Figure 7.

Evidence for axonal transport of GDF-15 by ligation of the sciatic nerve of adult mouse. a, Schematic image of the sciatic nerve and its distal and proximal segments adjacent to a double ligation at the mid-gluteal region. D, Distal, P, proximal; Dl, distal ligature, Pl, proximal ligature. b, Accumulation of radiolabeled GDF-15 in the ligated sciatic nerve 15 h after injection of ∼100–200 ng of radiolabeled GDF-15 into the gastrocnemius muscle. The amounts in the sciatic nerve segments (picograms, normalized to 10 ng in the injection site at time the animal was killed) are plotted as a function of distance along the sciatic nerve as indicated in a. Black circles, GDF-15 in sciatic nerve with ligatures (n = 4); gray squares, GDF-15 in sciatic nerve with ligatures and distal transection to abolish axonal transport (n = 3). Error bars, SEM. Statistical significance is indicated by *p < 0.025. c, Amounts of radiolabeled GDF-15 are plotted as in b for a sciatic nerve without ligation or transection (black diamonds), compared with the control side (gray triangles). Note the lack of a significant gradient from distal to proximal segments.