Expression of the aromatase cytochrome P450 encoding gene in cattle and sheep

Impact of sleep patterns upon female neuroendocrinology and reproductive outcomes: a comprehensive review

Sleep is vital to human bodily function. Growing evidence indicates that sleep deprivation, disruption, dysrhythmia, and disorders are associated with impaired reproductive function and poor clinical outcomes in women. These associations are largely mediated by molecular-genetic and hormonal pathways, which are crucial for the complex and time sensitive processes of hormone synthesis/secretion, folliculogenesis, ovulation, fertilization, implantation, and menstruation. Pathologic sleep patterns are closely linked to menstrual irregularity, polycystic ovarian syndrome, premature ovarian insufficiency, sub/infertility, and early pregnancy loss. Measures of success with assisted reproductive technology are also lower among women who engage in shift work, or experience sleep disruption or short sleep duration. Extremes of sleep duration, poor sleep quality, sleep disordered breathing, and shift work are also associated with several harmful conditions in pregnancy, including gestational diabetes and hypertensive disorders. While accumulating evidence implicates pathologic sleep patterns in impaired reproductive function and poor reproductive outcomes, additional research is needed to determine causality and propose therapeutic interventions.

Circadian Rhythms Within the Female HPG Axis: From Physiology to Etiology

Declining female fertility has become a global health concern. It results partially from an abnormal circadian clock caused by unhealthy diet and sleep habits in modern life. The circadian clock system is a hierarchical network consisting of central and peripheral clocks. It not only controls the sleep-wake and feeding-fasting cycles but also coordinates and maintains the required reproductive activities in the body. Physiologically, the reproductive processes are governed by the hypothalamic-pituitary-gonadal (HPG) axis in a time-dependent manner. The HPG axis releases hormones, generates female characteristics, and achieves fertility. Conversely, an abnormal daily rhythm caused by aberrant clock genes or abnormal environmental stimuli contributes to disorders of the female reproductive system, such as polycystic ovarian syndrome and premature ovarian insufficiency. Therefore, breaking the "time code" of the female reproductive system is crucial. In this paper, we review the interplay between circadian clocks and the female reproductive system and present its regulatory principles, moving from normal physiology regulation to disease etiology.

HIF1 driven transcriptional activity regulates steroidogenesis and proliferation of bovine granulosa cells

Hypoxia-inducible factor 1 (HIF1) is a heterodimeric transcription factor, consisting of a constitutively expressed β-subunit (HIF1B) and a regulated α-subunit (HIF1A). In the present study, we analyzed the HIF1 driven transcriptional activity in bovine granulosa cells (GC). Treatment of GC with FSH (follicle stimulating hormone) and IGF1 (insulin-like growth factor 1) resulted in the upregulation of HIF1A mRNA expression under normoxia. Immunohistochemistry of bovine ovarian sections showed distinct staining of HIF1A in the GC layer of different staged ovarian follicles. Suppression of HIF1 using echinomycin and gene knockdown procedures revealed that HIF1 transcriptionally regulates the genes associated with steroidogenesis (STAR, HSD3B and CYP19A1) and proliferation (CCND2 and PCNA) of GC. Further, our data suggest that CYP19A1, the key gene of estradiol production, is one of the plausible downstream targets of HIF1 in bovine GC as shown by gene expression, radioimmunoassay, and chromatin precipitation analysis. Based on these results, we propose that HIF1 driven transcriptional activity plays a crucial role in GC functionality, especially steroidogenesis and proliferation in developing bovine ovarian follicles.

Association of MTNR1A and CYP19 genes polymorphisms with sperm quality and testicular size in Sanjabi breed rams

The purpose of this study was to identify mutations in melatonin receptor 1A (MTNR1A) and aromatase cytochrome P450 (CYP19) genes using PCR-RFLP technique and their associations with sperm quality and testicular size traits in Sanjabi breed rams. The blood and sperm samples were collected from Sanjabi rams (n = 96). Genomic DNA was extracted from the blood. A 824bp fragment from exon II of MTNR1A gene and a 517bp fragment from promoter 2 (P2) of CYP19 gene were amplified using two pairs of specific primers. The PCR products were separately digested by two restriction enzymes, SsiI for MTNR1A locus and DraI for CYP19 locus. Digestion by SsiI restriction enzyme resulted in CC, CA and AA genotypes with frequency of 0.45, 0.41 and 0.14, respectively. However, digestion of 517bp fragment of CYP19 gene by DraI endonuclease determined two AG and AA genotypes with frequency 0.89 and 0.11, respectively. The Chi-square test proved that the two loci were in Hardy-Weinberg equilibrium (HWE). The significant effect was observed between different genotypes of MTNR1A gene and morphological trait (P<0.05) and there was a significant association between different genotypes of CYP19 gene and scrotal circumference trait (P<0.05). The results of this study indicated that polymorphisms of MTNR1A and CYP19 genes were not associated with most traits of sperm quality and testicular sizes. Therefore, it seems that further studies are needed to identify mutations in other regions of these genes and other genes responsible to genomic regions for the sperm quality and testicular size in Sanjabi ram in order to improve fertility in these herds.

