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Szeri F, Miko A, Navasiolava N, Kaposi A, Verschuere S, Molnar B, Li Q, Terry SF, Boraldi F, Uitto J, van de Wetering K, Martin L, Quaglino D, Vanakker OM, Tory K, Aranyi T. The pathogenic c.1171A>G (p.Arg391Gly) and c.2359G>A (p.Val787Ile) ABCC6 variants display incomplete penetrance causing pseudoxanthoma elasticum in a subset of individuals. Hum Mutat 2022; 43:1872-1881. [PMID: 36317459 PMCID: PMC9772137 DOI: 10.1002/humu.24498] [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: 04/11/2022] [Revised: 09/30/2022] [Accepted: 10/24/2022] [Indexed: 11/06/2022]
Abstract
ABCC6 promotes ATP efflux from hepatocytes to bloodstream. ATP is metabolized to pyrophosphate, an inhibitor of ectopic calcification. Pathogenic variants of ABCC6 cause pseudoxanthoma elasticum, a highly variable recessive ectopic calcification disorder. Incomplete penetrance may initiate disease heterogeneity, hence symptoms may not, or differently manifest in carriers. Here, we investigated whether incomplete penetrance is a source of heterogeneity in pseudoxanthoma elasticum. By integrating clinical and genetic data of 589 patients, we created the largest European cohort. Based on allele frequency alterations, we identified two incomplete penetrant pathogenic variants, c.2359G>A (p.Val787Ile) and c.1171A>G (p.Arg391Gly), with 6.5% and 2% penetrance, respectively. However, when penetrant, the c.1171A>G (p.Arg391Gly) manifested a clinically unaltered severity. After applying in silico and in vitro characterization, we suggest that incomplete penetrant variants are only deleterious if a yet unknown interacting partner of ABCC6 is mutated simultaneously. The low penetrance of these variants should be contemplated in genetic counseling.
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Affiliation(s)
- Flora Szeri
- Department of Dermatology and Cutaneous Biology, The Sidney Kimmel Medical College, and The PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA, USA,Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary,Department of Biochemistry, Semmelweis University, Budapest, Hungary
| | - Agnes Miko
- MTA-SE Lendület Nephrogenetic Laboratory, Budapest, Hungary,1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Nastassia Navasiolava
- PXE Consultation Center, MAGEC Nord Reference Center for Rare Skin Diseases, Angers University Hospital, Angers, France
| | - Ambrus Kaposi
- MTA-SE Lendület Nephrogenetic Laboratory, Budapest, Hungary,1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Shana Verschuere
- Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium
| | - Beatrix Molnar
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Qiaoli Li
- Department of Dermatology and Cutaneous Biology, The Sidney Kimmel Medical College, and The PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA, USA
| | | | - Federica Boraldi
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, The Sidney Kimmel Medical College, and The PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA, USA
| | - Koen van de Wetering
- Department of Dermatology and Cutaneous Biology, The Sidney Kimmel Medical College, and The PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA, USA
| | - Ludovic Martin
- PXE Consultation Center, MAGEC Nord Reference Center for Rare Skin Diseases, Angers University Hospital, Angers, France
| | - Daniela Quaglino
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy,Interuniversity Consortium for Biotechnologies (CIB), Italy
| | | | - Kalman Tory
- MTA-SE Lendület Nephrogenetic Laboratory, Budapest, Hungary,1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Tamas Aranyi
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary,Department of Molecular Biology, Semmelweis University, Budapest, Hungary.,Corresponding author:
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Zheng A, Thibodeau PH. Commentary on Variants in the ABCC6 Gene Implicated in Pseudoxanthoma Elasticum, a Heritable Ectopic Mineralization Disorder. J Invest Dermatol 2022; 142:1002-1003. [DOI: 10.1016/j.jid.2022.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 02/16/2022] [Accepted: 02/16/2022] [Indexed: 11/25/2022]
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Structural and Functional Characterization of the ABCC6 Transporter in Hepatic Cells: Role on PXE, Cancer Therapy and Drug Resistance. Int J Mol Sci 2021; 22:ijms22062858. [PMID: 33799762 PMCID: PMC8000515 DOI: 10.3390/ijms22062858] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/26/2022] Open
Abstract
Pseudoxanthoma elasticum (PXE) is a complex autosomal recessive disease caused by mutations of ABCC6 transporter and characterized by ectopic mineralization of soft connective tissues. Compared to the other ABC transporters, very few studies are available to explain the structural components and working of a full ABCC6 transporter, which may provide some idea about its physiological role in humans. Some studies suggest that mutations of ABCC6 in the liver lead to a decrease in some circulating factor and indicate that PXE is a metabolic disease. It has been reported that ABCC6 mediates the efflux of ATP, which is hydrolyzed in PPi and AMP; in the extracellular milieu, PPi gives potent anti-mineralization effect, whereas AMP is hydrolyzed to Pi and adenosine which affects some cellular properties by modulating the purinergic pathway. Structural and functional studies have demonstrated that silencing or inhibition of ABCC6 with probenecid changed the expression of several genes and proteins such as NT5E and TNAP, as well as Lamin, and CDK1, which are involved in cell motility and cell cycle. Furthermore, a change in cytoskeleton rearrangement and decreased motility of HepG2 cells makes ABCC6 a potential target for anti-cancer therapy. Collectively, these findings suggested that ABCC6 transporter performs functions that modify both the external and internal compartments of the cells.
