passages.id: split_5_test_21_passage
passages.type: progene_text
passages.text: We previously demonstrated - in transiently transfected COS-7 cells - that selected mutant V2 vasopressin receptors ( all of which have been identified in X - linked nephrogenic diabetes insipidus patients ) containing inactivating mutations in the C - terminal third of the receptor protein ( including missense , frameshift , or nonsense mutations ) can be functionally rescued by coexpression with a C - terminal V2 receptor fragment ( V2 - tail ) spanning the region where the various mutations occur .