Deletion of the mouse P450c17 gene causes early embryonic lethality

Attenuated glucose uptake promotes catabolic metabolism through activated AMPK signaling and impaired insulin signaling in zebrafish

Glucose metabolism in fish remains a controversial area of research as many fish species are traditionally considered glucose-intolerant. Although energy homeostasis remodeling has been observed in fish with inhibited fatty acid β-oxidation (FAO), the effects and mechanism of the remodeling caused by blocked glucose uptake remain poorly understood. In this study, we blocked glucose uptake by knocking out glut2 in zebrafish. Intriguingly, the complete lethality, found in Glut2-null mice, was not observed in glut2^-/- zebrafish. Approxiamately 30% of glut2^-/- fish survived to adulthood and could reproduce. The maternal zygotic mutant glut2 (MZglut2) fish exhibited growth retardation, decreased blood and tissue glucose levels, and low locomotion activity. The decreased pancreatic β-cell numbers and insulin expression, as well as liver insulin receptor a (insra), fatty acid synthesis (chrebp, srebf1, fasn, fads2, and scd), triglyceride synthesis (dgat1a), and muscle mechanistic target of rapamycin kinase (mtor) of MZglut2 zebrafish, suggest impaired insulin-dependent anabolic metabolism. Upregulated expression of lipolysis (atgl and lpl) and FAO genes (cpt1aa and cpt1ab) in the liver and proteolysis genes (bckdk, glud1b, and murf1a) in muscle were observed in the MZglut2 zebrafish, as well as elevated levels of P-AMPK proteins in both the liver and muscle, indicating enhanced catabolic metabolism associated with AMPK signaling. In addition, decreased amino acids and elevated carnitines of the MZglut2 zebrafish supported the decreased protein and lipid content of the whole fish. In summary, we found that blocked glucose uptake impaired insulin signaling-mediated anabolism via β-cell loss, while AMPK signaling-mediated catabolism was enhanced. These findings reveal the mechanism of energy homeostasis remodeling caused by blocked glucose uptake, which may be a potential strategy for adapting to low glucose levels.

Gene Expression in Embryos From Norwegian Red Bulls With High or Low Non Return Rate: An RNA-Seq Study of in vivo-Produced Single Embryos

During the last decade, paternal effects on embryo development have been found to have greater importance than previously believed. In domestic cattle, embryo mortality is an issue of concern, causing huge economical losses for the dairy cattle industry. In attempts to reveal the paternal influence on embryo death, recent approaches have used transcriptome profiling of the embryo to find genes and pathways affected by different phenotypes in the bull. For practical and economic reasons, most such studies have used in vitro produced embryos. The aim of the present study was to investigate the differences in the global transcriptome of in vivo produced embryos, derived from sires with either high or low field fertility measured as the non-return rate (NRR) on day 56 after first AI of the inseminated cows. Superovulated heifers (n = 14) in the age span of 12–15 months were artificially inseminated with semen from either high fertility (n = 6) or low fertility (n = 6) bulls. On day seven after insemination, embryos were retrieved through uterine flushing. Embryos with first grade quality and IETS stage 5 (early blastocyst), 6 (blastocyst) or 7 (expanded blastocyst) were selected for further processing. In total, RNA extracted from 24 embryos was sequenced using Illumina sequencing, followed by differential expression analysis and gene set enrichment analysis. We found 62 genes differentially expressed between the two groups (adj.p-value<0.05), of which several genes and their linked pathways could explain the different developmental capacity. Transcripts highly expressed in the embryos from low fertility bulls were related to sterol metabolism and terpenoid backbone synthesis, while transcripts highly expressed in the high fertility embryos were linked to anti-apoptosis and the regulation of cytokine signaling. The leukocyte transendothelial migration and insulin signaling pathways were associated with enrichments in both groups. We also found some highly expressed transcripts in both groups which can be considered as new candidates in the regulation of embryo development. The present study is an important step in defining the paternal influence in embryonic development. Our results suggest that the sire’s genetic contribution affects several important processes linked to pre-and peri implantation regulation in the developing embryo.

Effect of Differences in the Microbiome of Cyp17a1-Deficient Mice on Atherosclerotic Background

CYP17A1 is a cytochrome P450 enzyme that has 17-alpha-hydroxylase and C17,20-lyase activities. Cyp17a11 deficiency is associated with high body mass and visceral fat deposition in atherosclerotic female ApoE knockout (KO, d/d or -/-) mice. In the present study, we aimed to investigate the effects of diet and Cyp17a1 genotype on the gut microbiome. Female Cyp17a1 (d/d) × ApoE (d/d) (DKO) and ApoE (d/d) (controls) were fed either standard chow or a Western-type diet (WTD), and we demonstrated the effects of genetics and diet on the body mass of the mice and composition of their gut microbiome. We found a significantly lower alpha diversity after accounting for the ecological network structure in DKO mice and WTD-fed mice compared with chow-fed ApoE(d/d). Furthermore, we found a strong significant positive association of the Firmicutes vs. Bacteroidota ratio with body mass and the circulating total cholesterol and triglyceride concentrations of the mice when feeding the WTD, independent of the Cyp17a1 genotype. Further pathway enrichment and network analyses revealed a substantial effect of Cyp17a1 genotype on associated cardiovascular and obesity-related pathways involving aspartate and L-arginine. Future studies are required to validate these findings and further investigate the role of aspartate/L-arginine pathways in the obesity and body fat distribution in our mouse model.

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.

CYP17A1 deficient XY mice display susceptibility to atherosclerosis, altered lipidomic profile and atypical sex development

CYP17A1 is a cytochrome P450 enzyme with 17-alpha-hydroxylase and C17,20-lyase activities. CYP17A1 genetic variants are associated with coronary artery disease, myocardial infarction and visceral and subcutaneous fat distribution; however, the underlying pathological mechanisms remain unknown. We aimed to investigate the function of CYP17A1 and its impact on atherosclerosis in mice. At 4–6 months, CYP17A1-deficient mice were viable, with a KO:Het:WT ratio approximating the expected Mendelian ratio of 1:2:1. All Cyp17a1 knockout (KO) mice were phenotypically female; however, 58% were Y chromosome-positive, resembling the phenotype of human CYP17A1 deficiency, leading to 46,XY differences/disorders of sex development (DSD). Both male and female homozygous KO mice were infertile, due to abnormal genital organs. Plasma steroid analyses revealed a complete lack of testosterone in XY-KO mice and marked accumulation of progesterone in XX-KO mice. Elevated corticosterone levels were observed in both XY and XX KO mice. In addition, Cyp17a1 heterozygous mice were also backcrossed onto an Apoe KO atherogenic background and fed a western-type diet (WTD) to study the effects of CYP17A1 on atherosclerosis. Cyp17a1 x Apoe double KO XY mice developed more atherosclerotic lesions than Apoe KO male controls, regardless of diet (standard or WTD). Increased atherosclerosis in CYP17A1 XY KO mice lacking testosterone was associated with altered lipid profiles. In mice, CYP17A1 deficiency interferes with sex differentiation. Our data also demonstrate its key role in lipidomic profile, and as a risk factor in the pathogenesis of atherosclerosis.

