Mapping of the HSD17B2 gene encoding type II 17 beta-hydroxysteroid dehydrogenase close to D16S422 on chromosome 16q24.1-q24.2

Genome-wide analyses identify 21 infertility loci and over 400 reproductive hormone loci across the allele frequency spectrum

Genome-wide association studies (GWASs) may help inform treatments for infertility, whose causes remain unknown in many cases. Here we present GWAS meta-analyses across six cohorts for male and female infertility in up to 41,200 cases and 687,005 controls. We identified 21 genetic risk loci for infertility (P≤5E-08), of which 12 have not been reported for any reproductive condition. We found positive genetic correlations between endometriosis and all-cause female infertility (rg=0.585, P=8.98E-14), and between polycystic ovary syndrome and anovulatory infertility (rg=0.403, P=2.16E-03). The evolutionary persistence of female infertility-risk alleles in EBAG9 may be explained by recent directional selection. We additionally identified up to 269 genetic loci associated with follicle-stimulating hormone (FSH), luteinising hormone, oestradiol, and testosterone through sex-specific GWAS meta-analyses (N=6,095-246,862). While hormone-associated variants near FSHB and ARL14EP colocalised with signals for anovulatory infertility, we found no rg between female infertility and reproductive hormones (P>0.05). Exome sequencing analyses in the UK Biobank (N=197,340) revealed that women carrying testosterone-lowering rare variants in GPC2 were at higher risk of infertility (OR=2.63, P=1.25E-03). Taken together, our results suggest that while individual genes associated with hormone regulation may be relevant for fertility, there is limited genetic evidence for correlation between reproductive hormones and infertility at the population level. We provide the first comprehensive view of the genetic architecture of infertility across multiple diagnostic criteria in men and women, and characterise its relationship to other health conditions.

Retinoic acid (RA) regulates 17beta-hydroxysteroid dehydrogenase type 2 expression in endometrium: interaction of RA receptors with specificity protein (SP) 1/SP3 for estradiol metabolism

CONTEXT

The enzyme 17beta-hydroxysteroid dehydrogenase type 2 (HSD17B2) exerts a local antiestrogenic effect by metabolizing biologically active estradiol to inactive estrone in endometrial epithelial cells. Retinoic acid (RA) induces HSD17B2 expression, but the underlying mechanism is not known.

OBJECTIVE

Our objective was to elucidate the molecular mechanisms responsible for HSD17B2 expression in human endometrial cells.

METHOD

Human endometrial Ishikawa and RL95-2 cell lines were cultured in the presence or absence of RA to analyze endogenous HSD17B2 expression, transcription factor complex formation, and promoter activity.

RESULTS

RA induced HSD17B2 mRNA levels in a dose- and time-dependent manner in endometrial cells. The RA antagonist ANG11273 abolished RA-induced HSD17B2 expression. Small interfering RNA ablation of RA receptor (RAR)alpha or retinoid X receptor (RXR)alpha completely blocked RA-induced HSD17B2 gene expression. Analysis of serial deletion and site-directed mutants of the HSD17B2 promoter fused to a reporter gene indicated that RA induction requires a cis-regulatory sequence that binds the specificity protein (SP) class of transcription factors. Chromatin-immunoprecipitation-PCR and gel-shift assays showed that RARalpha/RXRalpha and SP1/SP3 interact with this HSD17B2 promoter sequence. Small interfering RNA ablation of SP1 and SP3 expression markedly decreased HSD17B2 basal expression and blocked RA-induced expression. Finally, immunoprecipitationimmunoblotting demonstrated RA-induced interactions between RARalpha/RXRalpha and SP1/SP3 in intact endometrial cells.

CONCLUSIONS

In endometrial epithelial cells, RA stimulates formation of a multimeric complex comprised of RARalpha/RXRalpha tethered to transcription factors SP1 and SP3 on the HSD17B2 promoter. Assembly of this transcriptional complex is necessary for RA induction of HSD17B2 expression and may be an important mechanism for local estradiol inactivation in the endometrium.