Estrogens in Male Physiology

Estrogens have historically been associated with female reproduction, but work over the last two decades established that estrogens and their main nuclear receptors (ESR1 and ESR2) and G protein-coupled estrogen receptor (GPER) also regulate male reproductive and nonreproductive organs. 17β-Estradiol (E2) is measureable in blood of men and males of other species, but in rete testis fluids, E2 reaches concentrations normally found only in females and in some species nanomolar concentrations of estrone sulfate are found in semen. Aromatase, which converts androgens to estrogens, is expressed in Leydig cells, seminiferous epithelium, and other male organs. Early studies showed E2 binding in numerous male tissues, and ESR1 and ESR2 each show unique distributions and actions in males. Exogenous estrogen treatment produced male reproductive pathologies in laboratory animals and men, especially during development, and studies with transgenic mice with compromised estrogen signaling demonstrated an E2 role in normal male physiology. Efferent ductules and epididymal functions are dependent on estrogen signaling through ESR1, whose loss impaired ion transport and water reabsorption, resulting in abnormal sperm. Loss of ESR1 or aromatase also produces effects on nonreproductive targets such as brain, adipose, skeletal muscle, bone, cardiovascular, and immune tissues. Expression of GPER is extensive in male tracts, suggesting a possible role for E2 signaling through this receptor in male reproduction. Recent evidence also indicates that membrane ESR1 has critical roles in male reproduction. Thus estrogens are important physiological regulators in males, and future studies may reveal additional roles for estrogen signaling in various target tissues.

Polymorphism C242T in the Cyp19 gene in meat sheep

Abstract The objective of this study was to evaluate the frequency of C242T polymorphism on the aromatase gene and the allelic and genotypic frequency of these variants in sheep belonging to four breed groups. Blood samples were collected from 187 animals of four breed groups: Dorper, Santa Inês, Texel and White Dorper, originated from herds in the region of Maringá/PR, Brazil. The genomic DNA was extracted using alkaline extraction, with subsequent amplification of the fragments via PCR with specific primer. The samples resulting from amplification were subjected to digestion process using the Dpn II restriction enzyme and to polyacrylamide gel electrophoresis 10.0% and stained with silver nitrate. Three distinct genotypes were observed: homozygous (CC), heterozygous (CT) and homozygous for no cut (TT). The resulting data were analyzed using the POPGENE software with 5% significance. Genotypic frequencies among the breed groups were: Texel (CC - 0.426; CT - 0.511; TT - 0.064), Dorper (CC - 0.073; CT - 0.732; TT - 0.439), White Dorper (CC - 0.021; CT - 0.255; TT - 0.723) and Santa Inês (CC - 0.115; CT - 0.462; TT - 0.423).

Factors regulating the bovine, caprine, rat and human ovarian aromatase promoters in a bovine granulosa cell model

The ovarian promoter of the primate and rodent genes encoding cytochrome P450 aromatase (CYP19A1) are robustly responsive to forskolin in luteinized cell models, whereas the ruminant ovarian promoter is minimally active. We explored this discrepancy by investigating the activity of the bovine ovarian promoter in two bovine granulosa cell models, luteinizing and non-luteinizing cells in vitro. In non-luteinizing cells, both FSH and IGF1 increased abundance of transcripts derived from the ovarian promoter. Comparison of the activity of promoters of several species in response to transcription factors (forskolin, NR5A2, FOXL2) in luteinizing cells demonstrated that a rat ovarian promoter-luciferase reporter was regulated mainly by forskolin (18-fold increase over basal expression) and addition of NR5A2 or FOXL2 had no further effect. Activity of a human promoter was significantly increased by NR5A2 plus forskolin (153-fold) compared with forskolin alone (71-fold over basal); addition of FOXL2 did not significantly increase promoter activity. Forskolin alone provoked minor activation of caprine and bovine promoter reporters (3-fold over basal), and addition of NR5A2 increased activity (7- to 11-fold). When forskolin, NR5A2 and FOXL2 treatments were combined, the activity of the caprine and bovine promoters increased to 20- and 34-fold, respectively. These data suggest that a major reason why CYP19A1 is not expressed in luteinized cells (and the corpus luteum) of ruminants may be the stimulatory effect of FOXL2, which does not appear to be the case in the human and rat.

