MiR-133b Regulates the Expression of the Actin Protein TAGLN2 during Oocyte Growth and Maturation: A Potential Target for Infertility Therapy

Infertility is an area of increasing in life science research. Although follicular maturation disorders and anovulation are the primary causations of infertility, its molecular mechanism is not well understood. Recent research has shown that microRNAs (miRNAs) might play an important role in the regulation of ovarian follicle development and maturation. In this study, the expression of miRNAs in metaphase I (MI) oocytes treated with or without insulin-like growth factor 1 (IGF-1) was observed by microRNA microarray analysis. Results show that 145 miRNAs were up-regulated and 200 miRNAs were down-regulated in MI oocytes after IGF-1 treatment. MiR-133b, which was up-regulated more than 30-fold, was chosen for further research. As a potential target of miR133b, transgelin 2 (TAGLN2) gene was down-regulated, at both transcription and translation levels, in miR-133b- over-expressed 293T cells, but TAGLN2 was up-regulated when the expression of miR-133b was inhibited. Furthermore, the expression level of TAGLN2 in the ovaries of 8-week- old mice was higher than that observed in 4-week-old mice. Immunofluorescence experiments showed that TAGLN2 was located in the cytoplasm. In general, our results indicate that miR-133b may play important roles in the growth and maturation of oocytes by regulating its potential target, TAGLN2, at both transcription and translation levels. Therefore, our research provides a potential new target for infertility therapy.