCIRG1 gene causes osteopetrosis in the Ashkenazi Jewish population. Clin Genet 2014; 88:74-9. [PMID: 24989235 DOI: 10.1111/cge.12448] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 06/11/2014] [Accepted: 06/19/2014] [Indexed: 12/27/2022]
Abstract
Osteopetrosis is a rare and heterogeneous genetic disorder characterized by dense bone mass that is a consequence of defective osteoclast function and/or development. Autosomal recessive osteopetrosis (ARO) is the most severe form and is often fatal within the first years of life; early hematopoietic stem cell transplant (HSCT) remains the only curative treatment for ARO. The majority of the ARO-causing mutations are located in the TCIRG1 gene. We report here the identification and characterization of an A to T transversion in the fourth base of the intron 2 donor splice site (c.117+4A→T) in TCIRG1, a mutation not previously seen in the Ashkenazi Jewish (AJ) population. Analysis of a random sample of individuals of AJ descent revealed a carrier frequency of approximately 1 in 350. Genotyping of five loci adjacent to the c.117+4A→T-containing TCIRG1 allele revealed that the presence of this mutation in the AJ population is due to a single founder. The identification of this mutation will enable population carrier testing and will facilitate the identification and treatment of individuals homozygous for this mutation.
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Affiliation(s)
- S L Anderson
- Department of Biological Sciences, Fordham University, Bronx, NY, 10458, USA
| | - C Jalas
- Bonei Olam, Center for Rare Jewish Genetic Disorders, Brooklyn, NY, 11204, USA
| | - A Fedick
- Department of Microbiology and Molecular Genetics, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA
| | - K F Reid
- Department of Biological Sciences, Fordham University, Bronx, NY, 10458, USA
| | - T O Carpenter
- Yale University School of Medicine, Departments of Pediatrics (Endocrinology) and Orthopedics and Rehabilitation, New Haven, CT, 06520, USA
| | - D Chirnomas
- Yale University School of Medicine, Departments of Pediatrics (Endocrinology) and Orthopedics and Rehabilitation, New Haven, CT, 06520, USA
| | - N R Treff
- Department of Microbiology and Molecular Genetics, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, 08854, USA.,Reproductive Medicine Associates of New Jersey, Department of Research, Morristown, NJ, 07960, USA
| | - J Ekstein
- Dor Yeshorim, The Committee for Prevention of Jewish Diseases, Brooklyn, NY, 11211, USA
| | - B Y Rubin
- Department of Biological Sciences, Fordham University, Bronx, NY, 10458, USA
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31
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Sobacchi C, Pangrazio A, Lopez AGM, Gomez DPV, Caldana ME, Susani L, Vezzoni P, Villa A. As little as needed: the extraordinary case of a mild recessive osteopetrosis owing to a novel splicing hypomorphic mutation in the TCIRG1 gene. J Bone Miner Res 2014; 29:1646-50. [PMID: 24535816 PMCID: PMC4258090 DOI: 10.1002/jbmr.2203] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/23/2014] [Accepted: 02/09/2014] [Indexed: 01/22/2023]
Abstract
Mutations in the TCIRG1 gene, coding for a subunit of the osteoclast proton pump, are responsible for more than 50% of cases of human malignant autosomal recessive osteopetrosis (ARO), a rare inherited bone disease with increased bone density owing to a failure in bone resorption. A wide variety of mutations has been described, including missense, nonsense, small deletions/insertions, splice-site mutations, and large genomic deletions, all leading to a similar severe presentation. So far, to the best of our knowledge, no report of a mild phenotype owing to recessive TCIRG1 mutations is present neither in our series of more than 100 TCIRG1-dependent ARO patients nor in the literature. Here we describe an 8-year-old patient referred to us with a clinical diagnosis of ARO, based on radiological findings; of note, no neurological or hematological defects were present in this girl. Surprisingly, we identified a novel nucleotide change in intron 15 of the TCIRG1 gene at the homozygous state, leading to the production of multiple aberrant transcripts, but also, more importantly, of a limited amount of the normal transcript. Our results show that a low level of normal TCIRG1 protein can dampen the clinical presentation of TCIRG1-dependent ARO. On this basis, a small amount of protein might be sufficient to rescue, at least partially, the severe ARO phenotype, and this is particularly important when gene therapy approaches are considered. In addition, we would also recommend that the TCIRG1 gene be included in the molecular diagnosis of mild forms of human ARO.
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Affiliation(s)
- Cristina Sobacchi
- Unitá Operativa di Supporto (UOS)/Institute of Genetic and Biomedical Research (IRGB), Milan Unit, National Research Council (CNR), Milan, Italy; Humanitas Clinical and Research Center, Rozzano, Italy
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32
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Waterval JJ, Borra VM, Van Hul W, Stokroos RJ, Manni JJ. Sclerosing bone dysplasias with involvement of the craniofacial skeleton. Bone 2014; 60:48-67. [PMID: 24325978 DOI: 10.1016/j.bone.2013.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 11/25/2013] [Accepted: 12/02/2013] [Indexed: 01/13/2023]
Abstract
In this review we provide a complete overview of the existing sclerosing bone dysplasias with craniofacial involvement. Clinical presentation, disease course, the craniofacial symptoms, genetic transmission pattern and pathophysiology are discussed. There is an emphasis on radiologic features with a large collection of CT and MRI images. In previous reviews the craniofacial area of the sclerosing bone dysplasias was underexposed. However, craniofacial symptoms are often the first symptoms to address a physician. The embryology of the skull and skull base is explained and illustrated for a better understanding of the affected areas.
