JAG1 and Miyoshi myopathy: Our recent data showed aberrant Notch activation in cultured and primary human MM cells.3, 5 In contrast, freshly isolated mature CD19+ B cells and CD19+ B cells, which we differentiated to CD38+ plasmablastic cells in vitro, were almost completely devoid of Notch expression.3, 5 To test whether the murine MM cell line MOPC315.BM has activated Notch signalling, we first confirmed expression of the full-length transmembrane-bound form of the Notch receptors (Notch1 and Notch2) and their ligands (Jagged1 and Jagged2) by immunoblotting.