Prominent intra-axonal inclusions were also generated in axons of neurons expressing PrPD177N(M128)-mCh (Fig. 1C), a point mutation (D178N/M129 in humans) that causes prion fatal familial insomnia (28), indicating that axonal aggregates are a generalized feature of at least some familial PrP mutations and not unique to PrPPG14. Here, PRNP is linked to fatal familial insomnia.