CADM1 is expressed as multiple alternatively spliced functional and dysfunctional isoforms in human mast cells

► Human mast cells express 6 alternatively spliced CADM1 isoforms: 4 functional and 2 dysfunctional. ► Long CADM1 SP1 and SP6 are restricted to differentiated human lung mast cells. ► Expression of mixed isoforms reduces adhesion of human mast cells to lung fibroblasts. ► Dysfunctional CADM1 isoforms are found in 40% of mast cells. ► Dysfunctional isoforms limit CADM1 expression and may predispose to various diseases.