Involvement of microRNA Lethal-7a in the Regulation of Embryo Implantation in Mice

Abstract

MicroRNAs interact with multiple mRNAs resulting in their degradation and/or translational repression. This report used the delayed implantation model to determine the role of miRNAs in blastocysts. Dormant blastocysts in delayed implanting mice were activated by estradiol. Differential expression of 45 out of 238 miRNAs examined was found between the dormant and the activated blastocysts. Five of the nine members of the microRNA lethal-7 (let-7) family were down-regulated after activation. Human blastocysts also had a low expression of let-7 family. Forced-expression of a family member, let-7a in mouse blastocysts decreased the number of implantation sites (let-7a: 1.1±0.4; control: 3.8±0.4) in vivo, and reduced the percentages of blastocyst that attached (let-7a: 42.0±8.3%; control: 79.0±5.1%) and spreaded (let-7a: 33.5±2.9%; control: 67.3±3.8%) on fibronectin in vitro. Integrin-β3, a known implantation-related molecule, was demonstrated to be a target of let-7a by 3′-untranslated region reporter assay in cervical cancer cells HeLa, and Western blotting in mouse blastocysts. The inhibitory effect of forced-expression of let-7a on blastocyst attachment and outgrowth was partially nullified in vitro and in vivo by forced-expression of integrin-β3. This study provides the first direct evidence that let-7a is involved in regulating the implantation process partly via modulation of the expression of integrin-β3. (200 words).

Comparative profiling of small RNAs of pig seminal plasma and ejaculated and epididymal sperm

“…miR-34c, which is also present in humans, mice and bull sperm (Amanai et al 2006, Krawetz et al 2011, Stowe et al 2014, was detected in all the three libraries from pig ejaculated sperm, epididymal sperm and seminal plasma, indicating that this miRNA species is highly conserved across mammals and confirming that it plays a significant biological role in spermatogenesis or in early embryonic development. We also found that three miRNAs (ssc-let-7a, ssc-miR26a and ssc-miR-10b) were shared in the top 10 most abundant miRNAs in the three libraries, and one of them (miR-let-7a) was detected in mouse epididymal sperm and human seminal plasma (Liu et al 2012a, Wu et al 2012, Cheong et al 2014) and shown to be involved in the regulation of embryo implantation in mice (Liu et al 2012a, Cheong et al 2014). Furthermore, the expression level of let-7a in human seminal plasma was significantly associated with male infertility (Wu et al 2012).…”

“…The functional significance of some miRNAs still seems to be compelling, although it is now commonly accepted that small RNAs play a pivotal role in fertilization and embryonic development (Liu et al 2012a, Chen et al 2016a,b, Yuan et al 2016). An early study suggested that sperm-borne miRNAs play a restricted role in mammalian fertilization (Amanai et al 2006); however, a subsequent study suggested that miRNAs play an important role in fertilization and pre-implantation embryonic development .…”

“…The complexity of non-coding RNA species has also been well characterized in the sperm (Krawetz et al 2011, Peng et al 2012, Jodar et al 2013, García-lópez et al 2015, Pantano et al 2015, and it is now commonly accepted that non-coding RNAs are critical for the process of embryogenesis (Liu et al 2012a, Chen et al 2016a,b, Yuan et al 2016. The miRNA family is the best Reproduction (2017) 153 [785][786][787][788][789][790][791][792][793][794][795][796] www.reproduction-online.org characterized of the small RNA species in sperm.…”

“…It has been demonstrated that mature miRNAs that are carried into the zygote by sperm during the fertilization are relatively rare compared with oocyte miRNAs (Yang et al 2016). Accumulating evidence shows that miRNAs are critical for fertilization and early embryonic development (Liu et al 2012a,b, Cheong et al 2014. However, the role of some miRNAs in the development of early embryos remains controversial (Amanai et al 2006, Yuan et al 2015.…”

PreImplantation factor promotes neuroprotection by targeting microRNA let-7

“…Let-7 repression in blastocysts facilitates embryo implantation in the mouse (57,58). Proper regulation of expression of IL-10 in trophoblasts and uterine immune cells has been implicated in placental health and fetal development (59).…”