Comprehensive Characterization of microRNAs and mRNAs in Maintenance and Differentiation of Human Embryonic Stem Cells

Recent advances in the study of human embryonic stem cells (hESCs) and induced-pluripotent stem cells (iPS) highlight their importance as both model systems for basic research and avenues for therapeutic applications. To gain better insight into these cells, a clearer understanding of their molecular properties is crucial. In this study, we analyze changes in the expression profile of microRNAs (miRNAs) and mRNAs in nine different, National Institutes of Health (NIH)-approved hESC lines. By examining both undifferentiated hESCs and cells exposed to an undirected differentiation scheme at early stages, we found those miRNAs and mRNAs enriched in the hESC lines, and those miRNAs and mRNAs initially regulated upon commitment. In comparing these profiles with those of an embryonal carcinoma (EC) cell line, NTera-2, we observed distinct patterns of miRNA expression in hESCs. Furthermore, we identify several new hESC-enriched miRNAs that respond rapidly to differentiation cues, in addition to miRNAs from a large cluster of hESC-enriched miRNAs located on chromosome 19, and miRNAs from the miR-302 cluster and the miR-17~92 family of clusters. We show that key miRNAs in the chromosome 19 cluster are highly enriched in hESCs in comparison to NTera-2, and might therefore serve as future diagnostic markers for stem cell capacity. Examination of changes in mRNA expression during early commitment further reveals that many differentiation-regulated genes are possible candidates for regulation by these hESC-enriched miRNAs. A set of 9 different NIH-approved hESC lines were treated with conditions to promote either maintenance of an undifferentiated state (mouse embryonic fibroblast- conditioned media) or undirected differentiation of the hESCs into various cell lineages (DMEM + 20% FBS). RNA was harvested from the cells and subjected to both mRNA and miRNA expression analysis on Affymetrix and Agilent microarray platforms, respectively. An embryonal carcinoma cell line, NTera-2, which shows growth characteristics similar to those of hESCs, was used an additional comparative sample. Human placental RNA samples were used as internal controls for the miRNA microarray slides (Agilent Technologies). The data were used to determine differential mRNA and miRNA expression in each specific cell line, as well as to make large-scale comparisons of the undifferentiated and differentiated hESC lines.