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Hellicar J, Stevenson NL, Stephens DJ, Lowe M. Supply chain logistics - the role of the Golgi complex in extracellular matrix production and maintenance. J Cell Sci 2022; 135:273996. [PMID: 35023559 PMCID: PMC8767278 DOI: 10.1242/jcs.258879] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The biomechanical and biochemical properties of connective tissues are determined by the composition and quality of their extracellular matrix. This, in turn, is highly dependent on the function and organisation of the secretory pathway. The Golgi complex plays a vital role in directing matrix output by co-ordinating the post-translational modification and proteolytic processing of matrix components prior to their secretion. These modifications have broad impacts on the secretion and subsequent assembly of matrix components, as well as their function in the extracellular environment. In this Review, we highlight the role of the Golgi in the formation of an adaptable, healthy matrix, with a focus on proteoglycan and procollagen secretion as example cargoes. We then discuss the impact of Golgi dysfunction on connective tissue in the context of human disease and ageing.
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Affiliation(s)
- John Hellicar
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK.,Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Proteos, Singapore, 138673
| | - Nicola L Stevenson
- Cell Biology Laboratories, School of Biochemistry, Faculty of Life Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, UK
| | - David J Stephens
- Cell Biology Laboratories, School of Biochemistry, Faculty of Life Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, UK
| | - Martin Lowe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
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2
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Copper in tumors and the use of copper-based compounds in cancer treatment. J Inorg Biochem 2021; 226:111634. [PMID: 34740035 DOI: 10.1016/j.jinorgbio.2021.111634] [Citation(s) in RCA: 101] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 10/05/2021] [Accepted: 10/12/2021] [Indexed: 12/12/2022]
Abstract
Copper homeostasis is strictly regulated by protein transporters and chaperones, to allow its correct distribution and avoid uncontrolled redox reactions. Several studies address copper as involved in cancer development and spreading (epithelial to mesenchymal transition, angiogenesis). However, being endogenous and displaying a tremendous potential to generate free radicals, copper is a perfect candidate, once opportunely complexed, to be used as a drug in cancer therapy with low adverse effects. Copper ions can be modulated by the organic counterpart, after complexed to their metalcore, either in redox potential or geometry and consequently reactivity. During the last four decades, many copper complexes were studied regarding their reactivity toward cancer cells, and many of them could be a drug choice for phase II and III in cancer therapy. Also, there is promising evidence of using 64Cu in nanoparticles as radiopharmaceuticals for both positron emission tomography (PET) imaging and treatment of hypoxic tumors. However, few compounds have gone beyond testing in animal models, and none of them got the status of a drug for cancer chemotherapy. The main challenge is their solubility in physiological buffers and their different and non-predictable mechanism of action. Moreover, it is difficult to rationalize a structure-based activity for drug design and delivery. In this review, we describe the role of copper in cancer, the effects of copper-complexes on tumor cell death mechanisms, and point to the new copper complexes applicable as drugs, suggesting that they may represent at least one component of a multi-action combination in cancer therapy.
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3
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Squitti R, Faller P, Hureau C, Granzotto A, White AR, Kepp KP. Copper Imbalance in Alzheimer's Disease and Its Link with the Amyloid Hypothesis: Towards a Combined Clinical, Chemical, and Genetic Etiology. J Alzheimers Dis 2021; 83:23-41. [PMID: 34219710 DOI: 10.3233/jad-201556] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The cause of Alzheimer's disease (AD) is incompletely defined. To date, no mono-causal treatment has so far reached its primary clinical endpoints, probably due to the complexity and diverse neuropathology contributing to the neurodegenerative process. In the present paper, we describe the plausible etiological role of copper (Cu) imbalance in the disease. Cu imbalance is strongly associated with neurodegeneration in dementia, but a complete biochemical etiology consistent with the clinical, chemical, and genetic data is required to support a causative association, rather than just correlation with disease. We hypothesize that a Cu imbalance in the aging human brain evolves as a gradual shift from bound metal ion pools, associated with both loss of energy production and antioxidant function, to pools of loosely bound metal ions, involved in gain-of-function oxidative stress, a shift that may be aggravated by chemical aging. We explain how this may cause mitochondrial deficits, energy depletion of high-energy demanding neurons, and aggravated protein misfolding/oligomerization to produce different clinical consequences shaped by the severity of risk factors, additional comorbidities, and combinations with other types of pathology. Cu imbalance should be viewed and integrated with concomitant genetic risk factors, aging, metabolic abnormalities, energetic deficits, neuroinflammation, and the relation to tau, prion proteins, α-synuclein, TAR DNA binding protein-43 (TDP-43) as well as systemic comorbidity. Specifically, the Amyloid Hypothesis is strongly intertwined with Cu imbalance because amyloid-β protein precursor (AβPP)/Aβ are probable Cu/Zn binding proteins with a potential role as natural Cu/Zn buffering proteins (loss of function), and via the plausible pathogenic role of Cu-Aβ.
