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PubMed1995

Mice deficient in the orphan receptor steroidogenic factor 1 lack adrenal glands and gonads but express P450 side-chain-cleavage enzyme in the placenta and have normal embryonic serum levels of corticosteroids.

The orphan nuclear receptor steroidogenic factor 1 (SF-1) is expressed in the adrenal cortex and gonads and regulates the expression of several P450 steroid hydroxylases in vitro. We examined the role of SF-1 in the adrenal glands and gonads in vivo by a targeted disruption of the mouse SF-1 gene. All SF-1-deficient mice died shortly after delivery. Their adrenal glands and gonads were absent, and persistent Mullerian structures were found in all genotypic males. While serum levels of corticosterone in SF-1-deficient mice were diminished, levels of adrenocorticotropic hormone (ACTH) were elevated, consistent with intact pituitary corticotrophs. Intrauterine survival of SF-1-deficient mice appeared normal, and they had normal serum level of corticosterone and ACTH, probably reflecting transplacental passage of maternal steroids. We tested whether SF-1 is required for P450 side-chain-cleavage enzyme (P450scc) expression in the placenta, which expresses both SF-1 and P450scc, and found that in contrast to its strong activation of the P450scc gene promoter in vitro, the absence of SF-1 had no effect on P450scc mRNA levels in vivo. Although the region targeted by our disruption is shared by SF-1 and by embryonal long terminal repeat-binding protein (ELP), a hypothesized alternatively spliced product, we believe that the observed phenotype reflects absent SF-1 alone, as PCR analysis failed to detect ELP transcripts in any mouse tissue, and sequences corresponding to ELP are not conserved across species. These results confirm that SF-1 is an important regulator of adrenal and gonadal development, but its regulation of steroid hydroxylase expression in vivo remains to be established.

Adrenal Cortex Hormones↗
PubMed2005

Short-term delay of puberty causes a transient reduction in bone strength in growing female rats.

Multiple factors affect the structural development of the skeleton; in particular, estrogen levels during growth are an important factor in the pathogenesis of bone fragility. The delay of menarche and infrequent menstrual cycles decrease estrogen levels during adolescence and decrease peak bone mass. The aim of this study was to determine if delayed puberty through administration of a GnRH antagonist initiated prior to the onset of the first estrus cycle would delay the increase in estrogen levels and impede bone strength development in female rats. Twenty-three-day-old female Sprague-Dawley rats were randomly assigned to one of four groups; 1) short-term control group (C-ST) (n = 12), 2) long-term control (C-LT) (n = 12), 3) short-term GnRH antagonist group (G-ST) (n = 12) and 4) long-term GnRH antagonist group (G-LT) (n = 12). Injections (0.2 ml) of either saline or GnRH antagonist (100 microg/day) (Cetrotide, Serono, Inc) were given intraperitoneally for a duration of 18 days. Pubertal and gonadal development was retarded as indicated by a delay in vaginal opening (an indicator of pubertal onset), lower ovarian and uterine weights and lower estradiol levels in the short-term experimental animals (G-ST). However, at maturity (G-LT), there were no significant differences found in these measures. A delay in the timing of puberty significantly attenuated the development of femoral bone strength at 6 weeks of age. Peak moment, yield moment and stiffness in the G-ST group were all significantly less than the C-ST group. Cortical width was significantly attenuated due to the increased percentage of marrow area per total bone area in the G-ST group. However, femoral bone strength was recovered at maturity (G-LT). In summary, a transient delay in pubertal timing has short-term effects on bone strength development. In the current animal model of delaying puberty through GnRH antagonist injections, there appears to be no long-term effects on bone strength.

Animals↗
PubMed2003

Short-term exposure of Chinook salmon (Oncoryhnchus tshawytscha) to o,p-DDE or DMSO during early life-history stages causes long-term humoral immunosuppression.

