Distinct prion proteins in short and long scrapie incubation period mice.

The Prn-i gene, controlling scrapie incubation period, is linked to or congruent with the murine prion protein (PrP) gene, Prn-p. In prototypic mouse strains with long (l/Ln) and short (NZW) incubation periods, Prn-p transcription is initiated at similar multiple sites. The predicted NZW and l/Ln PrP proteins differ at codons 108 and 189. Codon 189, highly conserved in mammals, lies within a polymorphic BstEll site that is retained in 17 mouse strains known to have short or intermediate incubation times, but is absent in l/Ln and two other inbred mice with long incubation times. Codon 108 in mice with short or intermediate incubation times encodes Leu; in mice with long incubation times it encodes Phe. The correlation of PrP sequence with length of scrapie incubation period suggests, but does not formally prove, congruency between Prn-p and Prn-i.