Nine prion-free Holstein cows were created by U.S.’s Agricultural Research Service. The study, released early January, reported that the 20-month old bovine participants had their prion gene successfully knocked out before birth, eliminating their ability to make any prions and theoretically, their ability to be infected by “mad cow.” Not only did scientists confirm their inability to be infected by prions, they are living proof that cattle-a natural hosts of prion diseases-can grow normally without prions in their bodies. Previous studies in mice, not a natural host of prion diseases, had shown some abnormalities when the prion gene was similarly manipulated, suggesting that prions play an essential role in animal development. That hypothesis has now been dethroned by these healthy, prion-deficient cattle.
The scientists say these cows might be a safe source of milk, gelatin, collagen, and other bovine-derived products we use in our everyday life. With the FDA’s Dec. 2006 safety approval of using cloned animals for food, these cattle are gaining more attention every day.
Yet the cattle’s existence has not answered a central question: if normal prions aren’t essential for growing up, why do they exist at all?
Source: Nature Biotechnology
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