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Affiliation(s)
- Rosanna Squitti
- Molecular Markers Laboratory, IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy
| | - Peter Faller
- Institut de Chimie, UMR 7177, CNRS, Université de Strasbourg, Strasbourg, France
| | | | - Alberto Granzotto
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA, USA.,Center for Advanced Sciences and Technology (CAST), University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy.,Department of Neuroscience, Imaging, and Clinical Sciences (DNISC), Laboratory of Molecular Neurology, University "G. d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | - Anthony R White
- Mental Health Program, QIMR Berghofer Medical Research Institute, Herston, Brisbane, QLD, Australia
| | - Kasper P Kepp
- DTU Chemistry, Technical University of Denmark, Lyngby, Denmark
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4
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Pili Torti: A Feature of Numerous Congenital and Acquired Conditions. J Clin Med 2021; 10:jcm10173901. [PMID: 34501349 PMCID: PMC8432236 DOI: 10.3390/jcm10173901] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/20/2021] [Accepted: 08/25/2021] [Indexed: 02/06/2023] Open
Abstract
Pili torti is a rare condition characterized by the presence of the hair shaft, which is flattened at irregular intervals and twisted 180° along its long axis. It is a form of hair shaft disorder with increased fragility. The condition is classified into inherited and acquired. Inherited forms may be either isolated or associated with numerous genetic diseases or syndromes (e.g., Menkes disease, Björnstad syndrome, Netherton syndrome, and Bazex-Dupré-Christol syndrome). Moreover, pili torti may be a feature of various ectodermal dysplasias (such as Rapp-Hodgkin syndrome and Ankyloblepharon-ectodermal defects-cleft lip/palate syndrome). Acquired pili torti was described in numerous forms of alopecia (e.g., lichen planopilaris, discoid lupus erythematosus, dissecting cellulitis, folliculitis decalvans, alopecia areata) as well as neoplastic and systemic diseases (such as cutaneous T-cell lymphoma, scalp metastasis of breast cancer, anorexia nervosa, malnutrition, cataracts, and chronic graft-vs.-host disease). The condition may also be induced by several drugs (epidermal growth factor receptor inhibitors, oral retinoids, sodium valproate, and carbamide perhydrate). The diagnosis of pili torti is based on trichoscopic or microscopic examination. As pili torti is a marker of numerous congenital and acquired disorders, in every case, the search for the signs of underlying conditions is recommended.
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5
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Møller LB, Mogensen M, Weaver DD, Pedersen PA. Occipital Horn Syndrome as a Result of Splice Site Mutations in ATP7A. No Activity of ATP7A Splice Variants Missing Exon 10 or Exon 15. Front Mol Neurosci 2021; 14:532291. [PMID: 33967692 PMCID: PMC8097048 DOI: 10.3389/fnmol.2021.532291] [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: 10/14/2020] [Accepted: 03/12/2021] [Indexed: 11/13/2022] Open
Abstract
Disease-causing variants in ATP7A lead to two different phenotypes associated with copper deficiency; a lethal form called Menkes disease (MD), leading to early death, and a much milder form called occipital horn syndrome (OHS). Some investigators have proposed that an ATP7A transcript missing exon 10 leads to a partly active protein product resulting in the OHS phenotype. Here, we describe an individual with OHS, a biology professor, who survived until age 62 despite a splice site mutation, leading to skipping of exon 15. ATP7A transcripts missing exon 10, or exon 15 preserve the reading frame, but it is unknown if either of these alternative transcripts encode functional protein variants. We have investigated the molecular consequence of splice site mutations leading to skipping of exon 10 or exon 15 which have been identified in individuals with OHS, or MD. By comparing ATP7A expression in fibroblasts from three individuals with OHS (OHS-fibroblasts) to ATP7A expression in fibroblasts from two individuals with MD (MD-fibroblasts), we demonstrate that transcripts missing either exon 10 or exon 15 were present in similar amounts in OHS-fibroblasts and MD-fibroblasts. No ATP7A protein encoded from these transcripts could be detected in the OHS and MD fibroblast. These results, combined with the observation that constructs encoding ATP7A cDNA sequences missing either exon 10, or exon 15 were unable to complement the high iron requirement of the ccc2Δ yeast strain, provide evidence that neither a transcript missing exon 10 nor a transcript missing exon 15 results in functional ATP7A protein. In contrast, higher amounts of wild-type ATP7A transcript were present in the OHS-fibroblasts compared with the MD-fibroblasts. We found that the MD-fibroblasts contained between 0 and 0.5% of wild-type ATP7A transcript, whereas the OHS-fibroblasts contained between 3 and 5% wild-type transcripts compared with the control fibroblasts. In summary these results indicate that protein variants encoded by ATP7A transcripts missing either exon 10 or exon 15 are not functional and not responsible for the OHS phenotype. In contrast, expression of only 3-5% of wild-type transcript compared with the controls permits the OHS phenotype.
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Affiliation(s)
- Lisbeth Birk Møller
- Department of Clinical Genetics, Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
| | - Mie Mogensen
- Department of Clinical Genetics, Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Glostrup, Denmark
| | - David D Weaver
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, United States
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6
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Genetic Disorders Associated with Metal Metabolism. Cells 2019; 8:cells8121598. [PMID: 31835360 PMCID: PMC6952812 DOI: 10.3390/cells8121598] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 12/04/2019] [Accepted: 12/05/2019] [Indexed: 12/12/2022] Open
Abstract
Genetic disorders associated with metal metabolism form a large group of disorders and mostly result from defects in the proteins/enzymes involved in nutrient metabolism and energy production. These defects can affect different metabolic pathways and cause mild to severe disorders related to metal metabolism. Some disorders have moderate to severe clinical consequences. In severe cases, these elements accumulate in different tissues and organs, particularly the brain. As they are toxic and interfere with normal biological functions, the severity of the disorder increases. However, the human body requires a very small amount of these elements, and a deficiency of or increase in these elements can cause different genetic disorders to occur. Some of the metals discussed in the present review are copper, iron, manganese, zinc, and selenium. These elements may play a key role in the pathology and physiology of the nervous system.