We evaluated the effect of short-term exposures to a xenobiotic chemical during early life-history stages on the long-term immune competence of chinook salmon (Oncoryhnchus tshawytscha). Immersion of chinook salmon eggs in a nominal concentration of o,p-dichlorodiphenyldichloroethylene (o,p-DDE; 10 ppm) for 1 hr at fertilization followed by immersion in the same dose for 2 hr at hatch resulted in a significant reduction in the ability of splenic leukocytes from fish 1 year after treatment to undergo blastogenesis upon in vitro stimulation with lipopolysaccharide. We also observed that the vehicle, dimethyl sulfoxide (DMSO), caused a significant reduction in the ability of the splenic leukocytes to express surface immunoglobin M (SIgM) at this time. The concentration of o,p-DDE in a pooled sample of whole fry from this treatment was 0.53 microg/g lipid 1 month after first feeding but was undetectable in all other treatments. Mortality rate, time to hatch, fish length, and weight were unaffected by treatment with o,p-DDE. Similarly, sex ratios, gonadal development, and concentrations of plasma estradiol and 11-ketotestosterone were not affected by the treatment. In addition, we found no evidence that plasma lysozyme concentrations or the mitogenic responses of splenic leukocytes to concanavalin A or polyinosinic-polycytidylic acid were influenced by the treatment. In this experiment, a brief period of exposure to o,p-DDE or DMSO during early development was able to induce long-term effects on humoral immune competence of chinook salmon. Such immunosuppression may increase susceptibility to disease, which may in turn be critical to regulating the population.

Animals↗
PubMed1979

A study of gonadal organogenesis, and the factors influencing regeneration following surgical castration in Deroceras reticulatum (Pulmonata:Limacidae).

At hatching, the hermaphrodite duct of Deroceras reticulatum consists of a single cell type designated the Gonadal Stem Cell (GSC). Proliferation of the GSC leads to the formation of numerous ductules each of which forms one of the acini of the gonad. The germinal and supporting cells are derived entirely from the GSC. The germ cells differentiate first, followed by the Sertoli and follicle cells. At the early sperm stage of gonadal development the hermaphrodite duct differentiates to function as a seminal vesicle. Once the GSC are committed to this change they lose their regenerative ability. The only remaining GSC are the cells of the acinar epithelium, and these retain their germinal potential until the death of the animal. Regeneration will occur from the hermaphrodite duct provided it is in the immature state, i.e., composed of GSC, and is exposed to the hormonal conditions of a young animal. Nervous connections and the presence of an artery are not necessary for this regeneration. The presence of a functional gonad does not inhibit regeneration.

Animals↗
PubMed1989

Androgen-specific critical periods for the organization of the major pelvic ganglion.

Previous studies indicate that the major pelvic ganglion (PG) is dependent on testosterone for normal development. Tyrosine hydroxylase (T-OH), DOPA decarboxylase, and choline acetyltransferase (CAT) activities are significantly reduced by postnatal castration on day 10-11, while testosterone replacement therapy reversed all developmental enzyme activity deficits (Melvin and Hamill, 1987). In the present studies castration on the day of birth combined with various testosterone-replacement paradigms produced effects demonstrating that the PG is sensitive to testosterone dosage and time of administration during early postnatal development. Gonadal hormone replacement experiments show that the androgens testosterone and dihydrotestosterone were effective in restoring T-OH and CAT activity deficits produced by neonatal castration. Estrogen therapy reversed the deficits in CAT activity, but was ineffective in reversing the alterations in T-OH activity. Treatment of pregnant dams with the anti-androgen flutamide altered the ontogeny of T-OH and CAT activities in pups despite replacement therapy on the day of birth. Thus, androgen-critical periods exist prenatally as well as postnatally. These studies suggest that the organization of PG development is critically dependent on both the time of exposure and dose of testosterone. Prenatal and postnatal critical periods appear to exist. In addition, the lack of an effect of estradiol on tyrosine hydroxylase activity suggests that androgens are specifically responsible for organizing the noradrenergic development of the PG.

Androgens↗
PubMed1975

[The circannual rhythm of reproductive activity in the starling (Sturnus vulgaris) under the influence of homosexual and heterosexual mates of the same species].

1. 30 European starlings, kept for 20 months under a constant 12-hour photoperiod and at constant temperature, were investigated at regular monthly intervals with regard to the state of gonadal development, bill coloration and moult. 8 male male lived in individual cages (group 1), 10 male male were housed together in a group cage (group 2), and 6 male male lived together with 6 female female in another group cage (group 3). All birds had acoustical contact with each other. In addition, the birds of groups 2 and 3 could see one another. 2. In all male male the testes regressed following the beginning of the experiment in April. Subsequently they carried out a complete postnuptial moult. In the following spring, all male male went through a full cycle of testicular size which was followed by a second postnuptial moult. The bills of all birds turned yellow as the testes grew and blackened as the testes regressed (fig. 1).--Most of the female female showed similar circannual rhythms of gonadal growth and regression, bill coloration and moult (fig. 2). 3. In 6 male male of groups 1 and 2, a small increase of testicular size was observed subsequent to the termination of the first postnuptial moult. This transient testicular activity most probably corresponds to the autumnal sexual activity known from freeliving starlings. Hence, these results suggest that both spring and autumnal sexual activity of the starling are endogenously preprogrammed. 4. The testes of most male male of group 3 developed to full size immediately after the termination of the first postnuptial moult; subsequently they remained active for at least 7 months. This observation suggests that stimuli emitted by the female female augment the endogenously preprogrammed readiness for autumnal sexual activity and prevent the subsequent testicular regression. It is concluded that exogenous factors from the social environment are capable of modifying the endogenous annual pattern of testicular function in the starling.

