Sex-dependent expression of a transcription factor, Ad4BP, regulating steroidogenic P-450 genes in the gonads during prenatal and postnatal rat development

Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review

In mammals, gonadal somatic cell lineage differentiation determines the development of the bipotential gonad into either the ovary or testis. Sertoli cells, the only somatic cells in the spermatogenic tubules, support spermatogenesis during gonadal development. During embryonic Sertoli cell lineage differentiation, relevant genes, including WT1, GATA4, SRY, SOX9, AMH, PTGDS, SF1, and DMRT1, are expressed at specific times and in specific locations to ensure the correct differentiation of the embryo toward the male phenotype. The dysregulated development of Sertoli cells leads to gonadal malformations and male fertility disorders. Nevertheless, the molecular pathways underlying the embryonic origin of Sertoli cells remain elusive. By reviewing recent advances in research on embryonic Sertoli cell genesis and its key regulators, this review provides novel insights into sex determination in male mammals as well as the molecular mechanisms underlying the genealogical differentiation of Sertoli cells in the male reproductive ridge.

Effects of sub-chronic exposure to microcystin-LR on the endocrine system of male rats

Microcystins (MCs) can cause reproductive and developmental toxicity and disrupt endocrine homeostasis in mammals. In the present study, male, Sprague-Dawley (SD) rats were administrated 3 or 30 μg MC-LR/kg, body mass (bm) per day via intraperitoneal (i.p.) injections for 6 weeks. Effects of MC-LR on histology, hormone concentrations, gene transcriptional profiles and protein expressions along the hypothalamic-pituitary-adrenal (HPA), -gonad (HPG) and -thyroid (HPT) axes were assessed. Sub-chronic administration with MC-LR caused histological damage to hypothalamus, pituitary, adrenal, testes and thyroid and affected relative masses of pituitary, adrenal and testes. The HPA axis was activated and serum concentrations of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were significantly augmented. Along the HPG axis, serum concentrations of gonadotropin-releasing hormone (GnRH) and dihydrotestosterone (DHT) were diminished, while concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T) and estradiol (E2) were augmented. For the HPT axis, only concentrations of free tetra-iodothyronine (fT4) were significantly diminished, while concentrations of thyrotropin-releasing hormone (TRH), thyroid-stimulating hormone (TSH) or free tri-iodothyronine (fT3) were not significantly changed. Also, several genes and proteins related to synthesis of steroid hormones were significantly altered. Findings of the present study illustrate that MC-LR can cause endocrine-disrupting effects through the disruption of synthesis and secretion of hormones along the HPA, HPG and HPT axes and negative feedback regulation. Also, there could be crosstalk among HPA, HPG and HPT axes. These findings elucidate mechanisms of endocrine-disrupting effects of MCs.

Nuclear Receptor Gene Variants Underlying Disorders/Differences of Sex Development through Abnormal Testicular Development

Gonadal development is the first step in human reproduction. Aberrant gonadal development during the fetal period is a major cause of disorders/differences of sex development (DSD). To date, pathogenic variants of three nuclear receptor genes (NR5A1, NR0B1, and NR2F2) have been reported to cause DSD via atypical testicular development. In this review article, we describe the clinical significance of the NR5A1 variants as the cause of DSD and introduce novel findings from recent studies. NR5A1 variants are associated with 46,XY DSD and 46,XX testicular/ovotesticular DSD. Notably, both 46,XX DSD and 46,XY DSD caused by the NR5A1 variants show remarkable phenotypic variability, to which digenic/oligogenic inheritances potentially contribute. Additionally, we discuss the roles of NR0B1 and NR2F2 in the etiology of DSD. NR0B1 acts as an anti-testicular gene. Duplications containing NR0B1 result in 46,XY DSD, whereas deletions encompassing NR0B1 can underlie 46,XX testicular/ovotesticular DSD. NR2F2 has recently been reported as a causative gene for 46,XX testicular/ovotesticular DSD and possibly for 46,XY DSD, although the role of NR2F2 in gonadal development is unclear. The knowledge about these three nuclear receptors provides novel insights into the molecular networks involved in the gonadal development in human fetuses.

Expression and Transcript Localization of star, sf-1, and dax-1 in the Early Brain of the Orange-Spotted Grouper Epinephelus coioides

We investigated the developmental expression and localization of sf-1 and dax-1 transcripts in the brain of the juvenile orange-spotted grouper in response to steroidogenic enzyme gene at various developmental ages in relation to gonadal sex differentiation. The sf-1 transcripts were significantly higher from 110-dah (day after hatching) and gradually increased up to 150-dah. The dax-1 mRNA, on the other hand, showed a decreased expression during this period, in contrast to sf-1 expression. At the same time, the early brain had increased levels of steroidogenic gene (star). sf-1 and star hybridization signals were found to be increased in the ventromedial hypothalamus at 110-dah; however, dax-1 mRNA signals decreased in the early brain toward 150-dah. Furthermore, the exogenous estradiol upregulated star and sf-1 transcripts in the early brain of the grouper. These findings suggest that sf-1 and dax-1 may have an antagonistic expression pattern in the early brain during gonadal sex differentiation. Increased expression of steroidogenic gene together with sf-1 during gonadal differentiation strongly suggests that sf-1 may play an important role in the juvenile grouper brain steroidogenesis and brain development.

Adrenal androgens, adrenarche, and zona reticularis: A human affair?

In humans, reticularis cells of the adrenal cortex fuel the production of androgen steroids, constituting the driver of numerous morphological changes during childhood. These steps are considered a precocious stage of sexual maturation and are grouped under the term "adrenarche". This review describes the molecular and enzymatic characteristics of the zona reticularis, along with the possible signals and mechanisms that control its emergence and the associated clinical features. We investigate the differences between species and discuss new studies such as genetic lineage tracing and transcriptomic analysis, highlighting the rodent inner cortex's cellular and molecular heterogeneity. The recent development and characterization of mouse models deficient for Prkar1a presenting with adrenocortical reticularis-like features prompt us to review our vision of the mouse adrenal gland maturation. We expect these new insights will help increase our understanding of the adrenarche process and the pathologies associated with its deregulation.

In utero cadmium and dibutyl phthalate combination exposure worsens the defects of fetal testis in rats

Testicular dysgenesis syndrome might be due to the fetal testis defects caused by endocrine disruptors. Here, we report the combined effects of in utero exposure to cadmium (CdCl₂, Cd) and di-n-butyl phthalate (DBP) on fetal testis development in rats. Pregnant Sprague-Dawley rats were randomly divided into four groups: control, Cd, DBP (250 mg/kg/day), and Cd + DBP. Cd (0.25 mg/kg/once) was intraperitoneally injected to the dam on gestational day 12 and DBP (250 mg/kg) was daily gavaged to the dam on gestational day 12 for 10 days. Cd, DBP, and Cd + DBP lowered serum testosterone levels in male fetuses. Cd and DBP did not alter fetal Leydig cell (FLC) number, but the combined exposure led to decreased FLC number. Cd did not affect FLC aggregation while DBP caused FLC aggregation and the combined exposure worsened FLC aggregation. Cd lowered FLC mRNA (Lhcgr, Star, Cyp11a1, and Insl3) levels and DBP lowered Lhcgr, Star, Insl3, and Nr5a1 levels. DBP up-regulated Scarb1 expression without affecting Cyp11a1 while the combined exposure antagonized DBP. These two chemicals and its combination did not affect Sertoli cell number and gene (Amh, Fshr, and Sox9) expression at current doses. In conclusion, the combined exposure of Cd and DBP exerts synergically antiandrogenic effects via targeting FLC development.