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7
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Beyens A, Van Meensel K, Pottie L, De Rycke R, De Bruyne M, Baeke F, Hoebeke P, Plasschaert F, Loeys B, De Schepper S, Symoens S, Callewaert B. Defining the Clinical, Molecular and Ultrastructural Characteristics in Occipital Horn Syndrome: Two New Cases and Review of the Literature. Genes (Basel) 2019; 10:genes10070528. [PMID: 31336972 PMCID: PMC6678539 DOI: 10.3390/genes10070528] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 07/10/2019] [Accepted: 07/11/2019] [Indexed: 12/15/2022] Open
Abstract
Occipital horn syndrome (OHS) is a rare connective tissue disorder caused by pathogenic variants in ATP7A, encoding a copper transporter. The main clinical features, including cutis laxa, bony exostoses, and bladder diverticula are attributed to a decreased activity of lysyl oxidase (LOX), a cupro-enzyme involved in collagen crosslinking. The absence of large case series and natural history studies precludes efficient diagnosis and management of OHS patients. This study describes the clinical and molecular characteristics of two new patients and 32 patients previously reported in the literature. We report on the need for long-term specialized care and follow-up, in which MR angiography, echocardiography and spirometry should be incorporated into standard follow-up guidelines for OHS patients, next to neurodevelopmental, orthopedic and urological follow-up. Furthermore, we report on ultrastructural abnormalities including increased collagen diameter, mild elastic fiber abnormalities and multiple autophagolysosomes reflecting the role of lysyl oxidase and defective ATP7A trafficking as pathomechanisms of OHS.
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Affiliation(s)
- Aude Beyens
- Center for Medical Genetics Ghent, Ghent University Hospital, 9000 Ghent, Belgium
- Department of Dermatology, Ghent University Hospital, 9000 Ghent, Belgium
| | - Kyaran Van Meensel
- Center for Medical Genetics Ghent, Ghent University Hospital, 9000 Ghent, Belgium
| | - Lore Pottie
- Center for Medical Genetics Ghent, Ghent University Hospital, 9000 Ghent, Belgium
| | - Riet De Rycke
- Department for Biomedical Molecular Biology, Ghent University, 9000 Ghent, Belgium
- VIB Center for Inflammation Research, 9000 Ghent, Belgium
- Ghent University Expertise Centre for Transmission Electron Microscopy and VIB BioImaging Core, 9000 Ghent, Belgium
| | - Michiel De Bruyne
- Department for Biomedical Molecular Biology, Ghent University, 9000 Ghent, Belgium
- VIB Center for Inflammation Research, 9000 Ghent, Belgium
- Ghent University Expertise Centre for Transmission Electron Microscopy and VIB BioImaging Core, 9000 Ghent, Belgium
| | - Femke Baeke
- Department for Biomedical Molecular Biology, Ghent University, 9000 Ghent, Belgium
- VIB Center for Inflammation Research, 9000 Ghent, Belgium
- Ghent University Expertise Centre for Transmission Electron Microscopy and VIB BioImaging Core, 9000 Ghent, Belgium
| | - Piet Hoebeke
- Department of Urology, Ghent University Hospital, 9000 Ghent, Belgium
| | - Frank Plasschaert
- Department of Orthopedic Surgery, Ghent University Hospital, 9000 Ghent, Belgium
| | - Bart Loeys
- Center for Medical Genetics, University of Antwerp/Antwerp University Hospital, Antwerp, Belgium
| | - Sofie De Schepper
- Department of Dermatology, Ghent University Hospital, 9000 Ghent, Belgium
| | - Sofie Symoens
- Center for Medical Genetics Ghent, Ghent University Hospital, 9000 Ghent, Belgium
| | - Bert Callewaert
- Center for Medical Genetics Ghent, Ghent University Hospital, 9000 Ghent, Belgium.
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8
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Moizard MP, Ronce N, Blesson S, Bieth E, Burglen L, Mignot C, Mortemousque I, Marmin N, Dessay B, Danesino C, Feillet F, Castelnau P, Toutain A, Moraine C, Raynaud M. Twenty-five novel mutations including duplications in the ATP7A gene. Clin Genet 2015; 79:243-53. [PMID: 21208200 DOI: 10.1111/j.1399-0004.2010.01461.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Twenty-five novel mutations including duplications in the ATP7A gene. Menkes disease (MD) and occipital horn syndrome (OHS) are allelic X-linked recessive copper deficiency disorders resulting from ATP7A gene mutations. MD is a severe condition leading to progressive neurological degeneration and death in early childhood, whereas OHS has a milder phenotype with mainly connective tissue abnormalities. Until now, molecular analyses have revealed only deletions and point mutations in both diseases. This study reports new molecular data in a series of 40 patients referred for either MD or OHS. We describe 23 point mutations (9 missense mutations, 7 splice site variants, 4 nonsense mutations, and 3 small insertions or deletions) and 7 intragenic deletions. Of these, 18 point mutations and 3 deletions are novel. Furthermore, our finding of four whole exon duplications enlarges the mutation spectrum in the ATP7A gene. ATP7A alterations were found in 85% of cases. Of these alterations, two thirds were point mutations and the remaining one third consisted of large rearrangements. We found that 66.6% of point mutations resulted in impaired ATP7A transcript splicing, a phenomenon more frequent than expected. This finding enabled us to confirm the pathogenic role of ATP7A mutations, particularly in missense and splice site variants.