DNAJC2 is required for mouse early embryonic development

DNAJC2 protein, also known as ZRF1 or MPP11, acts both as chaperone and as chromatin regulator. It is involved in stem cell differentiation and its expression is associated with various cancer malignancies. However, the role of Dnajc2 gene during mouse embryogenesis has not been assessed so far. To this aim, we invalidated Dnajc2 gene in FVB/Nj mice using the CrispR/Cas9 approach. We showed that this invalidation leads to the early post-implantation lethality of the nullizygous embryos. Furthermore, using siRNAs against Dnajc2 in mouse 1-cell embryos, we showed that maternal Dnajc2 mRNAs may allow for the early preimplantation development of these embryos. Altogether, these data demonstrate for the first time the requirement of DNAJC2 for early mouse embryogenesis.

Intracrine Regulation of Estrogen and Other Sex Steroid Levels in Endometrium and Non-gynecological Tissues; Pathology, Physiology, and Drug Discovery

Our understanding of the intracrine (or local) regulation of estrogen and other steroid synthesis and degradation expanded in the last decades, also thanks to recent technological advances in chromatography mass-spectrometry. Estrogen responsive tissues and organs are not passive receivers of the pool of steroids present in the blood but they can actively modify the intra-tissue steroid concentrations. This allows fine-tuning the exposure of responsive tissues and organs to estrogens and other steroids in order to best respond to the physiological needs of each specific organ. Deviations in such intracrine control can lead to unbalanced steroid hormone exposure and disturbances. Through a systematic bibliographic search on the expression of the intracrine enzymes in various tissues, this review gives an up-to-date view of the intracrine estrogen metabolisms, and to a lesser extent that of progestogens and androgens, in the lower female genital tract, including the physiological control of endometrial functions, receptivity, menopausal status and related pathological conditions. An overview of the intracrine regulation in extra gynecological tissues such as the lungs, gastrointestinal tract, brain, colon and bone is given. Current therapeutic approaches aimed at interfering with these metabolisms and future perspectives are discussed.

Steroidogenesis: Unanswered Questions

Until the mid-1980s studies of steroidogenesis largely depended on identifying steroid structures and measuring steroid concentrations in body fluids. The molecular biology revolution radically revolutionized studies of steroidogenesis with the cloning of known steroidogenic enzymes, by identifying novel factors, and delineating the genetic basis of known and newly discovered diseases. Unfortunately, this dramatic success has led many young research-oriented endocrinologists to regard steroidogenesis as a 'solved area'. However, many important and exciting questions remain, especially concerning the mechanisms of cholesterol delivery to the steroidogenic machinery, the biochemistry of androgen synthesis, the regulation and biological role of adrenarche, fetal adrenal development and involution, the roles of steroids made in 'extraglandular' cells, and the search for genetic disorders. This review outlines some of these questions, but this list is necessarily incomplete.

Suppressed oligodendrocyte steroidogenesis in multiple sclerosis: Implications for regulation of neuroinflammation

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Neurosteroids are reported to exert anti-inflammatory effects in several neurological disorders. We investigated the expression and actions of the neurosteroid, dehydroepiandrosterone (DHEA), and its more stable 3β-sulphated ester, DHEA-S, in MS and associated experimental models. CNS tissues from patients with MS and animals with experimental autoimmune encephalomyelitis (EAE) displayed reduced DHEA concentrations, accompanied by diminished expression of the DHEA-synthesizing enzyme CYP17A1 in oligodendrocytes (ODCs), in association with increased expression of inflammatory genes including interferon (IFN)-γ and interleukin (IL)-1β. CYP17A1 was expressed variably in different human neural cell types but IFN-γ exposure selectively reduced CYP17A1 detection in ODCs. DHEA-S treatment reduced IL-1β and -6 release from activated human myeloid cells with minimal effect on lymphocyte viability. Animals with EAE receiving DHEA-S treatment showed reduced Il1b and Ifng transcript levels in spinal cord compared to vehicle-treated animals with EAE. DHEA-S treatment also preserved myelin basic protein immunoreactivity and reduced axonal loss in animals with EAE, relative to vehicle-treated EAE animals. Neurobehavioral deficits were reduced in DHEA-S-treated EAE animals compared with vehicle-treated animals with EAE. Thus, CYP17A1 expression in ODCs and its product DHEA were downregulated in the CNS during inflammatory demyelination while DHEA-S provision suppressed neuroinflammation, demyelination, and axonal injury that was evident as improved neurobehavioral performance. These findings indicate that DHEA production is an immunoregulatory pathway within the CNS and its restoration represents a novel treatment approach for neuroinflammatory diseases.

CYP2C76 deficiency is embryonic lethal in cynomolgus macaques: The potential role of CYP2C76 in early embryogenesis

Cynomolgus macaques are an important primate species for drug metabolism studies; however cynomolgus CYP2C76, an important drug-metabolizing enzyme, accounts for drug metabolism differences to humans, so that CYP2C76-null animals might show drug-metabolizing properties more similar to humans. In this study, attempts were made to produce CYP2C76-null animals by assisted reproduction technology. Oocytes and sperm collected from the heterozygotes for the null allele (c.449TG > A) were subjected to intracytoplasmic sperm injection, and the embryos produced were cultured in vitro through the blastocyst stage. Preimplantation genetic diagnosis using a biopsied portion of the blastocyst revealed that none of the 32 blastocysts analyzed were homozygotes. In contrast, 2 of the 20 embryos analyzed were homozygotes at the 8-cell stage, indicating that CYP2C76-null embryos most likely stop developing between the 8-cell and blastocyst stage. By polymerase chain reaction, expression of CYP2C76 mRNA was detected in oocytes and blastocysts, but not in 2-, 4-, 8-, or 16/32-cell stage embryos. Metabolic assays showed that CYP2C76 metabolized progesterone. These results indicated that CYP2C76 null was likely embryonic lethal, suggesting its potential role during early embryogenesis in cynomolgus macaques.

Mild Calorie Restriction Does Not Affect Testosterone Levels and Testicular Gene Expression in Mutant Mice

The hypothalamic-pituitary-gonadal (HPG) axis and the somatotropic axis are influenced by nutritional factors. Calorie restriction (CR) extends lifespan but suppresses both the HPG and the somatotropic axes. Since most CR studies use a fairly severe (40%–60%) reduction of calorie intake, we hypothesized that a milder CR (20%) might not be deleterious to reproduction in male mice. To test this hypothesis, we evaluated the effects of 20% CR on testicular testosterone content and on testicular expression of genes that are relevant to testicular function and reproductive competence, including insulin-like growth factor-I, cytochrome P450 aromatase (Cyp19a1), androgen receptor, luteinizing hormone receptor, follicle-stimulating hormone receptor, cytochrome P450c17 and 3-β-hydroxysteroid dehydrogenase/isomerase. To relate CR effects to the activity of the somatotropic axis, we have used growth hormone–resistant GHR knockout mice as well as transgenic mice overexpressing GH. Mild CR did not affect testosterone levels in testis homogenates and had little effect on expression of the examined genes in the reproductive organs. Altered activity of the GH/insulin-like growth factor–1 axis had a major impact on the parameters analyzed. The results also suggest that expression of several key genes involved in the control of testicular function is preserved under conditions of mild CR and encourage speculation that mild regimens of CR can produce longevity benefits without impairing reproduction.