Circadian Clock genes Per2 and clock regulate steroid production, cell proliferation, and luteinizing hormone receptor transcription in ovarian granulosa cells

Circadian Clock genes are associated with the estrous cycle in female animals. Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression in follicle-stimulating hormone FSH-treated granulosa cells. Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom, whereas Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. Similarly, expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. Our data provide a new insight that Per2 and Clock have different action on ovarian granulosa cell functions.

An analysis of CYP19, CYP21 and ER genotypes in Polish Holstein-Friesian cows with regard to the selected reproductive traits

The aim of this study was to relate polymorphic variants of CYP19, CYP21 and ER1 genes to reproductive traits in 472 Polish Holstein-Friesian cows. High frequencies of one of the homozygous genotypes were found. The ER1/SnaBIAA homozygotes were not identified. In the first and third lactation, an average calving-to-conception interval (CLVC) in cows of ER1/SnaBIGG genotype was significantly shorter (P ≤ 0.05) than in heterozygous cows. In the cows of ER1/BglIGG genotype, significantly shorter CLVC (P ≤ 0.05) was observed compared to heterozygotes in the first lactation, whereas in the third lactation, CLVC in homozygous cows was significantly longer (P ≤ 0.05) than in heterozygous ones. It was also found that homozygous cows were characterized by significantly longer calving interval (CLVI; P ≤ 0.05) compared to heterozygotes in the third lactation. Longer CLVCs in CYP19AA cows were found, compared to heterozygotes, and this difference was significant in the first and third lactation (P ≤ 0.05). Similarly, the average CLVIs were longer in CYP19AA homozygotes than in heterozygous cows; however, significance was proven only in the third lactation (P ≤ 0.05). Description of the molecular mechanisms regulating reproduction, and thus identification of the individuals of genotypes with optimal potential may facilitate the employment of selected reproductive model by a breeder.

Intrauterine growth restriction alters hippocampal expression and chromatin structure of Cyp19a1 variants

We evaluated the impact of uteroplacental insufficiency (UPI), and subsequent intrauterine growth restriction (IUGR), on serum testosterone and hippocampal expression of Cyp19a1 variants and aromatase in rats. Additionally, we determined UPI induced histone modification of the promoter regions of Cyp19a1 variants using chromatin immunoprecipitation. Cyp19a1 is the gene encoding the protein aromatase, that catalyzes the biosynthesis of estrogens from androgens and is necessary for masculinization of the brain. IUGR was induced via bilateral uterine artery. UPI increased serum testosterone in day of life 0 (D(0)) and day of life 21 (D(21)) IUGR males to 224% and 299% of control values, respectively. While there was no significant impact of UPI on testosterone in D(0) females, testosterone in D(21) IUGR females was 187% of controls. Cyp19a1 variant 1.f and variant II are expressed in the rat hippocampus at D(0) and D(21). UPI significantly reduced expression of Cyp19a1 variant 1.f in D(0) males, with no impact in females. Similarly at D(0), UPI reduced expression of aromatase, the protein encoded by Cyp19a1, in males. Dimethylation of H3K4 was increased in the promoter region of variant 1.f (P1.f) and trimethylation of H3K4 was decreased in the promoter region of variant II (PII). At D(21), dimethylation of H3K4 is significantly reduced in PII of IUGR males. We conclude that UPI increases serum testosterone and reduces Cyp19a1 variant 1.f expression in the hippocampus of D(0) IUGR males. Additionally, UPI alters the chromatin structure of CYP19a1 at both D(0) and D(21).

Alternative 5'-untranslated first exons of the mouse Cyp19A1 (aromatase) gene

The human aromatase gene (CYP19A1) has eleven tissue-specific untranslated first exons, while only three have been described in the mouse Cyp19A1 namely brain-, ovary- and testis-specific exons 1. The present study aims to elucidate the complete structure of the mouse Cyp19A1 gene. We detected aromatase transcripts in mouse bone, aorta, hypothalamus, adipose, gonads and placenta, but not nulliparous mammary fat pad. BestFit algorithm analysis against the human CYP19A1 has identified ten putative first exons upstream of mouse Cyp19A1. Based on these putative sequences, we were able to design specific primers for RT-PCR and detected for the first time, the presence of exons I.4 and I.3 in murine fat and gonads, respectively. These are novel 5'UTRs of mouse Cyp19A1. Using RT-PCR and 5' RACE, we confirmed the expression of exon 1f in the hypothalamus and proximal exon P2 in the ovary. The testis-specific exon 1 begins 217bp further upstream than previously reported. Putative exons 2a, I.5, I.7, I.6 and I.2 were not detected in mouse tissues. Therefore, we showed that mouse Cyp19A1 contains more tissue-specific first exons than previously thought and displays a similar genomic organization to human CYP19A1.