Loss of heterozygosity in chromosomal region 16q24.3 associated with progression of prostate cancer

BACKGROUND

The molecular mechanisms underlying the development and progression of prostate cancer have remained poorly understood. To find out potential genetic markers likely to underlie tumor progression, the pattern of allelic loss on chromosome arm 16q in matched primary, locally recurrent, and metastatic prostate cancer specimens was analyzed in the present study.

METHODS

The frequency of loss of heterozygosity (LOH) in 74 tumor specimens (62 primary cancer foci and 12 metastatic tumors) collected from 33 prostate cancer patients was determined by fragment analysis using 17 polymorphic microsatellite markers.

RESULTS

The overall frequency of patients showing allelic loss at one or more loci on 16q was 68% (21/31) in primary tumors and 90% (28/31) in recurrent tumors. Of the individual markers, D16S520, locating in region 16q24.3, exhibited a statistically significant development of LOH during disease recurrence (P < 0.01). Regarding distant metastases, instead, there seemed to be no allelic loss events exclusively typical of metastatic tumors at 16q.

CONCLUSIONS

The data suggest the location of gene(s) related to prostate cancer progression at 16q24.3.

Postmenopausal serum androstenedione levels are associated with the calcitonin receptor gene polymorphism T1377c. A pilot study

We tested the hypothesis that homeostasis of sex-steroids is related to the calcitonin receptor (CALCR) genotype. To determine the CALCR genotype PCR amplification followed by digestion with Alul restriction enzyme were carried out according to Nakamura et al. Indeed, a single nucleotide difference at position 1377 of cDNA generates two alleles (CC genotype or TT genotype). Serum estradiol, testosterone and their precursors androstendione (AD) and DHEA levels were estimated in a cohort of 113 postmenopausal women. While serum DHEA levels did not differ between the individual allele combinations, AD levels as well as AD/DHEA ratio were higher in carriers of TC and CC genotypes than those with TT genotype (p<0.05 and p<0.02, respectively, ANCOVA). We postulate that the 3beta-hydroxysteroid dehydrogenase activity is associated with C allele at least in C19 steroids. The data correspond with the functionality of CALCR.

Inhibitors of type II 17beta-hydroxysteroid dehydrogenase

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) are involved in the last step of the biosynthesis of sex steroids from cholesterol. This family of steroidogenic enzymes constitutes an interesting target in the control of the concentration of estrogens and androgens. Among the isoforms of 17beta-HSD, type II preferentially catalyzes the oxidation of estradiol (E(2)), testosterone (T), dihydrotestosterone (DHT), and 20alpha-dihydroprogesterone (20alpha-DHP). Based on structure-activity relationship studies, we have developed steroidal spirolactones as inhibitors of type II 17beta-HSD using different steroid nuclei: a C18-steroid (lactones 1 and 10), an antiestrogenic nucleus (lactone 2), and a C19-steroid (lactone 28). We know these inhibitors are selective for type II 17beta-HSD as no or only weak inhibition was observed for types I and III. They also have no proliferative (androgenic) activity on androgen sensitive (AR(+)) Shionogi cells whereas their proliferative (estrogenic) activity on estrogen sensitive (ER(+)) ZR-75-1 cells depends on the nature of the steroid nucleus. Lactones 1 and 10 are weak estrogens, while lactones 2 and 28 do not exert estrogenic activity, in fact lactone 2 is an antiestrogen. Lactones 1, 2, 10 and 28 were also tested in an identical assay with a series of enzyme substrates, C19-steroid diols, and known inhibitors, for the oxidation of testosterone and estradiol into androstenedione and estrone, respectively. From this comparative study, the best inhibitors of type II 17beta-HSD (oxidase activity) were identified, but none of them were clearly more potent than the hydroxylated (reduced) forms of enzyme substrates, E2, T, and DHT. Such inhibitors remain, however, useful tools to, (1) further elucidate the role of type II 17beta-HSD, and (2) regulate the level of active estrogens, androgens and progesterone.

