Inhibition of Premature Oocyte Maturation: A Role for Bone Morphogenetic Protein 15 in Zebrafish Ovarian Follicles

Abstract

Bone morphogenetic protein-15 (BMP-15) is a member of the TGF-beta superfamily known to regulate ovarian functions in mammals. Recently, we cloned zebrafish BMP-15 (zfBMP-15) cDNA and demonstrated that it may play a role in oocyte maturation. In this study, we further investigated the role of BMP-15 in zebrafish follicular development and oocyte maturation using an antiserum developed for zfBMP-15 and by microinjection of follicles with antisense zfBMP-15 N-morpholino oligonucleotides or an expression construct containing zfBMP-15 cDNA. Injection with antiserum caused a significant decrease in maturation-incompetent [insensitive to maturation-inducing hormone (MIH)] early growth phase follicles and a concomitant increase in mature follicles in vivo. In vitro maturation assays showed that incubation with antiserum resulted in a significant increase in oocyte maturation as compared with follicles incubated in preimmune serum or media control. Next, early growth phase follicles were collected and preincubated with either antiserum, preimmune serum, or medium control before treatment with MIH or human chorionic gonadotropin (hCG). Antiserum significantly increased oocyte maturation in response to MIH, but not to hCG, and enhanced basal maturation rate in longer-term incubations. Knockdown of BMP-15 in early growth stage follicles with a BMP-15 antisense oligonucleotide resulted in increased oocyte maturation, whereas microinjection of BMP-15 cDNA into oocytes significantly reduced MIH- and hCG-induced oocyte maturation in normally competent, mid-growth-phase follicles. Collectively, these findings suggest that BMP-15 modulates follicular growth and prevents premature oocyte maturation in zebrafish, in part, by suppressing the sensitivity of follicles to MIH.

Conserved Anti-Müllerian Hormone: Anti-Müllerian Hormone Type-2 Receptor Specific Interaction and Intracellular Signaling in Teleosts1

“…It also matches the size of ≈ 60 kDa described for the native Japanese eel proAmh [12] and the 62 kDa fragment detected in black porgy testes [44]. The predominance of proAmh in sea bass testis agrees with observations in eel testis and also with findings in fish ovaries for other TGF-β factors such as Bmp15 and Gdf9 [45,46,47] and could be related to the dependence of binding of the noncovalent complex (AmhN,C) to the Amhr2 for the generation of the mature AmhC [48] To produce a biologically active sea bass Amh, we expressed in CHO cells an engineered sea bass amh cDNA that contained an optimized cleavage site for in vivo proteolytic processing by CHO cell convertases including furin. Although this strategy worked with rat and human recombinant AMHs [38,39,40], endogenous cleavage of recombinant sea bass Amh was highly inefficient.…”

Increase of fecundity by probiotic administration in zebrafish (Danio rerio)

“…Similar results have also been obtained with recombinant human BMP15, which also reduced hCG-induced oocyte maturation (Clelland et al 2006). Moreover, the knockdown of bmp15 in oocytes, by antisense oligonucleotides, increased paqr8 expression (Tan et al 2009), and the inhibition of bmp15 expression or function in class IIIa follicles has been found to induce their sensitivity to MIH (Clelland et al 2006(Clelland et al , 2007.…”

BMPRIB and BMPRII mRNA expression levels in goat ovarian follicles and the in vitro effects of BMP-15 on preantral follicle development

“…These data are not in agreement with some studies that report an involvement of BMP-15 in oocyte maturation and cumulus expansion in mice (Yoshino et al 2006) and pigs (Li et al 2008). However, recent studies in zebrafish have demonstrated that BMP-15 exerts a physiological role to inhibit oocyte maturation (Clelland et al 2006(Clelland et al , 2007Peng et al 2009). In this species, BMP-15 has shown the ability to prevent premature oocyte maturation, which has been considered important for the maintenance of oocyte quality and subsequent ovulation and fertilization (Peng et al 2009).…”