Aromatase gene and its effects on growth, reproductive and maternal ability traits in a multibreed sheep population from Brazil

We determined the polymorphism C242T of the aromatase gene (Cyp19) and its allelic frequency, as well as the effect of the variants on productive and reproductive traits in 71 purebred Santa Inês sheep, 13 purebred Brazilian Somali sheep, nine purebred Poll Dorset sheep, and 18 crossbred 1/2 Dorper sheep. The animals were genotyped using the PCR-RFLP technique. The influence of the animal's genotype on its performance or on the performance of its lambs was analyzed by the least square method. Another factor assessed was the importance of the animal's genotype in analysis models for quantitative breeding value estimates, and whether there were differences among the averages of breeding values of animals with different genotypes for this gene. In the sample studied, no AA individuals were observed; the AB and BB frequencies were 0.64 and 0.36, respectively. All Brazilian Somali sheep were of genotype BB. All 1/2 Dorper BB animals presented a lower age at first lambing, and the Santa Inês BB ewes presented a lower lambing interval. In these same genetic groups, AB ewes presented higher litter weight at weaning. This is evidence that BB ewes have a better reproductive performance phenotype, whereas AB ewes present a better maternal ability phenotype. However, in general, animals with genotype AB presented better average breeding values than those with genotype BB.

Adaptive evolution of mammalian aromatases: lessons from Suiformes

Estrogen synthesis evolved in chordates to control reproduction. The terminal enzyme in the cascade directly responsible for estrogen synthesis is aromatase cytochrome P450 (P450arom) encoded by the CYP19 gene. Mammals typically have a single CYP19 gene but pigs, peccaries and other Suiformes have two or more resulting from duplication in a common ancestor. Duplication of CYP genes in the steroid synthetic cascade has occurred for only one other enzyme, also terminal, 11beta-hydroxylase P450 (P450c11). P450arom and P450c11 share common substrates and even physiological functions as possible remnants from a common P450 progenitor, perhaps an ancestral P450arom, which is supported by phylogenetic analysis. Conserved tissue-specific expression patterns of P450arom paralogs in placenta and gonads of pigs and peccaries suggest how functional adaptation may have proceeded divergently and influenced adopted reproductive strategies including ovulation rate and litter size. Data suggest that the porcine placental paralog evolved catalytically to protect female conceptuses from testosterone produced by male siblings; the gonadal paralog to synthesize a novel, nonaromatizable testosterone metabolite (1OH-testosterone) that may increase ovulation rate. This would represent a coevolution facilitating litter bearing as pigs diverged from peccaries. Evidence of convergence between the peccary CYP19 genes and lower tissue expression may therefore represent initiation of loss of the functional paralogs. Studies on the Suiforme aromatases provide insights into the evolution of the steroidogenic cascade and metabolic pathways in general, how it translates into physiological adaptations (altered reproductive strategies for instance), and how duplicated genes become stabilized or disappear from genomes.

Molecular characterization of the injury-induced aromatase transcript in the adult zebra finch brain

In the zebra finch (Taeniopygia guttata), the aromatase gene is transcribed from one of two promoters resulting in two transcripts constitutively expressed in brain or ovary. These transcripts differ only in Exon 1 which lies in the 5' un-translated region (UTR). An inducible form of aromatase is expressed following brain injury in glia. Towards characterizing this transcript, we (a) examined the up-regulation of amplicons within the aromatase transcript using quantitative PCR (qPCR), (b) performed 5' and 3' rapid amplification of cDNA ends (RACE) on injured brain RNA and (c) sequenced the injury-induced aromatase transcript. qPCR suggested that inducible aromatase may contain a novel 3'UTR. However, neither 3' nor 5' RACE revealed novel UTRs in the injured telencephalon. We then sequenced aromatase from injured entopallium, a region that lacks detectable constitutive aromatase. Inducible aromatase was identical in sequence to the known neural aromatase transcript. These data suggest that injury-induced aromatase differs from ovarian, but is indistinguishable from neuronal aromatase. We suggest that an injury-specific signal in glia may modulate aromatase transcription. Alternatively, injury-induced aromatase transcription may be silenced under constitutive conditions. To the best of our knowledge, this is the first report that documents the sequence of inducible aromatase in any vertebrate.

