Function of the transcriptional regulating protein of 132 kDa (TReP-132) on human P450scc gene expression

Cytochrome P450scc catalyzes the important first step in the steroid synthesis pathway; however, it is clear that additional factors regulating the temporal and spacial specific expression of the CYP11A1 gene remain to be identified. To isolate novel transcription factors that regulate this gene, a cis-acting element of the 5'-flanking region from nucleotides -155 to -131 (-155/-131) was used to screen a human placental lambda gt11 cDNA expression library, and an interacting clone was isolated. The open reading frame of the cDNA encodes several domains that are characteristic of transcription factors including an acidic region, a region rich in prolines and three zinc-finger motifs. Expression of the cDNA by in vitro transcription/translation and by transient transfection in HeLa cells yielded a protein of 132 kDa, which concurs with the predicted size. Transfection of the cDNA in placental JEG-3 and adrenal NCI-H295 cells, stimulate expression of a reporter construct controlled by the P450scc gene 5'-flanking region from nucleotides -1676 to +49. This transcriptional regulating protein of 132kDa (TReP-132) when expressed in HeLa cells was demonstrated to interact with the -155/-131 region in bandshift analysis, and tandem copies of this region was shown to confer activation of the heterologous HSV thymidine kinase minimal promoter. Coexpression of CBP/p300 with TReP-132 further increased promoter activity, and the proteins were demonstrated to interact physically. RNA analysis demonstrated the highest levels of expression in the adrenal cortex and testis; and transcript expression is also found in the steroidogenic JEG-3, NCI-H295, and MCF-7 cell lines, but not in non-steroidogenic HepG2 and HK293 cells. Subsequently it has been shown that TReP-132 interacts with steroidogenic factor-1 (SF-1) through specific domains; and along with the interaction with CBP/p300 these factors are postulated to form a complex to regulate expression of the P450scc gene.

Progesterone production and actions in the human central nervous system and neurogenic tumors

Progesterone has been suggested to be involved in the functions of the nervous system, but it has yet to be examined in humans. Progesterone has also been postulated to be involved in the biological behavior of various human neurogenic tumors via progesterone receptors A and B (PR-A and PR-B). In this study we examined the expression of PR and the enzymes responsible for progesterone biosynthesis (P450scc, 3betahydroxysteroid dehydrogenase, and steroidogenic acute regulatory protein) in human brain. We also examined the distribution of PR isoforms in neurogenic tumors using immunohistochemistry and RT-PCR analysis. The presence of PR and mRNA for P450scc, 3beta-hydroxysteroid dehydrogenase, and steroidogenic acute regulatory protein was detected in human brain. PR isoforms were detected in neurogenic tumors. PR-A and PR-B were equally expressed in meningiomas, but PR-B was the predominant isoform compared with PR-A in astrocytic tumors and Schwannomas. There was a statistically significant inverse correlation between PR-A and the proliferation index in meningiomas and astrocytic tumors. These findings suggest that progesterone is locally synthesized and exerts its actions through PR in the human central nervous system, and that progesterone may be involved in regulation of the growth and development of neurogenic tumors via PR, especially in the inhibition of tumor cell proliferation via PR-A.

Mutant K-ras oncogene regulates steroidogenesis of normal human adrenocortical cells by the RAF-MEK-MAPK pathway

The result of our previous study has shown that the K-ras mutant (pK568MRSV) transfected human adrenocortical cells can significantly increase cortisol production and independently cause cell transformation. The aim of this study is to investigate the effect of the active K-ras oncogene on the cortisol production in normal human adrenocortical cells. First we used isopropyl thiogalactoside to induce the inducible mutant K-ras expression plasmid, pK568MRSV, in the stable transfected human adrenocortical cells. The result showed that the increase of RasGTP levels in transfected cells was time-dependent after isopropyl thiogalactoside induction. Additionally, results from Western blot analysis revealed significant elevation in phosphorylation of c-Raf-1 and Mitogen-activated protein kinase. We also detected the levels of mRNA encoding Cholesterol side-chain cleavage enzyme (P450(SCC)), 17alpha-Hydroxylase/17,20-lyase (P450(c17)) and 3beta-Hydroxysteroid dehydrogenase (3betaHSD) were increased in human adrenocortical cells transfected with mutant K-ras after IPTG treatment. The increase of mRNA amount in P450(scc) P450(c17) and 3betaHSD and the elevation of cortisol level were inhibited with a pretreatment of PD098059, a specific extracellular signal-regulated kinase inhibitor. In our previous report, we proved that lovastatin, a pharmacological inhibitor of p21(ras) function, also reversed the increase of cortisol level in mutant K-ras stably transfected human adrenocortical cells. Taken together, these findings proved that the active mutant Ras enhanced not only cell proliferation but also steroidogenesis in steroidogenic phenotype cells by activating Raf-MEK-MAPK related signal transduction pathway. Therefore, we believe that K-ras mutants influence regulation of steroidogenesis in adrenocortical cells through RAF-MEK-MAPK pathway.

