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Kantaputra P, Panichkul W, Sillapasorn P, Adisornkanj P, Kitsadayurach P, Kaewgaya M, Intachai W, Olsen B, Ngamphiw C, Leethanakul C, Jatooratthawichot P, Ketudat Cairns JR, Tongsima S. LRP4 mutations, dental anomalies, and oral exostoses. Int J Paediatr Dent 2024; 34:432-441. [PMID: 38013205 DOI: 10.1111/ipd.13141] [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: 08/30/2022] [Revised: 12/22/2022] [Accepted: 11/07/2023] [Indexed: 11/29/2023]
Abstract
BACKGROUND In order to generate a normal set of teeth, fine-tuning of Wnt/β-catenin signaling is required, in which WNT ligands bind to their inhibitors or WNT inhibitors bind to their co-receptors. Lrp4 regulates the number of teeth and their morphology by modulating Wnt/β-catenin signaling as a Wnt/β-catenin activator or inhibitor, depending on its interactions with the partner proteins, such as Sostdc1 and Dkk1. AIM To investigate genetic etiologies of dental anomalies involving LRP4 in a Thai cohort of 250 children and adults with dental anomalies. DESIGN Oral and radiographic examinations and whole exome sequencing were performed for every patient. RESULTS Two novel (p.Leu1356Arg and p.Ala1702Gly) and three recurrent (p.Arg263His, p.Gly1314Ser, and p.Asn1385Ser) rare variants in low-density lipoprotein receptor-related protein 4 (LRP4: MIM 604270) were identified in 11 patients. Oral exostoses were observed in five patients. CONCLUSION Antagonism of Bmp signaling by Sostdc1 requires the presence of Lrp4. Mice lacking Lrp4 have been demonstrated to have alteration of Wnt-Bmp-Shh signaling and an abnormal number of incisors. Therefore, the LRP4 mutations found in our patients may disrupt Wnt-Bmp-Shh signaling, thereby resulting in dental anomalies and oral exostoses. Root maldevelopment in the patients suggests an important role of LRP4 in root morphogenesis.
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Affiliation(s)
- Piranit Kantaputra
- Center of Excellence in Medical Genetics Research, Chiang Mai University, Chiang Mai, Thailand
- Division of Pediatric Dentistry, Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand
| | | | | | - Ploy Adisornkanj
- Center of Excellence in Medical Genetics Research, Chiang Mai University, Chiang Mai, Thailand
- Division of Pediatric Dentistry, Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand
- Dental Department, Sawang Daen Din Crown Prince Hospital, Sakon Nakhon, Thailand
| | | | - Massupa Kaewgaya
- Center of Excellence in Medical Genetics Research, Chiang Mai University, Chiang Mai, Thailand
| | - Worrachet Intachai
- Center of Excellence in Medical Genetics Research, Chiang Mai University, Chiang Mai, Thailand
| | - Bjorn Olsen
- Department of Developmental Biology, Harvard School of Dental Medicine, Harvard University, Boston, Massachusetts, USA
| | - Chumpol Ngamphiw
- National Biobank of Thailand, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathum Thani, Thailand
| | - Chidchanok Leethanakul
- Orthodontic Section, Department of Preventive Dentistry, Faculty of Dentistry, Prince of Songkla University, Songkhla, Thailand
| | - Peeranat Jatooratthawichot
- School of Chemistry, Institute of Science, and Center for Biomolecular Structure, Function and Application, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - James R Ketudat Cairns
- School of Chemistry, Institute of Science, and Center for Biomolecular Structure, Function and Application, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Sissades Tongsima
- National Biobank of Thailand, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathum Thani, Thailand
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2
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Akagi K, Baba S, Fujita H, Fuseya Y, Yoshinaga D, Kubota H, Kume E, Fukumura F, Matsuda K, Tanaka T, Hirata T, Saito MK, Iwai K, Takita J. HOIL-1L deficiency induces cell cycle alteration which causes immaturity of skeletal muscle and cardiomyocytes. Sci Rep 2024; 14:8871. [PMID: 38632277 PMCID: PMC11024103 DOI: 10.1038/s41598-024-57504-1] [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: 12/03/2023] [Accepted: 03/19/2024] [Indexed: 04/19/2024] Open
Abstract
HOIL-1L deficiency was recently reported to be one of the causes of myopathy and dilated cardiomyopathy (DCM). However, the mechanisms by which myopathy and DCM develop have not been clearly elucidated. Here, we sought to elucidate these mechanisms using the murine myoblast cell line C2C12 and disease-specific human induced pluripotent stem cells (hiPSCs). Myotubes differentiated from HOIL-1L-KO C2C12 cells exhibited deteriorated differentiation and mitotic cell accumulation. CMs differentiated from patient-derived hiPSCs had an abnormal morphology with a larger size and were excessively multinucleated compared with CMs differentiated from control hiPSCs. Further analysis of hiPSC-derived CMs showed that HOIL-1L deficiency caused cell cycle alteration and mitotic cell accumulation. These results demonstrate that abnormal cell maturation possibly contribute to the development of myopathy and DCM. In conclusion, HOIL-1L is an important intrinsic regulator of cell cycle-related myotube and CM maturation and cell proliferation.