Structure and activity of the murine type 5 17beta-hydroxysteroid dehydrogenase gene(1)

17beta-Hydroxysteroid dehydrogenases (17beta-HSDs) play a crucial role in the control of active sex steroid intracellular levels. Seven types of 17beta-HSD have been described. In this study, we report the cloning and characterization of the mouse type 5 17beta-HSD belonging to the aldo-keto reductase superfamily, in contrast with types 1, 2, 3, 4, 6, and 7 17beta-HSD which belong to the short-chain alcohol dehydrogenase family. The gene spans 16 kb and contains 9 exons separated by 8 introns. Primer extension analysis identified a major transcription start site beginning 50 nucleotides upstream from the ATG initiation codon. Northern blot analysis showed a high mRNA expression level in the liver and a weaker signal in the kidney. To determine more precisely the substrate specificity of the enzyme, we established a stable cell line expressing mouse type 5 17beta-HSD in transformed human embryonic kidney (293) cells. The transfected cell line preferentially catalyzes the transformation of 4-androstenedione (4-dione) and androstanedione (A-dione) into testosterone (T) and dihydrotestosterone (DHT), respectively. This data is somewhat in contradiction with a previous study that described the enzyme as estradiol 17beta-dehydrogenase. Our results indicate that the rate of transformation of estradiol (E(2)) to estrone (E(1)) represents only 1% of the rate of transformation of 4-dione to T. Mouse type 5 17beta-HSD shares 76% amino acid sequence identity with human type 5 17beta-HSD; 71%, 76%, 76% with rat 3alpha-HSD and human types 1 and 3 3alpha-HSDs, respectively; and 71%, 69% and 77% with mouse, rat and human 20alpha-HSD, respectively.

Fine mapping of low-density lipoprotein receptor gene by genetic linkage on chromosome 19p13.1-p13.3 and study of the founder effect of four French Canadian low-density lipoprotein receptor gene mutations

Familial hypercholesterolemia (FH) is one of the most common autosomal codominant diseases. FH is caused by mutations in the low-density lipoprotein receptor (LDLR) gene and is characterized by raised plasma LDL-cholesterol, tendon xanthomas, and premature coronary heart disease. The frequency of FH among French Canadians in northeastern Quebec is higher than in most other populations, 1:154 vs. 1:500 due to high prevalence of few recurrent mutations in the LDLR gene. In the French Canadian population, 11 mutations in the LDLR gene have been found to occur in geographically diverse areas and account for > 90% of cases. We have first constructed a high-resolution genetic map to locate several highly polymorphic markers close to LDLR locus, thus providing the necessary tools to study the origin of the four most common mutations which account for approximately 80% of our FH patients. We have then genotyped five markers (D19S413, D19S865, D19S221, D19S914, D19S586) in 102 heterozygotes (38 del > 15kb; 36 W66G; 16 C646Y; 12 E207K), two compound heterozygotes (del > 15kb/W66G; del > 15kb/C646Y) and seven homozygotes (three del > 15 kb; three W66G: one E207K) with FH unrelated to the first and second degree. We have found that patients bearing the same LDLR gene mutation carry a common haplotype at the LDLR locus although there is evidence for the early occurrence of a recombinational event between the LDLR and the D19S221 locus in the French Canadian patients bearing the W66G mutation. The fine mapping of LDLR gene close to several highly informative microsatellite markers provide fine mapping details of the LDLR region and additional tools for studies of association between plasma lipoprotein levels and LDLR gene.