The transcriptional regulating protein of 132 kDa (TReP-132) enhances P450scc gene transcription through interaction with steroidogenic factor-1 in human adrenal cells

The human P450scc gene is regulated by the tissue-specific orphan nuclear receptor, steroidogenic factor-1 (SF-1), which plays a key role in several physiologic processes including steroid synthesis, adrenal and gonadal development, and sexual differentiation. Several studies have demonstrated the interaction of SF-1 with different proteins. However, it is clear that additional factors not yet identified are involved with SF-1 to regulate different target genes. Recently, it was demonstrated that a novel transcriptional regulating protein of 132 kDa (TReP-132) regulates expression of the human P450scc gene. The overexpression of TReP-132 in adrenal cells increases the production of pregnenolone, which is associated with the activation of P450scc gene expression. Considering the colocalization of TReP-132 and SF-1 in steroidogenic tissues such as the adrenal and testis, and the presence of two putative LXXLL motifs in TReP-132 that can potentially interact with SF-1, the relationship between these two factors on the P450scc gene promoter was determined. The coexpression of SF-1 and TReP-132 in adrenal NCI-H295 cells cooperates to increase promoter activity. Pull-down experiments demonstrated the interaction between TReP-132 and SF-1, and this was further confirmed in intact cells by coimmunoprecipitation/Western blot and two-hybrid analyses. Deletions and mutations of the TReP-132 cDNA sequence demonstrate that SF-1 interaction requires the LXXLL motif found at the amino-terminal region of the protein. Also, the "proximal activation domain" and the "AF-2 hexamer" motif of SF-1 are involved in interaction with TReP-132. Consistent with previous studies showing interaction between CBP/p300 and SF-1 or TReP-132, the coexpression of these three proteins results in a synergistic effect on P450scc gene promoter activity. Taken together the results in this study identify a novel function of TReP-132 as a partner in a complex with SF-1 and CBP/p300 to regulate gene transcription involved in steroidogenesis.

Gonadal differentiation, sex determination and normalSryexpression in mice require direct interaction between transcription partners GATA4 and FOG2

In mammals, Sry expression in the bipotential, undifferentiated gonad directs the support cell precursors to differentiate as Sertoli cells, thus initiating the testis differentiation pathway. In the absence of Sry, or if Sry is expressed at insufficient levels, the support cell precursors differentiate as granulosa cells, thus initiating the ovarian pathway. The molecular mechanisms upstream and downstream of Sry are not well understood. We demonstrate that the transcription factor GATA4 and its co-factor FOG2 are required for gonadal differentiation. Mouse fetuses homozygous for a null allele of Fog2 or homozygous for a targeted mutation in Gata4 (Gata4ki) that abrogates the interaction of GATA4 with FOG co-factors exhibit abnormalities in gonadogenesis. We found that Sry transcript levels were significantly reduced in XY Fog2–/– gonads at E11.5, which is the time when Sry expression normally reaches its peak. In addition, three genes crucial for normal Sertoli cell function (Sox9, Mis and Dhh) and three Leydig cell steroid biosynthetic enzymes (p450scc, 3βHSD and p450c17) were not expressed in XY Fog2–/– and Gataki/ki gonads, whereas Wnt4, a gene required for normal ovarian development, was expressed ectopically. By contrast, Wt1 and Sf1, which are expressed prior to Sry and necessary for gonad development in both sexes, were expressed normally in both types of mutant XY gonads. These results indicate that GATA4 and FOG2 and their physical interaction are required for normal gonadal development.

Relationship Between Steroidogenic Acute Regulatory Protein Expression and Progesterone Production in Hen Granulosa Cells During Follicle Development1

The present studies were conducted to address cellular mechanisms responsible for regulating steroidogenic acute regulatory protein (StAR) expression and progesterone synthesis at maturational stages corresponding to both the time of hen follicle selection, as well as before and after the LH surge in preovulatory follicle granulosa cells. A recently published report has established that mitogen-activated protein (MAP) kinase signaling induced by transforming growth factor alpha (TGFalpha) treatment blocks FSH-induced differentiation and StAR expression in cultured hen granulosa cells, whereas inhibitors of MAP kinase signaling enhance FSH-induced differentiation. The present in vitro studies demonstrate that in addition to MAP kinase signaling, activation of protein kinase C (PKC) blocks both FSH-induced StAR expression and the initiation of progesterone production in prehierarchal follicle granulosa cells, whereas the pharmacologic inhibitor of PKC, GF109203X, potentiates FSH-induced StAR expression and, as a consequence, the initiation of progesterone synthesis. Moreover, we demonstrate in granulosa cells collected from preovulatory follicles that although an acute increase in progesterone production in response to LH treatment requires rapid transcription and translation of StAR, the magnitude of progesterone production is rate-limited by one or more factors other than StAR (e.g., the P450 cholesterol side-chain enzyme). Finally, the rapid turnover of StAR protein, such as occurs following the withdrawal of LH, provides an additional mechanism for the tight regulation of progesterone production that occurs during the hen ovulatory cycle, and explains the rapid loss of steroidogenesis in the postovulatory follicle. In summary, data reported herein support the proposal that paracrine/autocrine factors (including but not necessarily limited to TGFalpha) prevent premature expression of StAR in prehierarchal follicle granulosa cells by more than one receptor-mediated signaling pathway. Furthermore, subsequent to follicle selection into the preovulatory hierarchy, StAR transcription and translation is necessary but not sufficient for the full potentiation of the preovulatory surge of serum progesterone.