Transcriptome Analysis of WHV/c-myc Transgenic Mice Implicates Cytochrome P450 Enzyme 17A1 as a Promising Biomarker for Hepatocellular Carcinoma

Early detection of hepatocellular carcinoma (HCC) is critical for successful treatment and favorable prognosis. To identify novel HCC biomarkers, we used the WHV/c-myc transgenic (Tg) mice, an animal model of hepatocarcinogenesis. By analyzing their gene expression profiling, we investigated differentially expressed genes in livers of wild-type and Tg mice. The cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1), a hepatic P450 enzyme, was revealed to be overexpressed in the liver tissues of Tg mice at both preneoplastic and neoplastic stages. Mouse-to-human validation demonstrated that CYP17A1 mRNA and protein were also significantly increased in human HCC tissues compared with paired nontumor tissues (P = 0.00041 and 0.00011, respectively). Immunohistochemical studies showed that CYP17A1 was overexpressed in 67% (58 of 87) of HCC, and strong staining of CYP17A1 was observed in well-differentiated HCCs. Consistent with this, the median serum levels of CYP17A1 were also significantly higher in patients with HCC (140.2 ng/mL, n = 776) compared with healthy controls (31.4 ng/mL, n = 366) and to those with hepatitis B virus (57.5 ng/mL, n = 160), cirrhosis (46.1 ng/mL, n = 147), lung cancer (27.4 ng/mL, n = 109), and prostate cancer (42.1 ng/mL, n = 130; all P < 0.001). Notably, the elevations were seen in most AFP-negative HCC cases. Altogether, through mouse-to-human search and validation, we found that CYP17A1 is overexpressed in HCCs and it has great potentiality as a noninvasive marker for HCC detection. These results provide a rationale for the future development and clinical application of CYP17A1 measurement to diagnose HCC more precisely. Cancer Prev Res; 9(9); 739-49. ©2016 AACR.

The feto-placental unit, and potential roles of dehydroepiandrosterone (DHEA) in prenatal and postnatal brain development: A re-examination using the spiny mouse

Synthesis of dehydroepiandrosterone (DHEA) by the fetal adrenal gland is important for placental oestrogen production, and may also be important for modulating the effects of glucocorticoids on the developing brain. We have preciously shown that the enzymes and accessory proteins needed for DHEA synthesis-cytochrome P450 enzyme 17α-hydroxylase/17,20 lyase (P450c17), cytochrome-b5 (Cytb5), 3β-hydroxysteroid dehydrogenase (3βHSD)-are expressed in the adrenal gland from 30 days gestation, and DHEA, cortisol and aldosterone are present in fetal plasma from this time. Explant culture of fetal adrenal tissue showed that the spiny mouse adrenal gland, can synthesize and secrete DHEA from at least 0.75 of gestation, and suggest that DHEA may have an important role(s) in placental biosynthesis of oestrogens and in modulating the actions of glucocorticoids in the developing brain in this species. Post-natally, increased immuno-expression of P450c17 and Cytb5 expression in the zona reticularis of the adrenal gland and a significant increase in the synthesis and secretion of DHEA in plasma from 8 to 20 days of age in the spiny mouse, are representative of a period of high adrenal androgen production consistent with the human phenomenon of adrenarche. The studies summarised in this review also show that DHEA is produced de novo in the developing brain of the spiny mouse. These results showed that the spiny mouse brain can indeed produce DHEA from pregnenolone in a time-dependant manner, and coupled with the identification of P450c17 and Cytb5 protein in several regions of the brain, support the idea that DHEA is an endogenous neuro-active steroid in this species. Together, the studies outlined in this review indicate that the androgen DHEA is an important hormone of adrenal and Central Nervous System (CNS) origin in the fetal and postnatal spiny mouse. Disturbance of the development of these fetal tissues, and/or of the relationship between the fetal adrenal gland and placenta during pregnancy, may have significant consequences for fetal development, placental function, and maturation of the brain. It is proposed that such disturbances of normal adrenal function could account for some of the neuropathologies that arise in juvenile and adult offspring following illness and stress experienced by the mother during pregnancy.

Cholesterol-derived glucocorticoids control early fate specification in embryonic stem cells

Aside from its role in cell membrane integrity, cholesterol is a key component in steroid hormone production. The vital functions of steroid hormones such as estrogen, testosterone, glucocorticoids (Gcrts) and mineralocorticoids (Mnrts) in perinatal and adult life are well understood; however, their role during early embryonic development remains largely unexplored. Here we show that siRNA-mediated perturbation of steroid hormone production during mesoderm formation has important consequences on cardiac differentiation in mouse embryonic stem cells (mESC). Both Gcrts and Mnrts are capable of driving cardiac differentiation in mESC. Interestingly, the Gcrt receptor is widely expressed during gastrulation in the mouse, and is exclusively localized in the nuclei-and thus active-in visceral endoderm cells, suggesting that it functions much earlier than previously anticipated. We therefore studied Gcrt signaling in mESC as a model of the gastrulating embryo, and found that Gcrt signaling regulates expression of the transcription factor Hnf4a and the secreted Nodal and BMP inhibitor Cer1 in the early visceral endoderm. RNAi-mediated knockdown of Gcrt function blocked cardiomyocyte differentiation, with limited effects on other cardiovascular cell types including vascular endothelial cells and smooth muscle. Furthermore, the cardiogenic effect of Gcrts required Hnf4a and paracrine Cer1. These results establish a novel function for cholesterol-derived steroid hormones and identify Gcrt signaling in visceral endoderm cells as a regulator of Cer1 and cardiac fate.

Three novel cytochrome P450 genes identified in the marine polychaete Perinereis nuntia and their transcriptional response to xenobiotics

Polychaetes have previously been used as bioindicators of environmental pollution. Their ability to eliminate organic pollutants such as polycyclic aromatic hydrocarbons (PAH) has been extensively analyzed. However, the cytochrome P450 monooxygenases (CYP) genes in polychaetes, which catalyze the first step of oxidative degradation of PAHs, have received little attention. Based on the partial sequences of three CYP genes that were enriched by subtractive cDNA libraries of the polychaete Perinereis nuntia, we amplified and sequenced the full-length cDNA of these novel CYP genes. These genes were named CYP4BB2, CYP423A1 and CYP424A1 by the Cytochrome P450 Nomenclature Committee. The deduced amino acid sequence of CYP4BB2 in P. nuntia showed 68% sequence identity to CYP4BB1 in Nereis virens, and was listed as a new member of the CYP4BB subfamily. The sequence of CYP423A1 and CYP424A1 both share less than 40% sequence identity to all known CYP enzymes and were classed into new CYP families. CYP family members are composite parts of a larger group called a clan. CYP4BB2 and CYP424A1 are listed as CYP4 clan members, while CYP423A1 is of the CYP2 clan. The 3D structures of these P. nuntia CYPs were successfully predicted by homology-modeling using the SWISS-MODEL workspace. The models of CYP424A1 and CYP4BB2 were created using 1jpzB (CYP102A) as a template, while CYP423A1 utilized 3czhB (CYP2R1) as its template. The presence of characteristic CYP superfamily motifs, such as the F-G⋯C-G amino acid sequence, and the conservation of the three-dimensional CYP structure shown by the modeling, suggested that these novel P. nuntia CYP genes may contain conserved functional domains of CYP monooxygenases. To examine the effect of xenobiotics on living organisms, we analyzed the transcriptional levels of these three new CYP genes in sandworms (P. nuntia) exposed to seawater artificially contaminated with benzo[a]pyrene (BaP). We also exposed individuals to industrial wastewater collected from Quanzhou Bay, Fujian, China, which was known to be contaminated with PAHs. Worms exposed to BaP had significantly higher levels of CYP4BB2, CYP423A1 and CYP424A1 mRNA. Transcription was up-regulated 5.9-, 5.3- and 12.3-folds respectively compared with the control worms living in clean seawater. The transcriptional levels of CYPs in worms cultured in the diluted wastewater collected from Quanzhou Bay, all positively correlated with the levels of PAHs detected in the water. The transcriptional up-regulation of the three CYP genes observed in this study, suggest the monooxygenases encoded by these CYP genes may play an important role in the detoxification of PAHs in this polychaete worm. These CYPs maybe essential for the adaptation of worms to contaminated environments and may be useful in the assessment of xenobiotic exposure.

