The Expression Of FAST2 During Follicular Development In Mouse Ovaries And Early Embryos Development

The research contents of female mammals reproductive biology include: ovarian development, oogenesis, fertilization, embryonic development and implantation, normal pregnancy maintenance and varios processes. These processes are tightly controlled by multiple genes and signaling molecules. Xenopus forkhead activin signal transducer 1(x FAST 1) was first characterized as the transcriptional partner for Smad proteins. FAST2, which is the FAST related homologues in mouse, belongs to forkhead box(FOX) protein family and is coded by foxh1 gene. FAST2 primarily expressed during early developmental stages and played important roles in gastrulation and the development of the forebrain and heart. Deletion of foxh1 in mice resulted in failure to pattern the midline structure, anterior primitive streak(APS),node, prechordal mesoderm, notochord and definitive endoderm. But the functions of FAST2 in mouse ovaries and pre-implantation embryos development are unclear. So, we investigated the expressions of FAST2 in the ovaries of neonatal female mice, exogenous gonadotropin-induced immature female mice, meloxicam(MEL, prostaglandin synthase 2 activity inhibitor) treated and exogenous gonadotropin-induced immature female mice, GV stage oocytes and pre-implantation embryos by using immunohistochemical technique and Western Blot. We investgated the locations of FAST2 in ovaries and pre-implantation embryos.Immunohistochemical results showed that FAST2 expressed in the postnatal mouse ovarian follicle oocytes at postnatal day(PD) 1 and in the oocytes and theca cells by PD 8, and remained there at subsequent different time points. But the expression in granulosa cells was negative. During the follicular maturation and ovulation with exogenous gonadotropin administration, FAST2 continuously expressed in theca cells and oocytes of secondary follicles and mature follicles(PMSG 24 h and PMSG 48 h) and newly formed corpora lutea(CLs)(hCG24 h). As the CLs degenerated(hCG 48 h and hCG 72 h), the expression level of FAST2 dropped. Western Blot analysis revealed that FAST2 stably and highly expressed during PMSG0 h to hCG 24 h(the follicular maturation, ovulation and luteal phases), but FAST2 significantly reduced at hCG 48 h and 72 h(the luteal regression stage). These results consistedwith previous results of immunohistochemistry. In MEL-treated and exogenous gonadotropin-induced immature female mice, HE staining of the ovaries demonstrated that vehicle treated animals had multiple CLs at 18 h, 24 h and 36 h after hCG treatment. However,the ovulation of MEL treated immature animals was severely inhibited and emerged intact follicles with luteinized GCs and entrapped oocytes. Immunohistochemical analysis showed that FAST2 expressed in CLs in the vehicle treated mice, while in the MEL treated animals,FAST2 expressed in theca cells, luteinized GCs and entrapped oocytes. However, Western Blot result showed that there was no significant difference between the two groups. Confocal results showed that FAST2 existed in the whole of GV stage oocytes except the nucleolus. The expression pattern was similar between 1-8 cells early embryos stages and GV stage oocytes. In the later development stages, FAST2 were detected only in the cytoplasm of the morulae and ICM of the blastocysts.Taken together, FAST2 may play important roles in the development of follicular maturation,ovulation, luteinization and pre-implantation embryos.