Norwegian Dairy Goats Naturally Lack a Protein Linked to Prion Disease

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A group of Norwegian dairy goats carries a rare natural mutation in the PRNP gene, which normally provides instructions for making the cellular prion protein. The mutation creates an early stop signal, so goats that inherit two copies do not produce detectable cellular prion protein. The discovery was unusual because these goats appeared healthy despite lacking a protein found in virtually all other mammals. The mutation was first reported in 2012 after researchers screened Norwegian Dairy Goats. In the original genetic survey, the altered version of the gene appeared at an allele frequency of about 11 percent among 192 sampled animals. Researchers identified goats carrying two copies and found no obvious abnormalities in clinical and neurological examinations. The animals were also able to reproduce normally. Prion diseases occur when normally occurring prion protein becomes misfolded and accumulates in the nervous system. In goats, one important prion disease is scrapie. Earlier animal research had already shown that removing or greatly reducing cellular prion protein could protect against prion disease, but the Norwegian goats provided a naturally occurring, non-engineered example. Later experimental work tested goats with and without the natural mutation against scrapie. The goats lacking cellular prion protein remained healthy during the study and did not show the characteristic accumulation of abnormal prion protein, while goats producing the protein developed disease. Goats carrying only one altered copy showed delayed disease compared with goats carrying two normal copies. The discovery is scientifically interesting for two reasons. First, it suggests that cellular prion protein is not essential for normal survival in these goats, although its full biological role remains incompletely understood. Second, naturally resistant animals could potentially be useful for studying prion diseases and for developing livestock with greater resistance. This does not mean that eliminating the protein is automatically safe or useful in humans, because its biological functions and possible effects in different species still require careful study.