Notch signaling represses GATA4-induced expression of genes involved in steroid biosynthesis

Abstract

Notch2 and Notch3 and genes of the Notch signaling network are dynamically expressed in developing follicles, where they are essential for granulosa cell proliferation and meiotic maturation. Notch receptors, ligands, and downstream effector genes are also expressed in testicular Leydig cells, predicting a potential role in regulating steroidogenesis. In this study, we sought to determine if Notch signaling in small follicles regulates the proliferation response of granulosa cells to follicle stimulating hormone and represses the up-regulation steroidogenic gene expression that occurs in response to FSH as the follicle grows. Inhibition of Notch signaling in small preantral follicles led to the up-regulation of the expression of genes in the steroid biosynthetic pathway. Similarly, progesterone secretion by MA-10 Leydig cells was significantly inhibited by constitutively active Notch. Together, these data indicated that Notch signaling inhibits steroidogenesis. GATA4 has been shown to be a positive regulator of steroidogenic genes, including steroidogenic acute regulatory protein, P450 aromatase, and 3B-hydroxysteroid dehydrogenase. We observed that Notch downstream effectors HEY1, HEY2, and HEYL are able to differentially regulate these GATA4-dependent promoters. These data are supported by the presence of HEY/HES binding sites in these promoters. These studies indicate that Notch signaling has a role in the complex regulation of the steroidogenic pathway.

Effects of melatonin on the synthesis of estradiol and gene expression in pig granulosa cells

“…Specifically, NOTCH2 is expressed in all GCs of small growing follicles and Notch signaling induces the proliferation of many cell types, including GCs . Notch signaling could repress steroid synthesis in small preantral follicles and MA‐10 Leydig cells . Our finding agrees with that in previous reports; we found that NOTCH2 could be downregulated by melatonin and repress estradiol synthesis in pig GCs.…”

The role of Notch signaling in the mammalian ovary

“…In contrast to the findings above, transfection of a gonadotropin-responsive mouse cell line with NICD1 or NICD2 , leads to a decrease in progesterone production, implying that Notch activation normally functions to suppress steroidogenesis (George et al 2015). In addition, the expression of StAR , Cyp19a1 , and HSD3b1 are significantly upregulated following pharmacological suppression of Notch signaling in cultured preantral follicles and downregulated with transient transfection of NICD1-3 .…”

“…In addition, the expression of StAR , Cyp19a1 , and HSD3b1 are significantly upregulated following pharmacological suppression of Notch signaling in cultured preantral follicles and downregulated with transient transfection of NICD1-3 . Furthermore, activation of the Notch pathway represses the ability of GATA4 to induce the expression of these genes through Notch target gene expression and promoter binding, rather than through dimerization of Notch target genes with GATA4 (Figure 3C) (George et al 2015). These findings, together with studies employing DLL4 and γ-secretase inhibitors discussed above, indicate that alteration in the levels of basal Notch activity negatively impact progesterone production in steroidogenically active cells, suggesting complex regulatory effects of steroid hormone production by Notch signaling.…”

Functional evidence implicating NOTCH2 missense mutations in primary ovarian insufficiency etiology

“…The NOTCH system (ligands, receptors, and target genes) is expressed in the ovaries in different structures, such as oocytes, primary, secondary and antral follicles, corpora lutea, theca cells, ovarian surface epithelium, and vasculature (Vanorny & Mayo, and references therein). Various critical roles have been defined for NOTCH factors in ovary biology, such as follicle formation and growth, meiotic maturation, vasculogenesis, and hormone synthesis (George, Hahn, Rawls, Viger, & Wilson‐Rawls, ; Trombly, Woodruff, & Mayo, ; Vanorny & Mayo, ; Xu & Gridley, ). These findings support proposing NOTCH2 as a coherent candidate gene related to POI's etiology.…”