Morphometric analyses and gene expression related to germ cells, gonadal ridge epithelial-like cells and granulosa cells during development of the bovine fetal ovary

Cells on the surface of the mesonephros give rise to replicating Gonadal Ridge Epithelial-Like (GREL) cells, the first somatic cells of the gonadal ridge. Later germ cells associate with the GREL cells in the ovigerous cords, and the GREL cells subsequently give rise to the granulosa cells in follicles. To examine these events further, 27 bovine fetal ovaries of different gestational ages were collected and prepared for immunohistochemical localisation of collagen type I and Ki67 to identify regions of the ovary and cell proliferation, respectively. The non-stromal cortical areas (collagen-negative) containing GREL cells and germ cells and later in development, the follicles with oocytes and granulosa cells, were analysed morphometrically. Another set of ovaries (n = 17) were collected and the expression of genes associated with germ cell lineages and GREL/granulosa cells were quantitated by RT-PCR. The total volume of non-stromal areas in the cortex increased significantly and progressively with ovarian development, plateauing at the time the surface epithelium developed. However, the proportion of non-stromal areas in the cortex declined significantly and progressively throughout gestation, largely due to a cessation in growth of the non-stroma cells and the continued growth of stroma. The proliferation index in the non-stromal area was very high initially and then declined substantially at the time follicles formed. Thereafter, it remained low. The numerical density of the non-stromal cells was relatively constant throughout ovarian development. The expression levels of a number of genes across gestation either increased (AMH, FSHR, ESR1, INHBA), declined (CYP19A1, ESR2, ALDH1A1, DSG2, OCT4, LGR5) or showed no particular pattern (CCND2, CTNNB1, DAZL, FOXL2, GATA4, IGFBP3, KRT19, NR5A1, RARRES1, VASA, WNT2B). Many of the genes whose expression changed across gestation, were positively or negatively correlated with each other. The relationships between these genes may reflect their roles in the important events such as the transition of ovigerous cords to follicles, oogonia to oocytes or GREL cells to granulosa cells.

Fibroblast growth factor 16 stimulates proliferation but blocks differentiation of rat stem Leydig cells during regeneration

Objectives

We aim to investigate the effects of fibroblast growth factor 16 (FGF16) on Leydig cell regeneration in ethane dimethane sulphonate (EDS)‐treated rat testis.

Methods

We intraperitoneally inject 75 mg/kg EDS to adult male Sprague Dawley rats and then intratesticularly inject FGF16 (0, 10 and 100 ng/testis/day) from post‐EDS day 14 for 14 days. We investigate serum hormone levels, Leydig cell number, gene and protein expression in vivo. We also explore the effects of FGF16 treatment on stem Leydig cell proliferation in vitro.

Results

FGF16 lowers serum testosterone levels (21.6% of the control at a dose of 100 ng/testis) without affecting the levels of luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) on post‐EDS day 28 in vivo. FGF16 increases Leydig cell number at doses of 10 and 100 ng/mg without affecting Sertoli cell number, increases the percentage of PCNA‐positive Leydig cells, and down‐regulates the expression of Leydig cell genes (Lhcgr, Scarb1, Star, Cyp11a1, Cyp17a1 and Hsd17b3) and Sertoli cell genes (Fshr, Dhh and Sox9) and their proteins in vivo. FGF16 increases phosphorylation of AKT1 and AKT2 as well as EKR1/2 in vivo, indicating that it possibly acts via AKT1/ATK2 and ERK1/2 pathways. FGF16 also lowers medium testosterone levels and down‐regulates the expression of Leydig cell genes (Lhcgr, Scarb1, Star, Cyp11a1, Cyp17a1 and Hsd17b3) but increases EdU incorporation into stem Leydig cells in vitro.

Conclusions

These data suggest that FGF16 stimulates stem and progenitor Leydig cell proliferation but blocks their differentiation, thus lowering testosterone biosynthesis.

Introduction to the 2016 Keith L. Parker Memorial Lecturer: Douglas M. Stocco, Ph.D

Douglas M. (Doug) Stocco is Professor Emeritus at Texas Tech University Health Sciences Center in Lubbock, TX, and is internationally renowned for his work characterizing the steroidogenic acute regulatory protein, StAR. Stocco's laboratory isolated and cloned StAR from mouse Leydig MA-10 cells, collaborated on the demonstration that StAR mutations cause congenital lipoid adrenal hyperplasia, and delineated much of what is known about the intracellular pathways that regulate its production. This work resolved a decades-long quest to identify the mechanism underlying the acute regulation of steroidogenesis.

FOXL2 Is an Essential Activator of SF-1-Induced Transcriptional Regulation of Anti-Müllerian Hormone in Human Granulosa Cells

Anti-Müllerian hormone (AMH) is required for proper sexual differentiation by regulating the regression of the Müllerian ducts in males. Recent studies indicate that AMH could be an important factor for maintaining the ovarian reserve. However, the mechanisms of AMH regulation in the ovary are largely unknown. Here, we provide evidence that AMH is an ovarian target gene of steroidogenic factor-1 (SF-1), an orphan nuclear receptor required for proper follicle development. FOXL2 is an evolutionally conserved transcription factor, and its mutations cause blepharophimosis, ptosis, and epicanthus inversus syndrome (BPES), wherein affected females display eyelid defects and premature ovarian failure (POF). Notably, we found that functional FOXL2 is essential for SF-1-induced AMH regulation, via protein–protein interactions between FOXL2 and SF-1. A BPES-inducing mutant of FOXL2 (290–291delCA) was unable to interact with SF-1 and failed to mediate the association between SF-1 and the AMH promoter. Therefore, this study identified a novel regulatory circuit for ovarian AMH production; specifically, through the coordinated interplay between FOXL2 and SF-1 that could control ovarian follicle development.

A recurrent p.Arg92Trp variant in steroidogenic factor-1 (NR5A1) can act as a molecular switch in human sex development

Cell lineages of the early human gonad commit to one of the two mutually antagonistic organogenetic fates, the testis or the ovary. Some individuals with a 46,XX karyotype develop testes or ovotestes (testicular or ovotesticular disorder of sex development; TDSD/OTDSD), due to the presence of the testis-determining gene, SRY Other rare complex syndromic forms of TDSD/OTDSD are associated with mutations in pro-ovarian genes that repress testis development (e.g. WNT4); however, the genetic cause of the more common non-syndromic forms is unknown. Steroidogenic factor-1 (known as NR5A1) is a key regulator of reproductive development and function. Loss-of-function changes in NR5A1 in 46,XY individuals are associated with a spectrum of phenotypes in humans ranging from a lack of testis formation to male infertility. Mutations in NR5A1 in 46,XX women are associated with primary ovarian insufficiency, which includes a lack of ovary formation, primary and secondary amenorrhoea as well as early menopause. Here, we show that a specific recurrent heterozygous missense mutation (p.Arg92Trp) in the accessory DNA-binding region of NR5A1 is associated with variable degree of testis development in 46,XX children and adults from four unrelated families. Remarkably, in one family a sibling raised as a girl and carrying this NR5A1 mutation was found to have a 46,XY karyotype with partial testicular dysgenesis. These unique findings highlight how a specific variant in a developmental transcription factor can switch organ fate from the ovary to testis in mammals and represents the first missense mutation causing isolated, non-syndromic 46,XX testicular/ovotesticular DSD in humans.