Detection of haplotypes associated with prenatal death in dairy cattle and identification of deleterious mutations in GART, SHBG and SLC37A2

The regular decrease of female fertility over time is a major concern in modern dairy cattle industry. Only half of this decrease is explained by indirect response to selection on milk production, suggesting the existence of other factors such as embryonic lethal genetic defects. Genomic regions harboring recessive deleterious mutations were detected in three dairy cattle breeds by identifying frequent haplotypes (>1%) showing a deficit in homozygotes among Illumina Bovine 50k Beadchip haplotyping data from the French genomic selection database (47,878 Holstein, 16,833 Montbéliarde, and 11,466 Normande animals). Thirty-four candidate haplotypes (p<10(-4)) including previously reported regions associated with Brachyspina, CVM, HH1, and HH3 in Holstein breed were identified. Haplotype length varied from 1 to 4.8 Mb and frequencies from 1.7 up to 9%. A significant negative effect on calving rate, consistent in heifers and in lactating cows, was observed for 9 of these haplotypes in matings between carrier bulls and daughters of carrier sires, confirming their association with embryonic lethal mutations. Eight regions were further investigated using whole genome sequencing data from heterozygous bull carriers and control animals (45 animals in total). Six strong candidate causative mutations including polymorphisms previously reported in FANCI (Brachyspina), SLC35A3 (CVM), APAF1 (HH1) and three novel mutations with very damaging effect on the protein structure, according to SIFT and Polyphen-2, were detected in GART, SHBG and SLC37A2 genes. In conclusion, this study reveals a yet hidden consequence of the important inbreeding rate observed in intensively selected and specialized cattle breeds. Counter-selection of these mutations and management of matings will have positive consequences on female fertility in dairy cattle.

Cytochrome P450 17α-hydroxylase/C(17,20)-lyase immunoreactivity and molecular expression in the cerebellar nuclei of adult male rats

Several probes have been developed to identify steroidogenic activity in the brain of vertebrates. However, the presence of the cytochrome P450 17α-hydroxylase/C(17,20)-lyase (P450C(17)), an enzyme that converts pregnenolone and progesterone into dehydroepiandrosterone and androstenedione, in specific areas of the cerebellum such as the deep cerebellar nuclei, remains virtually unexplored. Using Western blot analysis and immunohistochemistry, we found molecular expression of P450C(17) in the lateral, interposed and medial deep cerebellar nuclei. Moreover, double immunofluorescence procedures enabled localization of P450C(17) mainly in neurons, axons and glutamatergic synapses. Taken together, these data demonstrate the occurrence of P450C(17) in the deep cerebellar nuclei, and enable the chemical characterization of the cells that express the cytochrome.

Methodological approaches to cytochrome P450 profiling in embryos

Cytochrome P450 enzymes (CYPs) are heme thiolate proteins essential for vertebrate development and also play important roles in toxicology as well as normal metabolic function. CYP enzymes catalyze the oxidative biotransformation of many endogenous and exogenous chemicals, including steroids and eicosanoids, and drugs and other xenobiotic toxicants. Many CYPs have known for their potential roles in development, and many chemicals that cause developmental abnormalities are substrates for CYPs. The roles and regulation of most xenobiotic metabolizing CYPs during development are unknown, impeding understanding of mechanisms of developmental toxicity. The zebrafish (Danio rerio) has become one of the premier models in vertebrate developmental biology, in large part because of the logistical advantages of rapid external development, high adult maintenance density, and significant (bio)technological tool availability. The increasing use of zebrafish in drug discovery and mechanistic toxicology demands knowledge of CYP gene regulation and function. Here, we present methods to examine CYP expression during early development in zebrafish, with an emphasis on developmental microarrays.

Expression of P450c17 in the human fetal nervous system

P450c17 catalyzes steroid 17α-hydroxylase and 17,20 lyase activities. P450c17 is expressed in human fetal and postnatal adrenals and gonads and in the developing mouse nervous system, but little is known about its expression in the human nervous system. We obtained portions of 9-, 10-, and 11-wk gestation human fetuses and delineated the pattern of expression of P450c17 in their peripheral nervous systems by immunocytochemistry using the P450c17 antiserum previously used to characterize P450c17 in the mouse brain. P450c17 was readily detected in the dorsal root ganglia (DRG) and spinal cord. Neural structures were identified with antisera to the cytoskeletal protein neural cell adhesion molecule; DRG were identified with antisera to the neuronal transcription factor BRN3A and neurotrophin receptor tropomyosin-receptor-kinase B. The identification of P450c17 was confirmed using commercial antisera directed against different domains of P450c17 and by using antisera immunodepleted with authentic human P450c17. We also found expression of the P450 cholesterol side-chain cleavage enzyme (P450scc) in the spinal cord and DRG. Expression of P450scc is limited to cell bodies; unlike P450c17, we never detected P450scc in fiber tracts. Catalysis by P450c17 requires electron donation from P450 oxidoreductase (POR). Dual-label immunohistochemistry detected P450c17 and POR colocalized in DRG bundles, but some fibers containing P450c17 lacked POR. These data suggest that neurosteroids synthesized via these two enzymes may act in the developing human nervous system. The expression of P450c17 in structures lacking POR means that P450c17 may not be steroidogenic in those locations, suggesting that P450c17 may have additional functions that do not require POR.

