by Andre on 28 February 2005
Anyone with an interest in applying quantitative methods in biology has probably come across references to systems biology, but it is not always clear what distinguishes systems biology from biophysics, genomics, or molecular biology. What is a “systems approach”? Here is an outsider’s attempt at an answer:
Most descriptions of systems biology begin with a description of the vast amounts of data generated during the human genome project and the resulting anticlimax upon its completion.* The number of genes was smaller than expected (~25 000) and it was immediately clear that drawing a one-to-one connection between a particular gene and a particular disease or biological function was not going to be a fruitful approach in general. This serves as motivation for an approach that considers genes, and the proteins they code for, in their logical and physical context. Logical context refers to where the gene or protein sits in a regulatory network. Physical context refers to where a gene or protein sits in the cell and how its interactions with its environment affect its function. Can a Biologist Fix a Radio? is an amusing article that also makes a case for something like a systems approach.
Simply acknowledging that a given protein or gene of interest is part of a larger biological system is obvious and does not constitute systems biology. On the other hand deciding what does constitute systems biology seems a bit harder. Here is a list of features that recur in experts’ descriptions:
1) It sees the forest and the trees (see) – Understanding interactions between components is complementary to understanding the components themselves, and only integrating these perspectives will give a full understanding of the properties that emerge in living systems.
2) It is quantitative – It attempts to quantify the effect of a perturbation on a system of interest, not just to determine that there has been some effect.
3) It involves modelling – Creating mathematical or computational models that account for features observed in experiments and suggest new lines of experimentation is considered essential. Modelling is not new in biology (although its impact so far has arguably been small), but including it as a defining feature of systems biology is an acknowledgment that pictorial and word models do not lead to a satisfying understanding of complex systems.
Whatever systems biology is, people claiming to do it are going to have an increasing impact in basic research and medicine. A quick search reveals that there are already several academic departments dedicated to systems biology, and given the hype surrounding the field, this number will likely increase.
If you are interested in learning more I would suggest reading this report written by some people at IBM.
*This is may be too harsh, since researchers involved in the project probably had much more realistic expectations, but the project was still over-hyped in my opinion.