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Affiliation(s)
- Kentaro Akagi
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Shiro Baba
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan.
| | - Hiroaki Fujita
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto City, Kyoto, 606-8501, Japan
| | - Yasuhiro Fuseya
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto City, Kyoto, 606-8501, Japan
| | - Daisuke Yoshinaga
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Hirohito Kubota
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto City, Kyoto, 606-8501, Japan
| | - Eitaro Kume
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Fumiaki Fukumura
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Koichi Matsuda
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Takayuki Tanaka
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Takuya Hirata
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Megumu K Saito
- Department of Clinical Application, Center for iPS Cell Research and Application (CiRA), Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
| | - Kazuhiro Iwai
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto City, Kyoto, 606-8501, Japan
| | - Junko Takita
- Department of Pediatrics, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto City, Kyoto, 606-8507, Japan
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Ghosh DK, Udupa P, Shrikondawar AN, Bhavani GS, Shah H, Ranjan A, Girisha KM. Mutant MESD links cellular stress to type I collagen aggregation in osteogenesis imperfecta type XX. Matrix Biol 2023; 115:81-106. [PMID: 36526215 PMCID: PMC7615836 DOI: 10.1016/j.matbio.2022.12.001] [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: 08/24/2022] [Revised: 11/19/2022] [Accepted: 12/12/2022] [Indexed: 12/15/2022]
Abstract
Aberrant forms of endoplasmic reticulum (ER)-resident chaperones are implicated in loss of protein quality control in rare diseases. Here we report a novel mutation (p.Asp233Asn) in the ER retention signal of MESD by whole exome sequencing of an individual diagnosed with osteogenesis imperfecta (OI) type XX. While MESDD233N has similar stability and chaperone activity as wild-type MESD, its mislocalization to cytoplasm leads to imbalance of ER proteostasis, resulting in improper folding and aggregation of proteins, including LRP5 and type I collagen. Aggregated LRP5 loses its plasma membrane localization to disrupt the expression of WNT-responsive genes, such as BMP2, BMP4, in proband fibroblasts. We show that MESD is a direct chaperone of pro-α1(I) [COL1A1], and absence of MESDD233N in ER results in cytosolic type I collagen aggregates that remain mostly not secreted. While cytosolic type I collagen aggregates block the intercellular nanotubes, decreased extracellular type I collagen also results in loss of interaction of ITGB1 with type I collagen and weaker attachment of fibroblasts to matrix. Although proband fibroblasts show increased autophagy to degrade the aggregated type I collagen, an overall cellular stress overwhelms the proband fibroblasts. In summary, we present an essential chaperone function of MESD for LRP5 and type I collagen and demonstrating how the D233N mutation in MESD correlates with impaired WNT signaling and proteostasis in OI.