Dehydroepiandrosterone biosynthesis, role, and mechanism of action in the developing neural tube

Dehydroepiandrosterone (DHEA) is synthesized from cholesterol by activity of P450scc and P450c17, enzymes that we previously characterized in the developing nervous system. We describe the localization of P450c17 in the differentiated field of the ventral spinal cord in different motor neuron subtypes. We show that, during organogenesis, P450c17 activity is regulated along the antero/posterior axis of the spinal cord concomitantly with the gradient of neurogenesis. To examine whether DHEA may modulate this process, we measured proliferation and differentiation of ventral neural precursors in primary and explant cultures. Our results showed that DHEA-induced the expression of class II protein Nkx6.1, motor neuron precursor Olig-2, and definitive motor neuron marker Isl-1/2. DHEA also promoted proliferation of ventrally committed precursors in isolated spinal cord precursor cultures and in whole spinal cord explants. Both the proliferative and inductive effects of DHEA were dependent on sonic hedgehog signaling. The possibilities that the effects observed with DHEA were due to its metabolism into androgens or to activation of NMDA receptors were excluded. These results support the hypothesis that the tight regulation of DHEA biosynthesis may be a biologic clock restricting the period of ventral neuronal-precursor proliferation, thus controlling the number of pre-committed neurons in the developing neural tube.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders

Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Identification and developmental expression of the full complement of Cytochrome P450 genes in Zebrafish

Background

Increasing use of zebrafish in drug discovery and mechanistic toxicology demands knowledge of cytochrome P450 (CYP) gene regulation and function. CYP enzymes catalyze oxidative transformation leading to activation or inactivation of many endogenous and exogenous chemicals, with consequences for normal physiology and disease processes. Many CYPs potentially have roles in developmental specification, and many chemicals that cause developmental abnormalities are substrates for CYPs. Here we identify and annotate the full suite of CYP genes in zebrafish, compare these to the human CYP gene complement, and determine the expression of CYP genes during normal development.

Results

Zebrafish have a total of 94 CYP genes, distributed among 18 gene families found also in mammals. There are 32 genes in CYP families 5 to 51, most of which are direct orthologs of human CYPs that are involved in endogenous functions including synthesis or inactivation of regulatory molecules. The high degree of sequence similarity suggests conservation of enzyme activities for these CYPs, confirmed in reports for some steroidogenic enzymes (e.g. CYP19, aromatase; CYP11A, P450scc; CYP17, steroid 17a-hydroxylase), and the CYP26 retinoic acid hydroxylases. Complexity is much greater in gene families 1, 2, and 3, which include CYPs prominent in metabolism of drugs and pollutants, as well as of endogenous substrates. There are orthologous relationships for some CYP1 s and some CYP3 s between zebrafish and human. In contrast, zebrafish have 47 CYP2 genes, compared to 16 in human, with only two (CYP2R1 and CYP2U1) recognized as orthologous based on sequence. Analysis of shared synteny identified CYP2 gene clusters evolutionarily related to mammalian CYP2 s, as well as unique clusters.

Conclusions

Transcript profiling by microarray and quantitative PCR revealed that the majority of zebrafish CYP genes are expressed in embryos, with waves of expression of different sets of genes over the course of development. Transcripts of some CYP occur also in oocytes. The results provide a foundation for the use of zebrafish as a model in toxicological, pharmacological and chemical disease research.

The effects of DHEA, 3beta-hydroxy-5alpha-androstane-6,17-dione, and 7-amino-DHEA analogues on short term and long term memory in the mouse

Neurosteroids have been reported to modulate memory processes in rodents. Three analogues of dehydroepiandrosterone (DHEA), two of them previously described (7beta-aminoDHEA and 7beta-amino-17-ethylenedioxy-DHEA), and a new one (3beta-hydroxy-5alpha-androstane-6,17-dione) were synthesized, and their effects were evaluated on memory. This study examined their effects on long term and short term memory in male (6 weeks old) NMRI mice in comparison with the reference drug. Long term memory was assessed using the passive avoidance task and short term memory (spatial working memory) using the spontaneous alternation task in a Y maze. Moreover, the effects of DHEA and its analogues on spontaneous locomotion were measured. In all tests, DHEA and analogues were injected at three equimolar doses (0.300-1.350-6.075 microM/kg). DHEA and its three analogues administered immediately post-training at the highest doses (6.075 microM/kg, s.c.) improved retention in passive avoidance test. Without effect per se in the spatial working memory task, the four compounds failed to reverse scopolamine (1mg/kg, i.p.)-induced deficit in spontaneous alternation. These data suggested an action of DHEA and analogues in consolidation of long term memory particularly when emotional components are implied. Moreover, data indicated that pharmacological modulation of DHEA as performed in this study provides derivatives giving the same mnemonic profile than reference molecule.

Steroid production and excretion by the pregnant mouse, particularly in relation to pregnancies with fetuses deficient in Delta7-sterol reductase (Dhcr7), the enzyme associated with Smith-Lemli-Opitz syndrome

This study has shown that the mouse has a great increase in steroid production during pregnancy in similar fashion to the human. Many steroids were provisionally identified in maternal urine of the wild-type mouse. The major progesterone metabolites appear to be hydroxylated pregnanolones, particularly with hydroxyl groups in the 16alpha position. Rather than estriol being the major end-product of feto-placental steroid synthesis as in the human, the pregnant mouse produces and excretes large amounts of androgen metabolites, ranging in polarity from androstanetriols to androstanepentols. These steroids have 15alpha- or 18-hydroxyl groups with additional hydroxylation at uncharacterized positions. From metabolite data the peak of pregnancy progesterone production appears to be between 7.5 and 14.5 gestational days, while for C(19) metabolites peak excretion is later. The starting-point of the studies was to study pregnancy steroid production by a mouse model for Smith-Lemli-Opitz syndrome, 7-dehydrosterol reductase (DHCR7) deficiency. In human pregnancies with DHCR7 deficient fetuses large amounts of 7- and 8-dehydrosteroids are excreted, products secondary to high fetal 7- and 8-dehydrocholesterol (DHC) accumulation. This agrees with existing evidence that human feto-placental steroid synthesis utilizes little maternal cholesterol as precursor. In contrast, this study has shown that pregnant mice carrying dhcr7 deficient fetuses with relatively high DHC production had essentially undetectable maternal excretions of steroids with Delta(7)- and Delta(8)-unsaturation. As mutant mouse mothers have essentially normal cholesterol production (little or no DHC build-up), this suggests maternal cholesterol is primarily utilized for pregnancy steroid synthesis in the mouse.

Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides

Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.

Oral administration of dehydroepiandrosterone-sulfate (DHEAS) increases in vitro lymphocyte function and improves in vivo response of pigs to immunization against keyhole limpet hemocyanin (KLH) and ovalbumin

The present study tested the hypothesis that the oral administration of DHEAS enhances the in vitro and the in vivo immune response of young pigs. Crossbred, female pigs (80 days of age; 49+/-2 kg) were separated into two treatment groups (n=4/treatment) receiving either 0mg/kg (control) or 1mg/kg DHEAS twice daily (DHEAS) for 5 weeks. On day 7 pigs were immunized against KLH and ovalbumin. Body weight increased weekly throughout the study but did not differ between treatment groups. While white blood cell counts increased in response to immunization but did not differ between treatments, the neutrophil:lymphocyte ratio was enhanced (P<0.05) in DHEAS-supplemented pigs. Concanavalin A (ConA) induced an in vitro dose-dependent increase (P<0.05) in lymphocyte proliferation, but treatment did not affect proliferation prior to immunization. However, lymphocytes isolated from DHEAS-supplemented pigs displayed a greater increase in proliferation following immunization relative to control pigs (P<0.05). Dexamethasone (DEX) attenuated ConA-induced lymphocyte proliferation, with DHEAS-supplemented pigs retaining a greater proliferative response relative to control pigs (P<0.05). Serum IgG concentrations and relative concentrations of antigen-specific IgG increased after immunization with maximum values attained at 21 and 28 days for control and DHEAS-supplemented pigs, respectively. The DHEAS-supplemented pigs had greater (P<0.05) concentrations of IgG and relative concentrations of antigen-specific IgG compared to control pigs. Collectively these data suggest DHEAS supplementation increases the responsiveness of young pigs to antigenic challenge, and may be beneficial for improving their immune function.

