Mineralization/Anti-Mineralization Networks in the Skin

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DESCRIPTION (provided by applicant): Aberrant mineralization of soft connective tissues has been linked to a number of clinical conditions with significant impact on the overall morbidity and mortality in humans. Furthermore, cutaneous mineralization (calcinosis cutis) is common in a number of acquired inflammatory disorders, including progressive systemic sclerosis, lupus erythematosus and dermatomyositis. The prototype of heritable ectopic mineralization disorders affecting primarily the skin is familial tumoral calcinosis (FTC), a group of disorders manifesting with deposition of calcium phosphate complexes in the skin and subcutaneous tissues, preceded by severe inflammatory reactions. The pathomechanistic links between inflammation/tissue injury and the mineralization processes are currently unknown. We have previously demonstrated that the normophosphatemic variant of FTC (NFTC) is caused by mutations in the SAMD9 gene, the expression of which is regulated by inflammatory cytokines, including TNF-¿ and IFN-¿. We have also shown that SAMD9 negatively regulates EGR1, a transcription factor with an established role in the regulation of tissue calcification and inflammation. Thus, NFTC, a monogenic disorder, provides a unique opportunity to study the mechanisms of ectopic calcification as a consequence of inflammation/tissue injury. The proposed studies are innovative, interdisciplinary and interinstitutional focusing on the central hypothesis that SAMD9 is a critical component of the mineralization/anti-mineralization networks in the skin. An intriguing observation of this gene is that while it is clearly present in the huma and rat genome, it has been deleted from the mouse as a result of genomic rearrangement during evolution. Thus, one of the innovative features of our proposal is to develop a SAMD9-/- knockout rat by zinc finger nuclease-based technologies that have recently been developed and adopted at Jefferson Animal Core Facilities. We are convinced that the proposed studies will provide novel insight into the poorly understood link between inflammation and ectopic mineralization in a number of acquired and heritable disorders, and they provide a novel platform to develop game changing treatments for this, currently intractable, group of disorders.