Figure 4

Quantification of proliferative Schwann cells in control vs. neurectomized larvae. (A) Schematic representation of the two areas of the larvae in which the number of proliferative (BrdU incorporating) Schwann cells was determined. The proximal area spans between the sixth to the eighth somites (two somites behind the neurectomy point) and the distal area begins two somites posterior to the anus. Proliferation was measured at different time points by BrdU incorporation in tg(foxd3:GFP) larvae (see Methods). (B, C) Schwann cells are actively proliferating from 3 to 4 dpf in control larvae. By day 6 however, there is a significant reduction in the number of proliferative cells in both areas analyzed, and by day 7 there is essentially no BrdU labeled Schwann cells. In (D), data from panels B and C is graphed to compare proliferation in both areas. (E) The proliferative response of Schwann cells to denervation was evaluated at days 6 and 7 post neurectomy, when proliferation in these cells has normally ceased. tg(foxd3:GFP) transgenic larvae were neurectomized at 5 dpf and the number of GFP+/BrdU + cells was quantified in control and neurectomized larvae at 6 dpf (24 hpn) and 7 dpf (48 hpn). The number of proliferating Schwann cells was different between control and neurectomized fish at 48 hpn in the proximal area. n.s: non-significant, **P <0.01, ***P <0.001.