TRDN and catecholaminergic polymorphic ventricular tachycardia: To date, there has only been limited success in defining the mechanism underlying CPVT caused by recessive mutations in CASQ2. CASQ2 works alongside RYR2 with the proteins junctin (gene ASPH, OMIM accession 600582) and triadin (gene TRDN, OMIM accession 603283) to form the calcium release unit (CRU) (Bal et al.