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Affiliation(s)
- Debasish Kumar Ghosh
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India.
| | - Prajna Udupa
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Akshaykumar Nanaji Shrikondawar
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500039, Telangana, India
| | - Gandham SriLakshmi Bhavani
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Hitesh Shah
- Department of Pediatric Orthopedics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Akash Ranjan
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500039, Telangana, India
| | - Katta M Girisha
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India.
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DePew AT, Mosca TJ. Conservation and Innovation: Versatile Roles for LRP4 in Nervous System Development. J Dev Biol 2021; 9:9. [PMID: 33799485 PMCID: PMC8006230 DOI: 10.3390/jdb9010009] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/09/2021] [Accepted: 03/11/2021] [Indexed: 02/07/2023] Open
Abstract
As the nervous system develops, connections between neurons must form to enable efficient communication. This complex process of synaptic development requires the coordination of a series of intricate mechanisms between partner neurons to ensure pre- and postsynaptic differentiation. Many of these mechanisms employ transsynaptic signaling via essential secreted factors and cell surface receptors to promote each step of synaptic development. One such cell surface receptor, LRP4, has emerged as a synaptic organizer, playing a critical role in conveying extracellular signals to initiate diverse intracellular events during development. To date, LRP4 is largely known for its role in development of the mammalian neuromuscular junction, where it functions as a receptor for the synaptogenic signal Agrin to regulate synapse development. Recently however, LRP4 has emerged as a synapse organizer in the brain, where new functions for the protein continue to arise, adding further complexity to its already versatile roles. Additional findings indicate that LRP4 plays a role in disorders of the nervous system, including myasthenia gravis, amyotrophic lateral sclerosis, and Alzheimer's disease, demonstrating the need for further study to understand disease etiology. This review will highlight our current knowledge of how LRP4 functions in the nervous system, focusing on the diverse developmental roles and different modes this essential cell surface protein uses to ensure the formation of robust synaptic connections.
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Affiliation(s)
| | - Timothy J. Mosca
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA;
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5
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Frykman H, Kumar P, Oger J. Immunopathology of Autoimmune Myasthenia Gravis: Implications for Improved Testing Algorithms and Treatment Strategies. Front Neurol 2020; 11:596621. [PMID: 33362698 PMCID: PMC7755715 DOI: 10.3389/fneur.2020.596621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/19/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is a heterogeneous condition, characterized by autoantibodies (Abs) that target functionally important structures within neuromuscular junctions (NMJ), thus affecting nerve-to-muscle transmission. MG patients are more often now subgrouped based on the profile of serum autoantibodies, which segregate with clinical presentation, immunopathology, and their response to therapies. The serological testing plays an essential role in confirming MG diagnosis and guiding disease management, although a small percentage of MG patients remain negative for antibodies. With the advancements in new highly effective pathophysiologically-specific immunotherapeutic options, it has become increasingly important to identify the specific Abs responsible for the pathogenicity in individual MG patients. There are several new assays and protocols being developed for the improved detection of Abs in MG patients. This review focuses on the divergent immunopathological mechanisms in MG, and discusses their relevance to improved diagnostic and treatment. We propose a comprehensive "reflex testing," algorithm for the presence of MG autoantibodies, and foresee that in the near future, the convenience and specificity of novel assays will permit the clinicians to consider them into routine systematic testing, thus stimulating laboratories to make these tests available. Moreover, adopting treatment driven testing algorithms will be crucial to identify subgroups of patients potentially benefiting from novel immunotherapies for MG.
