Pseudoxanthoma Elasticum as a Paradigm of Heritable Ectopic Mineralization Disorders

Pseudoxanthoma elasticum (PXE), caused by ABCC6/MRP6 mutation, is a heritable multisystem disorder in humans. The progressive clinical manifestations of PXE are accompanied by ectopic mineralization in various connective tissues. However, the pathomechanisms underlying the PXE multisystem disorder remains obscure, and effective treatment is currently available. In this study, we generated zebrafish abcc6a mutants using the transcription activator-like effector nuclease (TALEN) technique. In young adult zebrafish, abcc6a is expressed in the eyes, heart, intestine, and other tissues. abcc6a mutants exhibit extensive calcification in the ocular sclera and Bruch’s membrane, recapitulating part of the PXE manifestations. Mutations in abcc6a upregulate extracellular matrix (ECM) genes, leading to fibrotic heart with reduced cardiomyocyte number. We found that abcc6a mutation reduced levels of both vitamin K and pyrophosphate (PPi) in the serum and diverse tissues. Vitamin K administration increased the gamma-glutamyl carboxylated form of matrix gla protein (cMGP), alleviating ectopic calcification and fibrosis in vertebrae, eyes, and hearts. Our findings contribute to a comprehensive understanding of PXE pathophysiology from zebrafish models.

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Structural and Functional Characterization of the ABCC6 Transporter in Hepatic Cells: Role on PXE, Cancer Therapy and Drug Resistance

International Journal of Molecular Sciences ◽

10.3390/ijms22062858 ◽

2021 ◽

Vol 22 (6) ◽

pp. 2858

Author(s):

Faustino Bisaccia ◽

Prashant Koshal ◽

Vittorio Abruzzese ◽

Maria Antonietta Castiglione Morelli ◽

Angela Ostuni

Keyword(s):

Cancer Therapy ◽

Functional Characterization ◽

Physiological Role ◽

Pseudoxanthoma Elasticum ◽

Connective Tissues ◽

Functional Studies ◽

Extracellular Milieu ◽

Hepatic Cells ◽

Ectopic Mineralization ◽

Anti Cancer

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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Pseudoxanthoma elasticum with prominent arterial calcifications evoking CD73 deficiency

Vascular Medicine ◽

10.1177/1358863x19853360 ◽

2019 ◽

Vol 24 (5) ◽

pp. 461-464 ◽

Cited By ~ 4

Author(s):

Magali Devriese ◽

Anne Legrand ◽

Marie-Cécile Courtois ◽

Xavier Jeunemaitre ◽

Juliette Albuisson

Keyword(s):

Vascular Calcification ◽

Pseudoxanthoma Elasticum ◽

Arterial Calcification ◽

Elastic Fibers ◽

Connective Tissues ◽

Tibial Arteries ◽

Ectopic Mineralization ◽

Abcc6 Gene ◽

Next Generation Sequencing Ngs ◽

Eye Lesions

Pseudoxanthoma elasticum (PXE) is a rare disorder characterized by skin, eye, and cardiovascular lesions due to ectopic mineralization and fragmentation of elastic fibers of connective tissues. We present an atypical case of PXE with diffuse vascular calcification and negligible skin and eye lesions. The patient was a 37-year-old man suffering from severe bilateral arterial calcifications in superficial femoral and posterior tibial arteries. Eye fundoscopy and skin examination were first considered normal. This phenotype suggested first the diagnosis of Arterial Calcification due to Deficiency of CD73 (ACDC) characterized by mutations in NT5E gene. However, we found two variants in ABCC6 gene, and no variant in NT5E. Skin reexamination revealed few lateral skin papules confined to the scalp. Phenotypic overlap was described in vascular calcification disorders, between GACI and PXE phenotypes, and we discuss here expansion of this overlap, including ACDC phenotype. Identification of these expanding and overlapping phenotypes was enabled by genetic screening of the corresponding genes, in a systematic approach. We propose to create a calcification next generation sequencing (NGS) panel with NT5E, GGCX, ENPP1, and ABCC6 genes to improve the molecular diagnosis of vascular calcification.

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The Role of Vitamin K and Its Related Compounds in Mendelian and Acquired Ectopic Mineralization Disorders

International Journal of Molecular Sciences ◽

10.3390/ijms20092142 ◽

2019 ◽

Vol 20 (9) ◽

pp. 2142

Author(s):

Lukas Nollet ◽

Matthias Van Gils ◽

Shana Verschuere ◽

Olivier Vanakker

Keyword(s):

Vitamin K ◽

Current Knowledge ◽

Pseudoxanthoma Elasticum ◽

Ectopic Calcification ◽

Multifactorial Diseases ◽

Multiple Organs ◽

Keutel Syndrome ◽

Ectopic Mineralization ◽

Related Compounds

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders.

