Abstract
Previously, we reported that Sebox is a new maternal effect gene (MEG) that is required for early embryo development beyond the two-cell (2C) stage because this gene orchestrates the expression of important genes for zygotic genome activation (ZGA). However, regulators of Sebox expression remain unknown. Therefore, the objectives of the present study were to use bioinformatics tools to identify such regulatory microRNAs (miRNAs) and to determine the effects of the identified miRNAs on Sebox expression. Using computational algorithms, we identified a motif within the 3′UTR of Sebox mRNA that is specific to the seed region of the miR-125 family, which includes miR-125a-5p, miR-125b-5p and miR-351-5p. During our search for miRNAs, we found that the Lin28a 3′UTR also contains the same binding motif for the seed region of the miR-125 family. In addition, we confirmed that Lin28a also plays a role as a MEG and affects ZGA at the 2C stage, without affecting oocyte maturation or fertilization. Thus, we provide the first report indicating that the miR-125 family plays a crucial role in regulating MEGs related to the 2C block and in regulating ZGA through methods such as affecting Sebox and Lin28a in oocytes and embryos.
Highlights
Gene expression is a multi-step process that is regulated at both the transcriptional and translational levels as well as by the turnover of mRNAs and proteins [1]
As an assay of miRNA function, we evaluated the ability of each miR-125 family member to target endogenous skin-embryo-brainoocyte homeobox (Sebox) and Lin-28 homologue A (Lin28a) mRNAs in oocytes and mouse embryonic stem cells (mESCs) by microinjecting or transfecting cells with mimics of each miR-125 family member
Because we found that miR-125 family members concurrently suppressed Sebox and Lin28a, we searched for more potential maternal effect gene (MEG) targets of the miR-125 family using computational algorithms
Summary
Gene expression is a multi-step process that is regulated at both the transcriptional and translational levels as well as by the turnover of mRNAs and proteins [1]. MicroRNAs (miRNAs) are a class of endogenous, single-stranded and noncoding small RNAs (approximately 21–25 nucleotides) that primarily bind to complementary sequences in the 30UTRs of their target mRNAs; this binding results in mRNA degradation and/or repression of mRNA translation [2]. Complete complementarity between miRNA and mRNA rarely occurs in mammals, but binding at the seed region (6–8 nucleotides at the 50 end of the miRNA that exactly complements the target mRNA) sufficiently suppresses expression of that specific gene [3]. Disruption of Dicer, a key enzyme involved in miRNA processing, results in meiotic.
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