PRNP and prion disease: Since Mgrn1 over-expression rescued the endo-lysosomal trafficking defects associated with the presence of cytosolically exposed forms of PrP in vitro[9], we set out to test whether Mgrn1 levels influence PrPSc-mediated prion disease in vivo by inoculating mice that express no Mgrn1 and mice that over-express Mgrn1 with RML prions.