Expression Profile Of MiRNAs And Functions Of MiR-100 During Diapause Formation In Artemia

Cell quiescence is defined as reversible cell cycle arrest in which the cells are still poised to re-enter the cell cycle given the favourable conditions. Quiescence as a potential central feature of cell life suggests that its regulation may be critical to understanding normal development, degenerative diseases and even tumorigenesis. The model studied here, a primitive crustacean, Artemia, possesses two independent reproductive pathways, one is normal embryonic development outputting motile nauplii (ovoviviparity) generally under favourable surroundings, and another one is embryonic development arrested at the gastrulae stage outputting dormant eggs (also called "cysts") (oviparity) when encountering harsh environmental conditions. The cysts bring their metabolism to a reversible standstill demonstrating a remarkable resistance to unfavourable environmental conditions. For example, mortality of embryos in cysts under normal temperature and hydration is very low, even after two years of anoxia, and embryos commonly experience complete desiccation as part of their developmental program. These characteristics about diapause cysts made it a superior material for studying cell quiescence during embryo development.Using high-throughput sequencing, the expression profile of miRNAs was constructed in association with diapause formation. The sequence analysis showed that there are 370 corresponding miRNA distributing in 87 families as are known and 13 undistributed miRNAs. Among them, expression of 107 miRNAs was found to be difference during diapause formation and one miRNA of them were characterized and analyzed for its functions. Quantitative RT-PCR results showed that miR-100 is highly expressed during embryo development, but can barely be detected in diapause. In oviparous embryo, over-expression of miR-100 induced a disorder to arrest in gastrula stage and instead of arresting in a quiescent state; the embryos released were found apoptosis gradually. While depletion of miR-100 induced development dysfunctions in embryo and they were born as pseudo-diapause cysts without shell. The results of the analysis of mitosis markers indicated miR-100 regulates cell cycle arrest negatively in oviparous and cell division positively in ovoviviparous Artemia, respectively. Furthermore, miR-100 regulates cell cycle by targeting PLK1 through MEK-ERK-RSK1 cascade pathway in ovoviviparous Artemia.By comparing the miRNA expression profile in various periods of diapause formation, we found that miRNA may play an important role in the regulation of mitosis and cell quiescence. Besides, experimental results have revealed miR-100 regulates cell cycle arrest negatively and mitosis positively by control PLK1 as its target, thus influencing the reproduction mode of Artemia. Our findings may provide insights into the aspects of miR-100 function and suggest that expression profile of miRNA from Artemia may be important to demonstrate the function of other related miRNAs in cell cycle regulation.