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Affiliation(s)
- M-P Moizard
- CHRU de Tours, Service de Génétique, Tours, F-37044, France INSERM U930, Tours, F-37044, France CHU Hôpital Purpan, Service de Génétique médicale, Toulouse, F-31059, France CHU Hôpital d'Enfants Armand-Trousseau, AP-HP, Service de Génétique et Embryologie médicales, Paris, F-75571, France CHU Hôpital d'Enfants Armand-Trousseau, AP-HP, Service de Neuropédiatrie, Paris, F-75012, France Genetica Medica, Università di Pavia, Fondazione IRCCS S. Matteo, Pavia, I-27100, Italie Centre de Référence des Maladies Héréditaires du Métabolisme, INSERM U954. Hôpital d'Enfants, Vandoeuvre les Nancy, F-54511, France CHRU de Tours, Service de Neuropédiatrie, Tours, F-37044 France; Université François Rabelais Tours, F-37044, France
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9
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Tümer Z. An overview and update of ATP7A mutations leading to Menkes disease and occipital horn syndrome. Hum Mutat 2013; 34:417-29. [PMID: 23281160 DOI: 10.1002/humu.22266] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 12/11/2012] [Indexed: 01/28/2023]
Abstract
Menkes disease (MD) is a lethal multisystemic disorder of copper metabolism. Progressive neurodegeneration and connective tissue disturbances, together with the peculiar "kinky" hair, are the main manifestations. MD is inherited as an X-linked recessive trait, and as expected the vast majority of patients are males. MD occurs because of mutations in the ATP7A gene and the vast majority of ATP7A mutations are intragenic mutations or partial gene deletions. ATP7A is an energy-dependent transmembrane protein, which is involved in the delivery of copper to the secreted copper enzymes and in the export of surplus copper from cells. Severely affected MD patients die usually before the third year of life. A cure for the disease does not exist, but very early copper-histidine treatment may correct some of the neurological symptoms. This study reviews 274 published and 18 novel disease causing mutations identified in 370 unrelated MD patients, nonpathogenic variants of ATP7A, functional studies of the ATP7A mutations, and animal models of MD.
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Affiliation(s)
- Zeynep Tümer
- Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Rigshospitalet, Glostrup, Denmark.
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10
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Berk DR, Bentley DD, Bayliss SJ, Lind A, Urban Z. Cutis laxa: A review. J Am Acad Dermatol 2012; 66:842.e1-17. [DOI: 10.1016/j.jaad.2011.01.004] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 12/05/2010] [Accepted: 01/03/2011] [Indexed: 12/17/2022]
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11
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Vonk WIM, de Bie P, Wichers CGK, van den Berghe PVE, van der Plaats R, Berger R, Wijmenga C, Klomp LWJ, van de Sluis B. The copper-transporting capacity of ATP7A mutants associated with Menkes disease is ameliorated by COMMD1 as a result of improved protein expression. Cell Mol Life Sci 2011; 69:149-63. [PMID: 21667063 PMCID: PMC3249196 DOI: 10.1007/s00018-011-0743-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 05/26/2011] [Accepted: 05/30/2011] [Indexed: 01/02/2023]
Abstract
Menkes disease (MD) is an X-linked recessive disorder characterized by copper deficiency resulting in a diminished function of copper-dependent enzymes. Most MD patients die in early childhood, although mild forms of MD have also been described. A diversity of mutations in the gene encoding of the Golgi-resident copper-transporting P1B-type ATPase ATP7A underlies MD. To elucidate the molecular consequences of the ATP7A mutations, various mutations in ATP7A associated with distinct phenotypes of MD (L873R, C1000R, N1304S, and A1362D) were analyzed in detail. All mutants studied displayed changes in protein expression and intracellular localization parallel to a dramatic decline in their copper-transporting capacity compared to ATP7A the wild-type. We restored these observed defects in ATP7A mutant proteins by culturing the cells at 30°C, which improves the quality of protein folding, similar to that which as has recently has been demonstrated for misfolded ATP7B, a copper transporter homologous to ATP7A. Further, the effect of the canine copper toxicosis protein COMMD1 on ATP7A function was examined as COMMD1 has been shown to regulate the proteolysis of ATP7B proteins. Interestingly, in addition to adjusted growth temperature, binding of COMMD1 partially restored the expression, subcellular localization, and copper-exporting activities of the ATP7A mutants. However, no effect of pharmacological chaperones was observed. Together, the presented data might provide a new direction for developing therapies to improve the residual exporting activity of unstable ATP7A mutant proteins, and suggests a potential role for COMMD1 in this process.
