Mammary gland development in transgenic male mice expressing human P450 aromatase

We recently generated a transgenic mouse strain that expresses the human aromatase gene under the ubiquitin C promoter (AROM+). We have previously shown that in these mice the serum estradiol concentration is highly elevated, whereas the testosterone concentration is decreased. In the present study we examined mammary gland development in AROM+ male mice at different ages and found that the mammary glands of AROM+ males undergo ductal and alveolar development morphologically resembling that of terminally differentiated female mammary glands, expressing mRNA for a milk protein gene (beta-casein). The male mammary glands also express multiple hormone receptors typical for female mammary gland: estrogen receptor alpha and beta, progesterone receptor, and PRL receptor. Furthermore, data showed activation of the Stat5 (signal transducer and activator of transcription 5) signaling pathway in the AROM+ male mammary gland. Interestingly, the phenotype observed is in part reversible. Treatment with finrozole, a specific aromatase inhibitor, caused an involution of the differentiated phenotype of the mammary gland, marked by the disappearance of alveolar structures and the majority of the tertiary side branches of the ducts. The present animal model is a valuable tool for better understanding the cellular and molecular mechanisms involved in the development of gynecomastia.

Sperm volume regulation: maturational changes in fertile and infertile transgenic mice and association with kinematics and tail angulation

Laser light scatter analyzed by flow cytometry was used to monitor the volume of viable maturing murine spermatozoa. Upon release, dispersion, and dilution, epididymal sperm from fertile heterozygous c-ros knockout mice were smallest in the cauda region and largest in the corpus region. Cauda sperm from both infertile homozygous c-ros knockout and GPX5-Tag2 transgenic mice were abnormally large. When incubated, corpus and cauda sperm from normal mice became slightly enlarged and later returned to a smaller size. This suggests an immediate swelling due to high intracellular osmolality, which triggers a regulatory volume decrease (RVD) that results in a net volume reduction. Normal caput sperm increased in size continuously and became larger than the more mature sperm, indicating a lack of RVD. The ion-channel blocker quinine induced dose-dependent size increases in normal cauda sperm but not in caput sperm. Dose-dependent quinine action on mature sperm also included induction of tail angulation, and suppression of straight-line velocity and linearity. The kinematic effects were more sensitive, with a quicker onset, but they diminished with time in contrast to tail angulation, which intensified. These results suggest that kinematic changes are an early phenomenon of swelling, which gradually accumulates at the cytoplasmic droplet to cause flagellar angulation. Disruption of the epididymal maturation of sperm volume regulation capacity would hinder the transport of sperm in the female tract, and may thereby explain infertility under certain conditions, but may also provide a novel approach to male contraception.

Infravesical obstruction in aromatase over expressing transgenic male mice with increased ratio of serum estrogen-to-androgen concentration

PURPOSE

The potential role of estrogen in the development of infravesical obstruction is still unresolved. Aromatase over expressing transgenic mice provide a novel instrument for investigating the consequences of prolonged systemic or local increases in endogenous estrogen concentrations. Two aromatase over expressing transgenic mouse strains with different prostatic phenotypes (reduced and normal size, respectively) were compared in urodynamic studies with each other and with the wild-type strain.

MATERIALS AND METHODS

The bladder and urethra were exposed in adult male wild-type or transgenic mice. High frequency oscillations of intraluminal bladder pressure and flow rate from the distal urethra were simultaneously recorded with the mice under anesthesia.

RESULTS

No changes were observed in voiding in MMTV-arom+ mice. These mice are known to have only slightly elevated estradiol concentrations in serum, suggesting a localized increase in estrogen production. In AROM+ mice the aromatase gene was detected in several organs, including the testis and bladder. These mice are known to have markedly increased estrogen and decreased serum androgen concentrations, and reduced prostate size. Compared with wild-type mice AROM+ mice showed higher mean maximal bladder pressure plus or minus standard deviation (33.1 +/- 6.4 versus 25.6 +/- 4.8 mm. Hg, p = 0.046) and decreased mean maximal flow rate (3.1 +/- 1.6 versus 17.7 +/- 5.4 ml. per minute, p <0.0001), consistent with the presence of the infravesical obstruction. Morphologically the proximal rhabdosphincter in AROM+ mice showed atrophy (relative mean thickness 0.005 +/- 0.015 versus 0.013 +/- 0.002 mm., p <0.0001).

CONCLUSIONS

Activation of the aromatase gene during an earlier developmental stage under the ubiquitin C promoter and highly elevated serum estrogen concentrations may explain the differences in voiding and prostate size in the AROM+ mouse strain.

