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Prolactin (PRL) is a pituitary hormone that regulates multiple physiological processes. However, the mechanisms of PRL synthesis have not been fully elucidated. The aims of the present study were to study the functions and the related mechanisms of miR-375 regulating PRL synthesis. We initially found that miR-375 mainly expressed in the lactotrophs of mouse pituitary gland. To identify the function of miR-375 in the pituitary gland, the miR-375 knockout mice were generated by using Crispr/Cas9 technique. The results showed that miR-375 knockout resulted in the decline of pituitary PRL mRNA and protein levels by 75.7 and 60.4%, respectively, and the serum PRL level reduced about 46.1%, but had no significant effect on FSH, LH and TSH. Further, we identified that Estrogen receptor 1 (alpha) (Esr1) was a downstream molecule of miR-375. The real-time PCR and Western blot results showed that ESR1 mRNA and protein levels markedly decreased by 40.9 and 42.9% in the miR-375 knockout mouse pituitary, and these were subsequently confirmed by the in vitro study using transfections of miR-375 mimics and inhibitors in pituitary lactotroph GH4 cells. Further, Rasd1 was predicted by bioinformatic tools and proved to be the direct target of miR-375 in lactotrophs using the dual-luciferase reporter assay. Rasd1-siRNA transfection results revealed the negative effect of Rasd1 in regulating ESR1. Collectively, the results presented here demonstrate that miR-375 positively modulates PRL synthesis through Rasd1 and Esr1, which are crucial for understanding the regulating mechanisms of pituitary hormone synthesis.

Prostaglandin F2 α (PGF2 α) is a key factor in the triggering of the regression of the corpus luteum (CL). Furthermore, it has been reported that Slit/Robo signaling is involved in the regulation of luteolysis. However, the interactions between PGF2 α and Slit/Robo in the progression of luteolysis remain to be established. This study was designed to determine whether luteolysis is regulated by the interactions of PGF2 α and Slit/Robo in the mouse CL. Real-time PCR and immunohistochemistry results showed that Slit2 and its receptor Robo1 are highly and specifically co-expressed in the mouse CL. Functional studies showed that Slit/Robo participates in mouse luteolysis by enhancing cell apoptosis and upregulating caspase3 expression. Both in vitro and in vivo studies showed that PGF2 α significantly increases the expression of Slit2 and Robo1 during luteolysis through protein kinase C-dependent ERK1/2 and P38 MAPK signaling pathways, whereas an inhibitor of Slit/Robo signaling significantly decreases the stimulating effect of PGF2 α on luteolysis. These findings indicate that Slit/Robo signaling plays important roles in PGF2 α-induced luteolysis by mediating the PGF2 α signaling pathway in the CL.