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Affiliation(s)
- Hans Frykman
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Pankaj Kumar
- BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Joel Oger
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
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6
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Dennis EP, Edwards SM, Jackson RM, Hartley CL, Tsompani D, Capulli M, Teti A, Boot-Handford RP, Young DA, Piróg KA, Briggs MD. CRELD2 Is a Novel LRP1 Chaperone That Regulates Noncanonical WNT Signaling in Skeletal Development. J Bone Miner Res 2020; 35:1452-1469. [PMID: 32181934 DOI: 10.1002/jbmr.4010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/02/2020] [Accepted: 03/10/2020] [Indexed: 12/12/2022]
Abstract
Cysteine-rich with epidermal growth factor (EGF)-like domains 2 (CRELD2) is an endoplasmic reticulum (ER)-resident chaperone highly activated under ER stress in conditions such as chondrodysplasias; however, its role in healthy skeletal development is unknown. We show for the first time that cartilage-specific deletion of Creld2 results in disrupted endochondral ossification and short limbed dwarfism, whereas deletion of Creld2 in bone results in osteopenia, with a low bone density and altered trabecular architecture. Our study provides the first evidence that CRELD2 promotes the differentiation and maturation of skeletal cells by modulating noncanonical WNT4 signaling regulated by p38 MAPK. Furthermore, we show that CRELD2 is a novel chaperone for the receptor low-density lipoprotein receptor-related protein 1 (LRP1), promoting its transport to the cell surface, and that LRP1 directly regulates WNT4 expression in chondrocytes through TGF-β1 signaling. Therefore, our data provide a novel link between an ER-resident chaperone and the essential WNT signaling pathways active during skeletal differentiation that could be applicable in other WNT-responsive tissues. © 2020 American Society for Bone and Mineral Research. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research..
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Affiliation(s)
- Ella P Dennis
- Biosciences Institute, Newcastle University, International Centre for Life, Newcastle Upon Tyne, UK
| | - Sarah M Edwards
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester, UK
| | - Robert M Jackson
- Biosciences Institute, Newcastle University, International Centre for Life, Newcastle Upon Tyne, UK
| | - Claire L Hartley
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester, UK
| | - Dimitra Tsompani
- Biosciences Institute, Newcastle University, International Centre for Life, Newcastle Upon Tyne, UK
| | - Mattia Capulli
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Anna Teti
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | | | - David A Young
- Biosciences Institute, Newcastle University, International Centre for Life, Newcastle Upon Tyne, UK
| | - Katarzyna A Piróg
- Biosciences Institute, Newcastle University, International Centre for Life, Newcastle Upon Tyne, UK
| | - Michael D Briggs
- Biosciences Institute, Newcastle University, International Centre for Life, Newcastle Upon Tyne, UK
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7
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Takamori M. Myasthenia Gravis: From the Viewpoint of Pathogenicity Focusing on Acetylcholine Receptor Clustering, Trans-Synaptic Homeostasis and Synaptic Stability. Front Mol Neurosci 2020; 13:86. [PMID: 32547365 PMCID: PMC7272578 DOI: 10.3389/fnmol.2020.00086] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022] Open
Abstract
Myasthenia gravis (MG) is a disease of the postsynaptic neuromuscular junction (NMJ) where nicotinic acetylcholine (ACh) receptors (AChRs) are targeted by autoantibodies. Search for other pathogenic antigens has detected the antibodies against muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein-related protein 4 (Lrp4), both causing pre- and post-synaptic impairments. Agrin is also suspected as a fourth pathogen. In a complex NMJ organization centering on MuSK: (1) the Wnt non-canonical pathway through the Wnt-Lrp4-MuSK cysteine-rich domain (CRD)-Dishevelled (Dvl, scaffold protein) signaling acts to form AChR prepatterning with axonal guidance; (2) the neural agrin-Lrp4-MuSK (Ig1/2 domains) signaling acts to form rapsyn-anchored AChR clusters at the innervated stage of muscle; (3) adaptor protein Dok-7 acts on MuSK activation for AChR clustering from “inside” and also on cytoskeleton to stabilize AChR clusters by the downstream effector Sorbs1/2; (4) the trans-synaptic retrograde signaling contributes to the presynaptic organization via: (i) Wnt-MuSK CRD-Dvl-β catenin-Slit 2 pathway; (ii) Lrp4; and (iii) laminins. The presynaptic Ca2+ homeostasis conditioning ACh release is modified by autoreceptors such as M1-type muscarinic AChR and A2A adenosine receptors. The post-synaptic structure is stabilized by: (i) laminin-network including the muscle-derived agrin; (ii) the extracellular matrix proteins (including collagen Q/perlecan and biglycan which link to MuSK Ig1 domain and CRD); and (iii) the dystrophin-associated glycoprotein complex. The study on MuSK ectodomains (Ig1/2 domains and CRD) recognized by antibodies suggested that the MuSK antibodies were pathologically heterogeneous due to their binding to multiple functional domains. Focussing one of the matrix proteins, biglycan which functions in the manner similar to collagen Q, our antibody assay showed the negative result in MG patients. However, the synaptic stability may be impaired by antibodies against MuSK ectodomains because of the linkage of biglycan with MuSK Ig1 domain and CRD. The pathogenic diversity of MG is discussed based on NMJ signaling molecules.