Murine relaxin-like factor promoter: functional characterization and regulation by transcription factors steroidogenic factor 1 and DAX-1

The gene for mouse relaxin-like factor (RLF), a member of the insulin/IGF/relaxin family of hormones, appears to be predominantly expressed in testicular Leydig cells. Mice deficient in RLF have revealed a role for this peptide in testicular descent, but the regulatory mechanisms of its function are still insufficiently characterized. In the present study we showed that the RLF promoter was active in both mLTC-1 Leydig cells and luteinized KK-1 granulosa tumor cells. Interestingly, the activity of the RLF promoter as well as the expression of endogenous RLF correlated with the amount of steroidogenic factor 1 (SF-1) expression in the four cell lines tested. The highest transcriptional activity (29-fold over promoterless plasmid) was detected in mLTC-1 using the 188-bp promoter fragment immediately 5' of the CAP site, containing three consensus sequences for SF-1 binding. However, the promoter fragments including the 188-bp promoter also showed significant SF-1-independent promoter activity in both mLTC-1 and KK-1 cells, 8-fold induced over the promoterless construct. Mutagenesis studies showed that all three SF-1-binding sites were needed to obtain maximal SF-1-dependent trans-activation. The most distal SF-1-binding site at position -144 to -136 showed the highest affinity toward SF-1, but the promoter fragments, including the SF-1-binding site at position -115 to -107, showed the strongest response to SF-1 in terms of transcriptional activation. Moreover, DAX-1 inhibited RLF promoter activity in mLTC-1 Leydig tumor cells and totally abolished SF-1-dependent RLF expression in nonsteroidogenic HEK-293 cells. DAX-1 especially inhibited binding of SF-1 to the binding motifs locating at positions -64 to -56 and -115 to -107, whereas no decrease was seen in the expression of SF-1. Taken together, these observations suggest that the 188-bp RLF promoter includes elements for both SF-1-dependent and -independent gene expression in steroidogenic cells. The data, furthermore, indicate differential binding affinities for the three SF-1 binding motifs toward SF-1, of which the motif locating at position -115 to -107 was the most critical for the promoter activity.

Transgenic and knockout mouse models for the study of luteinizing hormone and luteinizing hormone receptor function

The main functions of luteinizing hormone (LH) are concerned with regulation of gonadal function, and these functions are today well delineated through previous physiological studies. However, novel information of less well-known aspects of actions of this hormone is currently emerging from studies on genetically modified mouse models, with either enhanced or suppressed LH/LH receptor (LHR) function. The novel functions of LH include its role, in specific situations, as promoter of formation and growth of gonadal and extragonadal tumors. Chronically elevated LH levels in transgenic (TG) mice can also induce responses to this hormone in extragonadal tissues. The knockout (KO) mouse for the LHR has elucidated various less well-known details in the function of LH during ontogeny and adult life. Finally, studies on LHR promoter function have revealed that the expression of this gene occurs in age, sex and tissues-specific fashion. The purpose of this brief review is to summarize some of our recent findings upon studies of TG and KO mice with altered function of LH or its receptor.

Structure of the 5' region of the Hst70 gene transcription unit: presence of an intron and multiple transcription initiation sites

The rat Hst70 gene and its mouse counterpart Hsp70.2 belong to the family of Hsp70 heat shock genes and are specifically expressed in male germ cells. Previous studies regarding the structure of the 5' region of the transcription unit of these genes as well as localization of the 'cis' elements conferring their testis-specific expression gave contradictory results [Widlak, Markkula, Krawczyk, Kananen and Huhtaniemi (1995) Biochim. Biophys. Acta 1264, 191-200; Dix, Rosario-Herrle, Gotoh, Mori, Goulding, Barret and Eddy (1996) Dev. Biol. 174, 310-321]. In the present paper we solve these controversies and show that the 5' untranslated region (UTR) of the Hst70 gene contains an intron which is localized similar to that of the mouse Hsp70.2 gene. Reverse transcriptase-mediated PCR, Northern blotting and RNase protection analysis revealed that the transcription initiation of both genes starts at two main distant sites, and one of them is localized within the intron. As a result two populations of Hst70 gene transcripts with similar sizes but different 5' UTR structures can be detected in total testicular RNA. Functional analysis of the Hst70 gene promoter in transgenic mice and transient transfection assays proved that the DNA fragment of approx. 360 bp localized upstream of the ATG transcription start codon is the minimal promoter required for testis-specific expression of the HST70/chloramphenicol acetyltransferase transgene. These experiments also suggest that the expression of the gene may depend on 'cis' regulatory elements localized within exon 1 and the intron sequences.

