MBTPS1 and Miyoshi myopathy: Since manipulation of GFI1 levels revealed a correlated modulation of c-Myc (Figure 3C,D,F), and c-Myc is considered a major contributor to the MM malignant phenotype [63,64], we further determined if GFI1-modulated S1P levels control MM cell viability through modulation of c-Myc expression and stability.