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Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells 2019; 8:cells8070671. [PMID: 31269763 PMCID: PMC6678492 DOI: 10.3390/cells8070671] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.
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Abstract
OBJECTIVES Congenital myasthenic syndromes (CMSs) are a genotypically and phenotypically heterogeneous group of neuromuscular disorders, which have in common an impaired neuromuscular transmission. Since the field of CMSs is steadily expanding, the present review aimed at summarizing and discussing current knowledge and recent advances concerning the etiology, clinical presentation, diagnosis, and treatment of CMSs. METHODS Systematic literature review. RESULTS Currently, mutations in 32 genes are made responsible for autosomal dominant or autosomal recessive CMSs. These mutations concern 8 presynaptic, 4 synaptic, 15 post-synaptic, and 5 glycosilation proteins. These proteins function as ion-channels, enzymes, or structural, signalling, sensor, or transporter proteins. The most common causative genes are CHAT, COLQ, RAPSN, CHRNE, DOK7, and GFPT1. Phenotypically, these mutations manifest as abnormal fatigability or permanent or fluctuating weakness of extra-ocular, facial, bulbar, axial, respiratory, or limb muscles, hypotonia, or developmental delay. Cognitive disability, dysmorphism, neuropathy, or epilepsy are rare. Low- or high-frequency repetitive nerve stimulation may show an abnormal increment or decrement, and SF-EMG an increased jitter or blockings. Most CMSs respond favourably to acetylcholine-esterase inhibitors, 3,4-diamino-pyridine, salbutamol, albuterol, ephedrine, fluoxetine, or atracurium. CONCLUSIONS CMSs are an increasingly recognised group of genetically transmitted defects, which usually respond favorably to drugs enhancing the neuromuscular transmission. CMSs need to be differentiated from neuromuscular disorders due to muscle or nerve dysfunction.
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Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Messerli Institute, Veterinary University of Vienna, Postfach 20, 1180, Vienna, Austria.
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Saadane A, Petrov A, Mast N, El-Darzi N, Dao T, Alnemri A, Song Y, Dunaief JL, Pikuleva IA. Mechanisms that minimize retinal impact of apolipoprotein E absence. J Lipid Res 2018; 59:2368-2382. [PMID: 30333155 DOI: 10.1194/jlr.m090043] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 10/17/2018] [Indexed: 01/28/2023] Open
Abstract
Apolipoprotein E (APOE) is a component of lipid-transporting particles and a recognition ligand for receptors, which bind these particles. The APOE isoform ε2 is a risk factor for age-related macular degeneration; nevertheless, APOE absence in humans and mice does not significantly affect the retina. We found that retinal cholesterol biosynthesis and the levels of retinal cholesterol were increased in Apoe-/- mice, whereas cholesterol elimination by metabolism was decreased. No focal cholesterol deposits were observed in the Apoe-/- retina. Retinal proteomics identified the most abundant cholesterol-related proteins in WT mice and revealed that, of these cholesterol-related proteins, only APOA4 had increased expression in the Apoe-/- retina. In addition, there were changes in retinal abundance of proteins involved in proinflammatory and antiinflammatory responses, cellular cytoskeleton maintenance, vesicular traffic, and retinal iron homeostasis. The data obtained indicate that when APOE is absent, particles containing APOA1, APOA4, and APOJ still transport cholesterol in the intraretinal space, but these particles are not taken up by retinal cells. Therefore, cholesterol biosynthesis inside retinal cells increase, whereas metabolism to oxysterols decreases to prevent cells from cholesterol depletion. These and other compensatory changes underlie only a minor retinal phenotype in Apoe-/- mice.