Expression and Regulation of Fushi Tarazu Factor-1 and Steroidogenic Genes During Reproduction in Arctic Char (Salvelinus alpinus)1

Teleost fushi tarazu factor-1 (FTZ-F1) is a potential regulator of steroidogenesis. The present study shows sex-specific regulation of Arctic char fushi tarazu factor-1 (acFF1) and steroidogenic genes during reproductive maturation and in response to hormone treatment. A link between gonadal expression of acFF1, steroidogenic acute regulatory protein (StAR), and cytochrome P450-11A (CYP11A), was observed in the reproductive maturation process, as elevated acFF1 mRNA and protein levels preceded increased StAR and CYP11A transcription. Sex-specific differences were observed as estrogen treatment resulted in down-regulated levels of acFF1 mRNA in testis and male head kidney, whereas no significant effect was observed in females. 11-Ketotestosterone (11-KT) down-regulated CYP11A and 3beta-hydroxysteroid dehydrogenase (3betaHSD) in head kidney and up-regulated CYP11A in testis. StAR remained unaffected by hormone treatment. This suggests that acFF1 is controlled by 17beta-estradiol, whereas the effects on CYP11A and 3betaHSD are mediated by 11-KT. Coexpression of acFF1, StAR, and CYP11A was observed in head kidney, in addition to gonads, indicating correlation between these steroidogenic genes. StAR and acFF1 were also coexpressed in liver, suggesting a potential role in cholesterol metabolism. Although these results indicate conserved steroidogenic functions for FTZ-F1 among vertebrates, they also raise the question of additional roles for FTZ-F1 in teleosts.

The roles of circulating high-density lipoproteins and trophic hormones in the phenotype of knockout mice lacking the steroidogenic acute regulatory protein

The steroidogenic acute regulatory protein (StAR) is essential for the regulated production of steroid hormones, mediating the translocation of intracellular cholesterol to the inner mitochondrial membrane where steroidogenesis begins. Steroidogenic cells lacking StAR have impaired steroidogenesis and progressively accumulate lipid, ultimately causing cytopathic changes and deterioration of steroidogenic capacity. Developmental studies of StAR knockout (KO) mice have correlated gonadal lipid deposits with puberty, suggesting that trophic hormones contribute to this lipid accumulation. To delineate the role of gonadotropins in this process, we examined double mutant mice deficient in both StAR and gonadotropins [StAR KO/hpg (hypogonadal)]. Lipid accumulation was ameliorated considerably in StAR KO/hpg mice but was restored by treatment with exogenous gonadotropins, directly linking trophic hormones with gonadal lipid accumulation. To define the relative roles of exogenous vs. endogenous cholesterol in the lipid accumulation, we also examined mice lacking both StAR and apolipoprotein A-I (StAR KO/Apo A-I KO). Steroidogenic tissues of StAR KO/Apo A-I KO mice had markedly decreased lipid deposits, supporting the predominant role of high-density lipoprotein-derived cholesterol in the lipid accumulation caused by StAR deficiency. Finally, we used electron microscopy to compare mitochondrial ultrastructure in StAR KO and cholesterol side-chain cleavage enzyme (Cyp11a1) KO mice; despite comparable lipid accumulation within adrenocortical cells, the effects of StAR deficiency and Cyp11a1 deficiency on mitochondrial ultrastructure were markedly different. These findings extend our understanding of steroidogenic cell dysfunction in StAR KO mice and highlight key roles of trophic hormones and high-density lipoprotein-derived cholesterol in lipid deposits within StAR-deficient steroidogenic cells.

Deletions in the loop surrounding the iron-sulfur cluster of adrenodoxin severely affect the interactions with its native redox partners adrenodoxin reductase and cytochrome P450(scc) (CYP11A1)

The redox active iron-sulfur center of bovine adrenodoxin is coordinated by four cysteine residues in positions 46, 52, 55 and 92 and is covered by a loop containing the residues Glu-47, Gly-48, Thr-49, Leu-50 and Ala-51. In plant-type [2Fe-2S] ferredoxins, the corresponding loop consists of only four amino acids. The loop is positioned at the surface of the proteins and forms a boundary separating the [2Fe-2S] cluster from solvent. In order to analyze the biological function of the five amino acids of the loop in adrenodoxin (Adx) for this electron transfer protein each residue was deleted by site-directed mutagenesis. The resulting five recombinant Adx variants show dramatic differences among each other regarding their spectroscopic characteristics and functional properties. The redox potential is affected differently depending on the position of the conducted deletion. In contrast, all mutations in the protein loop influence the binding to the redox partners adrenodoxin reductase (AdR) and cytochrome P450(scc) (CYP11A1) indicating the importance of this loop for the physiological function of this iron--sulfur protein.

