Considered for a long time to be insignificant variations around a significant mean, stochasticity in gene expression is now clearly demonstrated to be important in many situations and in many organisms [ 1- 16] and to participate in various biological processes [ 15- 20], as formerly proposed [ 21].
Many standard statistical models used to examine population dynamics ignore significant sources of stochasticity.
These results indicate that Teff-Treg cross-regulation is a key element in governing the oscillatory behavior of the immune system and drive the presence of relapses in MS, but at the same time indicate a significant component of stochasticity in the generation of clinical relapses, limiting our predictive ability.
Stochasticity gets significant when some discrete molecular events become rare.
Cell responses to these drugs clearly showed that both MFI and NV were affected, indicating that the chromatin environment of the reporter gene plays a significant role in the stochasticity of its expression.
This means that a stochastic approach would not offer significant benefits, as the intrinsic stochasticity in the system is negligible, and so a deterministic model was considered more appropriate to represent these species and their interactions.
However, as empirical studies are limited we have no a priori global estimate, and we might expect significant geographic variation or demographic stochasticity [39], [40].
Although assumptions (a) – (d) might appear restrictive, the specified class of reactions is generic and encompasses the standard equations used in the modelling of genetic and regulatory networks, the cellular circuits where stochasticity is most significant.
Thus, a significant part of demographic or environmental stochasticity is tightly linked with genetic heterogeneity between individuals and vice versa, and disentangling the relative influence of each process can be difficult.
Comparisons between deterministic and stochastic models of the Ostreococcus clock using a range of molecule numbers, including the levels experimentally observed here, have previously revealed that stochasticity indeed has potentially significant effects on free-running behavior and desynchronization of cells [ 20].
