Cardiovascular disease (CVD) is a leading cause of morbidity and mortality in Europe. This proposal addresses one of the hallmark changes in CVD and premature aging, namely medial vascular calcification (VCm). Considered a good target for diagnosis and prevention, a comprehensive understanding of the causes and consequences of VCm is lacking. We aim to contribute to this knowledge by studying a monogenic form of VCm, pseudoxanthoma elasticum (PXE), caused by ABCC6 mutations. Our first aim is to study the natural history of VCm in PXE patients, as this has not been done in a large cohort. Through our collaboration in a European consortium (EuroSoftCalcNet) we will gain insight in how VCm presents itself and how it progresses in a large patient group. Our second aim is to investigate the molecular mechanisms behind disease variability in VCm. The calcification inhibitor inorganic pyrophosphate (PPi) has a central role in the pathophysiology of VCm and was noted to be decreased in PXE. However, the underlying mechanisms and the role of PPi in disease variability and progression are unknown. We will study these mechanisms in an in vitro PXE model. Finally, modifier genes influencing the VCm phenotype will be identified using Whole Exome Sequencing and functionally validated in a zebrafish model. The outcome of this proposal will contribute to improving management and prognosis of PXE patients but also of patients with other VCm phenotypes such as chronic kidney disease or aging.