LOCALIZATION OF THE MESSENGER-RNA FOR A CHICKEN PRION PROTEIN BY INSITU HYBRIDIZATION

The infectious agent (prion) responsible for transmissible spongiform encephalopathies in humans and animals is composed primarily of a 33- to 35-kDa glycoprotein called PrP(Sc) (scrapie isoform of prion protei n), which is a posttranslationally modified form of the normal cell-su rface protein PrP(C). Little is known about the function of PrP(C). In terestingly, chPrP, the chicken homologue of PrP(C), copurifies with a factor from brain that stimulates synthesis of acetylcholine receptor s on skeletal muscle cells. Using in situ hybridization, we report her e that chPrP mRNA is widely distributed in cholinergic and noncholiner gic neurons throughout the adult central nervous system, including tho se in the telencephalic striata, thalamus and hypothalamus, optic tect um, medulla, cerebellum, and spinal cord. The mRNA is present in the b rain and spinal cord as early as embryonic day 6 and is also found in dorsal root ganglia, retina, intestine, and heart. Our data suggest th at if chPrP serves to regulate acetylcholine receptor number on postsy naptic targets, this is not its only function. It is likely that the p rotein plays a more widespread role in the central nervous system and perhaps elsewhere, possibly one related to intercellular communication , adhesion, or recognition. The chicken embryo represents an attractiv e experimental system in which to investigate the normal developmental function of PrP(C).