Gonadal tumors of mice double transgenic for inhibin-alpha promoter-driven simian virus 40 T-antigen and herpes simplex virus thymidine kinase are sensitive to ganciclovir treatment

We have previously produced transgenic (TG) mice expressing the mouse inhibin alpha-subunit promoter/Simian virus 40 T-antigen (Inhalpha/Tag) fusion gene. The mice develop gonadal somatic cell tumors at the age of 5-7 months; the ovarian tumors originate from granulosa cells, and those of the testes from Leydig cells. In the present study another TG mouse line was produced, expressing under the same inh-alpha promoter the herpes simplex virus thymidine kinase gene (Inhalpha/TK). Crossbreeding of the two TG mouse lines resulted in double TG mice (Inhalpha/TK-Inhalpha/Tag), which also developed gonadal tumors. The single (Inhalpha/Tag) and double TG (Inhalpha/TK-Inhalpha/Tag) mice, both bearing gonadal tumors, were treated at the age of 5.5-6.5 months with ganciclovir (GCV, 150 mg/kg body weight twice daily i.p.) for 14 days, or with aciclovir (ACV, 300-400 mg/kg body weight per day perorally) for 2 months. During GCV treatment, the total gonadal volume including the tumor, decreased in double TG mice by an average of 40% (P<0.05), while in single TG mice, there was a concomitant increase of 60% in gonadal size (P<0.05). GCV was also found to increase apoptosis in gonads of the double TG mice. Peroral treatment with ACV was less effective, it did not reduce significantly the gonadal volume. We also analyzed the in vitro efficacy of ACV and GCV treatments in transiently HSV-TK-transfected KK-1 murine granulosa tumor cells, originating from a single-positive Inhalpha/Tag mouse. GCV proved to be more effective and more specific than ACV in action. These results prove the principle that targeted expression of the HSV-TK gene in gonadal somatic cell tumors is potentially useful for tumor ablation by antiherpes treatment. The findings provide a lead for further development of somatic gene therapy for gonadal tumors.

Improved technique for detection of enhanced green fluorescent protein in transgenic mice

One of the most exciting recent advances in cell biology is the possibility to use the green fluorescent protein and its various mutated forms as reporter proteins in studies carried out in vitro and in vivo. In the present study, several detection techniques for the enhanced green fluorescent protein (EGFP) were compared in transgenic mice, using fluorescence and confocal microscopy. In addition, different tissue preparation techniques (squash preparations, vibratome sections, frozen sections) were evaluated. As a model we used transgenic mice expressing EGFP under the control of a 5.0-kb fragment of the glutathione peroxidase isoenzyme 5 protein promoter (GPX5-EGFP) or under a 3.8-kb fragment of the cysteine rich protein-1 promoter (CRISP1-EGFP). In the GPX5-EGFP mice, expression of EGFP was observed in the distal part of the caput epididymis, while the CRISP1 promoter directed EGFP expression in the tubular compartment of the testis. Among the various tissue preparation procedures tested, the best morphological and histological preservation, and reproducibility in EGFP detection, were obtained using frozen sections after a slow tissue-freezing protocol developed in the present study. After slow tissue freezing, specimens of testis and epididymis could be stored at -70 degrees C for at least six weeks without any affect on EGFP fluorescence. Hence, the method developed offers the possibility to analyze EGFP fluorescence in tissues several weeks after specimen collection. The sensitivity achieved was equal to that found in immunohistochemistry, applying biotin-streptavidin-FITC detection. Confocal microscopy is known to have the advantage that fluorescence can be detected from cells in different layers. This was found to be important as regards detecting EGFP fluorescence because the fluorescence was destroyed at the cut surfaces of sections produced by either vibratome or cryomicrotome.

Promoter function of different lengths of the murine luteinizing hormone receptor gene 5'-flanking region in transfected gonadal cells and in transgenic mice

The purpose of these studies was to explore the sex- and tissue-specific expression of the LH receptor (LHR) gene. Fusion genes containing three different lengths of the 5'-flanking region of the mouse LHR gene (7.4 kb, 2.1 kb, and 173 bp), beta-globin intron, and the beta-galactosidase (beta-GAL) reporter gene were constructed. Function of these fusion genes [LHR (7.4 kb)/beta-GAL, LHR (2.1 kb)/beta-GAL, and LHR (173 bp)/beta-GAL] was studied in vitro and in vivo. beta-GAL expression was higher in transfected mouse Leydig (mLTC-1) than in granulosa (KK-1) tumor cells with all three constructs. The shortest LHR (173 bp)/beta-GAL construct showed the highest level of beta-GAL expression in both cell types. beta-GAL expression was clearly suppressed with the 2.1-kb promoter and was nearly undetectable with the 7.4-kb construct. In transgenic mice, all three constructs directed beta-GAL expression to adult Leydig cells, displaying decreasing intensity with increasing promoter length. Unexpectedly, beta-GAL expression was also found in elongating spermatids, but not in fetal Leydig cells. There was no expression in any ovarian cell type with the three constructs used, except that one of five mouse lines with the LHR (7.4 kb)/beta-GAL construct expressed beta-GAL in their thecal cells. Two lines transgenic for the 7.4- and 2.1-kb promoter constructs each directed high beta-GAL expression to the brain, with higher intensity in 7.4-kb lines. All promoters directed expression to the pituitary gland, some faintly to the adrenal gland. Northern hybridization analysis of the beta-GAL transcripts in Leydig cells revealed that the 173-bp promoter mainly gave rise to the full-length beta-GAL messenger RNA, whereas the 2.1- and 7.4-kb promoters mainly induced transcription of truncated beta-GAL messages. This suggests that the 5'-flanking region, upstream of -173, determines the formation of splice variants of the structural gene to be transcribed. The present findings in transgenic mice provide in vivo evidence for basal transcriptional activity of the first 173 bp upstream of the LHR translation initiation codon. In conclusion, the promoter function of the mouse LHR 5'-flanking region is tissue, age, and sex specific. The sequence upstream of the basal promoter determines extragonadal LHR expression as well as the alternate splicing of its message. The promoter sequences directing LHR expression to fetal Leydig cells and ovary reside outside the 7.4-kb 5'-flanking region and remain to be identified.