Three independently deleted regions at chromosome arm 16q in human prostate cancer: allelic loss at 16q24.1-q24.2 is associated with aggressive behaviour of the disease, recurrent growth, poor differentiation of the tumour and poor prognosis for the patient

Loss of heterozygosity at chromosome arm 16q is a frequent event in human prostate cancer. In this study, loss of heterozygosity at 16q was studied in 44 prostate cancer patients exhibiting various clinical features. Fifteen polymorphic polymerase chain reaction (PCR) markers were used to identify the separately deleted areas and the findings were compared with clinicopathological variables and 5-year survival of the patients. The results indicated that there are at least three independently deleted regions at 16q. Allelic losses at the central and distal areas were associated significantly with aggressive behaviour of the disease (16q24.1-q24.2, P < 0.01, and 16q24.3-qter, P < 0.05), and the central area of deletion was further significantly associated with poorly differentiated tumour cells (P < 0.05) and with recurrent (P < 0.01) growth of the tumour. During the follow-up period, 28% of the patients initially with M0 disease developed distant metastases. Of the patients showing allelic loss at 16q24.1-q24.2, distant metastasis were found in 45% during the 5-year follow-up period, and 31% of the patients showing loss at 16q21.1 also developed distant metastases. After the 5-year follow-up period, 14 (32%) of the patients remained alive, whereas 19 (43%) had died because of their prostate cancer. The overall survival rate of the patients showing allelic loss at 16q21.1 or 16q24.1-q24.2 was significantly lower than that of the patients with retained heterozygosity.

17beta-hydroxysteroid dehydrogenases: physiological roles in health and disease

Androgens and estrogens play crucial roles in the growth and development of sex organs. Interconversion of these hormones between biologically active and inactive forms is catalyzed by 17beta-hydroxysteroid dehydrogenase (17beta-HSD) isozymes. Aberrations in the regulation or expression of the various 17beta-HSD isoforms has been implicated in the genesis/progression of hormonally dependent cancers of various tissues, including ovary, breast and prostate; in the predisposition of women with upper body obesity to several types of diseases, such as non-insulin dependent diabetes mellitus; and in the abnormal development of sexually ambiguous individuals, as seen in 17beta-HSD-deficient male pseudohermaphrodites. Of the five known 17beta-HSD isozymes, deleterious mutations in the type 3 isoform were found to give rise to male pseudohermaphroditism. The 16 mutations characterized to date include 12 missense mutations, three splice junction mutations, and one small deletion that results in a downstream premature stop codon. 17beta-HSD has also been studied in other species. The most notable species difference observed is the placental expression in humans of the 17beta-HSD type 1 isoform.

Characterization and regulation of UDP-glucuronosyltransferases in steroid target tissues

Conjugation of compounds by glucuronidation is a pathway found in all vertebrates studied to date. Although, it is widely recognized that the liver is a major site of glucuronidation, it is now clear that extrahepatic tissues are also involved in the conjugation of compounds to which these tissues are exposed. High levels of androsterone glucuronide and androstane-3alpha,17beta-diol glucuronide found in the human prostate, breast cyst fluid and ovary follicular fluid suggest that glucuronidation of 5alpha-reduced C19 steroids occurs in these tissues. Recently, we have reported the tissue distribution of UGT2B15, which can conjugate steroids in several human extrahepatic steroid target tissues including the skin, breast and prostate. We have also isolated a new UGT2B cDNA encoding UGT2B17, that conjugates ADT which is the major 5alpha-reduced C19 steroid glucuronide in the circulation of humans. UGT2B17 is also widely distributed in several human steroid target tissues. This gene was mapped to human chromosome 4q13 and has an exon/intron structure similar to that of rat UGT2B1 and UGT2B2. Both UGT2B15 and UGT2B17, which are able to catalyze the glucuronidation of DHT, are expressed in LNCaP cells. Interestingly, glucuronidation of steroids is markedly regulated by several factors including androgens and growth factors. Treatment of LNCaP cells with dihydrotestosterone (DHT) and epidermal growth factor (EGF) caused a decrease of DHT glucuronidation and UGT2B mRNA levels. RNase protection assays showed a specific decrease of UGT2B17 transcript in LNCaP cells treated with DHT and EGF however, the level of UGT2B15 mRNA was not affected. As well, Western blot analysis demonstrated a diminution of UGT2B17 protein level in response to DHT and EGF. These results demonstrate a differential regulation of different isoforms of steroid conjugating UGTs present in human prostate LNCaP cells. In addition, UGT2B17 was shown to be more labile than UGT2B15 indicating that regulation of UGT2B17 expression would lead to a more rapid change in the level of glucuronidated steroids. Expression of exogenous UGT2B17 in LNCaP cells by gene transfer led to a significant decrease in the androgen response. This result indicates the ability of UGT enzymes to regulate the androgen response by conjugating androgens which abolishes their interaction with their receptor and facilitates their clearance from the cell. The glucuronidation of steroids by UGT enzymes is an important mechanism by which the levels of steroids is regulated in steroid target tissues.

