Micro-RNA378 (miR-378) Regulates Ovarian Estradiol Production by Targeting Aromatase

Abstract

Estradiol is a steroid hormone that not only plays an important role in ovarian follicular development but also is associated with many reproductive disorders. Owing to the importance of aromatase in the production of estradiol, the regulation of aromatase gene expression at the transcriptional level has been an extensive area of study for over two decades. However, its regulation at the posttranscriptional level has remained unclear. Here, we show that micro-RNA378 (miR-378) is spatiotemporally expressed in porcine granulosa cells, the cells that generate estradiol in the ovary during follicular development, in an inverse manner compared with the expression of aromatase. In vitro overexpression and inhibition experiments revealed that aromatase expression, and therefore estradiol production, by granulosa cells, is posttranscriptionally down-regulated by miR-378. Furthermore, site-directed mutation studies identified two binding sites in the 3'-untranslated region (3'-UTR) of the aromatase coding sequence that are critical for the action of miR-378. Interestingly, overexpression of the aromatase 3'-UTR enhanced aromatase expression at the protein level in granulosa cells, possibly mediated by the binding of miR-378 within this region, thereby reducing the binding of this micro-RNA to the endogenous aromatase 3'-UTR.

MicroRNAs 125a and 455 Repress Lipoprotein-Supported Steroidogenesis by Targeting Scavenger Receptor Class B Type I in Steroidogenic Cells

“…Thus, miRNA-145 may not necessarily lead to the modulation of specific predicted functions or targets, but it has been reported to function as a regulator of cell proliferation and as a tumor suppressor (20,69,79,84). A number of studies have attempted to identify and characterize miRNAs in adrenal and gonadal tissues and cells (18,24,45,47,48,50,54,63,68,80,81,83), but information about their potential targets or hormonal regulation is generally lacking except in a few instances. For example, miRNA-378 has been reported to regulate estradiol production in porcine granulosa cells by targeting aromatase (47).…”

Characterization of microRNAs differentially expressed during bovine follicle development

“…Several studies have already reported effects of specific miRNAs on different aspects of granulosa cell function , including steroidogenesis (Yao et al 2010, Xu et al 2011, Yin et al 2012, Dai et al 2013, proliferation (Yao et al 2010, Yan et al 2012, Dai et al 2013, survival (Carletti et al 2010, Yang et al 2012, terminal differentiation (Kitahara et al 2013), and cumulus expansion (Yao et al 2014). With a few exceptions (Carletti et al 2010, Kitahara et al 2013, most evidence on follicular roles of miRNAs has been obtained using cultured cells, particularly rodent cells, and in some cases actual changes in the expression of these miRNAs during follicle development have not been demonstrated.…”

Identification of miRNAs associated with the follicular–luteal transition in the ruminant ovary

“…While these studies identified novel and ovarian-specific miRNA species, comparisons across different developmental stages were not performed. Separate studies identified hormoneresponsive miRNAs in the ovary and proposed different roles for some of those miRNAs including mediation of granulosa cell responses to transforming growth factor b1 (TGFb1) in pre-antral follicles (Yao et al 2010a), oestradiol (E 2 ) production (Xu et al 2011), prevention of early granulosa cell differentiation (Lei et al 2010), promotion of granulosa cell survival during ovulation (Carletti et al 2010), inhibition of anti-angiogenic factor expression during luteogenesis (Otsuka et al 2008) and ovarian aging (da Silveira et al 2012). It has not yet been established whether these proposed functions are conserved in large animal species and humans.…”