A novel transgenic model to characterize the specific effects of follicle-stimulating hormone on gonadal physiology in the absence of luteinizing hormone actions

Gonadal function is wholly reliant on the two pituitary-derived gonadotropins, FSH and LH. Identifying the specific effects of FSH has been difficult because of the intimate relationship between LH and FSH action and inherent limitations of classic research paradigms. We describe a novel transgenic model to characterize the definitive actions of FSH alone, distinct from LH effects, created by combining transgenic FSH expression with the gonadotropin-deficient background of the hypogonadal (hpg) mouse. A tandem transgene construct encoding each alpha- and beta-subunit of human FSH, under the rat insulin II promoter, expressed biologically active heterodimers at serum levels, by immunoassay, equivalent to circulating FSH concentrations in fertile humans (0.1-25 IU/liter). Transgenic mice were crossed into the hpg mouse genotype to obtain LH-deficient animals secreting FSH alone. Testis weights of adult FSHxhpg mice were increased up to 5-fold, relative to nontransgenic hpg controls (P < 0.001). However, only transgenic males with serum FSH levels more than 1 IU/liter showed testis weights increased relative to hpg controls, indicating a physiological FSH threshold for the testicular response. Histology of enlarged FSHxhpg testes revealed round spermatids and sparse numbers of elongated spermatids, demonstrating that the testosterone-independent FSH response targeting the Sertoli cell can facilitate completion of meiosis and minimal initiation, but not completion, of spermiogenesis. Transgenic FSH also induced inhibin B secretion in FSHxhpg mice, but showed a distinct sexual dimorphism with only females exhibiting a strong FSH dose-dependent increase in serum inhibin B levels (r(2) = 0.84). In addition, ovaries of FSHxhpg females were enlarged up to 10-fold (P < 0.001), characterized by increased follicular recruitment and development to type 7 antral follicles. Thus, these findings show that the transgenic FSHxhpg mouse provides a unique model for detailed investigations of the definitive in vivo actions of FSH alone.

Altered structure and function of reproductive organs in transgenic male mice overexpressing human aromatase

Aromatization of androgens is a key step in estrogen production, and it regulates the delicate balance between estrogens and androgens in the gonads and sex steroid target tissues. In the present study, we generated transgenic mice (AROM(+)) bearing the human ubiquitin C promoter/human P450 aromatase fusion gene. AROM(+) male mice are characterized by an imbalance in sex hormone metabolism, resulting in elevated serum E(2) concentrations, combined with significantly reduced testosterone and FSH levels, and elevated levels of PRL and corticosterone. AROM(+) males present a multitude of severe structural and functional alterations in the reproductive organs, such as cryptorchidism associated with Leydig cell hyperplasia, dysmorphic seminiferous tubules, and disrupted spermatogenesis. The males also have small or rudimentary accessory sex glands with abnormal morphology; a prominent prostatic utricle with squamous epithelial metaplasia, and edema in the ejaculatory ducts and vas deferens. In addition, the abdominal muscle wall is thin, and the adrenal glands are enlarged, with cortical hyperplasia. Some of the abnormalities, such as undescended testes and undeveloped prostate, resemble those observed in animals exposed perinatally to high levels of exogenous estrogen, indicating that the elevated aromatase activity results in excessive estrogen exposure during early phases of development. Some of the disorders in the reproductive organs, furthermore, can be explained by the fact that AROM(+) males are hypoandrogenic, and have elevated levels of serum PRL and corticosterone. Thus, the AROM(+) mouse model provides a novel tool to investigate the consequences of a prolonged increase in conversion of androgens to estrogens which results in complex hormonal disturbances altering the structure and function of various male reproductive organs.

