Fig. 5. Insulin is a dose-sensitive myogenic-instructive differentiation signal. The myogenic potential of MLNSC was determined as a function of insulin concentration. (A) The dose sensitivity of CD31^- CD35^- NSCs grown in MB-media to produced multilineage clones was determined. (B) The differentiation of NSCs into specific myogenic derivatives is also dose sensitive. Presented is the mean±s.d. of three experiments demonstrating that, as the concentration of insulin is increased, skeletal myogenic (sk-MHC⁺) differentiation is favored relative to cardiomyocytes (cardiac MHC and troponin immunoreactivity and the visual appearance of beating). (C,D) Increasing insulin signaling favors skeletal muscle differentiation. Presented is the mean±s.d. of three experiments using IR^low (C) and IR^high (D) fractionated NSCs. Cardiomyocyte differentiation is favored at low concentrations or when the number of receptors is reduced, whereas increased insulin signaling favored skeletal muscle formation.