Regulation of sex steroid formation by interleukin-4 and interleukin-6 in breast cancer cells

Sex steroids play a predominant role in the development and differentiation of normal mammary gland as well as in the regulation of hormone-sensitive breast cancer growth. There is evidence suggesting that local intracrine formation of sex steroids from inactive precursors secreted by the adrenals namely, dehydroepiandrosterone (DHEA) and 4-androstenedione (4-dione) play an important role in the regulation of growth and function of peripheral target tissues, including the breast. Moreover, human breast carcinomas are often infiltrated by stromal/immune cells secreting a wide spectra of cytokines. These might in turn regulate the activity of both immune and neoplastic cells. The present study was designed to examine the action of cytokines on 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) activities in human breast cancer cells. The various types of human 17beta-HSD (five types) and 3beta-HSD (two types), because of their tissue- and cell-specific expression and substrate specificity, provide each cell with necessary mechanisms to control the level of intracellular active androgens and estrogens. We first investigated the effect of exposure to IL-4 and IL-6 on reductive and oxidative 17beta-HSD activities in both intact ZR-75-1 and T-47D human breast cancer cells. In ZR-75-1 cells, a 6 d exposure to IL-4 and IL-6 decreased E2-induced cell proliferation, the half maximal inhibitory effect being exerted at 88 and 26 pM, respectively. In parallel, incubation with IL-4 and IL-6 increased oxidative 17beta-HSD activity by 4.4- and 1.9-fold, respectively, this potent activity being observed at EC50 values of 22.8 and 11.3 pM, respectively. Simultaneously, reductive 17beta-HSD activity leading to E2 formation was decreased by 70 and 40% by IL-4 and IL-6, respectively. Moreover, IL-4 and IL-6 exerted the same regulatory effects on 17beta-HSD activities when testosterone and 4-dione were used as substrates, thus strongly suggesting the expression of the type 2 17beta-HSD ZR-75-1 cells. In contrast, in T-47D cells, IL-4 increased the formation of E2, whereas IL-6 exerts no effect on this parameter. However, we found that T-47D cells failed to convert testosterone efficiently into 4-DIONE, thus suggesting that there is little or no expression of type 2 17beta-HSD in this cell line. The present findings demonstrate that the potent regulatory effects of IL-4 and IL-6 on 17beta-HSD activities depend on the cell-specific gene expression of various types of 17beta-HSD enzymes. We have also studied the effect of cytokines on the regulation of the 3beta-HSD expression in both ZR-75-1 and T-47D human breast cancer cells. Under basal culture conditions, there is no 3beta-HSD activity detectable in these cells. However, exposure to IL-4 caused a rapid and potent induction of 3beta-HSD activity, whereas IL-6 failed to induce 3beta-HSD expression. Our data thus demonstrate that cytokines may play a crucial role in sex steroid biosynthesis from inactive adrenal precursors in human breast cancer cells.