Evaluation of the 5'-flanking regions of murine glutathione peroxidase five and cysteine-rich secretory protein-1 genes for directing transgene expression in mouse epididymis

Based on strong epididymal expression of the mouse glutathione peroxidase 5 (GPX5) and cysteine-rich secretory protein-1 (CRISP-1) genes, we evaluated whether the 5.0-kilobase (kb)-long GPX5 and 3.8-kb-long CRISP-1 gene 5'-flanking regions could be used to target expression of genes of interest into the epididymis in transgenic mice. Of the two candidate promoters investigated, the CRISP-1 promoter-driven enhanced green fluorescent protein (EGFP) reporter gene was highly expressed in the tubular compartment of the testis in all stages of the seminiferous epithelial cycle between pachytene spermatocytes at stage VII to elongated spermatids at step 16. In contrast to CRISP-1, the 5.0-kb 5' region of the mouse GPX5 gene directed EGFP expression to the epididymis. In the various GPX5-EGFP mouse lines, strongest expression of EGFP mRNA was found in the epididymis, but low levels of reporter gene mRNA were detected in several other tissues. Strong EGFP fluorescence was found in the principal cells of the distal caput region of epididymis, and few fluorescent cells were also detected in the cauda region. No EGFP fluorescence was detected in the corpus region or in the other tissues analyzed. Hence, it is evident that the 5.0-kb 5'-flanking region of GPX5 promoter is suitable for directing the expression of structural genes of interest into the caput epididymidis in transgenic mice.

Normal prenatal but arrested postnatal sexual development of luteinizing hormone receptor knockout (LuRKO) mice

To study further the role of gonadotropins in reproductive functions, we generated mice with LH receptor (LHR) knockout (LuRKO) by inactivating, through homologous recombination, exon 11 on the LHR gene. LuRKO males and females were born phenotypically normal, with testes, ovaries, and genital structures indistinguishable from their wild-type (WT) littermates. Postnatally, testicular growth and descent, and external genital and accessory sex organ maturation, were blocked in LuRKO males, and their spermatogenesis was arrested at the round spermatid stage. The number and size of Leydig cells were dramatically reduced. LuRKO females also displayed underdeveloped external genitalia and uteri postnatally, and their age of vaginal opening was delayed by 5-7 days. The (-/-) ovaries were smaller, and histological analysis revealed follicles up to the early antral stage, but no preovulatory follicles or corpora lutea. Reduced gonadal sex hormone production was found in each sex, as was also reflected by the suppressed accessory sex organ weights and elevated gonadotropin levels. Completion of meiosis of testicular germ cells in the LuRKO males differs from other hypogonadotropic/cryptorchid mouse models, suggesting a role for FSH in this process. In females, FSH appears to stimulate developing follicles from the preantral to early antral stage, and LH is the stimulus beyond this stage. Hence, in each sex, the intrauterine sex differentiation is independent of LH action, but it has a crucial role postnatally for attaining sexual maturity. The LuRKO mouse is a close phenocopy of recently characterized human patients with inactivating LHR mutations, although the lack of pseudohermaphroditism in LuRKO males suggests that the intrauterine sex differentiation in this species is not dependent on LH action.

Use of matrix-assisted laser desorption/ionization time-of-flight mass mapping and nanospray liquid chromatography/electrospray ionization tandem mass spectrometry sequence tag analysis for high sensitivity identification of yeast proteins separated by two-dimensional gel electrophoresis

Current analytical techniques in protein identification by mass spectrometry are based on the generation of peptide mass maps or sequence tags that are idiotypic for the protein sequence. This work reports on the development of the use of mass spectrometric methods for protein identification in research on metabolic pathways of a genetically modified strain of the baker's yeast Saccharomyces cerevisiae. This study describes the use of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass mapping and liquid chromatography/quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS/MS) sequence tag analysis in identification of yeast proteins separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The spots were selected for analysis in order to collect information for future studies, to cover the whole pI range from 3 to 10, and to evaluate information from spots of different intensities. Mass mapping as a rapid, high-throughput method was in most cases sensitive enough for identification. LC/MS/MS was found to be more sensitive and to provide more accurate data, and was very useful when analyzing small amounts of sample. Even one sequence tag acquired by this method could be enough for unambiguous identification, and, in the present case, successfully identified a point mutation.

