Hybrid rhino embryos created in final bid to save species
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Scientists have created hybrid northern white rhinoceros embryos in a final attempt to prevent extinction of the charismatic, critically endangered species.
The species, which once widely roamed over Central and East Africa, was almost entirely wiped out by poachers. Following the death of the last male earlier this year, there are only two known northern white rhinos left: Najin (his daughter) and Fatu (his granddaughter). As both are female and Fatu has problems with her reproductive anatomy preventing her carrying embryos, this renders the species functionally extinct.
In a final attempt to save the seemingly doomed species, an international team of biotechnologists led by Professor Cesar Galli of Italian biotech lab, Avantea, are working to save the rhinos by combining the DNA of a remaining northern white rhino with a genetically similar subspecies.
They developed a technique for extracting eggs from 12 female southern white rhinos – which are threatened but not endangered – and fertilising them to create viable embryos which could eventually become rhinos.
17 eggs collected from the southern white rhinos were injected with sperm from living southern white rhino males to create three ‘pure’ southern white rhino embryos.
13 other eggs were injected with sperm from a deceased northern white rhino and four went on to form blastocysts (early embryos containing a few hundred cells). These embryos can be frozen and later implanted into surrogates to yield animals containing northern white rhino DNA. A test using stem cells generated from the pure southern white rhino embryos demonstrated that all the embryos were healthy and viable.
According to Professor Jeanne Loring, a director at the Scripps Research Institute in California, this is “an impressive step forward for the whole field”.
The researchers described the project in a paper published in Nature Communications.
Next, the researchers hope to harvest eggs from Najin and Fatu and fertilise them with northern white rhino sperm, then implant the embryos in a southern white rhino surrogate. If successful, this could result in the birth of pure northern white rhinos. While this would sustain the species for a few years longer, the resultant pool of living northern white rhinos would not be genetically diverse enough to sustain a healthy population.
In the future, the biotechnologists could attempt to use tissue collected from northern white rhinos to create stem cells which could develop into eggs and sperm; previously, stem cell lines have been created using cells collected from Fatu’s skin. Theoretically, there is enough genetic diversity (tissue stored from 12 males and females) to save the species.
According to conservation ecologist Professor Stuart Pimm, who is based at Duke University, US, the efforts are worth celebrating, although many threats to this species and others remain unresolved.
“It would be fantastic to see the northern white rhino back in its natural habitat,” said Pimm. “Let’s celebrate this endeavour, but keep it in perspective. We still live in a world in which we have lost an enormous number of rhinos to poaching and if we have any chance of putting their descendants back into the wild, we’ll have to prevent them from being killed the moment they’re released.”