COMPARISON OF C-JUN, JUNB, AND JUND MESSENGER-RNA EXPRESSION AND PROTEIN IN THE RAT DORSAL-ROOT GANGLIA FOLLOWING SCIATIC-NERVE TRANSECTION

The present study was designed to compare the expression of the Jun fa mily of protooncogenes following nerve injury. Adult rats were anesthe tized and the sciatic nerve transected. Dorsal root ganglia (DRG) at 1 , 2, 3, and 7 days after nerve transection were collected, their total RNA extracted, and Northern blots performed using P-32-labeled oligon ucleotide probes. The constitutive expression of c-jun mRNA was very l ow in DRG. Induction of c-jun mRNA was observed by day 1 after nerve t ransection, with a sixfold peak at 3 days and a twofold induction stil l present by day 7. The constitutive expression of junB mRNA was also low in the DRG, and sciatic nerve transection produced only a modest i nduction (1.7-fold by day 3) in the DRG ipsilateral to the nerve cut. junD mRNA was constitutively expressed at high levels in the DRG, and its level of expression did not change after sciatic nerve transection . Immunocytochemistry studies demonstrated a pattern of c-Jun, JunB, a nd JunD immunoreactivity (IR) associated with the cell nuclei of DRG n eurons. c-Jun IR was found at very low levels in the undamaged contral aterai DRG neurons, but sciatic nerve transection dramatically increas ed the number of c-Jun-immunoreactive neurons. Dot blot immunoblotting assay confirmed that the DRG ipsilateral to the sciatic nerve cut con tained a higher level of c-Jun protein than the contralateral control DRG. Similar to c-Jun LR, JunB IR was minimal in the undamaged contral ateral DRG. However, the DRG ipsilateral to the nerve transection did not show an increase in the number of immunoreactive neurons. JunD pro tein was expressed at high levels in the contralateral DRG, and this l evel of expression persisted after sciatic nerve transection in the ip silateral DRG. DNA gel retardation assay experiments with an AP-1 cons ensus sequence showed a single DNA-protein complex. This complex was i ncreased in ipsilateral as compared with contralateral DRG extracts. T he amount of DNA-protein complex was reduced by c-Jun protein antiseru m but was not altered when treated with a Fos antibody. We conclude th at c-jun, junB and junD mRNAs and proteins are differentially regulate d in the DRG after sciatic nerve transection. (C) 1995 Wiley-Liss, Inc .