Fig. 2. Northern blot analysis of Lbx1 expression in satellite cells during differentiation in vitro. (A-C) Differentiation of satellite cells in vitro. (A) Sphere-shaped cells after cultivation on a collagen-coated dish for 2 weeks at low density. (B) When cells were cultured at high density, most of the sphere-shaped cells differentiate into flat spindle-shaped cells within 1 day. (C) When cultured in differentiation medium for 5 days, most of the flat spindle-shaped cells eventually fuse to form mature myofibers. Bars, 25 µm. (D) Northern blot analysis. mRNAs were isolated from sphere-shaped cells shown in A (lane 1), flat spindle-shaped cells shown in B (lane 2) and myofibers shown in C (lane 3), and hybridized with probes against Lbx1, Pax7, Myog (myogenin) and Gapdh. Lbx1 and Pax7 were expressed at high levels in sphere-shaped cells (lane 1), and the expressions decreased during myogenic differentiation in vitro (lanes 2 and 3). By contrast, Myog expression was not detected in sphere-shaped cells and it increased during differentiation.