Feedforward Loop — Gene Regulatory Network Motif
The most over-represented 3-node motif in transcription networks — found in E. coli, yeast, and beyond
FFL Type
Topology:
Coherent Type 1 (AND gate)
Coherent Type 1 (OR gate)
Incoherent Type 1 (AND gate)
Incoherent Type 1 (OR gate)
S
x
signal (X activator):
1
Kinetic Parameters
α
Y
(Y max prod. rate):
2.0
α
Z
(Z max rate):
2.0
β
Y
(Y degradation):
1.0
β
Z
(Z degradation):
1.0
Theory
dY/dt = α
Y
·f
Y
(X,S) − β
Y
·Y
dZ/dt = α
Z
·f
Z
(X,Y,S) − β
Z
·Z
Hill activation: f = S^n/(K^n+S^n)
C1-AND: pulse filter
Rejects brief S pulses
Delays Z response to step
I1-AND: pulse generator
Produces Z pulse then adapts