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Estimating the size of the human interactome

Stumpf, Michael P.H., Thorne, Thomas, de Silva, Eric, Stewart, Ronald, An, Hyeong Jun, Lappe, Michael, Wiuf, Carsten
Proceedings of the National Academy of Sciences of the United States of America 2008 v.105 no.19 pp. 6959-6964
Caenorhabditis elegans, Drosophila melanogaster, fruit flies, genes, humans
After the completion of the human and other genome projects it emerged that the number of genes in organisms as diverse as fruit flies, nematodes, and humans does not reflect our perception of their relative complexity. Here, we provide reliable evidence that the size of protein interaction networks in different organisms appears to correlate much better with their apparent biological complexity. We develop a stable and powerful, yet simple, statistical procedure to estimate the size of the whole network from subnet data. This approach is then applied to a range of eukaryotic organisms for which extensive protein interaction data have been collected and we estimate the number of interactions in humans to be [almost equal to]650,000. We find that the human interaction network is one order of magnitude bigger than the Drosophila melanogaster interactome and [almost equal to]3 times bigger than in Caenorhabditis elegans.