Activin-A, but not inhibin, regulates 17beta-hydroxysteroid dehydrogenase type 1 activity and expression in cultured rat granulosa cells

17beta-Hydroxysteroid dehydrogenase type 1 (17HSD type 1) catalyzes the reduction of estrone (E(1)) to biologically more active estradiol (E(2)). In the present study, the effect of activin, inhibin, and follistatin on 17HSD activity and 17HSD type 1 expression in cultured, unluteinized rat granulosa cells was examined. Furthermore, the effects of these hormones on 17HSD type 1 expression were compared with the expression of P450 aromatase (P450arom). Rat granulosa cells were pre-incubated in serum-free media for 3 days, followed by a 2-day treatment with activin, inhibin, follistatin and 8-Br-cAMP. Activin in increasing concentrations appeared to effect a dose-dependent increase in 17HSD activity. In addition, increasing concentrations of activin also increased 17HSD type 1 mRNA expression. Addition of 8-Br-cAMP at concentrations of 0.25 and 1.5 mmol/l together with activin significantly augmented the stimulatory effects of activin alone in the cultured cells. Neither inhibin, nor follistatin, either alone or in combination with 8-Br-cAMP, had any notable effects on 17HSD activity and 17HSD type 1 expression. Preincubation of activin with increasing concentrations of follistatin significantly diminished the stimulatory effect of activin. In the presence of follistatin, activin did not significantly increase the 8-Br-cAMP-induced 17HSD activity and 17HSD type 1 expression. The culturing of granulosa cells in the presence or the absence of inhibin or follistatin with or without 8-Br-cAMP did not alter the effect of these peptides on P450arom expression in rat granulosa cells as judged by Northern blot analysis of total RNA. However, cAMP-induced P450arom expression was enhanced by activin treatment, except when follistatin was present. This is in line with the suggested role of follistatin as an activin-binding protein, which limits the bioavailability of activin to its membrane receptors. Thus, the results support the notion of a paracrine/autocrine role of activin in follicular steroidogenesis of growing follicles.

A common polymorphism in the human relaxin-like factor (RLF) gene: no relationship with cryptorchidism

The incidence of impaired testicular descent (cryptorchidism) is high; 1-2% of boys at the age of 3 mo are diagnosed for this condition in western countries. Recent data on mice with targeted disruption of the Insl3/relaxin-like factor (RLF) gene proposed that this factor plays a role in testicular descent in fetal life. Male RLF-/- mice exhibit bilateral cryptorchidism due to developmental abnormalities of the gubernaculum, associated with abnormal spermatogenesis and infertility. In the present study, we have sequenced the promoter region and both exons of the RLF gene in a cohort of 30 boys, seven of whom presented with a possible familial form of cryptorchidism and 23 with sporadic cryptorchidism. One of the nucleotide substitutions detected, G to A at position 178, predicted amino acid change. The mutation was localized to the C-peptide region, resulting in an alanine to threonine change and therefore classified as a conservative mutation. Four of the 30 cases analyzed were homozygous (13%), and 15 were heterozygous for the mutation (50%). However, the same mutation was also found in a control group of 89 men; 10% of them were homozygous, and 39% were heterozygous. Our results indicate that mutations in the RLF gene are not a common reason for cryptorchidism and that the common G178A polymorphism has no apparent relationship with this condition.

Elevated luteinizing hormone induces expression of its receptor and promotes steroidogenesis in the adrenal cortex

Transgenic (TG) female mice expressing bLHbeta-CTP (a chimeric protein derived from the beta-subunit of bovine luteinizing hormone [LH] and a fragment of the beta-subunit of human chorionic gonadotropin [hCG]) exhibit elevated serum LH, infertility, polycystic ovaries, and ovarian tumors. In humans, increased LH secretion also occurs in infertility and polycystic ovarian syndrome, often concomitant with adrenocortical dysfunction. We therefore investigated adrenal function in LH overexpressing bLHbeta-CTP female mice. The size of their adrenals was increased by 80% with histological signs of cortical stimulation. Furthermore, adrenal steroid production was increased, with up to 14-fold elevated serum corticosterone. Primary adrenal cells from TG and control females responded similarly to ACTH stimulation, but, surprisingly, the TG adrenals responded to hCG with significantly increased cAMP, progesterone, and corticosterone production. LH receptor (LHR) expression and activity were also elevated in adrenals from female TG mice, but gonadectomized TG females showed no increase in corticosterone, suggesting that the dysfunctional ovaries of the intact TG females promote adrenocortical hyperfunction. We suggest that, in intact TG females, enhanced ovarian estrogen synthesis causes increased secretion of prolactin (PRL), which elevates LHR expression. Chronically elevated serum LH, augmented by enhanced PRL production, induces functional LHR expression in mouse adrenal cortex, leading to elevated, LH-dependent, corticosterone production. Thus, besides polycystic ovaries, the bLHbeta-CTP mice provide a useful model for studying human disorders related to elevated LH secretion and adrenocortical hyperfunction.

