Network motifs: simple building blocks of transcription
networks.
Uri Alon
Molecular Cell Biology, Weizmann Institute of Science, Herzel 1,
Rehovot, 76100, Israel (urialon@weizmann.ac.il)
Cellular responses are regulated by complex networks of molecular
interactions. A major goal of systems biology is to understand the
behavior of these networks. In order to identify the basic building
blocks of these networks we defined 'network motifs': patterns of
connections that recur in the network much more often than in randomized
networks. We find that the transcription networks of S. cerevisae and E.
coli are composed of several highly significant network motifs. We
analyzed these motifs by means of high-resolution gene expression
experiments using GFP reporter-strain libraries developed in our lab. We
find that each of the network motifs has a specific information
processing role. We demonstrate how this approach can be used to detect
motifs in other biological networks, such as the synaptic connection
neuronal network of C. elegans. Some of the network motifs in the
neuronal network are the same as the network motifs found in
transcription networks, raising the possibility that these shared
circuit patterns perform similar information processing tasks. The
network motif detection algorithms can be applied to define the building
blocks of virtually any biological network [Shen-Orr et al, Nature
Genetics 31:64 2002; Milo et al Science 298:824 2002;
www.weizmann.ac.il/mcb/UriAlon].