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Affiliation(s)
- Willianne I M Vonk
- Department of Metabolic and Endocrine Diseases, Netherlands Metabolomics Center, University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands
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12
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Abstract
This Review summarizes recent advances in understanding copper-transporting ATPase 1 (ATP7A), and examines the neurological phenotypes associated with dysfunction of this protein. Involvement of ATP7A in axonal outgrowth, synapse integrity and neuronal activation underscores the fundamental importance of copper metabolism to neurological function. Defects in ATP7A cause Menkes disease, an infantile-onset, lethal condition. Neonatal diagnosis and early treatment with copper injections enhance survival in patients with this disease, and can normalize clinical outcomes if mutant ATP7A molecules retain small amounts of residual activity. Gene replacement rescues a mouse model of Menkes disease, suggesting a potential therapeutic approach for patients with complete loss-of-function ATP7A mutations. Remarkably, a newly discovered ATP7A disorder-isolated distal motor neuropathy-has none of the characteristic clinical or biochemical abnormalities of Menkes disease or its milder allelic variant occipital horn syndrome (OHS), instead resembling Charcot-Marie-Tooth disease type 2. These findings indicate that ATP7A has a crucial but previously unappreciated role in motor neuron maintenance, and that the mechanism underlying ATP7A-related distal motor neuropathy is distinct from Menkes disease and OHS pathophysiology. Collectively, these insights refine our knowledge of the neurology of ATP7A-related copper transport diseases and pave the way for further progress in understanding ATP7A function.
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13
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Hsi G, Cullen LM, Macintyre G, Chen MM, Glerum DM, Cox DW. Sequence variation in the ATP-binding domain of the Wilson disease transporter, ATP7B, affects copper transport in a yeast model system. Hum Mutat 2008; 29:491-501. [PMID: 18203200 DOI: 10.1002/humu.20674] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
ATP7B is a copper transporting P-type ATPase defective in the autosomal recessive copper storage disorder, Wilson disease (WND). Functional assessment of variants helps to distinguish normal from disease-causing variants and provides information on important amino acid residues. A total of 11 missense variants of ATP7B, originally identified in WND patients, were examined for their capacity to functionally complement a yeast mutant strain in which the yeast gene ortholog, CCC2, was disrupted. Solution structures of ATP7B domains were used to predict the effects of each variant on ATP7B structure. Three variants lie within the copper-binding domain and eight within the ATP-binding domain of ATP7B. All three ATP7B variants within the copper-binding domain and four within the ATP-binding domain showed full complementation of the yeast ccc2 phenotype. For the remaining four located in the ATP-binding domain, p.Glu1064Lys and p.Val1106Asp were unable to complement the yeast ccc2 high-affinity iron uptake deficiency phenotype, apparently due to mislocalization and/or change in conformation of the variant protein. p.Leu1083Phe exhibited a temperature-sensitive phenotype with partial complementation at 30 degrees C and a severe deficit at 37 degrees C. p.Met1169Val only partially complemented the ccc2 phenotype at 30 degrees C and 37 degrees C. Therefore, four variant positions were identified as important for copper transport and as disease-causing changes. Since the yeast assay specifically evaluates copper transport function, variants with normal transport could be defective in some other aspect of ATP7B function, particularly trafficking in mammalian cells. Functional assessment is critical for reliable use of mutation analysis as an aid to diagnosis of this clinically variable condition.
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Affiliation(s)
- Gloria Hsi
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
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14
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de Bie P, Muller P, Wijmenga C, Klomp LWJ. Molecular pathogenesis of Wilson and Menkes disease: correlation of mutations with molecular defects and disease phenotypes. J Med Genet 2007; 44:673-88. [PMID: 17717039 PMCID: PMC2752173 DOI: 10.1136/jmg.2007.052746] [Citation(s) in RCA: 244] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The trace metal copper is essential for a variety of biological processes, but extremely toxic when present in excessive amounts. Therefore, concentrations of this metal in the body are kept under tight control. Central regulators of cellular copper metabolism are the copper-transporting P-type ATPases ATP7A and ATP7B. Mutations in ATP7A or ATP7B disrupt the homeostatic copper balance, resulting in copper deficiency (Menkes disease) or copper overload (Wilson disease), respectively. ATP7A and ATP7B exert their functions in copper transport through a variety of interdependent mechanisms and regulatory events, including their catalytic ATPase activity, copper-induced trafficking, post-translational modifications and protein-protein interactions. This paper reviews the extensive efforts that have been undertaken over the past few years to dissect and characterise these mechanisms, and how these are affected in Menkes and Wilson disease. As both disorders are characterised by an extensive clinical heterogeneity, we will discus how the underlying genetic defects correlate with the molecular functions of ATP7A and ATP7B and with the clinical expression of these disorders.
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Affiliation(s)
- P de Bie
- Laboratory of Metabolic and Endocrine Diseases, Room KC.02.069.1, Lundlaan 6, 3584 EA Utrecht, The Netherlands
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15
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Donsante A, Tang J, Godwin SC, Holmes CS, Goldstein DS, Bassuk A, Kaler SG. Differences in ATP7A gene expression underlie intrafamilial variability in Menkes disease/occipital horn syndrome. J Med Genet 2007; 44:492-7. [PMID: 17496194 PMCID: PMC2597922 DOI: 10.1136/jmg.2007.050013] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Pronounced intrafamilial variability is unusual in Menkes disease and its variants. We report two unrelated families featuring affected members with unusually disparate clinical and biochemical phenotypes and explore the underlying molecular mechanisms. METHODS We measured biochemical markers of impaired copper transport in five patients from two unrelated families and used RNase protection, quantitative reverse transcription (RT)-PCR, Western blot analysis and yeast complementation studies to characterise two ATP7A missense mutations, A1362D and S637L. RESULTS In two brothers (family A) with A1362D, RNase protection and Western blot analyses revealed higher amounts of ATP7A transcript and protein in the older, mildly affected patient, who also had a higher plasma copper level and lower cerebrospinal fluid dihydroxyphenylalanine : dihydroxyphenylglycol ratio. These findings indicate greater gastrointestinal absorption of copper and higher activity of dopamine-beta-hydroxylase, a copper-dependent enzyme, respectively. In family B, three males with a missense mutation (S637L) in an exon 8 splicing enhancer showed equally reduced amounts of ATP7A transcript and protein by quantitative RT-PCR and western blot analysis, respectively, despite a more severe phenotype in the youngest. This patient's medical history was notable for cardiac arrest as a neonate, to which we attribute his more severe neurodevelopmental outcome. CONCLUSIONS These families illustrate that genetic and non-genetic mechanisms may underlie intrafamilial variability in Menkes disease and its variants.