Haploinsufficiency of SF-1 Causes Female to Male Sex Reversal in Nile Tilapia, Oreochromis niloticus

Steroidogenic factor-1 (Sf-1) (officially designated nuclear receptor subfamily 5 group A member 1 [NR5A1]) is a master regulator of steroidogenesis and reproduction in mammals. However, its function remains unclear in nonmammalian vertebrates. In the present study, we used immunohistochemistry to detect expression of Sf-1 in the steroidogenic cells, the interstitial, granulosa, and theca cells of the ovary, and the Leydig cells of the testis, in Nile tilapia. Clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (Cas9) cleavage of sf-1 resulted in a high mutation rate in the F0 generation and a phenotype of gonadal dysgenesis and reduced steroidogenic cells in XX and XY fish. Sf-1 deficiency also resulted in decreased cytochrome P450, family 19, subfamily A, polypeptide 1a, forkhead box L2 expression, and serum estradiol-17β in XX fish. In XY fish, Sf-1 deficiency increased cytochrome P450, family 19, subfamily A, polypeptide 1a and forkhead box L2 expression but decreased cytochrome P450, family 11, subfamily B, polypeptide 2 expression and serum 11-ketotestosterone levels. 17α-methyltestosterone treatment successfully rescued the gonadal phenotype of Sf-1-deficient XY fish, as demonstrated by normal spermatogenesis and production of F1 mutants. In contrast, estradiol-17β treatment only partially rescued the gonadal phenotype of Sf-1-deficient XX fish, as demonstrated by the appearance of phase II oocytes. Furthermore, both sf-1(+/-) F1 XX and XY mutants developed as fertile males, although spermatogenesis was delayed and efferent duct formation was disordered. Our data suggest that Sf-1 is a major regulator of steroidogenesis and reproduction in fish, as it is in mammals. Sf-1 deficiency resulted in gonadal dysgenesis and feminization of XY gonads. However, unlike in mammals, Sf-1 deficiency also resulted in female to male sex reversal in 8.1% of F0 and 92.1% of sf-1(+/-) F1 in XX fish.

Isolation and Characterization of Fetal Leydig Progenitor Cells of Male Mice

Fetal and adult Leydig cells develop in mammalian prenatal and postnatal testes, respectively. In mice, fetal Leydig cells (FLCs) emerge in the interstitial space of the testis at embryonic day 12.5 and thereafter increase in number, possibly through differentiation from progenitor cells. However, the progenitor cells have not yet been identified. Previously, we established transgenic mice in which FLCs are labeled strongly with enhanced green fluorescent protein (EGFP). Interestingly, fluorescence-activated cell sorting provided us with weakly EGFP-labeled cells as well as strongly EGFP-labeled FLCs. In vitro reconstruction of fetal testes demonstrated that weakly EGFP-labeled cells contain FLC progenitors. Transcriptome from the 2 cell populations revealed, as expected, marked differences in the expression of genes required for growth factor/receptor signaling and steroidogenesis. In addition, genes for energy metabolisms such as glycolytic pathways and the citrate cycle were activated in strongly EGFP-labeled cells, suggesting that metabolism is activated during FLC differentiation.

Regulation of Steroidogenesis, Development, and Cell Differentiation by Steroidogenic Factor-1 and Liver Receptor Homolog-1

Steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1) belong to the nuclear receptor superfamily and are categorized as orphan receptors. In addition to other nuclear receptors, these play roles in various physiological phenomena by regulating the transcription of target genes. Both factors share very similar structures and exhibit common functions. Of these, the roles of SF-1 and LRH-1 in steroidogenesis are the most important, especially that of SF-1, which was originally discovered and named to reflect such roles. SF-1 and LRH-1 are essential for steroid hormone production in gonads and adrenal glands through the regulation of various steroidogenesis-related genes. As SF-1 is also necessary for the development of gonads and adrenal glands, it is also considered a master regulator of steroidogenesis. Recent studies have clearly demonstrated that LRH-1 also represents another master regulator of steroidogenesis, which similarly to SF-1, can induce differentiation of non-steroidogenic stem cells into steroidogenic cells. Here, we review the functions of both factors in these steroidogenesis-related phenomena.

POD-1/Tcf21 overexpression reduces endogenous SF-1 and StAR expression in rat adrenal cells

During gonad and adrenal development, the POD-1/capsulin/TCF21transcription factor negatively regulates SF-1/NR5A1expression, with higher SF-1 levels being associated with increased adrenal cell proliferation and tumorigenesis. In adrenocortical tumor cells, POD-1 binds to the SF-1 E-box promoter region, decreasing SF-1 expression. However, the modulation of SF-1 expression by POD-1 has not previously been described in normal adrenal cells. Here, we analyzed the basal expression of Pod-1 and Sf-1 in primary cultures of glomerulosa (G) and fasciculata/reticularis (F/R) cells isolated from male Sprague-Dawley rats, and investigated whether POD-1 overexpression modulates the expression of endogenous Sf-1 and its target genes in these cells. POD-1 overexpression, following the transfection of pCMVMycPod-1, significantly decreased the endogenous levels of Sf-1 mRNA and protein in F/R cells, but not in G cells, and also decreased the expression of the SF-1 target StAR in F/R cells. In G cells overexpressing POD-1, no modulation of the expression of SF-1 targets, StAR and CYP11B2, was observed. Our data showing that G and F/R cells respond differently to ectopic POD-1 expression emphasize the functional differences between the outer and inner zones of the adrenal cortex, and support the hypothesis that SF-1 is regulated by POD-1/Tcf21 in normal adrenocortical cells lacking the alterations in cellular physiology found in tumor cells.

Steroidogenic factor 1 differentially regulates fetal and adult leydig cell development in male mice

The nuclear receptor steroidogenic factor 1 (SF-1, AD4BP, NR5A1) is a key regulator of the endocrine axes and is essential for adrenal and gonad development. Partial rescue of Nr5a1(-/-) mice with an SF-1-expressing transgene caused a hypomorphic phenotype that revealed its roles in Leydig cell development. In contrast to controls, all male rescue mice (Nr5a1(-/-);tg(+/0)) showed varying signs of androgen deficiency, including spermatogenic arrest, cryptorchidism, and poor virilization. Expression of various Leydig cell markers measured by immunohistochemistry, Western blot analysis, and RT-PCR indicated fetal and adult Leydig cell development were differentially impaired. Whereas fetal Leydig cell development was delayed in Nr5a1(-/-);tg(+/0) embryos, it recovered to control levels by birth. In contrast, Sult1e1, Vcam1, and Hsd3b6 transcript levels in adult rescue testes indicated complete blockage in adult Leydig cell development. In addition, between Postnatal Days 8 and 12, peritubular cells expressing PTCH1, SF-1, and CYP11A1 were observed in control testes but not in rescue testes, indicating SF-1 is needed for either survival or differentiation of adult Leydig cell progenitors. Cultured prepubertal rat peritubular cells also expressed SF-1 and PTCH1, but Cyp11a1 was expressed only after treatment with cAMP and retinoic acid. Together, data show SF-1 is needed for proper development of fetal and adult Leydig cells but with distinct primary functions; in fetal Leydig cells, it regulates differentiation, whereas in adult Leydig cells it regulates progenitor cell formation and/or survival.

