Amino-terminal phosphorylation of c-Jun regulates apoptosis in the retinal ganglion cells by optic nerve transection.

PURPOSE: To examine the involvement of c-Jun and c-Jun N-terminal phosphorylation (JNP) in apoptosis of retinal ganglion cells (RGCs) after the optic nerve (ON) transection.

METHODS

The expression and phosphorylation of c-Jun protein and apoptosis in RGCs were examined after ON transection in wild-type mice and mice in which both phosphoacceptor serines of Jun have mutated to alanines (c-Jun[AA] mice). The fluorescent tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was applied to the superior colliculi (SC), and the right ON was severed after 7 days. After two more weeks, the average number of RGCs per field was calculated.

RESULTS

JNP and TUNEL-labeled apoptotic nuclei were detected in the ganglion cell layer (GCL) of the retina of the wild-type mice in response to ON transection. The numbers of TUNEL-positive nuclei in the c-Jun(AA) mice was reduced in comparison to those in wild-type mice. Retrograde labeling showed that the number of the RGCs in the retinas on the injured side of the c-Jun(AA) mice was significantly higher than in wild-type mice 14 days after the lesion.

CONCLUSIONS

These results suggest that there is a partial but significant contribution of JNP to the induction of apoptosis in RGCs by ON transection.