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Affiliation(s)
- Anthony Donsante
- Unit on Pediatric Genetics, Laboratory of Clinical Genomics, National Institute of Child Health and Human Development, Bethesda, MD20892-1832, USA
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Tang J, Robertson S, Lem KE, Godwin SC, Kaler SG. Functional copper transport explains neurologic sparing in occipital horn syndrome. Genet Med 2007; 8:711-8. [PMID: 17108763 DOI: 10.1097/01.gim.0000245578.94312.1e] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE A range of neurologic morbidity characterizes childhood-onset copper transport defects, including severe Menkes disease and milder occipital horn syndrome. Both phenotypes are caused by mutations in ATP7A, which encodes a copper-transporting adenosine triphosphatase, although defects causing occipital horn syndrome are rarely reported and nearly always involve exon-skipping (six of eight prior reports). Our objective was to characterize a novel occipital horn syndrome mutation (N1304S) not associated with aberrant splicing and to determine whether functional copper transport was associated with this allele. METHODS We studied two brothers with typical occipital horn syndrome and used yeast complementation and timed growth assays, exploiting a Saccharomyces cerevisiae mutant strain, to assess in vitro N1304S copper transport. RESULTS We documented that N1304S has approximately 33% residual copper transport, a result not inconsistent with a similar patient we reported with an exon-skipping mutation whose cells showed correctly spliced mRNA transcripts 36% of normal. CONCLUSION These patients' mild neurologic phenotypes, together with our yeast complementation and growth experiments, imply that N1304S does not completely block copper transport to the developing brain early in life. The findings suggest that neurologic sparing in untreated occipital horn syndrome is associated with approximately 30% residual functional activity of ATP7A.
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Affiliation(s)
- Jingrong Tang
- Unit on Pediatric Genetics, Laboratory of Clinical Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1832, USA
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Hsi G, Cox DW. A comparison of the mutation spectra of Menkes disease and Wilson disease. Hum Genet 2003; 114:165-72. [PMID: 14579150 DOI: 10.1007/s00439-003-1045-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2003] [Accepted: 09/22/2003] [Indexed: 01/23/2023]
Abstract
The genes for two copper-transporting ATPases, ATP7A and ATP7B, are defective in the heritable disorders of copper imbalance, Menkes disease (MNK) and Wilson disease (WND), respectively. A comparison of the two proteins shows extensive conservation in the signature domains, with amino acid identities outside of the conserved domains being limited. The mutation spectra of MNK and WND were compared to confirm and refine further regions critical for normal function. Mutations were found to be relatively widespread; however, the majority was concentrated within defined functional domains and membrane-spanning segments, reinforcing the importance of these regions for protein function. Of the total published point mutations in ATP7A, 23.0% are splice-site, 20.7% nonsense, 17.2% missense, and 39.1% small insertions/deletions. There is a high prevalence (58.2%) of missense mutations in ATP7B. For the other mutations in ATP7B, 7.4% are splice-site, 7.4% nonsense, and 27.0% small insertions/deletions. A region of possible importance is the intervening sequence between the last copper-binding domain and the first transmembrane helix, as this region has a high percentage of MNK mutations. Similarly, the region containing the ATP-binding domain has 24.6% of all WND mutations. The study of mutation locations is useful for defining critical regions or residues and for efficient molecular diagnosis.
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Affiliation(s)
- Gloria Hsi
- Department of Medical Genetics, 8-39 Medical Sciences Building, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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Kodama H, Gu YH, Mizunuma M. Drug targets in Menkes disease - prospective developments. Expert Opin Ther Targets 2001; 5:625-635. [PMID: 12540288 DOI: 10.1517/14728222.5.5.625] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Menkes disease (MNK) is an X-linked recessive disorder characterised by a copper-transporting ATPase defect. In the affected cells, copper transport from the cytosol to the Golgi apparatus is disturbed, resulting in a reduction of copper efflux. Orally-administered copper, which accumulates in the intestine, cannot be absorbed and thus a copper deficiency arises. The characteristic features of MNK are progressive neurological degeneration, connective tissue disorders and hair abnormalities, which are caused by a reduction in the activity of several copper-dependent enzymes, due to concomitant copper deficiency. Subcutaneous injections of copper-histidine complex, which currently forms the accepted mode of treatment, prevent the neurological degeneration in some patients when the treatment is initiated soon after birth. However, when the treatment is started later, the neurological degenerative processes are not prevented. Moreover, the treatment does not improve the connective tissue disorders that are caused by the low activity of lysyl oxidase. In order to solve these problems, a form of the treatment aimed at delivering copper into the Golgi apparatus should be studied. An attempt is made in this review to present what is currently known about MNK and its variants, the efficacy and problems of currently accepted treatments and finally therapeutic targets in MNK.
