ORAI1 and anhidrosis: Of note, the total knockout of Orai1 in mice is lethal [22], and the tissue-specific deletion of Orai1 or the generation of chimeras through transplantation of hematopoietic Orai1−/− stem cells results in defective T cell activation in response to antigens [22,47], reduced platelet activation and thrombus formation [48], anhidrosis [41], amelogenesis imperfecta [22], and muscle weakness [49].