Evolution of suiform aromatases: ancestral duplication with conservation of tissue-specific expression in the collared peccary (Pecari tayassu)

Aromatase cytochrome P450 (P450arom), the enzyme that catalyzes estrogen synthesis, is required for successful reproduction and is encoded by a single copy gene (CYP19) in most mammals. However, pigs and their distant suiform relatives the peccaries experienced CYP19 duplication. Here, the evolutionary origin of CYP19 duplication, and the evolution of the gene paralogs, was explored further in collared peccaries (Pecari tayassu). Exons IV and V, and the intervening intron, representing duplicated CYP19 genes, were cloned and sequenced from collared peccary, pig, and hippopotamus. Sequence alignment and analysis identified a gene conversion in collared peccary with a breakpoint 102 base pairs (bp) upstream of exon V. Phylogenetic analyses of nucleotide and amino acid sequence upstream of the breakpoint supported a tree in which one peccary sequence was orthologous with the porcine gonadal gene. Cloning and sequencing of tissue transcripts, using reverse-transcriptase polymerase chain reaction techniques (RT-PCR), confirmed that the gonadal ortholog was expressed in collared peccary testis. Orthology of the other genomic sequence with the porcine placental gene was not resolved, but its placenta-specific expression in collared peccary was confirmed by similar transcript analysis. Immunoblot and enzyme activity in collared peccary testes demonstrated much lower levels of P450arom than in pig testis. Collared peccary placental P450arom expression also seemed much lower than pigs. Thus, suiform CYP19 genes arose from an ancestral duplication that has maintained gonad- and placenta-specific expression, but at lower levels in peccaries than pigs, perhaps facilitating the emergence of different reproductive strategies as Suiformes diverged and evolved.

Expression of P450-aromatase in the goat placenta throughout pregnancy

The enzyme P450-aromatase (P450-Aro) is essential for the conversion of androgens to estrogens. The objective was to study the expression and distribution of P450-Aro in goat placentae throughout pregnancy. For this purpose, we used reverse transcription-polymerase chain reaction (RT-PCR) with primers derived from the ovarian cDNA sequence found by our group. The expression of P450-Aro mRNA was first detected by in vitro RT-PCR in cotyledons at 4 months and was still present at term. Based on in situ RT-PCR, cotyledon microvilli expressed P450-Aro mRNA early in pregnancy; the signal was detected in the syncytiotrophoblast and in non-fused cytotrophoblasts inside the microvilli, but was scarce in the interstitial cells of the villous core. In the last 2 months of pregnancy (including at term), the expression of P450-Aro mRNA was still detected in the syncytiotrophoblast. However, P450-Aro was never detected in the caruncule (regardless of stage of pregnancy). In conclusion, P450-Aro was expressed in the goat placenta microvilli starting early in pregnancy; the expression and distribution of the enzyme increased throughout pregnancy and was still present at term.

0.2kb promoter sequence of the murine Cyp19 gene target beta-galactosidase expression to specific brain areas of transgenic mice

Cyp19 encodes the key enzyme of estrogen biosynthesis, aromatase cytochrome P450. In mice it is mainly expressed in the ovary and brain, where transcription is directed by a distal, brain-specific promoter (P(br)). In order to map functional sequence elements of P(br), portions of various length (0.2, 1.0, and 1.7[kb]) were fused to a lacZ reporter gene and analyzed in transgenic mice. Numbers of integrated reporter genes varied from 1 to 23 copies in different transgenic lines. These copy numbers however did not show any correlation to the levels of transgene expression. All of the constructs were found being expressed in the olfactory bulb, limbic cortex, amygdala, and hypothalamus. Additional expression in thalamic nuclei, bed nucleus of stria terminalis, and dorsal mesencephalon was found in transgenic lines with constructs 1.0 and 1.7, and expression in septal and preoptic nuclei was only found with construct 1.7. The data demonstrate that 0.2kb of P(br) target reporter gene expression to specific brain areas. The data also strongly suggest that the sequence between 0.2 and 1.7kb upstream, is necessary for expression in additional areas. However even 1.7kb of P(br) are not sufficient to consistently mimic the accurate expression pattern of Cyp19.

DNA methylation and chromatin accessibility of the proximalCyp19 promoter region 1.5/2 correlate with expression levels in sheep placentomes

Placental oestrogens play an important role as local regulators of placental growth and differentiation during gestation, and toward term they are also involved in the preparation of parturition. They are synthesized within the fetal cotyledons of placentomes by aromatase cytochrome P450 (P450arom; EC 1.14.14.1), the product of the Cyp 19 gene. The first step of regulation of P450arom expression, and hence enzyme activity and oestrogen production, takes place at the level of Cyp 19 transcription, which is driven by a proximal promoter region, P1.5/2, in the sheep placenta. The aim of the present study was to find out if different Cyp 19 expression levels, which previously had been observed in ovine placentome tissues, correlate with the tissue-specific chromatin structure of the promoter. To this end, we investigated the chromatin structure across the P1.5/2 region in caruncles and cotyledons from 100 and 125 days pregnant ewes, and in term placentae, respectively, by analyzing the DNA methylation and the accessibility to restriction digestion. Our data show that: (1) cotyledonal DNA was significantly lower methylated than caruncular DNA; (2) methylation of cotyledonal DNA was low at 100 and 125 days of pregnancy, and increased to a significant higher level in term placentae; and (3) concurrently, cotyledonal chromatin became inaccessible to restriction digestion at term of gestation. The results imply that DNA methylation and chromatin accessibility of the P1.5/2 promoter region correlate with expression levels of the Cyp 19 gene.