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Affiliation(s)
- J J Waterval
- Department of Otorhinolaryngology-Head & Neck Surgery, Maastricht University Medical Center, P.O. 5800, 6202AZ Maastricht, The Netherlands.
| | - V M Borra
- Department of Medical Genetics, University of Antwerp, Prins Boudewijnlaan 43, B-2650 Edegem, Belgium.
| | - W Van Hul
- Department of Medical Genetics, University of Antwerp, Prins Boudewijnlaan 43, B-2650 Edegem, Belgium.
| | - R J Stokroos
- Department of Otorhinolaryngology-Head & Neck Surgery, Maastricht University Medical Center, P.O. 5800, 6202AZ Maastricht, The Netherlands.
| | - J J Manni
- Department of Otorhinolaryngology-Head & Neck Surgery, Maastricht University Medical Center, P.O. 5800, 6202AZ Maastricht, The Netherlands.
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Supanchart C, Wartosch L, Schlack C, Kühnisch J, Felsenberg D, Fuhrmann JC, de Vernejoul MC, Jentsch TJ, Kornak U. ClC-7 expression levels critically regulate bone turnover, but not gastric acid secretion. Bone 2014; 58:92-102. [PMID: 24103576 DOI: 10.1016/j.bone.2013.09.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 08/16/2013] [Accepted: 09/27/2013] [Indexed: 12/17/2022]
Abstract
Mutations in the 2Cl(-)/1H(+)-exchanger ClC-7 impair osteoclast function and cause different types of osteoclast-rich osteopetrosis. However, it is unknown to what extent ClC-7 function has to be reduced to become rate-limiting for bone resorption. In osteoclasts from osteopetrosis patients expression of the mutated ClC-7 protein did not correlate with disease severity and resorption impairment. Therefore, a series of transgenic mice expressing ClC-7 in osteoclasts at different levels was generated. Crossing of these mice with Clcn7(-/-) mutants rescued the osteopetrotic phenotype to variable degrees. One resulting double transgenic line mimicked human autosomal dominant osteopetrosis. The trabecular bone of these mice showed a reduction of osteoblast numbers, osteoid, and osteoblast marker gene expression indicative of reduced osteoblast function. In osteoclasts from these mutants ClC-7 expression levels were 20 to 30% of wildtype levels. These reduced levels not only impaired resorptive activity, but also increased numbers, size and nucleus numbers of osteoclasts differentiated in vitro. Although ClC-7 was expressed in the stomach and PTH levels were high in Clcn7(-/-) mutants loss of ClC-7 did not entail a relevant elevation of gastric pH. In conclusion, we show that in our model a reduction of ClC-7 function by approximately 70% is sufficient to increase bone mass, but does not necessarily enhance bone formation. ClC-7 does not appear to be crucially involved in gastric acid secretion, which explains the absence of an osteopetrorickets phenotype in CLCN7-related osteopetrosis.
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Affiliation(s)
- C Supanchart
- Institute of Medical Genetics and Human Genetics, Charité-Universitaetsmedizin Berlin, Berlin, Germany
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34
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Sobacchi C, Schulz A, Coxon FP, Villa A, Helfrich MH. Osteopetrosis: genetics, treatment and new insights into osteoclast function. Nat Rev Endocrinol 2013; 9:522-36. [PMID: 23877423 DOI: 10.1038/nrendo.2013.137] [Citation(s) in RCA: 370] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Osteopetrosis is a genetic condition of increased bone mass, which is caused by defects in osteoclast formation and function. Both autosomal recessive and autosomal dominant forms exist, but this Review focuses on autosomal recessive osteopetrosis (ARO), also known as malignant infantile osteopetrosis. The genetic basis of this disease is now largely uncovered: mutations in TCIRG1, CLCN7, OSTM1, SNX10 and PLEKHM1 lead to osteoclast-rich ARO (in which osteoclasts are abundant but have severely impaired resorptive function), whereas mutations in TNFSF11 and TNFRSF11A lead to osteoclast-poor ARO. In osteoclast-rich ARO, impaired endosomal and lysosomal vesicle trafficking results in defective osteoclast ruffled-border formation and, hence, the inability to resorb bone and mineralized cartilage. ARO presents soon after birth and can be fatal if left untreated. However, the disease is heterogeneous in clinical presentation and often misdiagnosed. This article describes the genetics of ARO and discusses the diagnostic role of next-generation sequencing methods. The management of affected patients, including guidelines for the indication of haematopoietic stem cell transplantation (which can provide a cure for many types of ARO), are outlined. Finally, novel treatments, including preclinical data on in utero stem cell treatment, RANKL replacement therapy and denosumab therapy for hypercalcaemia are also discussed.
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Affiliation(s)
- Cristina Sobacchi
- Unit Of Support/Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Humanitas Clinical and Research Centre, Via Manzoni 113, 20089 Rozzano, Italy
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