A Swiss-American collaboration makes vivid just how specific the effect of cellular/tissue context is upon the impact of genetic variation. We have understood for several years that each tissue has a different (if highly overlapping) mix of expressed genes (mRNA). However this study shows, in a study of three different cell types in 75 individuals, that the variation in expression between individuals that is attributable to genetic variation in control elements (i.e. regulatory SNP's) is highly tissue dependent. That is, over half of the regulatory variants only have impact in particular tissues. This suggests that understanding the impact of human genetic variation will take a lot more detailed study and not only in one tissue (usually blood).
[Dimas, A.S., Deutsch, S., Stranger, B.E., Montgomery, S.B., Borel, C., Attar-Cohen, H., Ingle, C., Beazley, C., Arcelus, M.G., Sekowska, M., Gagnebin, M., Nisbett, J., Deloukas, P., Dermitzakis, E.T. and Antonarakis, S.E. (2009) Common Regulatory Variation Impacts Gene Expression in a Cell Type-Dependent Manner, Science.]