Animals↗
PubMedDate not supplied

Gonadal disorders in infancy and early childhood.

Disorders of gonadal development can result from chromosomal, genetic, endocrine, or structural abnormalities. The different conditions may have similar clinical features, but behavior and management will vary depending on the particular diagnosis. Disorders that appear in infancy and early childhood are often associated with ambiguous genitalia or abnormal sexual development. Distinction is made on the basis of cytogenetic, hormonal, and, when indicated, histopathologic studies. The current review groups the different abnormalities in the following categories: chromosomal and genetic disorders; structural defects; defective endocrine function; excessive endocrine activity. The principal conditions found in these categories are discussed in terms of pathogenesis and laboratory procedures required to establish a precise diagnosis.

Endocrine System Diseases↗
PubMed2001

Seasonal and age-related changes in blood parasite prevalence in Dark-eyed Juncos (Junco hyemalis, Aves, Passeriformes).

We determined seasonal changes in blood parasite infections in a free-living population of Dark-eyed Juncos (Junco hyemalis) breeding in interior Alaska (65 degrees N; 148 degrees W). The common parasites found in blood smears were Leucocytozoon fringillinarum (56%), Trypanosoma avium (33%), and Haemoproteus fringillae (9%). In males, parasite prevalences were relatively high at arrival on breeding grounds and increased during the breeding season. Intensity of infection with Leucocytozoon also increased between spring and summer, and then decreased at the time of migration (September). This decrease did not occur in adult females. Elevated prevalences during the breeding season probably reflected the addition of new cases via vector activity to positive status resulting from spring relapse. We observed neither an association between parasite species nor a consistent relationship between parasite intensity and body condition. To further study relationships between reproductive system activity and parasite infections, we compared prevalences in adult males that were undergoing their first cycle of gonadal development and regression (males in their second calendar year, or SY) with those of older males (males in their third or more calendar year, i.e., after-second-year males or ASY). Circulating testosterone concentrations declined in both groups between arrival on breeding grounds (end of April-early May) and the end of the reproductive period (July), and they were higher in May in ASY than in SY males. At the peak of the breeding season (June), ASY males also had a higher parasite prevalence than SY males. This difference may have resulted from immunosuppressive effects of gonadal hormones and/or from behavioral differences between SY and ASY males such that older males were exposed to more insect vectors than younger males. .

Age Factors↗
PubMed2005

Prostaglandin D2 induces nuclear import of the sex-determining factor SOX9 via its cAMP-PKA phosphorylation.

During mammalian gonadal development, nuclear import/export of the transcription factor SOX9 is a critical step of the Sry-initiated testis-determining cascade. In this study, we identify a molecular mechanism contributing to the SOX9 nuclear translocation in NT2/D1 cells, which is mediated by the prostaglandin D2 (PGD2) signalling pathway via stimulation of its adenylcyclase-coupled DP1 receptor. We find that activation of cAMP-dependent protein kinase A (PKA) induces phosphorylation of SOX9 on its two S64 and S181 PKA sites, and its nuclear localization by enhancing SOX9 binding to the nucleocytoplasmic transport protein importin beta. Moreover, in embryonic gonads, we detect a male-specific prostaglandin D synthase expression and an active PGD2 signal at the time and place of SOX9 expression. We thus propose a new step in the sex-determining cascade where PGD2 acts as an autocrine factor inducing SOX9 nuclear translocation and subsequent Sertoli cell differentiation.

Animals↗
PubMed2001

Chlorinated hydrocarbons and biomarkers of exposure in wading birds and fish of the lower Rio Grande Valley, Texas.

