Fig. 4. Axon-dependent regulation of the –31/+7 and –4.5/+40 Krox20/lacZ transgenes during nerve regeneration. (A-O) The sciatic nerves from adult –31/+7 and –4.5/+40 Krox20/lacZ transgenic and Krox20^lacZ/+ mice, either untreated (A-C), or cryolesioned (D-O). –31/+7 Krox20/lacZ transgenic and Krox20^lacZ/+ nerves after development for 8 days (D,G,F,I), 16 days (J,L) and 32 days (M,O) post-cryolesion. (E,H,K,N) –4.5/+40 Krox20/lacZ transgenic nerves after development for 12 days (E,H), 16 days (K) and 32 days (N). Teased nerves of the distal region of the sciatic nerve femural branch (A-F, J-O; distal) and proximal to the lesion on the distal side (G-I; proximal). (P-R) Nerves were also transected and teased from the proximal region of the distal stump (proximal) at 8 days for –31/+7 Krox20/lacZ transgenic (P) and Krox20^lacZ/+ (R) and 12 days for –4.5/+40 Krox20/lacZ transgenic (Q). Cryolesioned nerves from both the –31/+7 and –4.5/+40 Krox20/lacZ lines were analysed by immunohistochemistry for GFAP at 8 and 12 days, respectively (S,T; red-brown deposit). MBP from –31/+7 Krox20/lacZ lines was analysed at 8 (U) and 12 (W) days and at 12 days (V,X) from –4.5/+40 Krox20/lacZ lines. ß-galactosidase activity was analysed in teased nerves originating from the most distal side of the lesion (S-V) where significant activity was detected, or adjacent to the lesion (W,X). All preparations were stained for ß-galactosidase activity and counterstained with Nuclear Fast Red. The scale bar represents 25 µm.