Venn Diagrams depict the difference of miRNA transcript counts identified in intracellular and extracellular (secreted) miRNA sets. Due to statistical results presented on Figure 3, the transcript count domains are broadly separated into 3 main levels: Low (below 32 transcripts), Mid-range (32-10000) and High (>10000). Within each sub-interval of the miRNA expression value, Venn diagrams are used to analysis the degree of overlapping between experimental replicates. Kappa correlation coefficient, reflecting the degree of agreement between two sets (Cytel Studio@7) was calculated for each pair of replicates. In general, for intracellular compartment miRNAs the degree of overlapping (agreement between experiments) for the Low category is much lower compared to the mid-range and high data subset. This result suggests a good experimental responsibility of occurrence of miRNAs expressed at the moderate- and high-abundant expression levels. The low-abundant set of miRNA shows poor reproducibility, perhaps due to experimental and biological noise. For the extracellular miRNA samples, there were no transcripts at the high expression category. Moreover, a low probability of co-occurrence of the same miRNAs (non-significant kappa correlation) in low expression category or in moderate expression category is found.
Koh et al. BMC Genomics 2010 11(Suppl 1):S6 doi:10.1186/1471-2164-11-S1-S6