Insulin and IGF-I are necessary for FSH-induced cytochrome P450 aromatase but not cytochrome P450 side-chain cleavage gene expression in oestrogenic bovine granulosa cells in vitro

The earliest biochemical indicators of ovarian follicle deviation in cattle include lower oestradiol and free IGF concentrations in subordinate compared with dominant follicles. We determined if decreases in FSH, IGF-I or insulin cause decreased P450 aromatase (P450arom) or P450 cholesterol side-chain cleavage (P450scc) mRNA expression in oestrogenic bovine granulosa cells in vitro. In the first experiment, cells obtained from small follicles (2-5 mm diameter) were cultured in serum-free medium supplemented with physiological concentrations of FSH, IGF-I and insulin for 4 days. A decrease in specific hormone concentration was produced by replacing 70% of spent medium with medium devoid of FSH, insulin, or insulin and IGF-I on day 4 and again on day 5 of culture. Cultures were terminated on day 7. A reduction in FSH concentrations during the last 3 days of culture decreased P450arom and P450scc mRNA levels. A reduction in insulin reduced P450arom but not P450scc mRNA levels, and a reduction of both insulin and IGF-I concentrations further decreased P450arom mRNA levels and decreased P450scc mRNA levels. In a second experiment, cells obtained from small follicles (2-5 mm diameter) were cultured with insulin (100 ng/ml) without FSH for 4 days, and then insulin was withdrawn from the culture and FSH added for a further 3 days. The withdrawal of insulin decreased (P<0.02) oestradiol accumulation and reduced P450arom mRNA to below detectable levels, but did not affect P450scc mRNA levels. The addition of FSH transiently increased oestradiol secretion and P450arom mRNA levels, but P450arom mRNA levels were undetectable at the end of the culture period. The addition of FSH significantly enhanced P450scc mRNA levels and progesterone accumulation. These data demonstrated that a reduction of insulin-like activity reduced aromatase gene expression in bovine follicles without necessarily affecting progesterone synthetic capability, and thus may initiate follicle regression in cattle at the time of follicle divergence.

Molecular progress in infertility: polycystic ovary syndrome

OBJECTIVE

To review the evidence that polycystic ovary syndrome is a genetic disease.

DESIGN

Review of published literature.

RESULTS

The existing literature provides a strong basis for arguing that PCOS clusters in families. However, the mode of inheritance of the disorder is still uncertain, although the majority of studies are consistent with an autosomal dominant pattern, modified perhaps by environmental factors. In addition, studies on PCOS cells (theca, muscle, and adipocytes) in culture have documented a persistent biochemical and molecular phenotype that distinguishes them from normal cells. Although several loci have been proposed as PCOS genes including CYP11A, the insulin gene, and a region near the insulin receptor, the evidence supporting linkage is not overwhelming. The strongest case can be made for the region near the insulin receptor gene, as it has been identified in two separate studies. However, the responsible gene at chromosome 19p13.3 remains to be identified. Association studies have provided a number of potential loci with genetic variants that may create or add to a PCOS phenotype, including Calpain 10, IRS-1 and -2, and SHBG.

CONCLUSIONS

Collectively, these findings are consistent with the concept that a gene or several genes are linked to PCOS susceptibility. Because the mutations/genotypes associated with PCOS are rare, and their full impact on the phenotype incompletely understood, routine screening of women with PCOS or stigmata of PCOS for these genetic variants is not indicated at this time. Currently the treatment implications for individually identified genetic variants is uncertain and must be addressed on a case by case basis.

Liver receptor homologue-1 is expressed in human steroidogenic tissues and activates transcription of genes encoding steroidogenic enzymes

In the current study we test the hypothesis that liver receptor homologue-1 (LRH; designated NR5A2) is involved in the regulation of steroid hormone production. The potential role of LRH was assessed by first examining expression in human steroidogenic tissues and second by examining effects on transcription of genes encoding enzymes involved in steroidogenesis. LRH is closely related to steroidogenic factor 1 (SF1; designated NR5A1), which is expressed in most steroidogenic tissues and regulates expression of several steroid-metabolizing enzymes. LRH transcripts were expressed at high levels in the human ovary and testis. Adrenal and placenta expressed much lower levels of LRH than either ovary or liver. To examine the effects of LRH on steroidogenic capacity we used reporter constructs prepared with the 5'-flanking region of steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage (CYP11A1), 3beta hydroxysteroid dehydrogenase type II (HSD3B2), 17alpha hydroxylase, 17,20 lyase (CYP17), 11beta hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2). Co-transfection of these reporter constructs with LRH expression vector demonstrated that like SF1, LRH enhanced reporter activity driven by flanking DNA from StAR, CYP11A1, CYP17, HSD3B2, and CYP11B1. Reporter constructs driven by CYP11A1 and CYP17 were increased the most by co-transfection with LRH and SF1. Of the promoters examined only HSD3B2 was more sensitive to LRH than SF1. The high level of ovarian and testicular LRH expression make it likely that LRH plays an important role in the regulation of gonadal function.