Development of a general-purpose method for cell purification using Cre/loxP-mediated recombination

A mammalian body is composed of more than 200 different types of cells. The purification of a certain cell type from tissues/organs enables a wide variety of studies. One popular cell purification method is immunological isolation, using antibodies against specific cell surface antigens. However, this is not a general-purpose method, since suitable antigens have not been found in certain cell types, including embryonic gonadal somatic cells and Sertoli cells. To address this issue, we established a knock-in mouse line, named R26 KI, designed to express the human cell surface antigen hCD271 through Cre/loxP-mediated recombination. First, we used the R26 Kl mouse line to purify embryonic gonadal somatic cells. Gonadal somatic cells were purified from the R26 KI; Nr5a1-Cre-transgenic (tg) embryos almost equally as efficiently as from Nr5a1-hCD271-tg embryos. Second, we used the R26 KI mouse line to purify Sertoli cells successfully from R26 KI; Amh-Cre-tg testes. In summary, we propose that the R26 KI mouse line is a powerful tool for the purification of various cell types.

Adrenocortical growth and cancer

The adrenal gland consists of two distinct parts, the cortex and the medulla. Molecular mechanisms controlling differentiation and growth of the adrenal gland have been studied in detail using mouse models. Knowledge also came from investigations of genetic disorders altering adrenal development and/or function. During embryonic development, the adrenal cortex acquires a structural and functional zonation in which the adrenal cortex is divided into three different steroidogenic zones. Significant progress has been made in understanding adrenal zonation. Recent lineage tracing experiments have accumulated evidence for a centripetal differentiation of adrenocortical cells from the subcapsular area to the inner part of the adrenal cortex. Understanding of the mechanism of adrenocortical cancer (ACC) development was stimulated by knowledge of adrenal gland development. ACC is a rare cancer with a very poor overall prognosis. Abnormal activation of the Wnt/β-catenin as well as the IGF2 signaling plays an important role in ACC development. Studies examining rare genetic syndromes responsible for familial ACT have played an important role in identifying genetic alterations in these tumors (like TP53 or CTNNB1 mutations as well as IGF2 overexpression). Recently, genomic analyses of ACT have shown gene expression profiles associated with malignancy as well as chromosomal and methylation alterations in ACT and exome sequencing allowed to describe the mutational landscape of these tumors. This progress leads to a new classification of these tumors, opening new perspectives for the diagnosis and prognostication of ACT. This review summarizes current knowledge of adrenocortical development, growth, and tumorigenesis.

Fertility preservation in a family with a novel NR5A1 mutation

The common phenotype of nuclear receptor superfamily 5, group A, member 1 (NR5A1) gene mutations in 46,XY is gonadal dysgenesis without adrenal deficiency. Though the phenotype of gonadal dysgenesis is variable, ranging from complete female to normal male genitalia, an asymptomatic 46,XY male is rare. Preserved fertility has so far been described in only three affected 46,XY males with different mutations, but no functional analysis of these mutations has been performed. Here, we report on male siblings with hypospadias and their asymptomatic father in whom we identified a heterozygous NR5A1 mutation of c.910G>A, p.E304K. Western blotting and subcellular localization revealed no significant difference between the wild type (WT) and E304K. Electrophoretic mobility shift assay experiments showed that E304K abrogated DNA-binding ability. E304K reduced transactivation and had no dominant negative effect. In conclusion, we report on a novel hypomorphic NR5A1 mutation, which may be associated with the phenotype of the family.

Molecular identification of genes involved in testicular steroid synthesis and characterization of the responses to hormones stimulation in testis of Japanese sea bass (Lateolabrax japonicas)

Testicular steroids are critical hormones for the regulation of spermatogenesis in male teleosts and their productions have been reported to be regulated by gonadotropins and gonadotropin-releasing hormone. In the Japanese sea bass (Lateolabrax japonicas), the reproductive endocrine, particularly regarding the production and regulation of testicular steroids, are not well understood. For this reason, we first cloned and characterized the response of several key genes regulating the production of testicular steroids and, second, we analyzed the changes of mRNA profiles of these genes during testicular development cycle and in the administration of hCG and GnRHa with corresponding testosterone level in serum, GSI and histological analyses. We succeeded in cloning the full-length cDNAs for the fushi tarazu factor-1 (FTZ-F1) homologues (FTZ-F1a and FTZ-F1b), steroidogenic acute regulatory protein (StAR) and anti-Müllerian hormone (AMH) in Japanese sea bass. Multiple sequence alignment and phylogenetic analysis of these proteins clearly showed that these genes in Japanese sea bass were homologous to those of other piscine species. During the testicular development cycle and hCG/GnRHa administration, quantification of jsbStAR transcripts revealed a trend similar to their serum testosterone levels, while a reciprocal relationship was founded between the serum concentrations of testosterone and jsbAMH and the links between gonadal expression of jsbStAR, jsbAMH and jsbFTZ-F1 were also observed. Our results have identified for the first time several key genes involved in the regulation of steroid production and spermatogenesis in the Japanese sea bass testis and these genes are all detected under gonadotropic hormone and gonadotropin-releasing hormone control.

Glycolytic genes are targets of the nuclear receptor Ad4BP/SF-1

Genetic deficiencies in transcription factors can lead to the loss of certain types of cells and tissue. The steroidogenic tissue-specific nuclear receptor Ad4BP/SF-1 (NR5A1) is one such gene, because mice in which this gene is disrupted fail to develop the adrenal gland and gonads. However, the specific role of Ad4BP/SF-1 in these biological events remains unclear. Here we use chromatin immunoprecipitation sequencing to show that nearly all genes in the glycolytic pathway are regulated by Ad4BP/SF-1. Suppression of Ad4BP/SF-1 by small interfering RNA reduces production of the energy carriers ATP and nicotinamide adenine dinucleotide phosphate, as well as lowers expression of genes involved in glucose metabolism. Together, these observations may explain tissue dysgenesis as a result of Ad4BP/SF-1 gene disruption in vivo. Considering the function of estrogen-related receptor α, the present study raises the possibility that certain types of nuclear receptors regulate sets of genes involved in metabolic pathways to generate energy carriers.

Sertoli cell androgen receptor expression regulates temporal fetal and adult Leydig cell differentiation, function, and population size

We recently created a mouse model displaying precocious Sertoli cell (SC) and spermatogenic development induced by SC-specific transgenic androgen receptor expression (TgSCAR). Here we reveal that TgSCAR regulates the development, function, and absolute number of Leydig cells (LCs). Total fetal and adult type LC numbers were reduced in postnatal and adult TgSCAR vs control testes, despite normal circulating LH levels. Normal LC to SC ratios found in TgSCAR testes indicate that SC androgen receptor (SCAR)-mediated activity confers a quorum-dependent relationship between total SC and LC numbers. TgSCAR enhanced LC differentiation, shown by elevated ratios of advanced to immature LC types, and reduced LC proliferation in postnatal TgSCAR vs control testes. Postnatal TgSCAR testes displayed up-regulated expression of coupled ligand-receptor transcripts (Amh-Amhr2, Dhh-Ptch1, Pdgfa-Pdgfra) for potential SCAR-stimulated paracrine pathways, which may coordinate LC differentiation. Neonatal TgSCAR testes displayed normal T and dihydrotestosterone levels despite differential changes to steroidogenic gene expression, with down-regulated Star, Cyp11a1, and Cyp17a1 expression contrasting with up-regulated Hsd3b1, Hsd17b3, and Srd5a1 expression. TgSCAR males also displayed elevated postnatal and normal adult serum testosterone levels, despite reduced LC numbers. Enhanced adult-type LC steroidogenic output was revealed by increased pubertal testicular T, dihydrotestosterone, 3α-diol and 3β-diol levels per LC and up-regulated steroidogenic gene (Nr5a1, Lhr, Cyp11a1, Cyp17a1, Hsd3b6, Srd5a1) expression in pubertal or adult TgSCAR vs control males, suggesting regulatory mechanisms maintain androgen levels independently of absolute LC numbers. Our unique gain-of-function TgSCAR model has revealed that SCAR activity controls temporal LC differentiation, steroidogenic function, and population size.

