The use of synthetic non-coding RNAs for post-transcriptional regulation of gene 
expression has not only become a standard laboratory tool for gene functional 
studies but it has also opened up new perspectives in the design of new and 
potentially promising therapeutic strategies. Bioinformatics has provided 
researchers with a variety of tools for the design, the analysis, and the 
evaluation of RNAi agents such as small-interfering RNA (siRNA), short-hairpin 
RNA (shRNA), artificial microRNA (a-miR), and microRNA sponges. More recently, a 
new system for genome engineering based on the bacterial CRISPR-Cas9 system 
(Clustered Regularly Interspaced Short Palindromic Repeats), was shown to have 
the potential to also regulate gene expression at both transcriptional and 
post-transcriptional level in a more specific way. In this mini review, we 
present RNAi and CRISPRi design principles and discuss the advantages and 
limitations of the current design approaches.