Analysis of residual solvents in pharmaceuticals with purge-and-membrane mass spectrometry

A method using purge-and-membrane mass spectrometry (PAM-MS) was developed for the analysis of residual solvents in pharmaceutical products. The method combines dynamic headspace and membrane inlet mass spectrometry. The limits of detection for the compounds studied, benzene, toluene, chloroform, 2-pentene and 2-methyl- and 3-methylpentane, were 0.05-0.1 mg/kg. In quantitative analysis the method showed good linearity (r(2) > 0.998) and acceptable within-day (RSD = 7.9-18%) and between-day (RSD = 6.8-10%) repeatability. The PAM-MS method combined with the custom-made Solver program was compared with a method using purge-and-trap gas chromatography/mass spectrometry (P&T-GC/MS) for identification of residual solvents from authentic samples. The results showed that PAM-MS/Solver provides reliable identification of the main volatile organic compounds (VOCs) in the pharmaceuticals, but VOCs with low concentrations (below 0.5 mg/kg) were better identified by P&T-GC/MS. Other advantages of the PAM-MS method were short analysis times and non-requirement for pre-treatment of samples.

Age- and sex-specific promoter function of a 2-kilobase 5'-flanking sequence of the murine luteinizing hormone receptor gene in transgenic mice

A transgenic (TG) mouse model carrying a 2-kb murine LH receptor (LHR) promoter/beta-galactosidase (beta-GAL) fusion gene was created to study the regulatory function of the 5'-flanking region of the murine LHR gene. Of the five TG mouse lines produced, three displayed high beta-GAL expression in the testis, but none showed any expression in the ovary. In addition, all mouse lines of both sexes expressed beta-GAL consistently in the brain, most prominently in hippocampus, hypothalamus, midbrain, and cortex. Weak staining was found in a few pituitary samples. All other tissues examined were negative for transgene expression. In support of sex-specific gonadal expression of the transgene, transient transfection of the LHR/beta-GAL gene construct into immortalized mouse granulosa (KK-1) and Leydig (mLTC-1) tumor cells revealed a more than 5-fold higher expression level in the Leydig cells. Histological examination of the TG testes demonstrated strong beta-GAL expression in Leydig cells, but, unexpectedly, also in elongating spermatids of adult age and in some spermatogonia of the neonatal testis. The functional significance of the latter findings remains open. The transgene was only expressed in adult Leydig cells; no expression was found in the fetal population of these cells. Hence, these findings indicate that the immediate 2-kb fragment of the murine LHR 5'-flanking sequence is transcriptionally active only in adult Leydig cells and certain brain areas, but other promoter sequences are apparently needed for ovarian and fetal testicular expression of the LHR gene.

17Beta-hydroxysteroid dehydrogenases in normal human mammary epithelial cells and breast tissue

17Beta-hydroxysteroid dehydrogenase activity represents a group of several isoenzymes (17HSDs) that catalyze the interconversion between highly active 17beta-hydroxy- and low activity 17-ketosteroids and thereby regulate the biological activity of sex steroids. The present study was carried out to characterize the expression of 17HSD isoenzymes in human mammary epithelial cells and breast tissue. In normal breast tissues 17HSD types 1 and 2 mRNAs were both evenly expressed in glandular epithelium. In two human mammary epithelial cell lines, mRNAs for 17HSD types 1, 2 and 4 were detected. In enzyme activity measurements only oxidative 17HSD activity, corresponding to either type 2 or type 4 enzyme, was present. The role of 17HSD type 4 in estrogen metabolism was further investigated, using several cell lines originating from various tissues. No correlation between the presence of 17HSD type 4 mRNA and 17HSD activity in different cultured cell lines was detected. Instead, oxidative 17HSD activity appeared in cell lines where 17HSD type 2 was expressed and reductive 17HSD activity was present in cells expressing 17HSD type 1. These data strongly suggest that in mammary epithelial cell lines the oxidative activity is due to type 2 17HSD and that oxidation of 17beta-hydroxysteroids is not the primary activity of the 17HSD type 4 enzyme.

17Beta-hydroxysteroid dehydrogenase type 1 in normal breast tissue during the menstrual cycle and hormonal contraception

Our purpose was to assess 17beta-hydroxysteroid dehydrogenase (17HSD) type 1 protein expression in normal breast tissue during the menstrual cycle and hormonal contraception. We analyzed 17HSD type 1 protein expression by immunohistochemistry during the regular menstrual cycle (n = 12) and hormonal contraception (n = 7) in women undergoing reduction mammoplasty. 17HSD type 1 protein was detected in normal breast epithelial cells throughout the menstrual cycle and in all women using hormonal contraception. Mean 17HSD type 1 staining intensity was higher in alveolar epithelial cells in women using hormonal contraception (2.14) than in untreated women (1.25; P < 0.04). For ducts, this difference approached significance (2.29 vs. 1.41; P = 0.06). There was a negative correlation between serum estradiol (E2) levels and 17HSD type 1 protein expression for both alveolar (r(s) = -0.68; P = 0.004) and ductal (r(s) = -0.75; P = 0.002) breast epithelial cells. Enhanced 17HSD type 1 protein expression might increase the conversion to E2 in normal breast tissue during hormonal contraception. The negative correlation between serum E2 levels and 17HSD type 1 suggests this enzyme to be one of the regulatory mechanisms of intratissue E2 concentration in normal breast tissue.