Effect of phenol on ovarian secretion of 17β-estradiol in common carp Cyprinus carpio

Phenol is a common substance present in many industrial wastewaters and in nonspecific pesticides. Due to its solubility and volatility phenol is often found in marine and freshwater environment. It is lipophilic compound and has a high potential for accumulating along the trophic chain. Phenol thus is not only a threat to natural environment but also to human health. The effects of phenol on the secretion of 17β-estradiol were examined in female common carp Cyprinus carpio. Vitellogenic stage fish were exposed to physiological safe dose of phenol for 0, 24, 48 and 96 h. In the in vitro experiments, vitellogenic follicles were incubated with phenol and dose- and time-course effects on leuteinising hormone (LH) induced steroid production were examined. Exposure of fish with phenol gradually attenuated serum and ovarian 17β-estradiol levels with increasing time and maximum inhibition was noticed after 96 h. Administration of phenol significantly inhibited LH-induced secretion of 17β-estradiol by the ovarian follicles in vitro. To clarify the mechanism of attenuated production of 17β-estradiol in phenol-treated follicles, stimulated by LH, in vitro effect phenol and LH on aromatase activity (conversion of testosterone to 17β-estradiol) and cytochrome P450arom gene expression in carp ovarian follicles were investigated. Physiological safe dose of phenol significantly inhibited LH-stimulated aromatase activity and P450arom gene expression in ovarian follicles. The present study further demonstrated that LH-induced activation of ovarian steroidogenic factor-1 (SF-1) is strongly inhibited by phenol treatment. These results suggest that physiological safe dose of phenol as endocrine disruption (ED) potential and the effect can be mediated via several cellular pathways including the inhibition of SF-1 activity, aromatase activity and P450arom gene expression.

Embryonic stem cell-derived granulosa cells participate in ovarian follicle formation in vitro and in vivo

Differentiating embryonic stem cells (ESCs) can form ovarian follicle-like structures in vitro, consisting of an oocyte-like cell surrounded by somatic cells capable of steroidogenesis. Using a dual-fluorescence reporter system in which mouse ESCs express green fluorescent protein (GFP) under the control of a germ cell-specific Pou5f1 gene promoter and red fluorescent protein (Discosoma sp red [DsRed]) driven by the granulosa cell-specific Forkhead box L2 (Foxl2) gene promoter, we first confirmed in vitro formation of follicle-like structures containing GFP-positive cells surrounded by DsRed-positive cells. Isolated DsRed-positive cells specified from ECSs exhibited a gene expression profile consistent with granulosa cells, as revealed by the detection of messenger RNAs (mRNAs) for Foxl2, follistatin (Fst), anti-Müllerian hormone (Amh), and follicle-stimulating hormone receptor (Fshr) as well as by production of both progesterone and estradiol. In addition, treatment of isolated DsRed-expressing cells with follicle-stimulating hormone (FSH) significantly increased estradiol production over basal levels, confirming the presence of functional FSH receptors in these cells. Last, ESC-derived DsRed-positive cells injected into neonatal mouse ovaries became incorporated within the granulosa cell layer of immature follicles. These studies demonstrate that Foxl2-expressing ovarian somatic cells derived in vitro from differentiating ESCs express granulosa cell markers, actively associate with germ cells in vitro, synthesize steroids, respond to FSH, and participate in folliculogenesis in vivo.

Effect of cadmium chloride on secretion of 17β-estradiol by the ovarian follicles of common carp, Cyprinus carpio

Cadmium (Cd(2+)) is a common environmental pollutant present in wastes associated with mining, smelting and electroplating. It is a major constituent of the tobacco smoke. Exposure of this heavy metal has been linked to wide range of detrimental effects on mammalian reproduction particularly on ovarian steroidogenesis. Low doses of Cd(2+) are reported to stimulate ovarian luteal progesterone synthesis whereas high doses inhibited it. Cd(2+) exposure is also reported to inhibit gonadal function in fish. In the present study the effects of cadmium chloride (CdCl(2)) on the secretion of gonadotropin-induced 17β-estradiol was examined in female common carp Cyprinus carpio. Vitellogenic stage fish were exposed to physiological safe dose of CdCl(2) for 0, 24, 48 and 96 h and serum and ovarian 17β-estradiol levels were estimated. In the in vitro experiments, vitellogenic follicles were incubated with CdCl(2) and a dose- and time-dependent effects on steroid production were estimated induced by LH. Exposure of fish with CdCl(2) gradually attenuated serum and ovarian 17β-estradiol levels with increasing time and maximum inhibition was noticed after 96 h. Administration of CdCl(2) to the incubations significantly inhibited LH-induced release of 17β-estradiol in vitro. To clarify the mechanism of attenuated production of 17β-estradiol, in vitro effects of CdCl(2) on LH induced P450 aromatase activity (conversion of testosterone to 17β-estradiol) and cytochrome P450arom gene expression in carp ovarian follicles were evaluated. Results show that LH-stimulated P450 aromatase activity and P450arom gene expression in ovarian follicles were significantly inhibited by CdCl(2). The present study further demonstrated that LH-induced stimulation of ovarian steroidogenic factor-1 (SF-1) which activates aromatase enzyme, is strongly inhibited by cadmium chloride treatment.

NR5A1 (SF-1) gene variants in a group of 26 young women with XX primary ovarian insufficiency

OBJECTIVE

To determine whether NR5A1 (SF-1) variants are a cause of primary ovarian insufficiency (POI) in 26 young women with similar genetic background.

DESIGN

Genetic and functional mutation study.

SETTING

University hospitals.

PATIENT(S)

Genetic analysis of the NR5A1 gene in 26 XX girls with POI.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

NR5A1 molecular and functional analysis.

RESULT(S)

Genetic analysis revealed a new c.763C>T (p.Arg255Cys) mutation and a recurrent c.437G>C (p.Gly146Ala) variant. Functional analysis of the p.Arg255Cys mutant showed a marked decrease in transactivation on the Cyp11a1 and Amh promoters. The p.Gly146Ala variant was identified significantly more often in the patients (46.1%) than in ancestry-matched control subjects (10%).

CONCLUSION(S)

We identified one new NR5A1 mutation in a patient of our POI cohort (prevalence 3.8%). Moreover, although our study is limited in the number of cases, we report the high frequency of the p.Gly146Ala variant in this cohort compared with the ancestry-matched control subjects. This work highlights the important role of SF-1 in ovarian function.