Regulation of steroidogenic genes by insulin-like growth factor-1 and follicle-stimulating hormone: differential responses of cytochrome P450 side-chain cleavage, steroidogenic acute regulatory protein, and 3beta-hydroxysteroid dehydrogenase/isomerase in rat granulosa cells

The present study sought to characterize the concerted action of FSH and insulin-like growth factor-1 (IGF-1) on functional differentiation of prepubertal rat ovarian granulosa cells in culture. To this end, we examined the regulation of three key genes encoding pivotal proteins required for progesterone biosynthesis, namely, side-chain cleavage cytochrome P450 (P450(scc)), steroidogenic acute regulatory (StAR) protein, and 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD). Time-dependent expression profiles showed that P450(scc), StAR, and 3beta-HSD gene products accumulate in chronic, acute, and constitutive patterns, respectively. Each of these genes responded to FSH and/or IGF-1 in a characteristic manner: A synergistic action of IGF-1 was indispensable for FSH induction of P450(scc) mRNA and protein; IGF-1 did not affect FSH-mediated upregulation of StAR products; and IGF-1 alone was enough to promote expression of 3beta-HSD. The responsiveness of the genes to IGF-1 correlated well with their apparent susceptibility to the inhibitory impact of tyrphostin AG18, a potent inhibitor of protein tyrosine kinase receptors. Thus, IGF-1-dependent P450(scc) and 3beta-HSD expression was completely arrested in the presence of AG18, whereas StAR expression was unaffected in the presence of tyrphostin. These findings suggest that FSH/cAMP signaling and IGF-1/tyrosine phosphorylation events are interwoven in rat ovarian cells undergoing functional differentiation. We also sought the mechanism of IGF-1 synergy with FSH. In this regard, our studies were unable to demonstrate a stabilizing effect of IGF-1 on P450(scc) mRNA, nor could IGF-1 augment FSH-induced transcription examined using a proximal region of the P450(scc) promoter (-379/+6). Thus, the mechanism of IGF-1 and FSH synergy remains enigmatic and provides a major challenge for future studies.

Transcription of cholesterol side-chain cleavage cytochrome P450 in the placenta: activating protein-2 assumes the role of steroidogenic factor-1 by binding to an overlapping promoter element

Progesterone is essential to the sustenance of pregnancy in humans and other mammals. From the second trimester on, the human placenta is the sole origin of de novo synthesized steroid hormones. In mice, placentation at midgestation is accompanied by a temporal rise of steroid hormone synthesis commencing in the giant cells of the mouse trophoblast. In doing so, the giant trophoblasts, as any other steroidogenic cell, express high levels of the key steroidogenic enzyme, cholesterol side-chain cleavage cytochrome P450 (P450scc). Because steroidogenic factor 1 (SF-1), the transcription factor required for expression of P450scc in the adrenals and the gonads, is not expressed in the placenta, we hypothesized that placenta-specific nuclear factor(s) (PNF) assumes the role of SF-1 by binding to the same promoter region that harbors the SF-1 recognition site in the P450scc gene. To address this possibility, we used SCC1, a well conserved proximal region in the P450scc genes (-60/-32 in the rat gene) to purify PNF from human term placenta. Sequencing of the purified PNF revealed that it is the alpha isoform of the human activating protein-2 (AP-2alpha). Specific antibodies tested in EMSA confirmed that AP-2alpha is the predominant isoform that binds SCC1 in the human placenta, whereas AP-2gamma is the only mouse placental protein that binds this oligonucleotide. Functional studies showed that coexpression of the rat P450scc promoter (-378/+8 CAT) and AP-2 isoforms (alpha or gamma) in human embryonic kidney 293 cells results in a marked activation of chloramphenicol acetyltransferase (CAT) transcription that is dependent on an intact AP-2 motif, GCCTTGAGC. This motif conforms with consensus sequences previously determined for binding of the AP-2 alpha and gamma isoforms. Mutations of the AP-2 element ablated binding of AP-2 to SCC1, as well as severely diminished the promoter activity in primary mouse giant trophoblasts and human choriocarcinoma JAR cells. Collectively, these studies suggest that expression of placental P450scc is governed by AP-2 factors that bind to a cis-element that largely overlaps the sequence required for recognition of SF-1 in other steroidogenic tissues.

Steroid deficiency syndromes in mice with targeted disruption of Cyp11a1

Steroid deficiencies are diseases affecting salt levels, sugar levels, and sexual differentiation. To study steroid deficiency in more detail, we used a gene-targeting technique to insert a neo gene into the first exon to disrupt Cyp11a1, the first gene in steroid biosynthetic pathways. Cyp11a1 null mice do not synthesize steroids. They die shortly after birth, but can be rescued by steroid injection. Due to the lack of feedback inhibition by glucocorticoid, their circulating ACTH levels are exceedingly high; this results in ectopic Cyp21 gene expression in the testis. Male Cyp11a1 null mice are feminized with female external genitalia and underdeveloped male accessory sex organs. Their testis, epididymis, and vas deferens are present, but undersized. In addition, their adrenals and gonads accumulate excessive amounts of lipid. The lack of steroid production, abnormal gene expression, and aberrant reproductive organ development resemble various steroid deficiency syndromes, making these mice good models for studies of steroid function and regulation.