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Affiliation(s)
- Hiroko Kodama
- Department of Pediatrics, Teikyo University School of Medicine, 11-1, Kaga-2, Itabashi-ku, Tokyo 173-8605, Japan.
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Dagenais SL, Adam AN, Innis JW, Glover TW. A novel frameshift mutation in exon 23 of ATP7A (MNK) results in occipital horn syndrome and not in Menkes disease. Am J Hum Genet 2001; 69:420-7. [PMID: 11431706 PMCID: PMC1235313 DOI: 10.1086/321290] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2001] [Accepted: 05/15/2001] [Indexed: 11/03/2022] Open
Abstract
Menkes disease and occipital horn syndrome (OHS) are allelic, X-linked recessive copper-deficiency disorders resulting from mutations in ATP7A, or MNK. Classic Menkes disease has a severe phenotype, with death in early childhood, whereas OHS has a milder phenotype, with, mainly, connective-tissue abnormalities. Data suggest that steady-state localization of ATP7A to the trans-Golgi network (TGN) is necessary for proper activity of lysyl oxidase, which is the predominant cuproenzyme whose activity is deficient in OHS and which is essential for maintenance of connective-tissue integrity. Recently, it was reported that ATP7A-transcript levels as low as 2%-5% of normal are sufficient to result in the milder phenotype, OHS, rather than the phenotype of Menkes disease. In contrast to previously reported cases of OHS, we describe a case of OHS in which, because of a frameshift mutation, no normal ATP7A is produced. Although abundant levels of mutant transcript are present, there are substantially reduced levels of the truncated protein, which lacks the key dileucine motif L1487L1488. It has been demonstrated that the dileucine motif L1487L1488 functions as an endocytic signal for ATP7A cycling between the TGN and the plasma membrane. The present report is the first to describe an ATP7A truncation that results in OHS rather than in Menkes disease. The data from the present report support the concepts that (1) OHS results from lower levels of functional ATP7A and (2) ATP7A does not require the dileucine motif to function in copper efflux.
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Affiliation(s)
- S L Dagenais
- Departments of Pediatrics and Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA.
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Møller LB, Tümer Z, Lund C, Petersen C, Cole T, Hanusch R, Seidel J, Jensen LR, Horn N. Similar splice-site mutations of the ATP7A gene lead to different phenotypes: classical Menkes disease or occipital horn syndrome. Am J Hum Genet 2000; 66:1211-20. [PMID: 10739752 PMCID: PMC1288188 DOI: 10.1086/302857] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/1999] [Accepted: 01/18/2000] [Indexed: 11/03/2022] Open
Abstract
More than 150 point mutations have now been identified in the ATP7A gene. Most of these mutations lead to the classic form of Menkes disease (MD), and a few lead to the milder occipital horn syndrome (OHS). To get a better understanding of molecular changes leading to classic MD and OHS, we took advantage of the unique finding of three patients with similar mutations but different phenotypes. Although all three patients had mutations located in the splice-donor site of intron 6, only two of the patients had the MD phenotype; the third had the OHS phenotype. Fibroblast cultures from the three patients were analyzed by reverse transcriptase (RT)-PCR to try to find an explanation of the different phenotypes. In all three patients, exon 6 was deleted in the majority of the ATP7A transcripts. However, by RT-PCR amplification with an exon 6-specific primer, we were able to amplify exon 6-containing mRNA products from all three patients, even though they were in low abundance. Sequencing of these products indicated that only the patient with OHS had correctly spliced exon 6-containing transcripts. We used two different methods of quantitative RT-PCR analysis and found that the level of correctly spliced mRNA in this patient was 2%-5% of the level found in unaffected individuals. These findings indicate that the presence of barely detectable amounts of correctly spliced ATP7A transcript is sufficient to permit the development of the milder OHS phenotype, as opposed to classic MD.
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Affiliation(s)
- L B Møller
- The John F. Kennedy Institute, 2600 Glostrup, Denmark.
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Vockley J, Rogan PK, Anderson BD, Willard J, Seelan RS, Smith DI, Liu W. Exon skipping in IVD RNA processing in isovaleric acidemia caused by point mutations in the coding region of the IVD gene. Am J Hum Genet 2000; 66:356-67. [PMID: 10677295 PMCID: PMC1288088 DOI: 10.1086/302751] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Isovaleric acidemia (IVA) is a recessive disorder caused by a deficiency of isovaleryl-CoA dehydrogenase (IVD). We have reported elsewhere nine point mutations in the IVD gene in fibroblasts of patients with IVA, which lead to abnormalities in IVD protein processing and activity. In this report, we describe eight IVD gene mutations identified in seven IVA patients that result in abnormal splicing of IVD RNA. Four mutations in the coding region lead to aberrantly spliced mRNA species in patient fibroblasts. Three of these are amino acid altering point mutations, whereas one is a single-base insertion that leads to a shift in the reading frame of the mRNA. Two of the coding mutations strengthen pre-existing cryptic splice acceptors adjacent to the natural splice junctions and apparently interfere with exon recognition, resulting in exon skipping. This mechanism for missplicing has not been reported elsewhere. Four other mutations alter either the conserved gt or ag dinucleotide splice sites in the IVD gene. Exon skipping and cryptic splicing were confirmed by transfection of these mutations into a Cos-7 cell line model splicing system. Several of the mutations were predicted by individual information analysis to inactivate or significantly weaken adjacent donor or acceptor sites. The high frequency of splicing mutations identified in these patients is unusual, as is the finding of missplicing associated with missense mutations in exons. These results may lead to a better understanding of the phenotypic complexity of IVA, as well as provide insight into those factors important in defining intron/exon boundaries in vivo.