Reciprocal expression of 17α-hydroxylase-C17,20-lyase and aromatase cytochrome P450 during bovine trophoblast differentiation: a two-cell system drives placental oestrogen synthesis

No definitive information is yet available on the steroidogenic capacity of the two morphologically distinct cell types forming the bovine trophoblast, the uninucleated trophoblast cells (UTCs) and the trophoblast giant cells (TGCs). Hence, in order to localise 17α-hydroxylase-C17,20-lyase (P450c17) on a cellular level and to monitor its expression as a function of gestational age, placentomes from pregnant (days 80–284;n= 19), prepartal (days 273–282; 24–36 h prior to the onset of labour;n= 3) and parturient cows (n= 5) were immunostained for P450c17 using an antiserum against the recombinant bovine enzyme. At all stages investigated, P450c17 was exclusively found in the UTCs of chorionic villi (CV), where staining was ubiquitous between days 80 and 160, but was largely restricted to primary CV and the branching sites of secondary CV between days 160 and 240. Thereafter, a distinct ubiquitous staining reoccurred in the UTCs of all CV in late pregnant, prepartal and parturient animals. Using an antiserum against human aromatase cytochrome P450 (P450arom), specific cytoplasmic staining was observed in TGCs. In placentomes from pregnant cows, staining intensity was higher in mature compared with immature TGCs and was more pronounced in the trophoblast covering big stem villi compared with the trophoblast at other sites of the villous tree. In placentomes of a parturient cow, specific staining was only found in mature TGCs that survived the normal, but substantial, prepartal decline in TGC numbers. These results clearly showed that bovine UTCs and TGCs exhibit different steroidogenic capacities, constituting a ‘two-cell’ organisation for oestrogen synthesis. P450c17 expression appears to be quickly down-regulated and P450arom is up-regulated when UTCs enter the TGC differentiation pathway.

Expression of aromatase and oestrogen receptors in reproductive tissues of the stallion and a single cryptorchid visualised by means of immunohistochemistry

Androgen metabolism may proceed to amplify the action of testosterone by its aromatisation to oestradiol. Recently, a growing body of evidence suggests a role of oestrogens in the male reproductive tract via their specific oestrogen receptors (ERs). In order to check whether androgens are converted to oestrogens in the testis, epididymis and prostate of the stallion, the expression of aromatase was visualised by means of immunohistochemistry. Moreover, to show the cellular targets for oestrogens the presence of oestrogen receptor alpha (ERalpha) and oestrogen receptor beta (ERbeta) was demonstrated in these tissues. Finally, to show whether naturally occurring cryptorchidism has any influence on the localisation of aromatase and distribution of ERs, the reproductive tissues of a single horse, bilaterally cryptorchid, were also taken for this study. The results demonstrated that aromatase and ERs are ubiquitously distributed throughout the male reproductive tract, what indicates a putative role of oestrogens in modulating the function of the reproductive tissues of the stallion. In the cryptorchid horse the increase in conversion of androgen to oestrogen was observed as manifested by aromatase overexpression. This is the first report showing the cellular site of oestrogen biosynthesis not only in the testis but also in the epididymis and prostate of sexually mature stallion and a single, adult cryptorchid.

Fetal programming: prenatal testosterone treatment causes intrauterine growth retardation, reduces ovarian reserve and increases ovarian follicular recruitment

Exposure to testosterone (T) during d 30-90 of fetal life results in low-birth-weight offspring, hypergonadotropism, multifollicular ovaries, and early cessation of cyclicity. The multifollicular phenotype may result from failure of follicles to regress and consequent follicular persistence or, alternatively, increased follicular recruitment. We tested the hypothesis that prenatal exposure to excess T causes intrauterine growth retardation and increases ovarian follicular recruitment. Time-mated pregnant ewes were treated with 100 mg T propionate in cottonseed oil or vehicle twice weekly from d 30-90 of gestation. Ewes were euthanized near term, from d 139-141 of gestation (term is 147 d). After determining fetal measures and organ weights, ovaries were removed from fetuses of control and T-treated dams, and follicular distribution in each ovary was determined by morphometric quantification. Total number and percentage distribution of the various classes of follicles (primordial, primary, preantral, and antral follicles) were compared between treatment groups. Prenatally T-treated female fetuses were smaller in size, had an increased head circumference to fetal weight ratio (P < 0.01), increased adrenal to fetal weight ratio (P < 0.05), decreased number of follicles (P < 0.05), a decrease in percentage of primordial follicles (P < 0.001), and a corresponding increase in the remaining classes of follicles (P < 0.05). Ovarian findings support decreased ovarian reserve and enhanced follicular recruitment, potential contributors of early reproductive failure. The extent to which metabolic changes associated with intrauterine growth retardation contribute toward altered trajectory of ovarian folliculogenesis remains to be determined.

