RT Journal
A1 Wu, Chung-I
A1 Shen, Yang
A1 Tang, Tian
T1 Evolution under canalization and the dual roles of microRNAs—A hypothesis
JF Genome Research 
JO Genome Research 
YR 2009 
FD May 01 
VO 19 
IS 5 
SP 734 
OP 743 
DO 10.1101/gr.084640.108 
UL http://genome.cshlp.org/content/19/5/734.abstract 
AB Canalization refers to the process by which phenotypes are stabilized within species. Evolution by natural selection can proceed efficiently only when phenotypes are canalized. The existence and identity of canalizing genes have thus been an important, but controversial topic. Recent evidence has increasingly hinted that microRNAs may be involved in canalizing gene expression. Their paradoxical properties (e.g., strongly conserved but functionally dispensable) suggest unconventional regulatory roles. We synthesized published and unpublished results and hypothesize that miRNAs may have dual functions—in gene expression tuning and in expression buffering. In tuning, miRNAs modify the mean expression level of their targets, but in buffering they merely reduce the variance around a preset mean. In light of the constant emergence of new miRNAs, we further discuss the relative importance of these two functions in evolution.