Complex assembly on the human CYP17 promoter

Optimal steroid hormone biosynthesis occurs via the integration of multiple regulatory processes, one of which entails a coordinate increase in the transcription of all genes required for steroidogenesis. In the human adrenal cortex adrenocorticotropin (ACTH) activates a signaling cascade that promotes the dynamic assembly of protein complexes on the promoters of steroidogenic genes. For CYP17, multiple transcription factors, including steroidogenic factor-1 (SF-1), GATA-6, and sterol regulatory binding protein 1 (SREBP1), are recruited to the promoter during activated transcription. The ability of these factors to increase CYP17 mRNA expression requires the formation of higher order coregulatory complexes, many of which contain enzymatic activities that post-translationally modify both the transcription factors and histones. We discuss the mechanisms by which transcription factors and coregulatory proteins regulate CYP17 transcription and summarize the role of kinases, phosphatases, acetyltransferases, and histone deacetylases in controlling CYP17 mRNA expression.

Targeted inactivation of p12, CDK2 associating protein 1, leads to early embryonic lethality

Targeted disruption of murine Cdk2ap1, an inhibitor of CDK2 function and hence G1/S transition, results in the embryonic lethality with a high penetration rate. Detailed timed pregnancy analysis of embryos showed that the lethality occurred between embryonic day 3.5 pc and 5.5 pc, a period of implantation and early development of implanted embryos. Two homozygous knockout mice that survived to term showed identical craniofacial defect, including a short snout and a round forehead. Examination of craniofacial morphology by measuring Snout Length (SL) vs. Face Width (FW) showed that the Cdk2ap1(+/-) mice were born with a reduced SL/FW ratio compared to the Cdk2ap1(+/+) and the reduction was more pronounced in Cdk2ap1(-/-) mice. A transgenic rescue of the lethality was attempted by crossing Cdk2ap1(+/-) animals with K14-Cdk2ap1 transgenic mice. Resulting Cdk2ap1(+/-:K14-Cdk2ap1) transgenic mice showed an improved incidence of full term animals (16.7% from 0.5%) on a Cdk2ap1(-/-) background. Transgenic expression of Cdk2ap1 in Cdk2ap1(-/-:K14-Cdk2ap1) animals restored SL/FW ratio to the level of Cdk2ap1(+/-:K14-Cdk2ap1) mice, but not to that of the Cdk2ap1(+/+:K14-Cdk2ap1) mice. Teratoma formation analysis using mESCs showed an abrogated in vivo pluripotency of Cdk2ap1(-/-) mESCs towards a restricted mesoderm lineage specification. This study demonstrates that Cdk2ap1 plays an essential role in the early stage of embryogenesis and has a potential role during craniofacial morphogenesis.

Regulation of P450c17 expression in the early embryo depends on GATA factors

The enzyme P450c17 is required for glucocorticoid, sex steroid, and some neurosteroid biosynthesis. Defective human P450c17 causes sexual infantilism and 46,XY sex reversal but is compatible with life, whereas ablation of the corresponding mouse gene causes embryonic lethality at around E7. Normal mouse embryos express P450c17 protein and activity in the embryonic endoderm at E7. Adult adrenal and gonadal steroidogenesis requires steroidogenic factor-1 (SF-1), but SF-1 is not expressed in the early mouse embryo. We show that P450c17 is expressed in differentiated mouse parietal and visceral endoderm lineages, in cultured mouse F9 embryonic carcinoma stem cells, in mouse embryonic stem cells, and in cultured mouse P19 stem cells. Bases -110 to -55 (which contain an SF-1 site and two potential GATA sites) of the rat cyp17 gene confer promoter activity in F9 cells. Overexpression of SF-1 has no effect, whereas overexpression of GATA4 in F9 cells increases transcription from -110/-55 fused to a reporter and increases endogenous P450c17 mRNA. Chromatin immunoprecipitation assays show that GATA4 binds to -215/+55 of mouse cyp17. Stimulating F9 cells with retinoic acid and cAMP differentiates them into visceral and parietal endoderm. Commensurate with cell differentiation, quantitative PCR showed increased GATA4 and GATA6 mRNAs, temporally followed by increased P450c17 mRNA. Small interfering RNA inhibition of GATA4 or GATA6 in undifferentiated or differentiated F9 cells diminished endogenous cyp17 expression. Thus, P450c17 is expressed in mouse embryonic stem cells, its expression increases upon differentiation to an early embryonic endoderm lineage, and GATA4/6 are responsible for activation of P450c17 gene expression at this early stage of embryonic development.

Neurobiological and neuropsychiatric effects of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS)

DHEA and DHEAS are steroids synthesized in human adrenals, but their function is unclear. In addition to adrenal synthesis, evidence also indicates that DHEA and DHEAS are synthesized in the brain, further suggesting a role of these hormones in brain function and development. Despite intensifying research into the biology of DHEA and DHEAS, many questions concerning their mechanisms of action and their potential involvement in neuropsychiatric illnesses remain unanswered. We review and distill the preclinical and clinical data on DHEA and DHEAS, focusing on (i) biological actions and putative mechanisms of action, (ii) differences in endogenous circulating concentrations in normal subjects and patients with neuropsychiatric diseases, and (iii) the therapeutic potential of DHEA in treating these conditions. Biological actions of DHEA and DHEAS include neuroprotection, neurite growth, and antagonistic effects on oxidants and glucocorticoids. Accumulating data suggest abnormal DHEA and/or DHEAS concentrations in several neuropsychiatric conditions. The evidence that DHEA and DHEAS may be fruitful targets for pharmacotherapy in some conditions is reviewed.

Two CYP17 genes in the South African Angora goat (Capra hircus) - the identification of three genotypes that differ in copy number and steroidogenic output

In mammals, cytochrome P450 17alpha-hydroxylase/17-20 lyase (CYP17), which is encoded by a single gene, plays a critical role in the production of mineralocorticoids, glucocorticoids and androgens by the adrenal cortex. Two CYP17 isoforms with unique catalytic properties have been identified in the South African Angora goat (Capra hircus), a subspecies that is susceptible to cold stress because of the inability of the adrenal cortex to produce sufficient levels of cortisol. A real-time-based genotyping assay was used in this study to identify the distribution of the two CYP17 alleles in the South African Angora population. These data revealed that the two CYP17 isoforms were not the product of two alleles of the same gene, but two separate CYP17 genes encoding the two unique CYP17 isoforms. This novel finding was subsequently confirmed by quantitative real-time PCR. Goats were divided into three unique genotypes which differed not only in the genes encoding CYP17, but also in copy number. Furthermore, in vivo assays revealed that the identified genotypes differed in their ability to produce cortisol in response to intravenous insulin injection. This study clearly demonstrates the presence of two CYP17 genes in the South African Angora goat, and further implicates CYP17 as the primary cause of the observed hypocortisolism in this subspecies.

