The possibility of "duplicating" humans has moved a step closer with the news that a research group in the US has managed to clone a fellow primate, a rhesus macaque monkey, using an artificial twinning process.
Researchers from the Oregon Regional Primate Research Centre in Beverton used a method already employed to twin cattle artificially, but which has never been used to duplicate a primate. The work is published this morning in Science.
The Oregon group used a different technique from that of the scientists who cloned Dolly the sheep at the Roslin Institute in Edinburgh. Dolly came from two distinct cells, a hollowed-out egg cell and a separate adult udder cell, which were fused and encouraged to grow.
The creation of the female monkey, Tetra, involved splitting a very early embryo into pieces. This can occur naturally, resulting in identical twins, but researchers are only just learning how far they can go with the artificial division of early embryos.
The purpose of the experiments was to be able to create identical laboratory animals, according to the head of the project, Dr Gerald Schatten. "In order to move discoveries from the laboratory bench to a patient's bedside, we need to have genetically identical animals," he said.
The team made 368 embryo pieces by splitting 107 embryos into two or four pieces. It got just four pregnancies in 13 tries using its technique, but only Tetra survived. She developed from one of the quartered embryos.
Dolly is a clone and while her genetic material is a duplicate of the original source adult cell, she also carries some non-related material left behind in the hollowedout egg cell. Tetra would share the genetic material of her parents, but after division would be an exact copy of any other part of the source embryo that survived.
The work also raises issues related to human cloning. Humans and simians are closely related and if monkey embryos can be divided, then perhaps human embryos will also survive division. Clones of human embryos were produced at least once before, in 1993 when Dr Jerry Hall claimed to have cloned human embryos by splitting, after which he said he had destroyed them.