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Affiliation(s)
- J Vockley
- Mayo Clinic, Department of Medical Genetics, 200 First Street, SW, Rochester, MN 55905, USA.
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Chen B, Rigat B, Curry C, Mahuran DJ. Structure of the GM2A gene: identification of an exon 2 nonsense mutation and a naturally occurring transcript with an in-frame deletion of exon 2. Am J Hum Genet 1999; 65:77-87. [PMID: 10364519 PMCID: PMC1378077 DOI: 10.1086/302463] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Deficiency of the GM2 activator protein, encoded by GM2A, results in the rare AB-variant form of GM2 gangliosidosis. Four mutations have been identified, but the human gene structure has been only partially characterized. We report a new patient from a Laotian deme whose cells are deficient in both GM2-activator mRNA and protein. However, reverse transcription (RT)-PCR detected some normal-sized cDNA and a smaller cDNA species, which was not seen in the RT-PCR products from normal controls. Sequencing revealed that, although the patient's normal-sized cDNA contained a single nonsense mutation in exon 2, his smaller cDNA was the result of an in-frame deletion of exon 2. Long PCR was used to amplify introns 1 and 2 from patient and normal genomic DNA, and no differences in size, in 5' and 3' end sequences, or in restriction-mapping patterns were observed. From these data we developed a set of four PCR primers that can be used to identify GM2A mutations. We use this procedure to demonstrate that the patient is likely homozygous for the nonsense mutation. Other reports have associated nonsense mutations with dramatically reduced levels of mRNA and with an increased level of skipping of the exon containing the mutation, thus reestablishing an open reading frame. However, a recent article has concluded that, in some cases, the latter observation is caused by an artifact of RT-PCR. In support of this conclusion, we demonstrate that, if the competing, normal-sized cDNA is removed from the initial RT-PCR products, from both patient and normal cells, by an exon 2-specific restriction digest; a second round of PCR produces similar amounts of exon 2-deleted cDNA.
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Affiliation(s)
- B Chen
- Research Institute, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
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Tümer Z, Møller LB, Horn N. Mutation spectrum of ATP7A, the gene defective in Menkes disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 448:83-95. [PMID: 10079817 DOI: 10.1007/978-1-4615-4859-1_7] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
Our knowledge about Menkes disease (MD) has expanded greatly since its description in 1962 as a new X-linked recessive neurodegenerative disorder of early infancy. Ten years later a defect in copper metabolism was established as the underlying biochemical deficiency. In the beginning of 1990s efforts were concentrated on the molecular genetic aspects. The disease locus was mapped to Xq13.3 and the gene has been isolated by means of positional cloning. This was the beginning of a series of new findings which have greatly enhanced our understanding of copper metabolism not only in human, but also in other species. This review will focus on the molecular genetic aspects of Menkes disease and its allelic form occipital horn syndrome. The mutations will be compared briefly with those described in the animal model mottled mouse, and in Wilson disease, the autosomal recessive disorder of copper metabolism.
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Affiliation(s)
- Z Tümer
- Department of Medical Genetics, Panum Institute, University of Copenhagen, Denmark
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25
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Park VM, Pivnick EK. Neurofibromatosis type 1 (NF1): a protein truncation assay yielding identification of mutations in 73% of patients. J Med Genet 1998; 35:813-20. [PMID: 9783703 PMCID: PMC1051455 DOI: 10.1136/jmg.35.10.813] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Neurofibromatosis type 1 (NF1) is caused by mutations in a tumour suppressor gene located on chromosome 17 (17q11.2). Disease causing mutations are dispersed throughout the gene, which spans 350 kilobases and includes 59 exons. A common consequence of NF1 mutations is introduction of a premature stop codon, and the majority of mutant genes encode truncated forms of neurofibromin. We used a protein truncation assay to screen for mutations in 15 NF1 patients and obtained positive results in 11 of them (73%). Sequencing of cDNA and genomic DNA yielded identification of 10 different mutations, including four splicing errors, three small deletions, two nonsense mutations, and one small insertion. Nine mutations were predicted to cause premature termination of translation, while one mutation caused in frame deletion as a result ofexon skipping. In one other case involving abnormal splicing, five different aberrantly spliced transcripts were detected. One germline nonsense mutation (R1306X, 3916C>T) corresponded to the same base change that occurs by mRNA editing in normal subjects. The second nonsense mutation (R2496X) was the sole germline mutation that has been previously described. The subjects studied represented typically affected NF1 patients and no correlations between genotype and phenotype were apparent. A high incidence of ocular hypertelorism was observed.
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Affiliation(s)
- V M Park
- Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38163, USA
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Abstract
Cloning of the gene defective in the X-linked neurodegenerative disorder Menkes disease led to a cascade of new findings. Besides giving a better understanding of the intracellular copper homeostasis, these findings had important consequences from a clinical point of view. Today the underlying genetic defect has been described in several patients affected by one of the three hereditary disorders of copper metabolism: Menkes disease, occipital horn syndrome and wilson disease. In this review we discuss mainly Menkes disease and the impact of the recent findings on the diagnosis of this disorder.
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Affiliation(s)
- Z Tümer
- Department of Medical Genetics, Panum Institute, University of Copenhagen, Denmark
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