Study On The Diversity Of MicroRNAs In Sequences And Expression Patterns During Human ESCs Differentiated Into RPE Cells

Age-related macular degeneration(AMD) is a leading cause of visual impairment and disability in older people worldwide. AMD is a kind of eye disease with macular degeneration, and so far there is no good cure for AMD. In recent years, stem cell-derived retinal pigment epithelium(RPE) cells were developed into a new alternative treatment measure for AMD. During the course of embryonic stem cells(ESCs) differentiate into RPE, it involves the expression changes of many genes, which also including micro RNA(mi RNA) expression changes. In order to reveal the dynamic change and the roles of the related mi RNAs involved in the transformation process of cell differentiation, this study is the first systematic study to explore the variation of expression levels of the mi RNAs, mi RNAs of stage-specific expression, Dominant arm-switching mi RNAs and isomi Rs with changes of their potential functions in the four stages during human ESC differentiation into RPE. That is, the study focused on the changes of the expression level, expression patterns, sequence diversity, and their functions of the mi RNAs in cell differentiation. The details of the results are list below:1. 941 known mi RNA hairpins and 113 candidate mi RNA hairpins with expressing 196 novel mi RNAs have been identified during human ESC differentiation into RPE cells.2. Comparing with the first stage, there are 205 significantly up-regulated and 295 significantly down-regulated mi RNAs in the fourth stage, 172 significantly up-regulated and 175 significantly down-regulated mi RNAs at stage 2, and 227 significantly up-regulated and 331 significantly down-regulated mi RNAs at stage 3. In addition, there are 93 significantly up-regulated and 124 significantly down-regulated mi RNAs were shared at the three differentiation stages. And most of the enriched GO terms of the targets of mi RNAs down-regulated in RPE cells were similar to the targets of up-regulated mi RNAs because they share most targets with each other.3. There were 107 non-canonical mi RNAs with relatively higher expression level, while there were 19 common non-canonical mi RNAs(5′-isomi R) in all differentiation stages. The 19 non-canonical mi RNAs share more than half of the over-representation biological processes(P-value < 0.01) with their corresponding canonical mi RNAs, and the two groups of mi RNAs also take part in several obviously different biological processes.4. 27 statistically significant modification sites were identified in 24 different mi RNAs. None of them overlapped known human SNPs. Most of the editing events were located within the seed region of mature mi RNAs. Overall, only the editing sites in hsa-mi R-381-3p were found expressing in the early stages of ESC differentiation, while others were occurred in late stages. About nine inferred A-to-I editing sites are supported by the literature. And dramatic changes in mi RNA function among the four edited mi RNAs between their unedited and edited forms.5. Marked major-to-minor arm-switching events in 14 pre-mi RNAs have been found during the human ESC to RPE cell differentiation phases.The 14 arm-switching pre-mi RNAs expressed 27 mi RNAs. The results indicate that these dominant arm-switching mi RNAs are involved in ESC maintenance or in the differentiation of ESCs into RPE cells.