In vivo evidence for the crucial role of SF1 in steroid-producing cells of the testis, ovary and adrenal gland

Adrenal and gonadal steroids are essential for life and reproduction. The orphan nuclear receptor SF1 (NR5A1) has been shown to regulate the expression of enzymes involved in steroid production in vitro. However, the in vivo role of this transcription factor in steroidogenesis has not been elucidated. In this study, we have generated steroidogenic-specific Cre-expressing mice to lineage mark and delete Sf1 in differentiated steroid-producing cells of the testis, the ovary and the adrenal gland. Our data show that SF1 is a regulator of the expression of steroidogenic genes in all three organs. In addition, Sf1 deletion leads to a radical change in cell morphology and loss of identity. Surprisingly, sexual development and reproduction in mutant animals were not compromised owing, in part, to the presence of a small proportion of SF1-positive cells. In contrast to the testis and ovary, the mutant adult adrenal gland showed a lack of Sf1-deleted cells and our studies suggest that steroidogenic adrenal cells during foetal stages require Sf1 to give rise to the adult adrenal population. This study is the first to show the in vivo requirements of SF1 in steroidogenesis and provides novel data on the cellular consequences of the loss of this protein specifically within steroid-producing cells.

Evidence for almost complete sex-reversal in bovine freemartin gonads: formation of seminiferous tubule-like structures and transdifferentiation into typical testicular cell types

During mammalian sex determination of XY fetuses, SRY induces SOX9 in Sertoli cells, resulting in formation of testes with seminiferous tubules, interstitial Leydig cells and peritubular myoid cells. Meanwhile XX fetuses without SRY develop ovaries. In cattle, most XX heifers born with a male twin, so-called freemartins, develop nonfunctioning ovaries and genitalia with an intersex phenotype. Interestingly, freemartins sometimes develop highly masculinized gonads with seminiferous tubule-like structures despite the absence of SRY. However, in these cases, the degree of masculinization in each gonadal somatic cell type is unclear. Here, we report a rare case of a freemartin Japanese black calf with almost complete XX sexreversal. Gross anatomical analysis of this calf revealed the presence of a pair of small testis-like gonads with rudimentary epididymides, in addition to highly masculinized genitalia including a pampiniform plexus, scrotum and vesicular gland. Histological and immunohistochemical analyses of these masculinized gonads revealed well-defined seminiferous tubule-like structures throughout the whole gonadal parenchyma. In epithelia of these tubules, SOX9-positive supporting cells (i.e., Sertoli cells) were found to be arranged regularly along the bases of tubules, and they were also positive for GDNF, one of the major factors for spermatogenesis. 3β-HSD-positive cells (i.e., Leydig cells) and SMA-positive peritubular myoid cells were also identified around tubules. Therefore, for the first time, we found the transdifferentiation of ovarian somatic cells into all testicular somatic cell types in the XX freemartin gonads. These data strongly support the idea of a high sexual plasticity in the ovarian somatic cells of mammalian gonads.

Induction of ovarian maturation in Penaeus monodon by molecular signal interventional approach

Vitellogenin (VTG) synthesis in the hepatopancreas and ovary is negatively regulated by vitellogenesis-inhibiting hormone (VIH) produced in the neurosecretory cell of X-organ/sinus gland complex of the eyestalks of penaeid shrimp. Eyestalk ablation is used commercially to induce ovarian maturation in shrimps which leads to an eventual loss of the spawner. The aim of the present study was to understand the molecular mechanism of VIH regulation in ovarian development and its inhibition of VTG gene expression by using a MEK-specific inhibitor (U0126). The real-time quantitative PCR results showed VTG mRNA level was progressively increased in the ovary and hepatopancreas of unilateral eyestalk-ablated and inhibitor-treated shrimps. Western blot analysis also showed that phosphoMEK was detected only in the unilateral eyestalk-ablated and control shrimp, whereas phospho-MEK was not detected in inhibitor-treated shrimp. DAX-1, SF-1, and StAR expression correlated with changes in VIH mRNA and altered phospho-ERK levels. This is consistent with the hypothesis that suppression of DAX-1 results in SF-1-mediated StAR protein upregulation of estradiol that is implicated in vitellogenesis. This is the first report that demonstrates the molecular mechanism of VIH suppression via MEK pathway to induce ovarian maturation in female Penaeus monodon by molecular signal intervention, a less-invasive method than traditional eyestalk ablation.

Luteinizing hormone (LH) regulates production of androstenedione and progesterone via control of histone acetylation of StAR and CYP17 promoters in ovarian theca cells

Although luteinizing hormone (LH) affects androstenedione (A4) and progesterone (P4) production in theca cells, it is still unknown how LH influences molecular mechanism of A4 and P4 production. To examine the relationship between LH and transcription factors involved in A4 and P4 production, ovarian theca cells were cultured in the presence or absence of high concentrations of LH for 24 h (pre-treatment with high concentration of LH) and then cultured in the presence or absence of low concentration of LH for 48 h. Low LH enhanced production of A4 and P4, and expressions of CYP17 and StAR mRNA in theca cells without pre-treatment with high LH. In addition, low LH stimulated the expression of SF-1 protein in nuclear fractions from theca cells with or without pre-treatment with high LH. The binding of SF-1 to the CYP17 and StAR promoter regions increased in theca cells treated with low LH. Although GATA-4 and GATA-6 are both found in the nuclear fraction but not in the cytosol of theca cells, low LH enhanced the binding of GATA-6, but not of GATA-4, to the CYP17 promoter region without pre-treatment with high LH. Acetylation histone H3 in StAR and CYP17 promoter regions were changed by different LH-dosage. Overall, we showed that LH regulates the production of A4 and P4 by affecting the nuclear localization and switching of transcription factors in theca cells and that target transcription factors involved in steroid production in theca cells are changed by different LH concentration.

Male sex determination: insights into molecular mechanisms

Disorders of sex development often arise from anomalies in the molecular or cellular networks that guide the differentiation of the embryonic gonad into either a testis or an ovary, two functionally distinct organs. The activation of the Y-linked gene Sry (sex-determining region Y) and its downstream target Sox9 (Sry box-containing gene 9) triggers testis differentiation by stimulating the differentiation of Sertoli cells, which then direct testis morphogenesis. Once engaged, a genetic pathway promotes the testis development while actively suppressing genes involved in ovarian development. This review focuses on the events of testis determination and the struggle to maintain male fate in the face of antagonistic pressure from the underlying female programme.

SOX9 and SF1 are involved in cyclic AMP-mediated upregulation of anti-Mullerian gene expression in the testicular prepubertal Sertoli cell line SMAT1

In Sertoli cells, anti-Müllerian hormone (AMH) expression is upregulated by FSH via cyclic AMP (cAMP), although no classical cAMP response elements exist in the AMH promoter. The response to cAMP involves NF-κB and AP2; however, targeted mutagenesis of their binding sites in the AMH promoter do not completely abolish the response. In this work we assessed whether SOX9, SF1, GATA4, and AP1 might represent alternative pathways involved in cAMP-mediated AMH upregulation, using real-time RT-PCR (qPCR), targeted mutagenesis, luciferase assays, and immunocytochemistry in the Sertoli cell line SMAT1. We also explored the signaling cascades potentially involved. In qPCR experiments, Amh, Sox9, Sf1, and Gata4 mRNA levels increased after SMAT1 cells were incubated with cAMP. Blocking PKA abolished the effect of cAMP on Sox9, Sf1, and Gata4 expression, inhibiting PI3K/PKB impaired the effect on Sf1 and Gata4, and reducing MEK1/2 and p38 MAPK activities curtailed Gata4 increase. SOX9 and SF1 translocated to the nucleus after incubation with cAMP. Mutations of the SOX9 or SF1 sites, but not of GAT4 or AP1 sites, precluded the response of a 3,063-bp AMH promoter to cAMP. In conclusion, in the Sertoli cell line SMAT1 cAMP upregulates SOX9, SF1, and GATA4 expression and induces SOX9 and SF1 nuclear translocation mainly through PKA, although other kinases may also participate. SOX9 and SF1 binding to the AMH promoter is essential to increase the activity of the AMH promoter in response to cAMP.

