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King's College London - Health: More than a medical matter

First chimeric monkeys born in US

09 January 2012

By Suzanne Elvidge

Appeared in BioNews 639

Three chimeric rhesus monkeys born in the USA have been described as the world's first primate chimeras. Although the term 'chimera' is derived from Greek mythology, in genetics it is an animal made from cells from different fertilised embryos. This creates an organism that is a mixture of different sets of cells with different genetic material.

The team, from the Oregon National Primate Research Centre, created the three monkeys from cells from between three and six embryos. They took cells that can become any tissue in the body, known as totipotent cells, from early embryos and mixed them together.

They then allowed the 'mixed' embryos to develop and implanted them into female rhesus monkeys. The resulting offspring, one called Chimero, and twins called Roku and Hex (six in Japanese and Greek), are healthy and developing normally.

As co-author Dr Shoukhrat Mitalipov explains: 'The cells never fuse, but they stay together and work together to form tissues and organs'. For example, all three monkeys are biologically male, but Roku's body includes some patches of female cells.

Initially, the researchers tried to create chimeric monkeys using a technique similar to that previously used in mice – injecting embryonic stem cells into embryos. However these attempts were unsuccessful, which the researchers suggest may be because the cells used were pluripotent not totipotent. This means the cells can form any tissue except cells used for placental development, and are not able to form entire organisms.

Until now, researchers have carried out much stem cell research in mice, but this failure implies there are key differences between mouse and primate embryonic development.

Professor Robin Lovell-Badge, from the UK National Institute for Medical Research, who was not involved in the study, told BBC News: 'Assumptions about the way human embryos develop have always been based on the mouse', adding that this could be a 'dangerous assumption'.

'We cannot model everything in the mouse', said Dr Mitalipov. 'If we want to move stem cell therapies from the lab to clinics and from the mouse to humans, we need to understand what these primate cells can and can't do'.

The team also suggested that the supposedly pluripotent embryonic stem cells cultured for long periods in a laboratory may not be as 'potent' as those freshly isolated from an embryo, potentially losing the ability to develop into any tissue or organ.

The researchers have stressed that producing human chimeras is not necessary, and in the UK any chimeras containing human stem cells must be destroyed before they reach 14 days old.


Guardian | 05 January 2012
BBC | 05 January 2012
AFP | 05 January 2012
Generation of Chimeric Rhesus Monkeys
Cell | 05 January 2012
Telegraph | 05 January 2012


24 June 2013 - by Sarah Guy 
Researchers in Japan are one step closer to being able to implant human induced pluripotent stem (iPS) cells into an animal embryo. Their aim is to grow a fully-grown human pancreas in an animal, a pig, and ultimately harvest and transplant such organs into patients... [Read More]
07 January 2013 - by John Brinsley 
Mythical ideas of 'chimera', or animals formed or forged of parts derived from various different organisms, have endured throughout history, from Greek folklore and Homer's Iliad through to contemporary science fiction. In fact, organisms arising from human-nonhuman genetic combinations are already with us... [Read More]

10 October 2011 - by Tara Camm 
In 2008, important changes were made to the legislation governing the use of human embryos in research, the UK Human Fertilisation and Embryology Act (HFE Act) 1990. The legislation was extended to five categories of 'human admixed embryos' containing human and animal cellular or genetic components, which were brought within the licensing regime of the HFE Act... [Read More]
13 December 2010 - by Dr Lux Fatimathas 
American researchers have for the first time created mice with genetically two male parents. In a three-step process, utilising stem cell technology to create induced pluripotent stem cells (iPS)... [Read More]
28 April 2008 - by Fiona Fox 
Should scientists enter the media fray on the most controversial aspects of stem cell research when the row is clearly about much more than the science? This is a question that many in the scientific community have raised over the past year in relation to the furore over human-animal hybrid... [Read More]
03 September 2007 - by Professor Marcus Pembrey 
A Parliamentary committee has recently challenged several proposals in the UK Government's draft revised legislation for assisted reproduction and embryo research, published earlier this year. These areas of biomedical research and personal reproductive decisions raise important ethical and social issues. As such, the committee report is welcome, because it re-opens... [Read More]
10 April 2007 - by Antony Blackburn-Starza 
The House of Commons Science and Technology Committee has challenged the UK Government's decision to propose a ban on the creation of hybrid or chimera embryos, calling such a move 'unnecessary'. In the report, the MPs said: 'We find that the creation of human-animal chimera or hybrid... [Read More]

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