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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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Ralph D, Levine MA, Richard G, Morrow M, Flynn E, Uitto J, Li Q. Mutation update: Variants of the ENPP1 gene in pathologic calcification, hypophosphatemic rickets, and cutaneous hypopigmentation with punctate keratoderma. Hum Mutat 2022; 43:1183-1200. [PMID: 35475527 PMCID: PMC9357117 DOI: 10.1002/humu.24391] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/07/2022] [Accepted: 04/22/2022] [Indexed: 11/11/2022]
Abstract
ENPP1 encodes ENPP1, an ectonucleotidase catalyzing hydrolysis of ATP to AMP and inorganic pyrophosphate (PPi), and an endogenous plasma protein physiologically preventing ectopic calcification of connective tissues. Mutations in ENPP1 have been reported in association with a range of human genetic diseases. In this mutation update, we provide a comprehensive review of all the pathogenic variants, likely pathogenic variants, and variants of unknown significance in ENPP1 associated with three autosomal recessive disorders-generalized arterial calcification of infancy (GACI), autosomal recessive hypophosphatemic rickets type 2 (ARHR2), and pseudoxanthoma elasticum (PXE), as well as with a predominantly autosomal dominant disorder-Cole disease. The classification of all variants is determined using the latest ACMG guidelines. A total of 140 ENPP1 variants were curated consisting of 133 previously reported variants and seven novel variants, with missense variants being the most prevalent (70.0%, 98/140). While the pathogenic variants are widely distributed in the ENPP1 gene of patientsgen without apparent genotype-phenotype correlation, eight out of nine variants associated with Cole disease are confined to the somatomedin-B-like (SMB) domains critical for homo-dimerization of the ENPP1 protein.
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Affiliation(s)
- Douglas Ralph
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
- Genetics, Genomics and Cancer Biology Ph.D. Program, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA
- PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA
| | - Michael A. Levine
- Division of Endocrinology and Diabetes, Children’s Hospital of Philadelphia, Philadelphia, PA
| | | | | | | | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
- PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA
| | - Qiaoli Li
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
- PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA
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Ralph D, Nitschke Y, Levine MA, Caffet M, Wurst T, Saeidian AH, Youssefian L, Vahidnezhad H, Terry SF, Rutsch F, Uitto J, Li Q. ENPP1 variants in patients with GACI and PXE expand the clinical and genetic heterogeneity of heritable disorders of ectopic calcification. PLoS Genet 2022; 18:e1010192. [PMID: 35482848 PMCID: PMC9089899 DOI: 10.1371/journal.pgen.1010192] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 05/10/2022] [Accepted: 04/05/2022] [Indexed: 12/17/2022] Open
Abstract
Pseudoxanthoma elasticum (PXE) and generalized arterial calcification of infancy (GACI) are clinically distinct genetic entities of ectopic calcification associated with differentially reduced circulating levels of inorganic pyrophosphate (PPi), a potent endogenous inhibitor of calcification. Variants in ENPP1, the gene mutated in GACI, have not been associated with classic PXE. Here we report the clinical, laboratory, and molecular evaluations of ten GACI and two PXE patients from five and two unrelated families registered in GACI Global and PXE International databases, respectively. All patients were found to carry biallelic variants in ENPP1. Among ten ENPP1 variants, one homozygous variant demonstrated uniparental disomy inheritance. Functional assessment of five previously unreported ENPP1 variants suggested pathogenicity. The two PXE patients, currently 57 and 27 years of age, had diagnostic features of PXE and had not manifested the GACI phenotype. The similarly reduced PPi plasma concentrations in the PXE and GACI patients in our study correlate poorly with their disease severity. This study demonstrates that in addition to GACI, ENPP1 variants can cause classic PXE, expanding the clinical and genetic heterogeneity of heritable ectopic calcification disorders. Furthermore, the results challenge the current prevailing concept that plasma PPi is the only factor governing the severity of ectopic calcification. Biallelic inactivating mutations in the ENPP1 gene cause generalized arterial calcification of infancy (GACI), a frequently fatal disease characterized by infantile onset of widespread arterial calcification and/or narrowing of large and medium-sized vessels often resulting in the early demise of affected individuals. Significantly reduced, almost zero plasma levels of a potent and endogenous calcification inhibitor, inorganic pyrophosphate (PPi), is thought to be the underlying cause of vascular calcification in GACI. Mutations in ENPP1 have not been found in patients with pseudoxanthoma elasticum (PXE), another genetic multisystem ectopic calcification disorder caused by mutations in the ABCC6 gene. This study reports that ENPP1 mutations can also cause PXE with more favorable clinical outcomes. In addition, it was previously thought that plasma PPi levels correlate with vascular calcification severity. However, we here show that vascular calcification severity does not correlate with plasma PPi levels. The results suggest that in addition to PPi, the long-believed determinant of ectopic calcification, additional mechanisms may be at play in regulating ectopic calcification.
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Affiliation(s)
- Douglas Ralph
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- Genetics, Genomics and Cancer Biology Ph.D. Program, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | | | - Michael A. Levine
- Division of Endocrinology and Diabetes, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Matthew Caffet
- PXE International, Inc., Damascus, Maryland, United States of America
| | - Tamara Wurst
- PXE International, Inc., Damascus, Maryland, United States of America
| | - Amir Hossein Saeidian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- Genetics, Genomics and Cancer Biology Ph.D. Program, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Leila Youssefian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Hassan Vahidnezhad
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Sharon F. Terry
- PXE International, Inc., Damascus, Maryland, United States of America
| | - Frank Rutsch
- Münster University Children’s Hospital, Münster, Germany
| | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Qiaoli Li
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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4
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Li Q, Terry SF, Uitto J. Comment on "Clinical practice guidelines for pseudoxanthoma elasticum (2017)": The importance of mutation analysis. J Dermatol 2022; 49:e248-e249. [PMID: 35318717 DOI: 10.1111/1346-8138.16354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 02/22/2022] [Accepted: 02/24/2022] [Indexed: 11/30/2022]
Affiliation(s)
- Qiaoli Li
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | | | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,PXE International Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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