During 1997 we evaluated reproductive success in colonial water birds nesting in the Lower Rio Grande Valley (LRGV), Texas, and correlated success with concentrations of contaminants in eggs. We also measured steroid hormones and gonadosomatic index (GSI) as biomarkers of endocrine effects in common carp (Cyprinus carpio). Nest and fledging success of green herons (Butorides virescens) and great egrets (Ardea alba) were similar to those found in other parts of North America; however, nesting success of black-crowned night-herons (Nycticorax nycticorax) was lower, very likely due to flooding of the nesting area. Except for DDE and toxaphene, all chlorinated pesticides in bird eggs were low and not of concern for negative effects on any of the three species. DDE was highest in green heron eggs and seemed to increase along a geographic gradient from west to east, with eggs from Falcon Reservoir containing low concentrations, and those at Los Indios containing the highest concentrations (approx. 11,000 ng/g WW), near or above the threshold for reproductive impairment. DDE levels in great egrets and black-crowned night-herons were below those that are associated with reproductive impairment. Mean DDE levels in carp at the JAS Farms site were above the threshold level suggested for predator protection. Toxaphene was detected in about 20% of the samples with high levels observed in green heron eggs from Los Indios (mean = 4,402 ng/g WW). These are the highest toxaphene levels reported in bird eggs in the LRGV. Toxaphene levels in fish ranged between 90 and 312 ng/g WW. In general, PCBs in bird eggs and fish tissue were low and at levels not of concern for reproductive effects. The greatest concentrations of testosterone and 11-ketotestosterone were detected in fish from the JAS Farms site, which also had the greatest concentrations of DDE. Increased androgen production and gonad development in fish at this site, relative to Pharr, could be possibly associated with endocrine disrupting effects of p,p'-DDE. DDE, toxaphene, PCBs, and hormones were highest in birds and fish from the eastern edge of the study area.

Abnormalities, Drug-Induced↗
PubMed2001

In vivo and in vitro effects of prochloraz and nonylphenol ethoxylates on trout spermatogenesis.

We investigated the effects of in vivo exposure to non-lethal concentrations of two chemicals commonly discharged into the aquatic environment, prochloraz and nonylphenol diethoxylate (NP2EO - Igepal(R) 210), on the development of spermatogenesis in trout. The in vitro effects on basal and insulin-like growth factor-1 (IGF-I) stimulated DNA synthesis by early germ cells were also studied. In vivo, rainbow trout were exposed for 2 or 3 weeks to waterborne prochloraz (21 and 175 nmol/l) and/or NP2EO (68-970 nmol/l) renewed continuously, or periodically. Only the highest concentrations of NP2EO (225-970 nmol/l) induced a significant increase in blood plasma vitellogenin in juvenile or maturing male trout. When prepubertal fish were exposed for 15 days to prochloraz, the spermatogenetic process was significantly inhibited as shown by the stage of gonadal development reached 3 weeks after exposure. This effect was, to a great extent, reversible within 9 weeks post-exposure. When fish in the initial stage of spermatogenesis were exposed for 21-27 days to 580 nmol/l NP2EO, a 20-40% reduction of the gonadosomatic index was observed 4.5 weeks post-exposure, and the spermatogenetic process was partly inhibited. In vitro, testicular cells obtained at different stages of spermatogenesis were cultured for 4.5 days in the presence or not of the tested molecules and with IGF-I or not. 3H-thymidine (3H-Tdr) incorporation was measured according to Loir (Mol. Reprod. Dev. 53 (1999) 424) and 125I-IGF-I specific binding was determined according to Le Gac et al. (Mol. Reprod. Dev. 44 (1996) 35). Irrespective of the spermatogenetic stage, basal 3H-Tdr incorporation was decreased by prochloraz concentrations > or =10 micromol/l. The presence of IGF-I (10-100 ng/ml) stimulated 3H-Tdr incorporation; this response to IGF-I began to decrease at 25-50 micromol/l prochloraz. In parallel, a dose-dependent increase of IGF-I specific binding was induced by prochloraz 1-100 micromol/l. Similarly, basal and IGF-I-stimulated 3H-Tdr incorporation was decreased by nonylphenol polyethoxylate (NpnEO; starting at 10 micromol/l), NP2EO and NP (30 micromol/l); a dose-dependent increase of IGF-I specific binding was also induced by NP and NPnEO. While 1-100 nmol/l 17beta-estradiol had no effect in our in vitro system, Triton(R) X-100 acted as NPnEO on 3H-Tdr incorporation. Beside their known endocrine disrupting effects on sex steroid production or action, these lipophilic molecules could act on germ cells by disrupting cell membrane receptivity to peptide hormones like growth factors.

Animals↗
PubMed1993

Control of cell fates in the central body region of C. elegans by the homeobox gene lin-39.

