After 40 years of deep freezing of DNA, scientists cloned an endangered horse

San Diego Zoo scientists are rebuilding horse cells after 40 years of deep-freezing to clone an endangered species. The San Diego Union-Tribune reports.

Kurt, a 2-month-old foal, looks and behaves like any other young horse. However, it is the Przewalski’s horse, a species native to Central Asia that was once extinct in the wild and is still under threat of extinction. There are only about 2,000 individuals left on the planet.

The San Diego Zoo has high hopes that Kurt will help make a difference for his species. It was cloned from stallion skin cells taken in 1980 and stored at Frozen Zoo, a vast repository of 10,000 cell lines from over 1,100 species and subspecies at San Diego Zoo Global.

San Diego Zoo Global is a non-profit organization that operates the eponymous zoo, safari park, the zoo’s Conservation Research Institute and the zoo’s Global Wildlife Conservation.

In this way, scientists hope to reclaim some of the gene pool that would have otherwise been lost, explains Oliver Ryder, director of genetics at San Diego Zoo Global.

This is the first time that anyone has successfully cloned Przewalski’s horse. Every living horse is associated with 12 wild ancestors. This does not bode well for either of these species, as genetic diversity is required to adapt to changing habitats and fight new diseases.

The researchers were happy to find a stallion with DNA fragments that were largely missing from the rest of its species.

This particular stallion’s ancestors did not reproduce to the same extent as other Przewalski’s horses, so it had rare DNA fragments that would be lost forever if not preserved.

For 40 years, the stallion’s cells were kept frozen at minus 160°C – colder than an evening on the planet Mercury. Now the researchers revived the cells and fused one of them with the unfertilized egg of a domesticated horse. Since the scientists removed the nucleus of the egg, which contains the mother horse’s DNA, almost all of the genetic material came from the stallion.

The team then transplanted the egg back into the horse, which acted as a surrogate mother. This is the same method that was widely used to clone Dolly Sheep in 1996 and has been used since then to clone cattle, cats, deer, and horses, among other species.

Kurt was born on August 6 at a Texas Veterinary Center. The scientists’ plan is to eventually bring Kurt to Safari Park, where he will join 14 Przewalski’s horses at the park as part of a conservation and breeding program.