The dynamics of a feed-forward loop depends on the regulator type in its indirect pathway

Gene networks frequently contain a motif with a feed-forward loop, in which a transcription factor regulates target-gene expression both directly and indirectly via another regulator that also controls the target gene. The results of mathematical modeling of the feed-forward loops with either transcription factor or miRNA as a repressor in the indirect pathway are described. The behavior of such loops in time has been studied. As has been shown, replacement of the second transcription factor with miRNA changes the dynamics of feed-forward loops, conferring new properties to a biological system that are critical for fine tuning of its functions. © 2015, Pleiades Publishing, Inc.