January 5, 2012

expert reaction to generation of chimeric rhesus monkeys as published in Cell

New research demonstrated the possibility of generating chimeric monkeys.

Prof Robin Lovell-Badge, Head of Division, National Institute for Medical Research, said:

“Chimeras have been and continue to be a very powerful experimental tool to help understand details of embryo development. For example, to determine which cell type in an early embryo gives rise to a specific tissue, or to ask when do cells in a particular location in the embryo become restricted to a specific fate, such as forming the embryo proper or extraembryonic tissues? However, almost all of these details have been determined using the mouse and it has only been an assumption that human and other mammals develop in similar ways. As this paper shows, this assumption is wrong for the macaque monkey, and as macaques are much closer to humans than mice, the same may be true for us. For example, it was far more difficult to make chimeras, suggesting that embryo organisation and decisions of cell fate occur comparatively earlier and are more rigid in the macaque than in the mouse. Chimeras are also used to explore cell potential, where cells can be totipotent, pluripotent, multipotent or unipotent. They are frequently used in the mouse to test the pluripotentiality of cell lines such as embryonic stem (ES) cells and induced pluripotent stem (iPS) cells by their ability to contribute to a wide range of tissues. There has been a suspicion for some time that most human and monkey ES and iPS cell lines are different, and this work supports this notion as the macaque ES cells tested were unable to mix in with cells of the host embryos. This may be reassuring to those who worry that human ES cells could be used to make chimeric people (although in itself this should not be a concern, as such rare individuals already exist from the spontaneous merger of two early embryos), but it may be a concern for regenerative medicine if such cells are not as flexible as hoped. However, there are new methods to make pluripotent human cell lines that more closely resemble mouse ES cells, and it is important that the potential of equivalent monkey cells are explored in chimeric embryos.

“Chimeras are also frequently used in research to ask questions about gene function, and the type of chimera made in this study may also prove to be a valuable way to test whether this is conserved from mouse to monkey.”

‘Generation of Chimeric Rhesus Monkeys’ by Masahito Tachibana et al., published in Cell on Thursday 5th January 2012.