Cyclic AMP in sheep ovarian follicles: site of production and response to gonadotrophins

Developmental and hormonal regulation of ubiquitin-like with plant homeodomain and really interesting new gene finger domains 1 gene expression in ovarian granulosa and theca cells of cattle

Ubiquitin-like with plant homeodomain and really interesting new gene finger domains 1 (UHRF1) is a multi-domain nuclear protein that plays an important role in epigenetics and tumorigenesis, but its role in normal ovarian follicle development remains unknown. Thus, the present study evaluated if UHRF1 mRNA abundance in bovine follicular cells is developmentally and hormonally regulated, and if changes in UHRF1 are associated with changes in DNA methylation in follicular cells. Abundance of UHRF1 mRNA was greater in granulosa cells (GC) and theca cells (TC) from small (<6 mm) than large (≥8 mm) follicles and was greater in small-follicle GC than TC. In GC and TC, fibroblast growth factor 9 (FGF9) treatment increased (P < 0.05) UHRF1 expression by 2-fold. Also, luteinizing hormone (LH) and insulin-like growth factor 1 (IGF1) increased (P < 0.05) UHRF1 expression in TC by 2-fold, and forskolin (an adenylate cyclase inducer) alone or combined with IGF1 increased (P < 0.05) UHRF1 expression by 3-fold. An E2F transcription factor inhibitor (E2Fi) decreased (P < 0.05) UHRF1 expression by 44% in TC and by 99% in GC. Estradiol, progesterone, and dibutyryl-cAMP decreased (P < 0.05) UHRF1 mRNA abundance in GC. Treatment of GC with follicle-stimulating hormone (FSH) alone had no effect but when combined with IGF1 enhanced the UHRF1 mRNA abundance by 2.7-fold. Beauvericin (a mycotoxin) completely inhibited the FSH plus IGF1-induced UHRF1 expression in small-follicle GC. Treatments that increased UHRF1 mRNA (i.e., FGF9) in GC tended to decrease (by 63%; P < 0.10) global DNA methylation, and those that decreased UHRF1 mRNA (i.e., E2Fi) in GC tended to increase (by 2.4-fold; P < 0.10) global DNA methylation. Collectively, these results suggest that UHRF1 expression in both GC and TC is developmentally and hormonally regulated, and that UHRF1 may play a role in follicular growth and development as well as be involved in ovarian epigenetic processes.

Effects of fibroblast growth factor 9 (FGF9) on steroidogenesis and gene expression and control of FGF9 mRNA in bovine granulosa cells

Gene expression of fibroblast growth factor-9 (FGF9) is decreased in granulosa cells (GC) of cystic follicles compared with normal dominant follicles in cattle. The objectives of this study were to investigate the effects of FGF9 on GC steroidogenesis, gene expression, and cell proliferation and to determine the hormonal control of GC FGF9 production. GC were collected from small (1-5 mm) and large (8-22 mm) bovine follicles and treated in vitro with various hormones in serum-free medium for 24 or 48 h. In small- and large-follicle GC, FGF9 inhibited (P < 0.05) IGF-I-, dibutyryl cAMP-, and forskolin-induced progesterone and estradiol production. In contrast, FGF9 increased (P < 0.05) GC numbers induced by IGF-I and 10% fetal calf serum. FGF9 inhibited (P < 0.05) FSHR and CYP11A1 mRNA abundance in small- and large-follicle GC but had no effect (P > 0.10) on CYP19A1 or StAR mRNA. In the presence of a 3β-hydroxysteroid dehydrogenase inhibitor, trilostane, FGF9 also decreased (P < 0.05) pregnenolone production. IGF-I inhibited (P < 0.05) whereas estradiol and FSH had no effect (P > 0.10) on FGF9 mRNA abundance. TNFα and wingless-type mouse mammary tumor virus integration site family member-3A decreased (P < 0.05) whereas T(4) and sonic hedgehog increased (P < 0.05) FGF9 mRNA abundance in control and IGF-I-treated GC. Thus, GC FGF9 gene expression is hormonally regulated, and FGF9 may act as an autocrine regulator of ovarian function by slowing follicular differentiation via inhibiting IGF-I action, gonadotropin receptors, the cAMP signaling cascade, and steroid synthesis while stimulating GC proliferation in cattle.

The endocrinology of the menstrual cycle: the interaction of folliculogenesis and neuroendocrine mechanisms

(1) The gonadotropins are secreted in a pulsatile fashion in response to the similar pulsatile release of GnRH from neurosecretory neurons centered in the arcuate nucleus of the medial basal hypothalamus. (2) The gonadal steroids appear to exert their feedback effects both directly on the pituitary and through modulation of the pulsatile pattern of GnRH secretion. They may also influence the degree of sialylation and subsequent biologic activity of the gonadotropins. (3) GnRH release is under the control of catecholaminergic neurotransmitters. Norepinephrine appears to act as an excitatory agent, whereas dopamine inhibits GnRH secretion. (4) Dopamine also directly inhibits PRL release and may be the prolactin-inhibiting factor. (5) The endorphins are endogeneous opiate peptides and are derived from a common ACTH/ beta-lipotropin precursor. Through modulation of neurotransmitter mechanisms, the endorphins may affect both PRL and gonadotropin secretion. (6) The catecholestrogens, by virtue of their structural similarity to the neurotransmitters, may mediate the central feedback actions of the gonadal steroids.