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Neural differentiation of mouse epiblast stem cells by inactivating the FGF signalling pathway. Molecular mechanisms to differentiate human and mouse stem cells may be similar but may also vary substantially on occasion. (Credit: Boris Greber)ScienceDaily (Mar. 9, 2010) — They are considered to be the most important model organism for research into human biology: mice may look totally different, but they are in many ways similar to Homo sapiens on a fundamental level. For instance, an impressive 99 per cent of the mouse genes are matched by a corresponding sequence in the human genome. That is also why the law in this part of the world only permits scientists to conduct research on human embryo stem cells when they have "clarified in advance" their specific questions by using animal cells as far as possible. However, such tests are often pointless -- and sometimes even misleading, as a recent study by scientists working with Hans Schöler at the Max Planck Institute for Molecular Biomedicine in Münster demonstrates.

For years scientists have puzzled over to what extent the findings of studies on the embryonic stem cells (ES cells) of mice are transferable to humans. It is certainly true that human and mouse ES cells are both pluripotent. That means they are capable of forming any of the body's cell types, numbering more than 200 in all. And both types of cells have an active Oct4 transcription factor, for example. This is the gene that is essential for maintaining pluripotency, and is what makes egg cells, as well as embryonic stem cells and early embryos, potentially immortal. In other aspects, though, as scientists have known for some time now, human and mouse ES cells differ enormously.

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