Store-operated Ca2+ entry is the major route of replenishment of intracellular Ca2+ in animal cells in response to depletion of Ca2+ stores in the endoplasmic reticulum. It is primarily mediated by the Ca2+ selective release-activated Ca2+ (CRAC) channel which consists of the pore-forming subunits ORAI1–3 and the Ca2+ sensors, STIM1 and STIM2. Recessive loss-of-function mutations in STIM1 or ORAI1 result in immune deficiency and nonprogressive myopathy. Heterozygous gain-of-function mutations in STIM1 cause non-syndromic myopathies as well as syndromic forms of miosis and myopathy with tubular aggregates and Stormorken syndrome; some of these syndromic forms are associated with thrombocytopenia. Increased concentration of Ca2+ as a result of store-operated Ca2+ entry is essential for platelet activation. York Platelet syndrome (YPS) is characterized by thrombocytopenia, striking ultrastructural platelet abnormalities including giant electron opaque organelles and massive, multi-layered target bodies and deficiency of platelet Ca2+ storage in delta granules. We present clinical and molecular findings in 7 YPS patients from 4 families, demonstrating that YPS patients have a chronic myopathy associated with rimmed vacuoles and heterozygous gain-of-function STIM1 mutations. These findings expand the phenotypic spectrum of STIM1-related human disorders and define the molecular basis of YPS.

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Epigenetic dysregulation of miR-34A may comprise an important path in TP53-associated cancer predisposition and represents a therapeutically actionable target with potential clinical relevance.

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