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Affiliation(s)
- Aicha Saadane
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Alexey Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Tung Dao
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Ahab Alnemri
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Ying Song
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Joshua L Dunaief
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
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Affiliation(s)
- Lei Li
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
| | - Lin Mei
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
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12
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Mori S, Motohashi N, Takashima R, Kishi M, Nishimune H, Shigemoto K. Immunization of mice with LRP4 induces myasthenia similar to MuSK-associated myasthenia gravis. Exp Neurol 2017; 297:158-167. [PMID: 28823823 DOI: 10.1016/j.expneurol.2017.08.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 08/11/2017] [Accepted: 08/11/2017] [Indexed: 12/21/2022]
Abstract
Since the first report of experimental animal models of myasthenia gravis (MG) with autoantibodies against low-density lipoprotein receptor-related protein 4 (LRP4), there have not been any major reports replicating the pathogenicity of anti-LRP4 antibodies (Abs). Recent clinical studies have cast doubt on the specificity and pathogenicity of anti-LRP4 antibodies for MG, highlighting the need for further research. In this study, we purified antigens corresponding to the extracellular region of human LRP4 stably expressed with chaperones in 293 cells and used these antigens to immunize female A/J mice. Immunization with LRP4 protein caused mice to develop myasthenia having similar electrophysiological and histological features as are observed in MG patients with circulating Abs against muscle-specific kinase (MuSK). Our results clearly demonstrate that active immunization of mice with LRP4 proteins causes myasthenia similar to the MG induced by anti-MuSK Abs. Further experimental and clinical studies are required to prove the pathogenicity of anti-LRP4 Abs in MG patients.
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Affiliation(s)
- Shuuichi Mori
- Department of Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Norio Motohashi
- Department of Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Rumi Takashima
- Department of Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Masahiko Kishi
- Department of Internal Medicine, Toho University Sakura Medical Center, Chiba, Japan
| | - Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, United States
| | - Kazuhiro Shigemoto
- Department of Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
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Mesd extrinsically promotes phagocytosis by retinal pigment epithelial cells. Cell Biol Toxicol 2016; 32:347-58. [PMID: 27184668 DOI: 10.1007/s10565-016-9339-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 05/09/2016] [Indexed: 01/09/2023]
Abstract
Phagocytosis is a critical process to maintain tissue homeostasis. In the retina, photoreceptor cells renew their photoexcitability by shedding photoreceptor outer segments (POSs) in a diurnal rhythm. Shed POSs are phagocytosed by retinal pigment epithelial (RPE) cells to prevent debris accumulation, retinal degeneration, and blindness. Phagocytosis ligands are the key to understanding how RPE recognizes shed POSs. Here, we characterized mesoderm development candidate 2 (Mesd or Mesdc2), an endoplasmic reticulum (ER) chaperon for low-density lipoprotein receptor-related proteins (LRPs), to extrinsically promote RPE phagocytosis. The results showed that Mesd stimulated phagocytosis of fluorescence-labeled POS vesicles by D407 RPE cells. Ingested POSs were partially degraded within 3 h in some RPE cells to dispense undegradable fluorophore throughout the cytoplasm. Internalized POSs were colocalized with phagosome biomarker Rab7, suggesting that Mesd-mediated engulfment is involved in a phagocytosis pathway. Mesd also facilitated phagocytosis of POSs by primary RPE cells. Mesd bound to unknown phagocytic receptor(s) on RPE cells. Mesd was detected in the cytoplasm, but not nuclei, of different retinal layers and is predominantly expressed in the ER-free cellular compartment of POSs. Mesd was not secreted into medium from healthy cells but passively released from apoptotic cells with increased membrane permeability. Released Mesd selectively bound to the surface of POS vesicles and apoptotic cells, but not healthy cells. These results suggest that Mesd may be released from and bind to shed POSs to facilitate their phagocytic clearance.
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