Cells in the mid-body region of the nematode C. elegans develop differently from their anterior or posterior homologs. The gene lin-39 is required for mid-body region-specific development. In lin-39 mutants, mid-body cells express fates characteristic of more anterior or posterior homologs, and the migration of a neuroblast through the mid-body is defective. lin-39 acts cell autonomously in these mid-body cells and in the migrating neuroblast. lin-39 encodes a protein with an Antennapedia class homeodomain, most similar to those of the Drosophila homeotic genes Deformed and Sex combs reduced, and is located in a homeotic gene cluster with two other regional homeotic genes, mab-5 and egl-5. lin-39 and mab-5 function combinatorially in 2 ectodermal cells and have redundant functions in gonad development.

Amino Acid Sequence↗
PubMed2001

Mitochondrial respiratory chain deficiency in Caenorhabditis elegans results in developmental arrest and increased life span.

The growth and development of Caenorhabditis elegans are energy-dependent and rely on the mitochondrial respiratory chain (MRC) as the major source of ATP. The MRC is composed of approximately 70 nuclear and 12 mitochondrial gene products. Complexes I and V are multisubunit proteins of the MRC. The nuo-1 gene encodes the NADH- and FMN-binding subunit of complex I, the NADH-ubiquinone oxidoreductase. The atp-2 gene encodes the active-site subunit of complex V, the ATP synthase. The nuo-1(ua1) and atp-2(ua2) mutations are both lethal. They result in developmental arrest at the third larval stage (L3), arrest of gonad development at the second larval stage (L2), and impaired mobility, pharyngeal pumping, and defecation. Surprisingly, the nuo-1 and atp-2 mutations significantly lengthen the life spans of the arrested animals. When MRC biogenesis is blocked by chloramphenicol or doxycycline (inhibitors of mitochondrial translation), a quantitative and homogeneous developmental arrest as L3 larvae also results. The common phenotype induced by the mutations and drugs suggests that the L3-to-L4 transition may involve an energy-sensing developmental checkpoint. Since approximately 200 gene products are needed for MRC assembly and mtDNA replication, transcription, and translation, we predict that L3 arrest will be characteristic of mutations in these genes.

Animals↗
PubMed1994

Role of leukemia inhibitory factor and its receptor in mouse primordial germ cell growth.

The pleiotropic cytokine leukemia inhibitory factor (LIF) is able to promote the growth of mouse primordial germ cells (PGCs) in culture. It is unclear whether LIF acts directly on PGCs or indirectly via feeder cells or embryonic somatic cells. To understand the role of LIF in PGC growth, we have carried out molecular and cell culture analyses to investigate the role of both the LIF ligand and its receptor in PGC development. LIF is able to stimulate PGC growth independently of the presence of feeder cells supporting the hypothesis that LIF acts directly on PGCs to promote their growth. We show here that transcripts for the low-affinity LIF receptor (LIFR), an integral component of the functional LIF receptor complex, are expressed in the developing gonad. Fluorescence-activated cell sorter (FACS) analysis, using an anti-LIFR antiserum, demonstrates that LIFR is present on the surface of PGCs, suggesting that PGCs are likely to be a direct target of LIF action in culture. Signalling via LIFR is essential for PGC growth in culture since the anti-LIFR antiserum, which blocks LIF binding to its receptor, abolishes PGC survival in culture. Two LIF-related cytokines, namely oncostatin M and ciliary neurotrophic factor, can also promote PGC growth in culture in addition to LIF. Thus one or more of these LIFR-dependent cytokines may play an important role in PGC development in mice.

Animals↗
PubMed2003

WT1 and DAX-1 regulate SF-1-mediated human P450arom gene expression in gonadal cells.

Binding activity of steroidogenic factor-1 (SF-1) to promoters of the majority of steroidogenic genes in response to gonadotropins is a critical mechanism that regulates steroidogenesis in gonads. Thus, the modulation of SF-1 action may be essential for the differential regulation of formation of sex steroids in the ovary. Aromatase P450 (P450arom) is the rate-limiting enzyme for estrogen formation. In this study, we characterize another nuclear receptor half site in the gonadal aromatase promoter which we show to be important for aromatase regulation. We also show herein that the stimulation of P450arom promoter activity by SF-1 in ovarian granulosa, testicular Sertoli and JEG-3 choriocarcinoma cells is inhibited by two transcription factors, Wilms' tumor suppressor gene (WT1) and dosage sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Given the characterized roles of these transcription factors in gonadal development and function, modulation of SF-1 action by WT1 and DAX-1 may represent an important key mechanism in steroidogenesis.