Androstenedione increases cytochrome P450 aromatase messenger ribonucleic acid transcripts in nonluteinizing bovine granulosa cells

The objective of this study was to determine if androgens regulate granulosa cell steroidogenesis at physiological doses found in small bovine follicles. Bovine granulosa cells were cultured under serum-free conditions that permit the induction and maintenance of FSH-dependent estradiol secretion. Increasing androstenedione concentrations from 0.1 to 1 or 10 microM significantly increased estradiol accumulation and cytochrome P450 aromatase (P450arom) mRNA abundance. No increase in progesterone accumulation or abundance of mRNA for P450 side-chain cleavage or 3beta-hydroxysteroid dehydrogenase enzymes was observed. The addition of 0.1, 1, or 10 microM progestins or estrogens had no stimulatory effect on P450arom mRNA levels. An analysis of the 5'-untranslated region of P450arom mRNA transcripts indicated that the majority was derived from Cyp19 ovary-specific promoter 2, with some contribution from promoters 1.1 and 1.5. Transcripts from these three promoters were all significantly increased by androstenedione. Testosterone increased promoter 1.1 and 1.5-derived transcripts, but only promoter 2-derived transcripts at the highest dose tested (100 microM). Dihydrotestosterone (DHT) did not affect Cyp19 expression. Collectively, these data show that androgens may exert specific stimulatory effects on P450arom mRNA concentrations in granulosa cells. Interestingly, different androgens had different effects on Cyp19 promoter usage, suggesting differential regulation of aromatase gene expression in the developing follicle.

Transcription of a lepidopteran cytochrome P450 promoter is modulated by multiple elements in its 5' UTR and repressed by 20-hydroxyecdysone

The biochemical response to the phytochemical xanthotoxin encountered in the diet of black swallowtail larvae is the induction of P450s capable of detoxifying this and other toxic furanocoumarins. As the xenobiotic response element to xanthotoxin (XRE-xan) is necessary but not sufficient for transcription of the CYP6B1v3 gene in Sf9 cells, sequences upstream of it, such as a putative EcRE, and downstream of it, such as a putative C/EBP binding site and Inr, have been tested for their roles in regulation. Mutation of the putative EcRE has indicated that it affects basal transcription of this promoter but not repression by 20-hydroxyecdysone. Mutation of the more proximal promoter sequence, including the C/EBP and Inr, have indicated that many core promoter elements between the TATA box and translation start site modulate basal and xanthotoxin-inducible expression of this composite promoter.

Cattle and sheep use different promoters to direct the expression of the aromatase cytochrome P450 encoding gene, Cyp19, during pregnancy

Gestagens and oestrogens are important regulators of pregnancy and parturition. The aim of the present study was the comparative quantification of steroidogenic transcripts in placenta and corpus luteum of cattle and sheep during pregnancy and post partum. Cyp19 transcript variants, derived from different promoters, as well as transcripts of Hsd3b, Cyp11A1, and Cyp17, encoding the steroidogenic enzymes P450arom, 3beta-HSD, P450SCC, and P450C17, respectively, were quantified by newly developed real-time PCR assays. All steroidogenic transcripts were detected in ovine and bovine corpus luteum and placenta during pregnancy, however at a very different concentration. In both species Cyp11A1 and especially Hsd3b transcripts predominated in corpus luteum, outnumbering transcripts of Cyp17 and Cyp19 by more than two and three orders of magnitude, respectively. Cyp19 transcript were found at high concentration in the placenta and at a very low concentration in corpus luteum. Cyp17 transcripts had a relatively low concentration in both, placenta and corpus luteum, however showed a peak of expression in the ovine and bovine term placenta. Tissue- and species-specific Cyp19 transcripts derived from different promoters were detected. In order to map all promoters, the bovine Cyp19 locus was reconstructed by in silico analysis. In the placenta, transcripts were primarily derived from the proximal promoter P1.5 in sheep, but from the distally located P1.1 in cattle. Corpora lutea of both species predominantly expressed P1.1 derived transcripts. Contrary to the bovine, the sheep corpus luteum also showed considerable P1.5 derived expression. This demonstrates that cattle and sheep use different promoters to direct Cyp19 expression during pregnancy.