Targeted deletion of Tssk1 and 2 causes male infertility due to haploinsufficiency

Targeted deletion of Tssk1 and 2 resulted in male chimeras which produced sperm/spermatogenic cells bearing the mutant allele, however this allele was never transmitted to offspring, indicating infertility due to haploinsufficiency. Morphological defects in chimeras included failure to form elongated spermatids, apoptosis of spermatocytes and spermatids, and the appearance of numerous round cells in the epididymal lumen. Characterization of TSSK2 and its interactions with the substrate, TSKS, were further investigated in human and mouse. The presence of both kinase and substrate in the testis was confirmed, while persistence of both proteins in spermatozoa was revealed for the first time. In vivo binding interactions between TSSK2 and TSKS were established through co-immunoprecipitation of TSSK2/TSKS complexes from both human sperm and mouse testis extracts. A role for the human TSKS N-terminus in enzyme binding was defined by deletion mapping. TSKS immunoprecipitated from both mouse testis and human sperm extracts was actively phosphorylated. Ser281 was identified as a phosphorylation site in mouse TSKS. These results confirm both TSSK 2 and TSKS persist in sperm, define the critical role of TSKS' N-terminus in enzyme interaction, identify Ser 281 as a TSKS phosphorylation site and indicate an indispensable role for TSSK 1 and 2 in spermiogenesis.

Endogenous and synthetic neurosteroids in treatment of Niemann-Pick Type C disease

The functions for neurosteroids during development and in response to nervous system injury are beginning to be identified. We focused on a mouse model in which we believed neurosteroid production would be altered, and which had a neurodegenerative phenotype. Niemann-Pick Type-C (NP-C) is an autosomal recessive neurodegenerative disease caused by mutations in NPC1 (95%) or NPC2 (5%), resulting in lysosomal accumulation of unesterified cholesterol and glycolipids. The NIH mouse model of NP-C has a mutation in the NPC1 gene, and exhibits several pathological features of the most severe NP-C patients. How lysosomal storage and trafficking defects lead to neurodegeneration is unknown. We found that these mice had normal neurosteroidogenic enzyme activity during development, but lost this activity in the early neonatal period, prior to onset of neurological symptoms. Neurons that expressed P450scc, 3beta HSD, as well as those that expressed 3alpha HSD and 5alpha reductase were lost in adult NP-C brains, resulting in diminished concentrations of allopregnanolone. We treated NP-C mice with allopregnanolone and found that a single dose in the neonatal period resulted in a doubling of life span, substantial delay in onset of neurological symptoms, survival of cerebellar Purkinje and granule cell neurons, and reduction in cholesterol and ganglioside accumulation. The mechanism by which allopregnanolone elicited these effects is unknown. Our in vitro studies showed that Purkinje cell survival promoted by allopregnanolone was lost by treatment with bicuculline, suggesting GABA(A) receptors may play a role. We treated NP-C mice with a synthetic GABA(A) neurosteroid, ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one). Ganaxolone treatment of NP-C mice produced beneficial neurological effects, but these effects were not as robust as those obtained using allopregnanolone. Thus, allopregnanolone may elicit its effects through GABA(A) receptors and through other mechanisms. Additional studies also suggest that allopregnanolone may elicit its effects through pregnane-X-receptors (PXR). Our data suggest that mouse models of neurodegeneration may be beneficial in establishing both physiologic and pharmacologic actions of neurosteroids. These animal models further establish the wide range of functions of these compounds, which may ultimately be useful for treatment of human diseases.

Transcriptional regulation of adrenocortical steroidogenic gene expression

By serving as ligands for nuclear and plasma membrane receptors, steroid hormones are key regulators of a diverse array of physiological processes. These hormones are synthesized from cholesterol in tissues such as the adrenal cortex, ovaries, testes, and placenta. Because steroid hormones control the expression of numerous genes, steroidogenic cells utilize multiple mechanisms that ensure tight control of the synthesis of these molecules. This review will give an overview of the molecular mechanisms by which the expression of steroidogenic genes is regulated in the human adrenal cortex.

Human fetal ovary development involves the spatiotemporal expression of p450c17 protein

OBJECTIVE

The purpose of this research was to characterize the spatiotemporal expression of P450c17 in the human fetal ovary.

DESIGN

P450c17 protein was visualized in sections of control and anencephalic ovaries using immunohistochemistry.

SUBJECTS

Subjects included control (nonanencephalic) and anencephalic human fetal ovaries during the second and third trimesters.

RESULTS

In second-trimester control ovaries, P450c17 was highly expressed in primary interstitial cells (PIC) located between the ovigerous cords near the cortical-medullary border where meiosis and primordial follicle formation were occurring. Morphometric analysis revealed a progressive decrease in the number of PIC during the second trimester, suggesting that PIC might have a finite lifetime. Between 25 and 32 wk, relatively few cells stained positive for P450c17; however, after 33 wk, P450c17 was strongly expressed in theca interstitial cells (TIC) bordering developing follicles. Surprisingly, the TIC appeared remarkably early during folliculogenesis, e.g. as early as the primary-to-secondary transition, and exhibited notable hyperplasia throughout preantral and early antral follicle growth. Owing to large numbers of developing preantral follicles, the third trimester was characterized by an increased abundance of P450c17-positive TIC. During this time period, P450c17 was strongly expressed in the hilus interstitial cells juxtaposed to the rete ovarii. Studies of ovaries of anencephalic fetuses revealed a similar spatiotemporal pattern of P450c17 expression in the PIC, TIC, and hilus interstitial cells, consistent with the possibility that pituitary hormones may not be involved in P450c17 expression in fetal ovaries.

CONCLUSION

We identified three different classes of P450c17-expressing interstitial cells in the human fetal ovary, each having a different spatiotemporal pattern of P450c17 expression and, presumably, a different set of physiological functions.

Molecular and neurochemical evidence for the biosynthesis of dehydroepiandrosterone in the adult rat spinal cord

Various studies have indicated that exogenous dehydroepiandrosterone (DHEA) modulates several mechanisms in the CNS of rodents. As adult rodent glands do not secrete significant amounts of DHEA, its role as endogenous modulator of the CNS remains possible only if DHEA is produced by nerve cells. Therefore, the last decade has been marked by diverse unsuccessful investigations aiming to demonstrate the activity of cytochrome P450c17 (P450c17), the key DHEA-synthesizing enzyme, in adult rodent CNS. Here, we combined molecular, anatomical, cellular and neurochemical approaches to provide the first demonstration of the existence of P450c17 and bioactivity in adult rat spinal cord (SC). Real-time RT-PCR revealed P450c17 gene expression in all SC segments. Western blot analyses allowed identification of a specific P450c17 protein in the SC and immunohistochemical studies localized P450c17 in neurones and glial cells. Pulse-chase experiments combined with HPLC and radioactive steroid detection showed that SC slices converted [3H]pregnenolone into [3H]DHEA, a conversion markedly reduced by ketoconazole, a P450c17 inhibitor. Kinetics studies revealed accumulation of [3H]DHEA newly synthesized by SC slices in the incubation medium as its amount declined slowly. This first cellular mapping of an active P450c17 in adult rodent SC suggests that endogenous DHEA synthesized in spinal neural networks may control various spinally-mediated activities.