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Abstract
Drug transporters are integral membrane proteins that play a critical role in drug disposition by affecting absorption, distribution, and excretion. They translocate drugs, as well as endogenous molecules and toxins, across membranes using ATP hydrolysis, or ion/concentration gradients. In general, drug transporters are expressed ubiquitously, but they function in drug disposition by being concentrated in tissues such as the intestine, the kidneys, the liver, and the brain. Based on their primary sequence and their mechanism, transporters can be divided into the ATP-binding cassette (ABC), solute-linked carrier (SLC), and the solute carrier organic anion (SLCO) superfamilies. Many X-ray crystallography and cryo-electron microscopy (cryo-EM) structures have been solved in the ABC and SLC transporter superfamilies or of their bacterial homologs. The structures have provided valuable insight into the structural basis of transport. This chapter will provide particular focus on the promiscuous drug transporters because of their effect on drug disposition and the challenges associated with them.
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Affiliation(s)
- Arthur G Roberts
- Pharmaceutical and Biomedical Sciences Department, University of Georgia, Athens, GA, USA.
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Marques JP, Bernardes J, Geada S, Soares M, Teixeira D, Farinha C, Pires I, Cachulo ML, Silva R. Non-exudative macular neovascularization in pseudoxanthoma elasticum. Graefes Arch Clin Exp Ophthalmol 2020; 259:873-882. [PMID: 33074374 DOI: 10.1007/s00417-020-04979-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/24/2020] [Accepted: 10/09/2020] [Indexed: 12/30/2022] Open
Abstract
PURPOSE To characterize morphological changes in the retina and to report the frequency and natural history of non-exudative macular neovascularization (MNV) in a cohort of pseudoxanthoma elasticum (PXE). METHODS A single-center, retrospective study was complemented by a cross-sectional examination. Consecutive patients with a definitive genetic and/or clinical diagnosis of PXE, visiting our department between January 2019 and December 2019, and with a minimum follow-up of 6 months were recruited. Baseline data were retrieved from each patient file. Additionally, a cross-sectional examination comprising color fundus photography, spectral-domain optical coherence tomography (SD-OCT), OCT-Angiography (OCT-A), and fundus autofluorescence was performed. The presence of typical PXE-related findings, as well as related complications, was multimodally evaluated. The prevalence and natural history of non-exudative MNV were assessed. All images were graded by two independent graders. RESULTS Forty-eight eyes from 24 patients (mean age 59.11 ± 18.14) with a median follow-up of 53.00 months were included. Angioid streaks and peau d'orange were observed in 46/48 and 42/48 eyes, while MNV was present in 75.00% of the cohort. The prevalence of non-exudative MNV was 33.33% (6/18). In the 2 eyes that developed exudation, time to conversion was 9.50 ± 4.95 months. No significant difference in visual acuity was found between eyes with non-exudative MNV and those with no signs of MNV. CONCLUSION We have shown that non-exudative MNV is a frequent finding in PXE but the majority of eyes did not develop exudation during follow-up. Our results are a clear evidence of the utility of OCT-A in the management of PXE.
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Affiliation(s)
- João Pedro Marques
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal.
- University Clinic of Ophthalmology, Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal.
- Clinical Academic Center of Coimbra (CACC), Coimbra, Portugal.
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra (FMUC), University of Coimbra, Coimbra, Portugal.