Expression of the bovine aromatase cytochrome P450 gene (Cyp19 ) is primarily regulated by promoter 2 in bovine follicles and by promoter 1.1 in corpora lutea

Follicular development and differentiation are closely associated with increasing steroidogenesis. During the present study transcript concentration of Cyp19, Cyp11A1, and 3beta-hydroxysteroid dehydrogenase delta (3beta-HSD) encoding the steroidogenic enzymes P450(arom), P450(SCC), and 3beta-HSD were determined by real-time PCR in bovine granulosa cells (GC) as potential markers for follicular differentiation. Ovaries were collected from a local abattoir (experiment 1) and from synchronized animals at day 4 of estrus cycle (experiment 2). To study effects of luteinization, steroidogenic transcripts were also quantified in corpora lutea (CL) 4 and 20 days after fertilization. In most follicles, all three steroidogenic transcripts were detected, however, at very different concentration. Expression of 3beta-HSD and Cyp11A1 was highly significantly co-regulated and showed a significant correlation with follicular size. Contrary, Cyp19 expression was extremely variable even in follicles of similar size. Cyp19 transcripts were derived predominantly from promoter P2 and less abundant from promoters P1.1 and P1.5. After luteinization, the concentration of 3beta-HSD and Cyp11A1 transcripts increased (75-fold and fivefold, respectively) whereas the Cyp19 transcript level dropped (160-fold). Residual Cyp19 transcripts in CL were almost exclusively derived from P1.1. The data indicate that Cyp19 expression in GC is predominantly regulated by P2 and to a minor extend by P1.1, whereas P1.1 is almost exclusively responsible for residual Cyp19 expression in CL. Correlation analyses suggest that the expression of 3beta-HSD and Cyp11A1 primarily depend on the size of follicles whereas the concentration of P2 derived Cyp19 transcripts in GC is a marker for follicular differentiation towards selection and dominance.

Temporal relationships between FSH receptor, type 1 insulin-like growth factor receptor, and aromatase expression during FSH-induced differentiation of bovine granulosa cells maintained in serum-free culture

A serum-free culture system has been developed in ruminants that allows gonadotrophin-responsive induction of oestradiol (E2) production by non-differentiated granulosa cells (GC) from small antral follicles. Critical determinants are dose of FSH and insulin-like growth factor (IGF), and the plating density of the GC. Over the first 16 h of culture when cells remained as a dispersed monolayer, expression declined in FSH receptors (FSHr) (P <0.001), IGF type 1 receptor (IGF-1r) (P <0.08) and p450 arom (CYP19, P <0.001). Characteristic GC clusters formed from 16 h and further enlarged between 24 and 48 h, accompanied by marked increases in FSHr (P <0.01), IGF-1r (P <0.05), and p450 arom (P <0.01) expression, and preceded induction and subsequent peak E2 production, at 96 and 144 h, respectively (P <0.01). In conclusion, isolation and dispersion of GC appears to induce reversion to an immature state resulting in loss of receptor expression. Re-establishment of cell-cell communications in the presence of FSH and IGF results in receptor up-regulation and induction of cellular differentiation.

Three different promoters control expression of the aromatase cytochrome p450 gene (cyp19) in mouse gonads and brain

Aromatase cytochrome P450, the key enzyme of estrogen biosynthesis, is encoded by Cyp19. To elucidate the complex regulation of this gene in mouse gonads (ovary and testis) and brain (thalamic/hypothalamic areas), Cyp19 transcripts were isolated using rapid amplification of cDNA 5' ends and transcript concentrations were estimated in juveniles at different postnatal days (P0, P7, and P14) and in adult animals by real time polymerase chain reaction (PCR). In addition, the murine Cyp19 locus including all known exons and promoters was reconstructed from a recently published sequence of a mouse bacterial artificial chromosome. From each of the tissues investigated, Cyp19 transcripts with a specific 5' untranslated region (5' UTR) were isolated: T(ov) from ovary, T(br) from brain, and T(tes) from testis. T(tes) included a novel 5' UTR that did not show sequence similarities to other Cyp19 transcripts. Real time PCR experiments revealed similar levels of Cyp19 transcript concentrations in neonatal gonads of both sexes. The majority of transcripts were T(ov) in ovaries and T(tes) in testes. During further postnatal development, testicular Cyp19 transcript concentrations transiently decreased, but the contributions of different transcript variants basically remained unchanged. However, ovarian Cyp19 transcript concentrations increased by about 100 times, and almost 100% of all Cyp19 transcripts were identified as T(ov) in adult ovaries. Brains of both sexes showed highest transcript concentrations at P0. However, concentrations in female brains were reduced to adult levels earlier than in male brains. In brains of both sexes, T(br) was found to predominate throughout postnatal life. The results suggest that the mouse Cyp19 gene includes three different promoters that specifically direct expression in ovary, testis, and brain.