Differential Expression of Steroidogenic Factor-1 and FTF/LRH-1 in the Rodent Ovary

Abstract

Steroidogenic factor-1 (SF-1) (NR5A1) is an orphan nuclear receptor that plays a premier role in ovarian organogenesis. Recent studies document mRNA expression of the structurally related factor NR5A2 (FTF, LRH-1, SF-2) in the adult ovary and more specifically in granulosa cells and luteal cells but not theca cells. Conversely, SF-1 was shown to be expressed at higher levels in theca/interstitial cells. These latter observations raised the possibility that FTF/LRH-1 may control target gene expression in granulosa cells of developing follicles. Using quantitative PCR our results show that FTF/LRH-1 message is expressed at higher levels in the ovary than in liver or other tissues analyzed. We show by in situ hybridization and LacZ expression in ovaries of transgenic mice bearing an FTF-promoter-LacZ fusion gene that FTF/LRH-1 is selectively expressed in granulosa cells of rat and mouse ovaries and is not present in theca cells or interstitial cells. However, by a variety of approaches, we showed that SF-1 mRNA and protein are expressed in greater amounts than FTF/LRH-1 in granulosa cells of follicles at all stages of development. Expression of SF-1 mRNA and protein in granulosa cells was verified by in situ hybridization, immunohistochemistry of ovarian sections, and immunocytochemistry of cultured rat granulosa cells. The significance of SF-1 in regulating target gene activation was supported by EMSA. An abundant granulosa cell protein binding to the SF-1-binding motif (CCAAGGTCA) present in the aromatase promoter and an FTF/LRH-1 motif (TGTCCTTGAACA) in the alpha-fetoprotein promoter was supershifted by two SF-1-specific antibodies but not by an FTF antibody. Conversely, with the same probes, a less abundant protein/DNA complex present in liver and ovarian cell extracts was shifted by an FTF antibody but not by the SF-1 antibodies. SF-1 and FTF/LRH-1 were differentially regulated in vivo by estradiol, FSH and prolactin. Collectively these data indicate that granulosa cells of small and preovulatory follicles express both SF-1 and FTF/LRH-1 and that each orphan receptor may regulate target gene expression in these cells.

Aromatase expression in the ovary: Hormonal and molecular regulation

“…Moreover, overexpression of constitutively active mutant FOXO1, which prevents aromatase stimulation by FSH and activin, also decreases SF-1 expression [58]. Levels of SF-1 protein do not exhibit major changes during follicular growth or in response to low levels of FSH in culture but decrease rapidly after the LH surge along with the downregulation of aromatase [115], further supporting the idea of an important role for SF-1 in the regulation of aromatase expression.…”

“…In fact, in vitro translated mouse SF-1 and LRH-1 proteins [104] or SF-1 expressed in bacteria [55] bind to oligonucleotides containing the NREa present in the aromatase gene. However, because both factors are expressed in granulosa cells [115,116], whether SF-1 or LRH-1 or both are important for aromatase expression in these cells remains under debate (describe below), although evidence suggests that SF-1 has a more prominent role.…”

The Role of α1-Fetoprotein Transcription Factor/LRH-1 in Bile Acid Biosynthesis

“…Harvesting of the indicated tissues was done at the middle of the dark period. FTF ϩ/Ϫ mice were a generous gift from Dr. L. Belá nger (Laval University, Quebec) and have been described previously (23). FTF ϩ/Ϫ mice were received at the Virginia Commonwealth Animal Facility after at least 10 generations of inbreeding.…”

The nuclear receptor liver receptor homolog-1 is an estrogen receptor target gene

“…This nuclear receptor plays important developmental functions in the mouse, as demonstrated by the genetic dissection of LRH-1 KO mice (Falender et al, 2003;Pare et al, 2004). LRH-1À/À mice die at e6.5-7.5, due to profound developmental defects, such as impaired node formation and gastrulation (Pare et al, 2004).…”

“…During adulthood, LRH-1 plays important roles in cholesterol and lipid homeostasis by controlling the expression of genes involved in these metabolic pathways (for a review see Fayard et al, 2004). Several studies reported elevated expression of LRH-1 in granulosa cells and corpus luteum of the ovary, suggesting potential functions for this nuclear receptor in follicular growth and function (Falender et al, 2003;Hinshelwood et al, 2003). By controlling expression of cyclin E1 and D1 through interaction with b-catenin, LRH-1 has recently been shown to promote intestinal cell renewal (Botrugno et al, 2004).…”