Prion protein (PRNP) gene is well known for affecting mammal transmissible spongiform encephalopathies (TSE), and is also reported to regulate phenotypic traits (e.g. growth traits) in healthy ruminants. PRNP is fundamental in the pathogenesis of transmissible spongiform encephalopathies. Generally, PRNP gene is associated with prion diseases, whereas variants of the PRNP gene may also explain some cases of Alzheimer disease (AD) and frontotemporal dementia (FTD) in Caucasian populations.