Compound heterozygous mutations in the cholesterol side-chain cleavage enzyme gene (CYP11A) cause congenital adrenal insufficiency in humans

Cholesterol side-chain cleavage enzyme (P450scc) catalyzes the conversion of cholesterol to pregnenolone in mitochondria, which is the first step in the biosynthesis of all steroid hormones. Until now, no homozygous or compound heterozygous mutations in CYP11A have been described in humans. Here we describe novel compound heterozygous mutations in CYP11A in a patient with congenital adrenal insufficiency born to healthy parents. One mutation, a maternally inherited R353W mutation, resulted in markedly reduced P450scc activity by the single amino acid substitution, indicating that Arg(353) is a crucial amino acid residue for P450scc activity. The other mutation, a de novo A189V mutation in the paternal allele, did not affect the P450scc activity by the single amino acid substitution and turned out to be a splicing mutation, which created a novel alternative splice-donor site. It resulted in a deletion of 61 nucleotides in the open reading frame and thus partially inactivated CYP11A. These experimental data are consistent with the clinical findings indicating that the patient had partially preserved ability to synthesize adrenal steroid hormones. This is the first report of the compound heterozygote for the CYP11A mutations with congenital adrenal insufficiency and the phenotypically normal heterozygote in humans.

[Polycystic ovary syndrome: recent genetic contributions]

Polycystic ovary syndrome is the most common endocrine disorder in women of reproductive age. It is characterized by hyperandrogenism, chronic anovulation and it is often associated with hyperinsulinemia, insulin resistance and dyslipidaemia. The pathophysiology of polycystic ovary syndrome seems to implicate primary defects in ovarian steroidogenesis, influenced by environment, insulin action and obesity. Polycystic ovary syndrome is probably both a multigenetic and environmental disease. Knowing the genes of polycystic ovary syndrome would be helpful to develop therapeutics and prevention. Genes of gonadotrophins, steroid hormone synthesis and insulin resistance seem not to be directly involved, except perhaps the CYP 11 a gene. On the other hand, identification of the signal transduction pathways involved in these genes may provide valuable information that can be applied to other clinical manifestations of polycystic ovary syndrome (follicular growth arrest, insulin resistance, obesity and endometrial cancer...).

Influence of cytokines and growth factors on distinct steroidogenic enzymes in vitro: a short tabular data collection

Cytokines (IL-1, IL-6, IL-8, IL-11, TNF, IFN-gamma, and TGF-beta) and growth factors (EGF, bFGF, aFGF, and KGF) play an important role in modulation of hormone secretion by directly influencing specific enzyme steps of steroidogenesis in various endocrine cell types. For this tabular data collection, the following enzyme steps were considered: steroidogenic acute regulatory protein (StAR), side chain cleavage enzyme (P450scc), 3 beta-hydroxysteroid dehydrogenase, 17-alpha-hydroxylase/17,20-lyase (P450c17), 17-beta-hydroxysteroid-dehydrogenase, aromatase complex, 5-alpha-reductase, P450c21, DHEAS sulfatase, and DHEA sulfotransferase. This collection summarizes the current information on how the mentioned cytokines and growth factors influence particular enzyme steps.

Salt-inducible kinase represses cAMP-dependent protein kinase-mediated activation of human cholesterol side chain cleavage cytochrome P450 promoter through the CREB basic leucine zipper domain

Salt-inducible kinase (SIK), one of the serine/threonine protein kinases, was transiently expressed in Y1 cells during the early phase of the ACTH/cAMP-dependent protein kinase (PKA)-mediated signal transduction. The overexpression of SIK(N), the SIK's N-terminal kinase domain, repressed the expression of the side chain cleavage cytochrome P450 (CYP11A) gene. To elucidate the mechanism of the repression by SIK, several CYP11A promoter constructs were tested for the promoter activities in the presence of PKA and/or SIK(N). A cAMP-response element (CRE)-like sequence present in the promoter was shown to be responsible not only for the PKA-mediated promoter activation but also for the SIK(N)-mediated repression. When the Gal4 DNA binding domain-linked full-length CRE-binding protein (CREB) construct was cotransfected with Gal4 reporter gene, SIK(N) repressed the PKA-induced reporter gene expression. However, SIK(N) could not repress the PKA-induced reporter activity conferred by Gal4 DNA binding domain-linked basic leucine zipper (bZIP)-less CREB or bZIP-disrupted CREB. On the other hand, SIK(N) could repress the kinase-inducible domain-disrupted CREB-dependent reporter gene expression in the presence of PKA. The in vitro kinase reaction studies showed that SIK(N) could not phosphorylate CREB, and PKA failed to phosphorylate SIK(N). Taken together, these results suggest that SIK(N), cooperating with PKA, may act on the CREB's bZIP domain and repress the CREB-mediated transcriptional activation of the CYP11A gene.

