The agent that causes prion diseases is thought to be identical to PrPSc, a conformer of the normal prion protein PrPC. Recently a novel protein, termed Doppel (Dpl), was identified that shares significant biochemical and structural homology with PrPC. To investigate the function of Dpl in neurogenesis and in prion pathology, we generated embryonic stem (ES) cells harbouring a homozygous disruption of the Prnd gene that encodes Dpl. After in vitro differentiation and grafting into adult brains of PrPC-deficient Prnp0/0 mice, Dpl-deficient ES cell-derived grafts contained all neural lineages analyzed, including neurons and astrocytes. When Prnd-deficient neural tissue was inoculated with scrapie prions, typical features of prion pathology including spongiosis, gliosis and PrPSc accumulation, were observed. Therefore, Dpl is unlikely to exert a cell-autonomous function during neural differentiation and, in contrast to its homologue PrPC, is dispensable for prion disease progression and for generation of PrPSc.