MiR-98 is involved in rat embryo implantation by targeting Bcl-xl

• We examine the expression and regulation of miR-98 during early pregnancy.
• MiR-98 expression is regulated by blastocyst activation.
• Bcl-xl is the target gene of miR-98.
• Enforced miR-98 expression inhibits ESC proliferation by targeting Bcl-xl.

In a previous study, via microRNA microarray analysis we found that miR-98 is differentially expressed in rat uteri during the peri-implantation period (unpublished data). However, the role of miR-98 in rat embryo implantation remains elusive. Here, we found that the level of miR-98 is lower on day 5 and 6 of gestation (g.d. 5–6) than that on g.d. 3–4 and g.d. 7–8 in rat. MiR-98 expression is significantly decreased by delayed implantation. Down-regulation of miR-98 promotes ESC proliferation and inhibits apoptosis. Up-regulation of miR-98 displays opposite effects. Further investigation revealed that miR-98 can bind to the 3′-untranslated region (3′-UTR) of B-cell lymphoma-extra large (Bcl-xl) to inhibit Bcl-xl translation. Collectively, down-regulation of miR-98 in rat uterus during the receptive phase is linked to the increase of cell proliferation via targeting Bcl-xl.