Characteristics of microRNA co-target networks

The database of microRNAs and their predicted target genes in humans were used to extract a microRNA co-target network. Based on the finding that more than two miRNAs can target the same gene, we constructed a microRNA co-target network and analyzed it from the perspective of the complex network. We found that a network having a positive assortative mixing can be characterized by small-world and scale-free characteristics which are found in most complex networks. The network was further analyzed by the nearest-neighbor average connectivity, and it was shown that the more assortative a microRNA network is, the wider the range of increasing average connectivity. In particular, an assortative network has a power-law relationship of the average connectivity with a positive exponent. A percolation analysis of the network showed that, although the network is diluted, there is no percolation transition in the network. From these findings, we infer that the microRNAs in the network are clustered together, forming a core group. The same analyses carried out on different species confirmed the robustness of the main results found in the microRNA networks of humans.