Inhibition of 17beta-hydroxysteroid oxidoreductase by flavonoids in breast and prostate cancer cells

Several flavonoids and isoflavonoids were found to inhibit 17beta-oxidoreduction of estrogens by the purified 17beta-HSOR type 1, or in cell lines expressing 17beta-HSOR type 1 enzyme (T-47D breast cancer cells) or type 2 (PC-3 prostate cancer cells). The structural demands for the inhibition of estrone (E1) reduction and estradiol (E2) oxidation catalyzed by 17beta-HSOR types 1 and 2, respectively, were not identical. Flavones, flavanones, and isoflavones hydroxylated at both the double ring (positions 5 and 7) and ring B (position 4') were the most potent inhibitors of E1 reduction in T-47D cells, and by the purified type 1 enzyme whereas flavones hydroxylated at positions 3, 5, and 7 of rings A and C, with or without a hydroxyl group in ring B, were capable of inhibiting E2 oxidation in PC-3 cells. Change to flavanone structure, or hydroxylation at position 3 of ring C of flavones, or methylation of the hydroxyl group at position 4' of ring B of flavones and isoflavones reduced or abolished their inhibitory activity on E1 reduction in T-47D cells. On the contrary, hydroxyl group at position 3 of flavones (flavonol structure) markedly increased the inhibition of E2 oxidation in PC-3 cells. Thus, changes in the number and location of hydroxyl groups may discriminate inhibition of E1 reduction and E2 oxidation. Some of the differences may be due to differences in pharmacokinetics of these compounds in T-47D and PC-3 cells. Inhibition of 17beta-HSORs could lead to an alteration in the availability of the highly active endogenous estrogen, but the effects of these compounds in vivo cannot be predicted on the basis of these results alone. Some of these compounds (isoflavones) are estrogenic per se, and they may replace endogenous estrogens, whereas flavones are only very weakly estrogenic or nonestrogenic. Regarding prevention or treatment of estrogen-related diseases, apigenin, coumestrol, and genistein raise special interest.

Characterization of rat 17 beta-hydroxysteroid dehydrogenase type 1 gene and mRNA transcripts

In the present study, the gene encoding rat 17 beta-hydroxysteroid dehydrogenase type 1 (rHSD17B1 gene) was cloned and characterized. Like the analogous human gene (hHSD17B1), rHSD17B1 contains six exons and five introns spanning approximately 2.2 kb. The identity between the exons and introns of the two genes ranges from 58% to 82% and 42% to 57%, respectively. In contrast to hHSD17B1, rHSD17B1 is not duplicated. The cap site for rHSD17B1 was localized to position -41 upstream of the ATG translation initiation codon. Sequence comparison of the first 200 bp upstream of the cap site showed 72% identity between the human and rat HSD17B1 genes, including a conserved GC-rich area. Further upstream, no significant identity between the two genes was observed and several, cis-acting elements known to modulate the expression of hHSD17B1 are not conserved in the rat gene. Rat HSD17B1 unlike hHSD17B1 with two cap sites, possesses two polyadenylation signals, thus resulting in two mRNAs.

Growth factors and phorbol-12-myristate-13-acetate modulate the follicle-stimulating hormone- and cyclic adenosine-3',5'-monophosphate-dependent regulation of 17beta-hydroxysteroid dehydrogenase type 1 expression in rat granulosa cells

In the present study primary cultures of rat granulosa cells obtained from diethylstilbestrol (DES)-primed immature rats were used to study the regulation of 17beta-hydroxysteroid dehydrogenase (17HSD) activity and type 1 expression via protein kinase A (PKA)- and C (PKC)-dependent pathways, and by several autocrine and/or paracrine growth factors. Follicle-stimulating hormone (FSH), 8-bromo-cyclic adenosine-3',5'-monophosphate (8-Br-cAMP) and transforming growth factor beta1 (TGFbeta1) strongly enhanced 17HSD activity and type 1 expression. The stimulatory effects of FSH and 8-Br-cAMP were further potentiated by TGFbeta1. In contrast, neither phorbol-12-myristate-13-acetate (PMA), epidermal growth factor (EGF), transforming growth factor alpha (TGFalpha) nor fibroblast growth factor (bFGF) affected 17HSD activity or type 1 expression when given alone. However, they effectively neutralized the stimulatory effects of 8-Br-cAMP and FSH. The present data suggest that, in rat granulosa cells 17HSD type 1 expression is primarily induced by FSH acting via PKA-dependent pathway and the extent of the induction is modulated by PKC-dependent inhibition and autocrine/paracrine growth factors present in the ovary.