Pseudoxanthoma elasticum (PXE), a heritable disorder characterized by progressive calcification of elastic structures in the skin, eyes and the cardiovascular system, is caused by mutations in the ABCC6 gene, which encodes MRP6, a member of the ABC transporter family of proteins. Surprisingly, ABCC6 is primarily expressed in the liver and the kidneys, tissues not known to be involved in PXE, suggesting that PXE is a metabolic disease. The precise function of MRP6, consequences of the ABCC6 mutations at the mRNA and protein levels, and the pathomechanisms leading to calcification of the elastic structures are currently unknown. In this application, we propose multidisciplinary state-of-the-art approaches to dissect the pathomechanisms leading to the PXE phenotype based on the unifying hypothesis that PXE is a metabolic disorder of the genome/environment interface.
Specific Aim 1 proposes development of animal models for PXE by ablation of the ABCC6 gene in global and liver-specific manner utilizing gene targeting by mouse ES cell technology. In fact, we have already developed an ABCC-/+ mouse which demonstrates ectopic mineralization in the skin, the retina, and the mid-sized arteries, thus recapitulating features of PXE. The transgenic animals will be examined further for phenotypic manifestations by clinical, histopathological, immunohistochemical, and electron microscopic means. Towards development of potential gene therapy for PXE, the ABCC6-/- mice will be used as a target of gene transfer of the ABCC6 gene under control of liver-specific promoter. Furthermore, we will examine the effects of syngenic liver transplantation and cell-based reconstitution on PXE phenotype in ABCC6 mice.
Specific Aim 2 deals with elucidation of consequences of the ABCC6 mutations at the cellular and tissue level. First, to test the hypothesis that PXE is a primary metabolic disorder, we will subject plasma, urine, and bile from ABCC6-/- mice and plasma and urine from PXE patients for metabolic screen with emphasis on conjugated anionic organic compounds. An alternate hypothesis, viz. that the mutations lead to altered gene expression in the resident cells localized in the lesional tissues, will be tested by gene expression profiling of cells from PXE patients' skin as well as from ABCC6-/- mice, using microarray hybridization technology. Finally, towards identification of the endogenous substrate for MRP6, we will generate a transgenic mouse which traffics MRP6 to the apical, rather than normal baso-lateral membrane location, allowing analysis of bile as the source of the endogenous metabolite responsible for PXE phenotype.We anticipate that these approaches will disclose the pathomechanisms explaining the consequences of ABCC6 gene mutations at the phenotypic level. Such information is critical for development of translational strategies to counteract this devastating multi-system disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR028450-26
Application #
7448689
Study Section
Arthritis, Connective Tissue and Skin Study Section (ACTS)
Program Officer
Baker, Carl
Project Start
1987-01-01
Project End
2010-06-30
Budget Start
2008-07-01
Budget End
2009-06-30
Support Year
26
Fiscal Year
2008
Total Cost
$316,863
Indirect Cost
Name
Thomas Jefferson University
Department
Dermatology
Type
Schools of Medicine
DUNS #
053284659
City
Philadelphia
State
PA
Country
United States
Zip Code
19107
Li, Qiaoli; Kingman, Joshua; van de Wetering, Koen et al. (2017) Abcc6 Knockout Rat Model Highlights the Role of Liver in PPi Homeostasis in Pseudoxanthoma Elasticum. J Invest Dermatol 137:1025-1032
Li, Qiaoli; Kingman, Joshua; Sundberg, John P et al. (2016) Dual Effects of Bisphosphonates on Ectopic Skin and Vascular Soft Tissue Mineralization versus Bone Microarchitecture in a Mouse Model of Generalized Arterial Calcification of Infancy. J Invest Dermatol 136:275-283
Li, Qiaoli; Kingman, Joshua; Uitto, Jouni (2015) Mineral content of the maternal diet influences ectopic mineralization in offspring of Abcc6(-/-) mice. Cell Cycle 14:3184-9
Jin, Liang; Jiang, Qiujie; Wu, Zhengsheng et al. (2015) Genetic heterogeneity of pseudoxanthoma elasticum: the Chinese signature profile of ABCC6 and ENPP1 mutations. J Invest Dermatol 135:1294-1302
Li, Qiaoli; Sundberg, John P; Levine, Michael A et al. (2015) The effects of bisphosphonates on ectopic soft tissue mineralization caused by mutations in the ABCC6 gene. Cell Cycle 14:1082-9
Li, Qiaoli; Price, Thea P; Sundberg, John P et al. (2014) Juxta-articular joint-capsule mineralization in CD73 deficient mice: similarities to patients with NT5E mutations. Cell Cycle 13:2609-15
Li, Qiaoli; Guo, Haitao; Chou, David W et al. (2014) Mouse models for pseudoxanthoma elasticum: genetic and dietary modulation of the ectopic mineralization phenotypes. PLoS One 9:e89268
Li, Qiaoli; Pratt, C Herbert; Dionne, Louise A et al. (2014) Spontaneous asj-2J mutant mouse as a model for generalized arterial calcification of infancy: a large deletion/insertion mutation in the Enpp1 gene. PLoS One 9:e113542
Boraldi, Federica; Bartolomeo, Angelica; Li, Qiaoli et al. (2014) Changes in dermal fibroblasts from Abcc6(-/-) mice are present before and after the onset of ectopic tissue mineralization. J Invest Dermatol 134:1855-1861
Li, Qiaoli; Brodsky, Jill L; Conlin, Laura K et al. (2014) Mutations in the ABCC6 gene as a cause of generalized arterial calcification of infancy: genotypic overlap with pseudoxanthoma elasticum. J Invest Dermatol 134:658-665

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