PTPRC and Miyoshi myopathy: We observed that inoculation of 1 × 106 Vκ*MYC cells into transgenic B6.129S4-Arg1tm1Lky/J mice (hereafter referred to as YARG mice) leads to a progressive increase in the serum monoclonal protein levels as well as the number of B220-CD138+ MM cells in the bone marrow and the spleens (Fig. 1A, B).