Interplay of degeneracy and non-degeneracy in fluctuations propagation in coherent feed-forward loop motif

TL;DR

This paper develops a stochastic framework to analyze how fluctuations propagate through coherent feed-forward loop motifs, considering different pathways and integration mechanisms, revealing diverse fluctuation behaviors and identifying a maximal fluctuation level in type 1 motifs.

Contribution

It introduces a comprehensive analytical model for fluctuations in coherent feed-forward loops, accounting for pathway contributions and integration mechanisms, which was not previously available.

Findings

Analytical expression for output fluctuation contributions.

Diverse degeneracy and non-degeneracy in fluctuation terms.

Maximal fluctuation level identified in type 1 motifs.

Abstract

We present a stochastic framework to decipher fluctuations propagation in classes of coherent feed-forward loops. The systematic contribution of the direct (one-step) and indirect (two-step) pathways is considered to quantify fluctuations of the output node. We also consider both additive and multiplicative integration mechanisms of the two parallel pathways (one-step and two-step). Analytical expression of the output node's coefficient of variation shows contributions of intrinsic, one-step, two-step, and cross-interaction in closed form. We observe a diverse range of degeneracy and non-degeneracy in each of the decomposed fluctuations term and their contribution to the overall output fluctuations of each coherent feed-forward loop motif. Analysis of output fluctuations reveals a maximal level of fluctuations of the coherent feed-forward loop motif of type 1.