Estimating the size of the human interactome

M. P H Stumpf, Thomas Thorne, Eric De Silva, Ronald Stewart, Jun A. Hyeong, Michael Lappe, Carsten Wiuf

Research output: Contribution to journalArticlepeer-review


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 ≈650,000. We find that the human interaction network is one order of magnitude bigger than the Drosophila melanogaster interactome and ≈3 times bigger than in Caenorhabditis elegans.

Original languageEnglish
Pages (from-to)6959-6964
Number of pages6
JournalProceedings of the National Academy of Sciences
Issue number19
Publication statusPublished - 13 May 2008


  • Evolutionary systems biology
  • Network evolution
  • Network inference
  • Network sampling theory


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