Around 15% of all prion diseases arise due to dominantly inherited mutations in the PRNP gene, which encodes the ubiquitously expressed, highly conserved prion protein, PrP^C. The normal function of PrP remains elusive, however, and we have learnt relatively little about this from PrP knockout mice. These are phenotypically essentially normal apart from some subtle deficits. Roles for PrP in cell signaling, peripheral nerve myelination and maintenance of circadian rhythms have all been proposed. More recently, a role for PrP in neuronal development is emerging in supporting the proliferation and rate of differentiation of neuronal precursor cells.1 Is there more to be learnt about PrP function from the effects of mutant forms associated with inherited prion disease? Perhaps through …