Analysis of prion protein mRNA by in situ hybridization in brain and placenta of sheep.

In this study, prion protein (PrP) mRNA was focally detected in brain and placenta of pregnant sheep by Northern blot analysis. In addition, host-encoded cellular prion protein (PrP(C)) was observed in brain and placenta of the ruminant by Western blot analysis as well. Localization of PrP mRNA in pregnant sheep tissues was rendered possible with in situ hybridization. In sheep brain, PrP mRNA was predominantly localized within large neocortical neurons in the cerebrum, Purkinje cells and neurons of the molecular and granule cell layers in the cerebellum. In the placenta, signals were observed in the myometrium, including stratum longitudinale tunicae muscles and circular layers of muscular tunics. In the caruncle and placentome, signals were stronger by in situ hybridization. Since accumulation of the scrapie isoform PrP (PrP(Sc)) is required to PrP(C), these results suggest that brain and placenta of sheep may be important organs and sites for the conversion of PrP(C) to PrP(Sc).