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Dysregulation of gene expression in ABCC6 knockdown HepG2 cells

Cellular & Molecular Biology Letters ◽

10.2478/s11658-014-0208-2 ◽

2014 ◽

Vol 19 (4) ◽

Cited By ~ 17

Author(s):

Rocchina Miglionico ◽

Maria Armentano ◽

Monica Carmosino ◽

Antonella Salvia ◽

Flavia Cuviello ◽

...

Keyword(s):

Hepg2 Cells ◽

Autosomal Recessive ◽

Pseudoxanthoma Elasticum ◽

Arterial Calcification ◽

Elastic Fibers ◽

Ectopic Calcification ◽

Ectopic Mineralization ◽

Abcc6 Gene ◽

Basolateral Plasma Membrane

AbstractABCC6 protein is an ATP-dependent transporter that is mainly found in the basolateral plasma membrane of hepatocytes. ABCC6 deficiency is the primary cause of several forms of ectopic mineralization syndrome. Mutations in the human ABCC6 gene cause pseudoxanthoma elasticum (PXE), an autosomal recessive disease characterized by ectopic calcification of the elastic fibers in dermal, ocular and vascular tissues. Mutations in the mouse ABCC6 gene were also associated with dystrophic cardiac calcification. Reduced levels of ABCC6 protein were found in a β-thalassemic mouse model. Moreover, some cases of generalized arterial calcification in infancy are due to ABCC6 mutations. In order to study the role of ABCC6 in the pathogenesis of ectopic mineralization, the expressions of genes involved in this process were evaluated in HepG2 cells upon stable knockdown of ABCC6 by small hairpin RNA (shRNA) technology. ABCC6 knockdown in HepG2 cells causes a significant upregulation of the genes promoting mineralization, such as TNAP, and a parallel downregulation of genes with anti-mineralization activity, such as NT5E, Fetuin A and Osteopontin. Although the absence of ABCC6 has been already associated with ectopic mineralization syndromes, this study is the first to show a direct relationship between reduced ABCC6 levels and the expression of pro-mineralization genes in hepatocytes.

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INZ-701, a recombinant ENPP1-Fc protein, prevents ectopic mineralization in a mouse model of pseudoxanthoma elasticum

Bone Reports ◽

10.1016/j.bonr.2021.100768 ◽

2021 ◽

Vol 14 ◽

pp. 100768

Author(s):

Zhiliang Cheng ◽

Joely D. Jacobs ◽

Kevin O'Brien ◽

David Thompson ◽

Jouni Uitto ◽

...

Keyword(s):

Mouse Model ◽

Pseudoxanthoma Elasticum ◽

Ectopic Mineralization

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Administration of Bone Marrow Derived Mesenchymal Stem Cells into the Liver: Potential to Rescue Pseudoxanthoma Elasticum in a Mouse Model (Abcc6−/−)

Journal of Biomedicine and Biotechnology ◽

10.1155/2012/818937 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Qiujie Jiang ◽

Shunsuke Takahagi ◽

Jouni Uitto

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Mesenchymal Stem Cells ◽

Pseudoxanthoma Elasticum ◽

Loss Of Function ◽

Hepatic Differentiation ◽

Ectopic Mineralization ◽

Stromal Cell Derived Factor ◽

Intrasplenic Injection ◽

Partial Correction

Pseudoxanthoma elasticum (PXE) is a heritable ectopic mineralization disorder caused by loss-of-function mutations in theABCC6gene which is primarily expressed in the liver. There is currently no effective treatment for PXE. In this study, we characterized bone marrow derived mesenchymal stem cells (MSCs) and evaluated their ability to contribute to liver regeneration, with the aim to rescue PXE phenotype. The MSCs, isolated from GFP-transgenic mice by magnetic cell sorting, were shown to have high potential for hepatic differentiation, with expression ofAbcc6, in culture. These cells were transplanted into the livers of 4-week-old immunodeficientAbcc6−/−mice by intrasplenic injection one day after partial hepatectomy, when peak expression of the stromal cell derived factor-1 (SDF-1) in the liver was observed. Fluorescent bioimaging analyses indicated that transplanted MSCs homed into liver between day 1 and 7, and significant numbers of GFP-positive cells were confirmed in the liver by immunofluorescence. Moreover, enhanced engraftment efficiency was observed with MSCs with high expression levels of the chemokine receptor Cxcr4, a receptor for SDF-1. These data suggest that purified MSCs have the capability of differentiating into hepatic lineages relevant to PXE pathogenesis and may contribute to partial correction of the PXE phenotype.

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