User:Kaira Hosnedl/New sandbox

The First Cloned Przewalski's Horse
On August 6th, 2020, the world’s first cloned Przewalski’s horse was born. The foal was given the name Kurt, and his cloning process utilized the method of somatic cell nuclear transfer, otherwise referred to as SCNT. This cloning method allowed for the creation of a viable embryo by way of transplanting the DNA of a somatic cell into an enucleated oocyte, or an immature egg cell without a nucleus, thus resulting in the production of an offspring identical to that of the somatic cell donor. To be more specific, a technique known as interspecies cloning, or iSCNT, was utilized due to the fact that the somatic cell and oocyte came from two different species of horse.

The somatic cell donor was a Przewalski’s horse, a stallion that went by the name of Kuporovic. Kuporovic was originally born in the UK in 1975 and was relocated to the US three years later where he eventually died in the year 1998. Due to the conservationists' awareness of the loss of genetic variation among the population of the endangered Przewalski’s horse, Kuporovic’s DNA underwent cryopreservation at the Frozen Zoo in San Diego with hopes that cloning techniques would advance in the near future. The oocyte utilized for the cloning of Kurt came from a domestic horse. With access to a somatic cell and oocyte donor, the cloning of a mammal using nuclei from adult somatic cells could take place. The cryopreserved skin fibroblasts of Kuporovic were removed from the Frozen Zoo and placed in culture until grown at the G1 phase, also known as the first phase of the cell cycle. The nucleus of the oocyte containing the DNA of the domestic horse was removed, thus becoming an enucleated oocyte. After this process was complete, the nucleus from the skin cell was transplanted into the enucleated egg and fused together with an electric current, thus activating the egg. The embryo was then cultured until the formation of a blastocyst was observed, signifying that the embryo was ready to be transplanted into the surrogate mother, which was a different domestic horse. In this case, the male and female gametes, or sperm and egg, are not needed to create a clone. All of the genetic information is coming from the skin cell. This is due to the fact that every cell in an organism’s body has every gene in its genome. This idea that every cell possesses one’s entire genome is referred to as genomic equivalence. Therefore, germ cells were not necessary to clone Kurt since the skin cell from the Przewalski’s stallion already contained two copies of each chromosome, which are usually inherited from the sperm and the egg. After successful transplantation of the embryo into the surrogate mother, it was carried to term resulting in the birth of Kurt, the cloned Przewalski’s horse that is genetically identical to the Przewalski’s stallion Kuporovic.

Kurt the cloned Przewalski’s horse was named after Dr. Kurt Benirschke, a forward-thinking geneticist who developed the idea of cryopreserving genetic material from species considered to be endangered. His ideas led to the creation of a genetic library at the San Diego Zoo called the Frozen Zoo. A collaboration between San Diego Zoo Global (SDZG), ViaGen Equine, and Revive & Restore worked together to make the cloning of Kurt possible, following through with Dr. Benirschke original intentions. Once Kurt matures, he will be relocated to the San Diego Zoo where he will pass on his genes to increase the genetic variation of his species.