Upstream stimulatory factor induces Nr5a1 and Shbg gene expression during the onset of rat Sertoli cell differentiation

Within the testis, each Sertoli cell can support a finite number of developing germ cells. During development, the cessation of Sertoli cell proliferation and the onset of differentiation establish the final number of Sertoli cells and, thus, the total number of sperm that can be produced. The upstream stimulatory factors 1 and 2 (USF1 and USF2, respectively) differentially regulate numerous Sertoli cell genes during differentiation. To identify genes that are activated by USF proteins during differentiation, studies were conducted in Sertoli cells isolated from 5- and 11-day-old rats, representing proliferating and differentiating cells, respectively. Usf1 mRNA and USF1 protein levels were increased between 5 and 11 days after birth. In vitro studies revealed that USF1 and USF2 DNA-binding activity also increased at 11 days for the promoters of four potential target genes, Fshr, Gata4, Nr5a1, and Shbg. Chromatin immunoprecipitation assays confirmed that USF recruitment increased in vivo between 5 and 11 days after birth at the Fshr, Gata4, and Nr5a1 promoters. Expression of Nr5a1 and Shbg, but not of Fshr or Gata4, mRNAs was elevated in 11-day-old Sertoli cells compared with 5-day-old Sertoli cells. Transient transfection of USF1 and USF2 expression vectors up-regulated Nr5a1 and Shbg promoter activity. RNA interference assays demonstrated that USF1 and USF2 contribute to Nr5a1 and Shbg expression in differentiating cells. Together, these data indicate that increased USF levels induce the expression of Nr5a1 and Shbg during the differentiation of Sertoli cells, whereas Fshr and Gata4 expression is not altered by USF proteins during differentiation.

Teasing out the role of aromatase in the healthy and diseased testis

Scientific discoveries over the past decade have shifted the stereotypical view of androgens as male hormones and estrogens as female hormones. It is now recognized that a delicate balance of both androgens and estrogens, a process controlled by aromatase, is fundamental for normal testicular development and fertility. While the site-specific actions of these two classes of steroids within the testis are becoming better documented, the role and regulation of estrogen biosynthesis by aromatase within the testis remains unclear. The majority of data comes from a wide range of animal species, particularly genetically modified mouse models; aromatase knockout (ArKO) and overexpressing (AROM(+)), with limited information on humans, however the existence of congenital aromatase mutations has provided some insight into its effects on individual parameters of the testis. This review dissects out the localization and activity of aromatase in the healthy and diseased testis, addresses the cellular insult to the testis that occurs in its absence and over abundance and proposes potential molecular mechanisms of aromatase regulation in the testis.

Endogenous biotin as a marker of adrenocortical cells with steroidogenic potential

Interpretation of adrenal cortex phenotypes is greatly facilitated by simultaneous examination of multiple markers at single cell resolution. However, the availability of multiple appropriate antibodies can be rate limiting, while their cognate antigens are often subject to variable accessibility. Specific markers not subject to these constraints thus have obvious utility. Here we report that endogenous biotin, when detected in fixed, frozen tissue sections using fluorescent streptavidin, is a specific marker of apparently all cells with steroidogenic potential in the murine adrenal cortex. While streptavidin stains presteroidogenic and mature cortical cells, it does not label the adrenal capsule, medulla or vascular endothelium. Developmental profiles reveal adrenal endogenous biotin labeling from E13.5 through adulthood. Comparisons with zonal markers, hypothalamic-pituitary-adrenal (HPA) axis-remodeled tissue, transgenic Shh-nLacZ or Gli1-nLacZ animals, and Shh mutant embryos further demonstrate the utility of this approach. Fluorescent streptavidin applied using a simple one-step staining protocol thus provides a potent counterstain for use in adrenal analyses.

The fetal and adult adrenal cortex

The orphan nuclear receptor AD4BP/SF-1 (adrenal-4-binding protein/steroidogenic factor-1 (NR5A1)) is essential for the proper development and function of reproductive and steroidogenic tissues. Although the expression of Ad4BP/Sf-1 is specific for those tissues, the mechanisms underlying this tissue-specific expression remain unknown. Our transgenic studies have identified the tissue-specific enhancers for the fetal adrenal cortex, ventromedial hypothalamus, and pituitary in Ad4BP/Sf-1 gene. The adrenal cortex forms morphologically distinct compartments, the inner (fetal) and outer (definitive or adult) zones. Despite considerable effort, the mechanisms that mediate the differential development of the fetal and adult adrenal cortex remain incompletely understood. It remained controversial whether a true fetal type adrenal cortex is present in mice, and this argument was complicated by the postnatal development of the so-called X-zone. Using transgenic mice with lacZ driven by the fetal adrenal enhancer (FAdE), we clearly identified a fetal adrenal cortex in mice, and the X-zone is the fetal adrenal cells accumulated at the juxtamedullary region after birth. We combined the FAdE with the Cre/loxP system to trace cell lineages in which the FAdE was active at some stage in development. These lineage tracing studies establish definitively that the adult cortex derives from precursor cells in the fetal cortex in which the FAdE was activated before the organization into two distinct zones. The potential of these fetal adrenocortical cells to enter the pathway that eventuate in cells of the adult cortex disappeared by E14.5. Thus, these studies demonstrate a direct link between the fetal and adult cortex involving a transition that must occur before a specific stage of development.

Two regions within the proximal steroidogenic factor 1 promoter drive somatic cell-specific activity in developing gonads of the female mouse

Targets of steroidogenic factor 1 (SF1; also known as NR5A1 and AD4BP) have been identified within cells at every level of the hypothalamic-pituitary-gonadal and -adrenal axes, revealing SF1 to be a master regulator of major endocrine systems. Mouse embryos express SF1 in the genital ridge until Embryonic Day 13.5 (E13.5). Thereafter, expression persists in the male and is substantially lower in the female gonad until birth. We hypothesize that the sexually dimorphic expression of Sf1 during gonadogenesis is mediated by sex-specific regulation of its promoter. To investigate dimorphic regulation within the fetal gonad, we developed an experimental strategy using transient transfection of E13.5 gonad explant cultures and evaluated various Sf1 promoter constructs for sexually dimorphic DNA elements. The proximal Sf1 promoter correctly targeted reporter activity to SF1-expressing cells in both XY and XX gonads. Stepwise deletion of sequences from the Sf1 promoter revealed two regions that affected regulation within female gonads. Mutation of both sequences together did not cause further disruption of reporter activity, suggesting the two sites might work in concert to promote activity in female somatic cells. Results from gel mobility shift assays and fetal gonad-chromatin immunoprecipitation showed that TCFAP2 binds to one of the two female-specific sites within the proximal promoter of Sf1. Together, we show that transient transfection experiments performed within developing testes and ovaries are a powerful tool to uncover elements within the Sf1 promoter that contribute to sex-specific expression.