Haploinsufficiency of cytochrome P450 17alpha-hydroxylase/17,20 lyase (CYP17) causes infertility in male mice

Cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) is critical in determining cortisol and sex steroid biosynthesis. To investigate how CYP17 functions in vivo, we generated mice with a targeted deletion of CYP17. Although in chimeric mice Leydig cell CYP17 mRNA and intratesticular and circulating testosterone levels were dramatically reduced (80%), the remaining testosterone was sufficient to support spermatogenesis as evidenced by the generation of phenotypical black C57BL/6 mice. However, male chimeras consistently failed to generate heterozygous CYP17 mice and after five matings chimeric mice stopped mating indicating a change in sexual behavior. These results suggested that CYP17 deletion caused a primary phenotype (infertility), probably not due to the anticipated androgen imbalance and a secondary phenotype (change in sexual behavior) due to the androgen imbalance. Surprisingly, CYP17 mRNA was found in mature sperm, and serial analysis of gene expression identified CYP17 mRNA in other testicular germ cells. CYP17 mRNA levels were directly related to percent chimerism. Moreover, more than 50% of the sperm from high-percentage chimeric mice were morphologically abnormal, and half of them failed the swim test. Furthermore, 60% of swimming abnormal sperm was devoid of CYP17. These results suggest that CYP17, in addition to its role in steroidogenesis and androgen formation, is present in germ cells where it is essential for sperm function, and deletion of one allele prevents genetic transmission of mutant and wild-type alleles causing infertility followed by change in sexual behavior due to androgen imbalance.

DNA sequence-dependent regulation of SF-1-mediated transcription

Rat P450c17 gene transcription is regulated by several nuclear factors, including steroidogenic factor-1 (SF-1), nerve growth factor-inducible protein B (NGF-IB, Nurr77), COUP-TF, SET, and Ku autoimmune antigen. A region of this gene, -447/-419, that mediates both basal and cAMP-stimulated transcription, contains two binding sites for orphan nuclear receptors. While SF-1 activates transcription through a single binding site, we show that both binding sites at -447/-419 are required for transcriptional activation by SF-1 and cAMP. Both SF-1 and a novel factor, Steroidogenic Factor-Inducer of Transcription-2 (StF-IT-2) bind to this region, suggesting that a DNA-dependent interaction between StF-IT-2 and SF-1 may be required for full transcriptional activity. Each of the two orphan nuclear receptor sites -429/-424 and at -444/-439 are sufficient for SF-1 binding but are insufficient for SF-1-mediated transcription. Increasing the distance between or changing the orientation of these two sites does not affect basal or SF-1-stimulated activity. Circular permutation analysis, which measures the degree of DNA bending caused by protein binding, indicates that SF-1 binding to -447/-419 induces a different degree of DNA bending than it does at another SF-1-responsive site. However, similar domains of the SF-1 protein are required for its actions at these two regions. Southwestern blots suggest that StF-IT-2 is a approximately 33 kDa protein, and gel shift assays suggest it is expressed primarily in the gonad and brain early in rodent development. These data suggest that the mechanism by which SF-1 stimulates transcription is DNA sequence dependent, and may require additional proteins, such as StF-IT-2, for activation at specific regions of DNA.

Are genes of human intelligence related to the metabolism of thyroid and steroids hormones? – Endocrine changes may explain human evolution and higher intelligence

We propose the hypothesis that genes of human intelligence are related with metabolism of thyroid and steroids hormones, which have a crucial role in brain development and function. First, there is evidence to support the idea that during hominid evolution small genetic differences were related with significant endocrine changes in thyroid and steroids hormones. Second, these neuroactive hormones are also related with unique features of human evolution such as body and brain size increase, penis and breast enlargement, pelvic sexual dimorphism, active sexuality, relative lack of hair and higher longevity. Besides underling many of the differences between humans and great apes, steroids hormones promote brain growth and development, are important in the myelination process, explain sexual dimorphisms in brain and intelligence and improve specific cognitive abilities in humans. Supporting our hypothesis, recent studies indicate differences in neuroactive hormones metabolism between humans and non-human primates. Furthermore, a link between X chromosome genes and sex steroids may explain why the frequency of genes affecting intelligence is so high on the X chromosome. This association suggests that, during hominid evolution, there was a positive feedback in both sexes on the same genes responsible for secondary sexual character development and intelligence. This interaction leads to acceleration of development of human brain and intelligence. Finally, we propose that neuroactive hormone therapy may provide significant improvement in some cognitive deficits in all stages of human life and in cases of neurodegenerative diseases. However, further investigation is needed, mainly in the enzymatic machinery, in order to understand the direct role of these hormones in intelligence.

The influence of dehydroepiandrosterone on early pregnancy in mice

The aim of the present report was to study the role of high levels of dehydroepiandrosterone (DHEA) on the ovarian function and embryonic resorption during early pregnancy in BALB/c mice. Pregnant animals were injected with DHEA following both the post-implantatory (DHEA-2) and peri-implantatory (DHEA-6) models. Morphological studies of implantation sites showed 40% of embryonic resorption in the DHEA-2 group while 100% of resorption was observed in the DHEA-6 group. Serum samples of both DHEA-2 and DHEA-6 groups showed higher estradiol levels and a lower progesterone concentration than those of control groups. Ovarian prostaglandin E levels after both DHEA-2 and DHEA-6 treatments increased when compared to control groups. The antioxidant metabolite glutathione diminished during both DHEA treatments. In summary, the data presented here suggest that DHEA treatment during early pregnancy modulates the ovarian function and is responsible for embryonic resorption with different degrees depending on when it is administered.

Niemann pick type C disease as a model for defects in neurosteroidogenesis

Many functions have been attributed to neurosteroids including actions as anxiolytics, roles in myelination, inhibitors of neuronal toxicity and ischemia, and roles in neuronal growth and differentiation. To understand the functions of neurosteroids during nervous system development, we used two mouse models: one, in which the cyp17 gene was ablated, thus ablating synthesis of the neurosteroid DHEA, and a second, in a mouse model of a human childhood fatal neurodegenerative disease, Niemann-Pick Type C (NP-C). Cyp17-/- mice died unexpectedly approximately embryonic day 7. Cyp17 was expressed in the embryonic endoderm at E7, where 17alpha hydroxylase and c17,20 lyase activities were found. Hormonal replacement was ineffective in rescuing the embryos. The function of P450c17 and/or its steroid products in early mouse development is unknown. In the second model, we used a naturally-occurring NP-C mutant mouse. Mutations in the npc1 gene results in lysosomal accumulation of cholesterol and gangliosides in humans and in the mouse, which also recapitulates the onset of neurological deficits, neuronal loss and death typical of the most severe form of the human disease. We showed that there is a substantial reduction in the synthesis of the neurosteroid allopregnanolone (ALLO) at birth, which may lead to abnormal neural development. ALLO treatment was highly effective; ALLO-treated NP-C mice had substantially increased survival and delays in neurologic impairments, coinciding with marked improvements in neuronal survival, and reduction of gangliosides. These data suggest that neurosteroids play an important role in brain development and maturation and may be an effective therapy for NP-C and perhaps other lysosomal storage diseases.