Amino Acid Motifs↗
PubMed2000

Photoperiodic regulation of the male house sparrow song control system: gonadal dependent and independent mechanisms.

The primary and secondary sexual characteristics of many species of passerine birds undergo dramatic seasonal variation in response to the change in the length of photoperiod. Among the many physiological processes that undergo seasonal changes, bird song and the song control system underlying it undergo similar seasonal variation in size and function. The mechanisms of this seasonal variation are largely unknown but are at least partially due to steroidal action from the gonads. The present study determined the relative roles played by the gonads and the photoperiodic timing system that controls gonadal development on song control nuclei in the brain of the male house sparrow, Passer domesticus. Sparrows maintained in short photoperiods (SD) possessed small regressed testes. Transfer to long photoperiods (LD) for 6 weeks evoked a dramatic increase in testes size, but, after 20 weeks under the same conditions (LDLD), testes completely collapsed. Song control nuclei HVC and RA were smaller in SD than in LD but regressed only moderately in LDLD. Castration of sparrows in SD reduced the amplitude of the seasonal variation but did not completely abolish it. The data support the view that the song control system of the house sparrow is regulated by the photoperiodic timing system independently of gonadal influence, but that the gonads augment seasonal regulation of song, presumably via steroidal hormone secretion.

Animals↗
PubMed2001

Immunolocalization of cytochrome P450 aromatase in rat testis during postnatal development.

Aromatization of androgens into estrogens in rat testis is catalyzed by the microsomal enzyme cytochrome P450 aromatase. In this work, aromatase cellular site was investigated in prepuberal, peripuberal and postpuberal testis, from 10-, 21- and 60-day-old rats respectively. Paraffin-embedded testis sections were processed for P450arom immunostaining using a rabbit polyclonal antiserum generated against purified human placental cytochrome P450 aromatase. Next, biotinylated anti-rabbit IgG was applied, followed by ABC/HRP/complex amplification with diaminobenzidine as chromogen. Prepuberal testis sections showed a strong immunoreactivity of aromatase in Sertoli cell cytoplasm while interstitial cells were immunonegative. In peripuberal testis sections, cytoplasmic immunoreaction was weak in Sertoli cells, but it was strong in spermatocytes and sporadic in Leydig cells. Postpuberal testis sections displayed a moderate aromatase immunoexpression in spermatocytes while a strong immunostaining was observed in round and elongated spermatids, as well as in Leydig cells. These results indicate a different age-dependence of aromatase localization in rat testicular cells during gonadal development. In particular, inside the seminiferous tubules, the aromatization site moves from Sertoli cells to late germ cells, suggesting a proliferative role of aromatase in prepuberal testis and its subsequent involvement in meiotic and post-meiotic germ cell maturation.

Aging↗
PubMed1997

Temperature-dependent aromatase expression in developing diamondback terrapin (Malaclemys terrapin) embryos.

In the diamondback terrapin, Malaclemys terrapin, males hatch at incubation temperatures below 28 degrees C whereas females hatch at temperatures above 30 degrees C. When estrogen is applied to the eggs at male temperatures early in development, females are produced. These data suggest that the enzyme necessary for estrogen synthesis (CYP19, aromatase) in the developing gonad plays a critical role in sex determination in these vertebrates. Accordingly, we have begun an examination of the role and regulation of the aromatase gene in sex determination in the diamond back terrapin, Malaclemys terrapin. We have obtained full-length cDNAs for terrapin ovarian aromatase. Using reverse transcription-polymerase chain reaction (RT-PCR) on mRNA from various tissues we have determined that aromatase is expressed in the female brain and ovary, whereas it is only expressed in the brain of the male. Brain expression of aromatase occurs before stage 15, the beginning of the temperature-dependent sex determining period. Ovarian expression occurs sometime later. To quantify expression levels, we have developed a competitive RT-PCR technique to study the ontogeny of aromatase transcript levels throughout development. The sensitivity of our assay (0.001-10 atmol of transcript) permits us to analyse individual embryonic adrenal/kidney/gonadal complexes without pooling samples. Female hatchlings (stage 26) brains express higher aromatase mRNA levels than male brains (381 +/- 80 vs 202 +/- 85 atmol/microg RNA, respectively). Similarly, ovaries express significantly higher aromatase mRNA levels than hatchling testes (352 +/- 117 vs <0.001 atmol/microg RNA, respectively).

Animals↗