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Scientists said to clone embryos of extinct frog

March 18, 2013
Courtesy of the University of New South Wales
and World Science staff

An extinct frog that used to give birth through its mouth has had its genes re­vived in em­bryos created through cloning tech­nol­o­gy, bio­lo­gists have an­nounced.

The bi­zarre Aus­tral­ian gastric-brooding frog, Rheo­ba­tra­chus silus – which swal­lowed its eggs, brooded its young in its stom­ach then bore the lit­tle frogs through its mouth – died out in 1983.

The scientists said they re­cov­ered cell nu­clei from tis­sues col­lect­ed in the 1970s and kept in a deep freez­er. In re­peat­ed ex­pe­ri­ments over five years, they used a lab­o­r­a­to­ry tech­nique known as so­mat­ic cell nu­clear trans­fer, im­planting a “dead” cell nu­cle­us in­to a fresh egg from an­oth­er frog spe­cies.

They took fresh do­nor eggs from the dis­tantly re­lat­ed Great Barred Frog, Mixo­phyes fas­ci­o­la­tus, in­ac­ti­vat­ed the egg nu­clei and re­placed them with dead nu­clei from the ex­tinct frog. Some of the eggs spon­ta­ne­ously be­gan to di­vide and grow to early em­bry­o stage – a ti­ny ball of many liv­ing cells.

Al­though none of the em­bry­os sur­vived be­yond a few days, tests con­firmed that the di­vid­ing cells con­tained the ex­tinct frog’s ge­net­ic ma­te­ri­al, the sci­en­tists said.

“We are watch­ing Laz­a­rus arise from the dead, step by ex­cit­ing step,” said Mike Arch­er of the Uni­vers­ity of New South Wales in Syd­ney, Aus­tral­ia, lead­er of the re­search team, known as the Laz­a­rus Proj­ect. Lazarus is a Bib­lical fi­gure said to have been raised from the dead by Je­sus.

“We’re in­creas­ingly con­fi­dent that the hur­dles ahead are tech­no­log­i­cal and not bi­o­log­i­cal and that we will suc­ceed. Im­por­tant­ly, we’ve dem­on­strat­ed al­ready the great prom­ise this tech­nol­o­gy has as a con­serva­t­ion tool when hun­dreds of the world’s am­phib­i­an spe­cies are in cat­a­stroph­ic de­cline.”

Arch­er al­so dis­cussed his in­ter­est in cloning the ex­tinct Aus­tral­ian thy­la­cine, or Tas­ma­ni­an ti­ger, over the week­end at the TEDx De­Ex­tinc­tion event in Wash­ing­ton DC, hosted by Re­vive and Re­store and the Na­t­ional Ge­o­graph­ic So­ci­e­ty. Re­search­ers from around the world are gath­ered there to dis­cuss prog­ress and plans to “de-ex­tinct” oth­er ex­tinct an­i­mals and plants. Pos­si­ble can­di­date spe­cies in­clude the woolly mam­moth, do­do, Cuban red ma­caw and New Zealand’s gi­ant moa.


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Biologists say they have revived and reactivated the genome of an extinct frog through cloning technology. The bizarre Australian gastric-brooding frog, Rheobatrachus silus – which swallowed its eggs, brooded its young in its stomach and gave birth through its mouth – died out in 1983. The team, known as the Lazarus Project, recovered cell nuclei from tissues collected in the 1970s and kept in a deep freezer. In repeated experiments over five years, the researchers used a laboratory technique known as somatic cell nuclear transfer, implanting a “dead” cell nucleus into a fresh egg from another frog species. They took fresh donor eggs from the distantly related Great Barred Frog, Mixophyes fasciolatus, inactivated the egg nuclei and replaced them with dead nuclei from the extinct frog. Some of the eggs spontaneously began to divide and grow to early embryo stage – a tiny ball of many living cells. Although none of the embryos survived beyond a few days, tests confirmed that the dividing cells contained the extinct frog’s genetic material, the scientists said. “We are watching Lazarus arise from the dead, step by exciting step,” said the leader of the Lazarus Project team, Professor Mike Archer, of the University of New South Wales in Sydney, Australia. “We’ve reactivated dead cells into living ones and revived the extinct frog’s genome in the process.” “We’re increasingly confident that the hurdles ahead are technological and not biological and that we will succeed. Importantly, we’ve demonstrated already the great promise this technology has as a conservation tool when hundreds of the world’s amphibian species are in catastrophic decline.” Archer also discussed his interest in cloning the extinct Australian thylacine, or Tasmanian tiger, over the weekend at the TEDx DeExtinction event in Washington DC, hosted by Revive and Restore and the National Geographic Society. Researchers from around the world are gathered there to discuss progress and plans to ‘de-extinct’ other extinct animals and plants. Possible candidate species include the woolly mammoth, dodo, Cuban red macaw and New Zealand’s giant moa.