Regulation of expression of ovarian mRNA encoding steroidogenic enzymes and gonadotrophin receptors by FSH and GH in hypogonadotrophic cattle

A study was conducted to determine the effects of FSH and bovine somatotrophin on the expression of mRNA encoding the gonadotrophin receptors and steroidogenic enzymes in ovarian follicles of cattle rendered hypogonadotrophic by treatment with a GnRH agonist. Hereford x Friesian heifers were allotted into two pretreatment groups: controls (n = 10) and GnRH agonist-treated (n = 20). Ovaries of control cows were removed on day 2 of the first follicular wave after synchronized oestrus. GnRH agonist-treated heifers were given either FSH or no FSH. FSH was infused at 50 microg h(-1) for 48 h. Ovaries in GnRH agonist-treated heifers were removed at the end of exogenous hormone treatment. The control, GnRH agonist and GnRH agonist plus FSH treatment groups were divided further into bovine somatotrophin or no bovine somatotrophin treatments (n = 5 per treatment). Bovine somatotrophin (25 mg day(-1) by s.c. injection) was administered for 3 days. Ovaries were scanned once a day by ultrasonography. Blood samples for hormone measurements were collected three times a day from oestrus until the time of removal of ovaries. Expression of mRNAs for the FSH and LH receptors and cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17) and cytochrome P450 aromatase (P450arom) enzymes was localized by in situ hybridization and quantified by image analysis. Ovarian follicular growth was arrested at < or = 4.5 mm in diameter in GnRH agonist-treated heifers. There was no effect of bovine somatotrophin on follicular dynamics, gonadotrophin secretion or expression of mRNA for either the gonadotrophin receptors or steroidogenic enzymes. Infusion of FSH to GnRH agonist-treated heifers increased FSH concentrations in serum to the physiological concentrations observed in controls and stimulated growth of follicles to a size similar (5.5-8.0 mm in diameter) to recruited follicles in control cows. FSH induced mRNA expression of P450scc and P450arom in granulosa cells of follicles at a smaller size (< or = 4.5 mm in diameter) than in controls and increased (P < 0.001) expression in larger (> 4.5 mm in diameter) follicles. Expression of mRNAs for P450scc and P450c17 increased (P < 0.001) with increasing follicle size and was higher (P < 0.01) in theca cells of GnRH agonist plus FSH-treated heifers than in the other groups. There were no treatment differences in expression of FSH receptor in granulosa cells or LH receptor in theca cells, but expression of both receptors increased with follicle size. There was no expression of LH receptor in the granulosa cells of cows from any treatment group. In conclusion, FSH treatment in GnRH agonist-treated heifers induced similar changes in follicular growth to those observed during the first follicular wave, but despite similar peak concentrations, prolonged exposure to high FSH induced precocious expression of mRNAs for P450scc and P450arom in granulosa cells from small follicles and markedly upregulated expression of these enzymes in granulosa cells from recruited follicles. The results of this study demonstrate the key role that FSH plays in the induction of follicular growth and differentiation.

The cDNA cloning and tissue expression of the cytochrome P450scc from Syrian hamster (Mesocricetus auratus)

In this study we report the cloning and sequencing of a cDNA for cholesterol side chain cleavage cytochrome P450scc from Syrian hamster adrenal glands. Isolation of P450scc mRNA was carried out with degenerate primer PCR together with 5' and 3' RACE protocol. The full-length cDNA comprises an open reading frame of 1563 bp encoding a polypeptide of 520 amino acid residues. The predicted protein sequence exhibits well-preserved heme- and steroid-binding domains and shares 89% amino acid sequence identity with rat and mouse enzymes. Transient transfection of HEK-293 cells with the cloned cDNA leads to the formation of pregnenolone from 25-hydroxycholesterol. Northern blot analysis showed expression of mRNAs for P450scc in the major steroidogenic tissues, namely, the adrenal cortex, testis, and ovary. In addition, tissue distribution analysis using the coupled reaction of RT-PCR and Southern blotting revealed that the mRNA of the enzyme is also expressed in various nonendocrine tissues, including the epididymis, Harderian gland, and lungs. The relative abundance of specific transcripts at these novel sites suggests that P450scc could potentially play an important role in regulating local steroid hormone synthesis.

