JAG1 and Miyoshi myopathy: Here, we demonstrate that JAG1 and JAG2: (1) exhibit widespread expression in both MM cell lines and MM cells derived from primary BMBs; (2) represent prognostic factors for MM patients, and (3) are tractable as promising therapeutic targets, as demonstrated by a MM xenograft model wherein conditional knockdown (KD) of JAG1 and JAG2 leads to notable effects.