MicroRNA Expression Profile In Different Human Diseases And Tissues

MicroRNAs (miRNAs) are a kind of small non-coding RNA molecules whose lengthare~22nt. MiRNAs are involved in many physiological and pathological processes. Withthe development of sequencing techniques, more and more researchers begin to focus onmiRNAs and try to understand their functions.In this study, we collected410human small RNA sequencing data sets, in whichmany diseases and tissues were involved. After a parameter test, we built a pipeline forstandard analysis of miRNA sequencing data. Using this pipeline, we analyzed theexpression of miRNAs in all data sets. We have identified some disease and tissue specificexpressed miRNAs, as well as differentially expressed miRNAs between cases andcontrols. Furthermore, we found that6miRNAs were almost highly expressed in allsamples including diseases and normal samples. These miRNAs are hsa-miR-21-5p,hsa-let-7f-5p, hsa-let-7a-5p, hsa-miR-26a-5p, hsa-miR-103a-3p and hsa-miR-191-5p.We established an integrative database, HMED (http://115.156.249.50/smallRNA/),to store the miRNA expression data. In HMED, there are miRNA analysis results of the410data sets, containing data set information, miRNA quantification and so on. Thedatabase provides researchers valuable data sources of miRNA expression through auser-friendly interface, a humanized search function and comprehensive information ofmiRNA.Moreover, we discussed isomiR and arm switching of miRNAs. We found thatisomiRs played an important role in miRNA expression. In some cases, the expressions ofisomiRs were higher than the reference sequence. These isoforms greatly increase thevariety of miRNAs. For some miRNAs, they prefer to accumulate5p mature sequences insome tissues, but3p mature sequences in other tissues. We call this arm switching.However, most miRNAs function through a regular arm.Our study collected large scale data sets of small RNA sequencing to discuss miRNAexpression profile in different situations. Through these miRNA expression data analyses,we provide functional clues and important resources for further study of miRNA.