| | - João Bernardes
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
| | - Sara Geada
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
| | - Mário Soares
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
| | - Dora Teixeira
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
| | - Cláudia Farinha
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
- University Clinic of Ophthalmology, Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Clinical Academic Center of Coimbra (CACC), Coimbra, Portugal
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra (FMUC), University of Coimbra, Coimbra, Portugal
| | - Isabel Pires
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
- University Clinic of Ophthalmology, Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Clinical Academic Center of Coimbra (CACC), Coimbra, Portugal
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra (FMUC), University of Coimbra, Coimbra, Portugal
| | - Maria Luz Cachulo
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
- University Clinic of Ophthalmology, Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
- Clinical Academic Center of Coimbra (CACC), Coimbra, Portugal
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra (FMUC), University of Coimbra, Coimbra, Portugal
| | - Rufino Silva
- Ophthalmology Unit, Centro de Responsabilidade Integrado em Oftalmologia (CRIO), Centro Hospitalar e Universitário de Coimbra (CHUC), Praceta Prof. Mota Pinto, 3000-075, Coimbra, Portugal
- University Clinic of Ophthalmology, Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
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Reassessment of causality of ABCC6 missense variants associated with pseudoxanthoma elasticum based on Sherloc. Genet Med 2020; 23:131-139. [PMID: 32873932 DOI: 10.1038/s41436-020-00945-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 08/10/2020] [Accepted: 08/11/2020] [Indexed: 01/25/2023] Open
Abstract
PURPOSE Pseudoxanthoma elasticum (PXE) is a heritable disorder affecting elastic fibers in the skin, eyes, and cardiovascular system. It is caused by biallelic pathogenic variants in the ABCC6 gene. To date, over 300 ABCC6 variants are associated with PXE, more than half being missense variants. Correct variant interpretation is essential for establishing a direct link between the variant and the patient's phenotype and has important implications for diagnosis and treatment. METHODS We used a systematic approach for interpretation of 271 previously reported and 15 novel ABCC6 missense variants, based on the semiquantitative classification system Sherloc. RESULTS Only 35% of variants were very likely to contribute directly to disease, in contrast to reported interpretations in ClinVar, while 59% of variants are currently of uncertain significance (VUS). Subclasses were created to distinguish VUS that are leaning toward likely benign or pathogenic, increasing the number of (likely) pathogenic ABCC6 missense variants to 47%. CONCLUSION Besides highlighting discrepancies between the Sherloc, American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP), ClinVar, and Leiden Open Variation Database (LOVD) classification, our results emphasize the need for segregation analysis, functional assays, and detailed evidence sharing in variant databases to reach a confident interpretation of ABCC6 missense variants and subsequent appropriate genetic and preconceptual counseling.
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Ostuni A, Carmosino M, Miglionico R, Abruzzese V, Martinelli F, Russo D, Laurenzana I, Petillo A, Bisaccia F. Inhibition of ABCC6 Transporter Modifies Cytoskeleton and Reduces Motility of HepG2 Cells via Purinergic Pathway. Cells 2020; 9:cells9061410. [PMID: 32517079 PMCID: PMC7349786 DOI: 10.3390/cells9061410] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 05/29/2020] [Accepted: 06/01/2020] [Indexed: 12/22/2022] Open
Abstract
ABCC6, belonging to sub-family C of ATP-binding cassette transporter, is an ATP-dependent transporter mainly present in the basolateral plasma membrane of hepatic and kidney cells. Although the substrates transported are still uncertain, ABCC6 has been shown to promote ATP release. The extracellular ATP and its derivatives di- and mono-nucleotides and adenosine by acting on specific receptors activate the so-called purinergic pathway, which in turn controls relevant cellular functions such as cell immunity, inflammation, and cancer. Here, we analyzed the effect of Abcc6 knockdown and probenecid-induced ABCC6 inhibition on cell cycle, cytoskeleton, and motility of HepG2 cells. Gene and protein expression were evaluated by quantitative Reverse Transcription PCR (RT-qPCR) and western blot, respectively. Cellular cycle analysis was evaluated by flow cytometry. Actin cytoskeleton dynamics was evaluated by laser confocal microscopy using fluorophore-conjugated phalloidin. Cell motility was analyzed by in vitro wound-healing migration assay. Cell migration is reduced both in Abcc6 knockdown HepG2 cells and in probenecid treated HepG2 cells by interfering with the extracellular reserve of ATP. Therefore, ABCC6 could contribute to cytoskeleton rearrangements and cell motility through purinergic signaling. Altogether, our findings shed light on a new role of the ABCC6 transporter in HepG2 cells and suggest that its inhibitor/s could be considered potential anti-metastatic drugs.
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Affiliation(s)
- Angela Ostuni
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
- Correspondence: (A.O.); (F.B.); Tel.: +39-0971-205453 (A.O.); Tel.: +39-0971-205462 (F.B.)
| | - Monica Carmosino
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
| | - Rocchina Miglionico
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
| | - Vittorio Abruzzese
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
| | - Fabio Martinelli
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
| | - Daniela Russo
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
| | - Ilaria Laurenzana
- Laboratory of Preclinical and Translational Research, IRCCS-Referral Cancer Center of Basilicata (CROB), 85028 Rionero in Vulture, Italy;
| | - Agata Petillo
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
| | - Faustino Bisaccia
- Department of Sciences, University of Basilicata, viale Ateneo Lucano 10, 85100 Potenza, Italy; (M.C.); (R.M.); (V.A.); (F.M.); (D.R.); (A.P.)
- Correspondence: (A.O.); (F.B.); Tel.: +39-0971-205453 (A.O.); Tel.: +39-0971-205462 (F.B.)
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