However, certain prion strains have been shown to break these genotypic transmission barriers, e.g., the H95+ and 116AG CWD strains from white-tailed deer were able to produce terminal prion disease in Tg60 mice expressing the 96S deer PrPC, a mouse model resistant to transmission from other CWD isolates [14,16]. This evidence concerns the gene PRNP and prion disease.