Abnormal epithelial cell polarity and ectopic epidermal growth factor receptor (EGFR) expression induced in Emx2 KO embryonic gonads

The gonadal primordium first emerges as a thickening of the embryonic coelomic epithelium, which has been thought to migrate mediodorsally to form the primitive gonad. However, the early gonadal development remains poorly understood. Mice lacking the paired-like homeobox gene Emx2 display gonadal dysgenesis. Interestingly, the knockout (KO) embryonic gonads develop an unusual surface accompanied by aberrant tight junction assembly. Morphological and in vitro cell fate mapping studies showed an apparent decrease in the number of the gonadal epithelial cells migrated to mesenchymal compartment in the KO, suggesting that polarized cell division and subsequent cell migration are affected. Microarray analyses of the epithelial cells revealed significant up-regulation of Egfr in the KO, indicating that Emx2 suppresses Egfr gene expression. This genetic correlation between the two genes was reproduced with cultured M15 cells derived from mesonephric epithelial cells. Epidermal growth factor receptor signaling was recently shown to regulate tight junction assembly through sarcoma viral oncogene homolog tyrosine phosphorylation. We show through Emx2 KO analyses that sarcoma viral oncogene homolog tyrosine phosphorylation, epidermal growth factor receptor tyrosine phosphorylation, and Egfr expression are up-regulated in the embryonic gonad. Our results strongly suggest that Emx2 is required for regulation of tight junction assembly and allowing migration of the gonadal epithelia to the mesenchyme, which are possibly mediated by suppression of Egfr expression.

Differential requirements for neurogenin 3 in the development of POMC and NPY neurons in the hypothalamus

The neuroendocrine hypothalamus regulates a spectrum of essential biological processes and underlies a range of diseases from growth failure to obesity. While the exploration of hypothalamic function has progressed well, knowledge of hypothalamic development is poor. In particular, very little is known about the processes underlying the genesis and specification of the neurons in the arcuate and ventromedial nuclei. Recent studies demonstrate that the proneural basic helix-loop-helix transcription factor Mash1 is required for neurogenesis and neuronal subtype specification in the ventral hypothalamus. We demonstrate here that Ngn3, another basic helix-loop-helix transcription factor, is expressed in mitotic progenitors in the arcuate and ventromedial hypothalamic regions of mouse embryos from embryonic days 9.5-17.5. Genetic fate mapping and loss of function studies in mice demonstrate that Ngn3+ progenitors contribute to subsets of POMC, NPY, TH and SF1 neurons and is required for the specification of these neuronal subtypes in the ventral hypothalamus. Interestingly, while Ngn3 promotes the development of arcuate POMC and ventromedial SF1 neurons, it inhibits the development of NPY and TH neurons in the arcuate nuclei. Given the opposing roles of POMC and NPY neurons in regulating food intake, these results indicate that Ngn3 plays a central role in the generation of neuronal populations controlling energy homeostasis in mice.

A missense mutation of the Dhh gene is associated with male pseudohermaphroditic rats showing impaired Leydig cell development

Development of the male gonads is a complex process with interaction of various cells in the gonads including germ, Sertoli, Leydig, and myoid cells. TF is a mutant rat strain showing male pseudohermaphroditism, with agenesis of Leydig cells and androgen deficiency controlled by an autosomal single recessive gene (mp). The mp locus was mapped on the distal region of rat chromosome 7 by linkage analysis, but the gene responsible for the mp mutation has not been identified. In this study, we performed fine linkage mapping and sequence analysis to determine the causative gene of the mp mutation, and performed an immunohistochemical study using a Leydig cell-specific marker to investigate detailed phenotypes of the mutant rats during the testicular development. As a result, we found a missense mutation of the gene encoding Desert hedgehog (Dhh) in the mutant rat, which could result in loss of function of the DHH signaling pathway. Histochemical examination revealed remarkably reduced number of fetal Leydig cells and lack of typical spindle-shaped adult Leydig cell in the mp/mp rats. These phenotypes resembled those of the Dhh-null mice. Additionally, testosterone levels were significantly lower in the mp/mp fetus, indicating androgen deficiency during embryonic development. These results indicate that the mutation of the Dhh gene may be responsible for the pseudohermaphrodite phenotypes of the mutant rat, and that the Dhh gene is probably essential for the development of Leydig cells.

The mechanism of sex determination in vertebrates-are sex steroids the key-factor?

In many vertebrate species, sex is determined at fertilization of zygotes by sex chromosome composition, knows as genotypic sex determination (GSD). But in some species-fish, amphibians and reptiles-sex is determined by environmental factors; in particular by temperature-dependent sex determination (TSD). However, little is known about the mechanisms involved in TSD and GSD. How does TSD differ from GSD? As is well known, genes that activated downstream of sex-determining genes are conserved throughout all classes of vertebrates. What is the main factor that determines sex, then? Sex steroids can reverse sex of several species of vertebrate; estrogens induce the male-to-female sex-reversal, whereas androgens do the female-to-male sex-reversal. For such sex-reversal, a functioning sex-determining gene is not required. However, in R. rugosa CYP19 (P450 aromatase) is expressed at high levels in indifferent gonads before phenotypic sex determination, and the gene is also active in the bipotential gonad of females before sex determination. Thus, we may predict that an unknown factor, a common transcription factor locates on the X and/or W chromosome, intervenes directly or indirectly in the transcriptional up-regulation of the CYP19 gene for feminization in species of vertebrates with both TSD and GSD. Similarly, an unknown factor on the Z and/or Y chromosome probably intervenes directly or indirectly in the regulation of androgen biosynthesis for masculinization. In both cases, a sex-determining gene is not always necessary for sex determination. Taken together, sex steroids may be the key-factor for sex determination in some species of vertebrates.

Localization and regulation of aromatase liver receptor homologue-1 in the developing rat testis

The enzyme aromatase converts androgens to estrogens, which have recently been postulated to be essential for testicular development and fertility. Understanding the mechanisms that regulate aromatase activity in the testis may therefore have implications for treatment of male infertility. Aromatase is encoded by the CYP19 gene, which uses multiple tissue-specific alternative promoters. In the testis, the proximal promoter PII drives aromatase expression. PII activity requires a nuclear receptor half-site, CAAGGTCA, to which two orphan receptors; SF-1 and LRH-1, have been shown to bind in vitro. The aim of this study was to investigate expression of aromatase and LRH-1 in the developing rat testis and define the ability of LRH-1 to induce aromatase expression in the testicular cells where both are expressed. We show that aromatase and LRH-1 are present throughout all stages of development of the rat testis, although the sites and levels of expression vary. The pattern of LRH-1 expression was broadly similar to that of aromatase. In adult animals higher levels of expression were observed in Leydig and germ cells. Over-expression of LRH-1 in primary rat Leydig and germ cells by adenoviral infection strongly increased endogenous aromatase mRNA levels, demonstrating the ability of LRH-1 to stimulate aromatase expression in vivo. We also observed binding of endogenous LRH-1 to the aromatase promoter II by chromatin immunoprecipitation. These data provide evidence that LRH-1 plays an important role in the regulation of testicular aromatase expression, and implicate LRH-1 as a regulator of rat spermatogenesis, in which estrogens are emerging as important mediators.