We used our list of consensus predictions to determine the proportion of down-regulated mRNAs potentially targeted by more than one of the up-regulated miRNAs. Of the 131 down-regulated mRNAs, 102 (78%) were predicted to have miRNA recognition sequences for more than one miRNA. This proportion is significantly higher than expected by chance (hypergeometric P = 2.7×10−5). Analysis of the corresponding proportion on the randomized control group (54/95, 57%) additionally evidenced the significant over-representation of putative targets regulated by multiple miRNAs (z-test P = 0.00068). There was no such over-representation amongst the set of up-regulated mRNAs. This suggests that post-transcriptional mRNA processing in the frontal cortex of alcoholics may be the result of the combined effects of multiple miRNAs acting on the same mRNA.
