Distribution of miRNA expression across human tissues
We present a human miRNA tissue atlas by determining the abundance of 1997 miRNAs in 61 tissue biopsies of different organs from two individuals collected post mortem. One thousand three hundred sixty four miRNAs were discovered in at least one tissue, 143 were present in each tissue. To define the distribution of miRNAs, we utilized a tissue specificity index (TSI) The majority of miRNAs (82.9% fell in a middle TSI range i.e. were neither specific for single tissues (TSI 0.85) nor housekeeping miRNAs (TSI 0.5) Nonetheless, we observed many different miRNAs and miRNA families that were predominantly expressed in certain tissues. Clustering of miRNA abundances revealed that tissues like several areas of the brain clustered together. Considering 3p and 5p mature forms we observed miR 150 with different tissue specificity. Analysis of additional lung and prostate biopsies indicated that inter organism variability was significantly lower than inter organ variability. Tissue specific differences between the miRNA patterns appeared not to be significantly altered by storage as shown for heart and lung tissue. MiRNAs TSI values of human tissues were significantly (P 10 8) correlated with those of rats; miRNAs that were highly abundant in certain human tissues were likewise abundant in according rat tissues. We implemented a web based repository enabling scientists to access and browse the data (https:/ccb web.cs.uni saarland.de/tissueatlas)
Nucleic acids research