Elevated expression of jun and fos-related proteins in transplanted striatal neurons.

The basal expression of the immediate-early gene protein products fos, fos-related antigens (FRA's), jun and krox-24 was examined using immunocytochemical methods in intrastriatal grafts derived from fetal striatal primordia. Whereas very few, if any, normal adult striatal neurons expressed jun, many neurons in the striatal graft expressed jun at high levels. FRA's, but not fos, were also occasionally induced in some grafted striata. krox-24 was expressed in normal adult striatal neurons, and to a lesser extent in transplanted striatal neurons. These results show that neurons of intrastriatal grafts express jun at substantially higher levels than host striatal neurons, and this may be related to the previously reported increased transcription of neuropeptides in striatal grafts, and/or to the possible failure of transplanted neurons to fully establish normal connections with the host tissue.