Role of pituitary POMC-peptides and insulin-like growth factor II in the developmental biology of the adrenal gland

During fetal life, it is critical that there is coordinate regulation of the growth, zonation and differentiation of the fetal adrenal cortex to ensure that cells in key tissues and organs are exposed in a programmed temporal sequence to the actions of glucocorticoids. Glucocorticoids are essential for maturation of key target organs before birth, including the lung, brain, liver, gut, kidney and adrenal, and the prepartum increase in glucocorticoid synthesis and secretion by the fetal adrenal gland is critical for the successful transition to postnatal life. It is also evident that premature or abnormal exposure of embryonic or fetal tissues to glucocorticoids during critical windows of development can irreversibly alter the programmed development of organ systems. Premature or abnormal exposure of the fetus to excess glucocorticoids may occur either as a consequence of endogenous stimulation of the fetal hypothalamo-pituitary-adrenal axis (HPAA) or as a consequence of exposure to exogenous glucocorticoids in a therapeutic context. Administration of synthetic glucocorticoids to women at risk of preterm labour, for example, is a routine clinical practice designed to improve respiratory function and neonatal outcome. It is clearly important to understand what endogenous factors regulate the growth and functional maturation of the adrenal cortex during development and the consequent likelihood of exposure of developing tissues to excess corticosteroids. To date, investigations have centred on the role of ACTH 1-39 in the stimulation of adrenal growth and steroidogenesis in long gestation species, such as the primate and sheep, where maturation and differentiation of organ systems occurs predominantly before birth. In this review, we will focus on the evidence that in addition to ACTH 1-39, other pro-opio-melanocortin (POMC) derived peptides, which are synthesized, processed and secreted by the fetal pituitary, play a role in the coordinate regulation of the specific phases of growth and functional development of the fetal adrenal gland in vivo. We will discuss our recent findings on the direct in vivo actions of N-POMC 1-77 and separately, insulin like growth factor II (IGF-II), as adrenal growth factors. These studies provide an understanding of the separate regulatory mechanisms which control activation of adrenal growth and stimulation of adrenal steroidogenesis in the late gestation fetus.

Changes in Leydig cell gene expression during development in the mouse

Developmental changes in the expression of 18 Leydig cell-specific mRNA species were measured by real-time polymerase chain reaction to partially characterize the developmental phenotype of the cells in the mouse and to identify markers of adult Leydig cell differentiation. Testicular interstitial webs were isolated from mice between birth and adulthood. Five developmental patterns of gene expression were observed. Group 1 contained mRNA species encoding P450 side chain cleavage (P450(scc)), P450(c17), relaxin-like factor (RLF), glutathione S-transferase 5-5 (GST5-5), StAR protein, LH receptor, and epoxide hydrolase (EH); group 2 contained 3beta-hydroxysteroid dehydrogenase (3beta-HSD) VI, 17beta-hydroxysteroid dehydrogenase (17beta-HSD) III, vascular cell adhesion molecule 1, estrogen sulfotransferase, and prostaglandin D (PGD)-synthetase; group 3 contained patched and thrombospondin 2 (TSP2); group 4 contained 5alpha-reductase 1 and 3alpha-hydroxysteroid dehydrogenase; group 5 contained sulfonylurea receptor 2 and 3beta-HSD I. Group 1 contained genes that were expressed in fetal and adult Leydig cells and which increased in expression around puberty toward a maximum in the adult. Group 2 contained genes expressed only in the adult Leydig cell population. Group 3 contained genes with predominant fetal/neonatal expression in the interstitial tissue. Group 4 contained genes with a peak of expression around puberty, whereas genes in group 5 show little developmental change in expression. Highest mRNA levels in descending order were RLF, P450(c17), EH, 17beta-HSD III, PGD-synthetase, GST5-5, and P450(scc). Results identify five genes expressed in the mouse adult Leydig cell population, but not in the fetal population, and one gene (TSP2) that may be expressed only in the fetal Leydig cell population. The developmental pattern of gene expression suggests that three distinct phases of adult Leydig cell differentiation occur.

Onset of steroidogenic enzyme gene expression during ovarian follicular development in sheep

Steroidogenesis is a major function of the developing follicle. However, little is known about the stage of onset of steroid regulatory proteins during follicular development in sheep. In this study, several steroidogenic enzymes were studied by immunohistochemistry and/or in situ hybridization; cytochrome P450 side chain cleavage (P450(scc)), cytochrome P450 17alpha-hydroxylase (17alphaOH), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 aromatase (P450(arom)), steroidogenic factor 1 (SF-1), steroidogenic acute regulatory protein (StAR), and LH receptor (LH-R). To define the stages of follicular growth, ovarian maps were drawn from serial sections of ovine ovaries, and follicles were located and classified at specific stages of growth based on morphological criteria. In this way, the precise onset of gene expression with respect to stages of follicular growth for all these proteins could be observed. The key findings were that ovine oocytes express StAR mRNA at all stages of follicular development and that granulosa cells in follicle types 1-3 express 3beta-HSD and SF-1. Furthermore, the onset of expression in theca cells of StAR, P450(scc), 17alphaOH, 3beta-HSD, and LH-R occurred in large type 4 follicles just before antrum formation. This finding suggests that although the theca interna forms from the type 2 stage, it does not become steroidogenically active until later in development. These studies also confirm that granulosa cells of large type 5 follicles express SF-1, StAR, P450(scc), LH-R, and P450(arom) genes. These findings raise new questions regarding the roles of steroidogenic regulatory factors in early follicular development.