CHARTING OF JUN FAMILY MEMBER PROTEINS IN THE RAT FOREBRAIN AND MIDBRAIN - IMMUNOCYTOCHEMICAL EVIDENCE FOR A NEW JUN-RELATED ANTIGEN

Immunocytochemistry was used to localize members of the Jun family of immediate-early genes in the forebrain and midbrain of non-stimulated male rats. Antibodies against specific peptide sequences of c-Jun (Ab- 1 and Ab-2 from Oncogene Science) and against expressed proteins of Ju nB and JunD (both from Dr. R. Brave) revealed widespread and unique di stributions for each of these antigens. Charts were made of the distri bution of each antigen, and extensive comparisons were made of previou s results obtained using in situ hybridization to localize mRNAs for c -jun, junB and junD. Our results indicate a generally favorable compar ison between immuno-reactivity and distribution of mRNAs for JunB and JunD, but in the case of c-Jun, immunoreactivity and mRNA were compara ble only with the Ab-1 antibody. Indeed, the immunocytochemical distri bution of the antigen recognized by the c-Jun Ab-2 antibody was distin ctly different from that of the other Jun proteins or mRNAs in the rat brain. This antibody (Ab-2) recognized a nuclear protein found extens ively in the caudate-putamen, nucleus accumbens, layer II of the olfac tory tubercle, the central nucleus of the amygdala, and the lateral di vision of the bed nucleus of the stria terminalis. Scattered labeled n uclei were found in a few other forebrain structures. Within the cauda te-putamen, immunoreactivity was restricted to the matrix compartment, as determined by immunostaining of adjacent sections with the matrix- marker calbindin D-28k. Western blots of caudate-putamen demonstrated that this antibody recognized a protein doublet of molecular masses ap proximately 37 and 34 kDa, distinct from the molecular masses of c-Jun , JunB and JunD. This unique neuroanatomical distribution and molecula r mass suggests that this antibody recognizes a previously undescribed Jun-related antigen.