cis versus trans effects
Nuzhdin SV, Tufts DM & Hahn MW 2008 Abundant genetic variation in transcript level during early Drosophila development. Evol Dev 10:683-689.
- one standard interpretation of our results finding a small number of factors for both the segmentation and the dorsal-ventral GRNs is that there may be just a few mutations controlling all of the downstream variation
- this would imply that most of the variation in gene expression that we observe lies in trans-acting factors
- rather than many cis-acting changes in the varying genes
- this contradicts some previous results in Drosophila (e.g., Wittkopp et al. 2004)
- an alternative interpretation, however, is that the structure of the GRNs is such that even multiple cis-acting mutations acting throughout genes in the network would result in only a small number of factors
- this would come about because the network strongly constrains the effects of each member gene
- if each can only act locally as either an activator or a repressor, the emergent behavior of the network may resemble the action of only two factors
- as we cannot distinguish between these two possibilities at the moment, an answer will have to await further linkage studies (e.g., Wayne et al. 2004)
