Characterization and expression of lin-28a involved in lin28/let-7signal pathway during early development of P. olivaceus
Heterochronic lin-28 is a conserved RNA-binding protein that plays a key role in the timing of developmental events in organisms. As a crucial heterochronic gene, the protein controls developmental events of the second of four larval stages in Caenorhabditi elegans. Heterochronic let-7 miRNAs are often present in various species and highly conserved in sequence and biological function and are required for various biological processes. Previous studies showed that ten let-7 miRNAs were identified in the Japanese flounder (Paralichthys olivaceus) and that they were primarily expressed during metamorphosis. In this study, we clone and characterize the lin-28a gene from P. olivaceus and exhibit its dynamic expression pattern at different developmental stages and various adult tissues. The results show that the P. olivaceus lin-28a gene has high sequence similarity with other species and is highly expressed in the embryonic stage but weakly expressed in the larval stage. In addition, lin-28a overexpression causes cell proliferation and significantly promotes the levels of pre-let-7a and pre-let-7d while markedly depressing let-7a and let-7d expression in FEC (Flounder Embryonic Cell), which indicate that lin-28 possibly blocks the maturation of let-7 miRNAs. Additionally, lin-28a is identified as a target gene of let-7 miRNAs, and let-7 miRNAs directly regulate lin-28a expression by targeting its 3′ UTR. Taken together, lin-28a along with let-7 miRNA participates in a lin-28/let-7 axis pathway that regulates cell division and timing of embryonic and metamorphic events in P. olivaceus.
KeywordsP. olivaceus lin-28a let-7 miRNAs Embryonic development Metamorphosis
This work was supported by the Open Fund of Key Laboratory of Experimental Marine Biology, Chinese Academy of Sciences (No. KF2015No01), the National Natural Science Foundation of China (No. 41506159 and No. 41306128), the Natural Science Foundation of Shanghai (No. 15ZR1420600), the Innovation Programme of Shanghai Municipal Education Commission (No. 15ZZ083), and the Science and Technology Development Foundation of Shanghai Ocean University (No. A2-0203-00-100204). We also thank Liu Haijin and Hou Jilun for experimental fish, and we thank Chen Songlin for FEC.
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