The key role of 17 beta-hydroxysteroid dehydrogenases in sex steroid biology

17 beta-Hydroxysteroid dehydrogenase (17 beta-HSD) controls the last step in the formation of all androgens and all estrogens. This crucial role of 17 beta-HSD is performed by at least five 17 beta-HSD isoenzymes having individual cell-specific expression, substrate specificity, regulation mechanisms, and reductive or oxidative catalytic activity. Both estrogenic and androgenic 17 beta-HSD activities were found in all 25 rhesus monkey and 15 human peripheral intracrine tissues examined. Type 1 17 beta-HSD is a protein of 327 amino acids catalyzing the formation of 17 beta-estradiol from estrone. Its x-ray structure was the first to be determined among mammalian steroidogenic enzymes. Initially crystallized with NAD, the crystal structure of type 1 17 beta-HSD has just been determined as a complex with 17 beta-estradiol, thereby illustrating the conformation of the substrate-binding site. Type 2 17 beta-HSD degrades 17 beta-estradiol into estrone and testosterone into androstenedione, and type 4 17 beta-HSD mainly degrades 17 beta-estradiol into estrone and androst-5-ene-3 beta, 17 beta-diol into dehydroepiandrosterone. Types 3 and 5 17 beta-HSD, on the other hand, catalyze the formation of testosterone from androstenedione in the testis and peripheral tissues, respectively. The various types of human 17 beta-HSD, because of their tissue-specific expression and substrate specificity, provide each peripheral cell with the necessary mechanisms to control the level of intracellular androgens and/or estrogens, a new area of hormonal control that we call intracrinology.

Localization of a breast cancer tumour-suppressor gene to a 3-cM interval within chromosomal region 16q22

Allelic losses on chromosome 16q in tumour cells are frequent in a variety of malignancies, suggesting the presence of one or more tumour-suppressor genes in the region. Among 210 sporadic breast cancers we examined using 15 microsatellite markers on the long arm of chromosome 16, heterozygosity for at least one locus was lost in 141 (67%). Detailed deletion mapping revealed two distinct commonly deleted regions. One region was defined as a 3-cM interval flanked by markers D16S512 and D16S515 at 16q22; the second consisted of a 9.5-cM interval flanked by markers D16S498 and D16S303 at q24.3. Allelic loss on 16q was observed frequently in small tumours, tumours without lymph node metastasis and tumours of the non-invasive histological type as well as in tumours of more advanced phenotype, suggesting that inactivation of one of at least two tumour-suppressor genes on 16q plays a role in early stage breast carcinogenesis.

Analysis of the human gene encoding the kidney isozyme of 11 beta-hydroxysteroid dehydrogenase

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) catalyzes the conversion of cortisol to cortisone. This activity may be deficient in the syndrome of apparent mineralocorticoid excess (AME). 11 beta-HSD L (Type I), isolated from liver, is widely expressed and utilizes NADP+ as a cofactor. The gene for 11 beta-HSD L was found to be normal in patients of AME. A second isoform, 11 beta-HSD K (Type II), isolated from kidney, is more tissue specific in expression and utilizes NAD+ as a cofactor. The cDNA clone encoding 11 beta-HSD K was isolated from sheep kidney. The cDNA is 1.8 kb in length and encodes a protein of 404 amino acid residues with a predicted M(r) 43,953. The recombinant enzyme functions as an NAD(+)-dependent 11 beta-dehydrogenase with very high affinity for steroids, but it has no detectable reductase activity. It is 37% identical in amino acid sequence to an NAD(+)-dependent isozyme of 17 beta-hydroxysteroid dehydrogenase. It is expressed at high levels in the kidney, placenta, adrenal and at lower levels in colon, stomach, heart and skin. The human 11 beta-HSD K gene consists of five exons spread over 6 kb. The nucleotide binding domain lies in the first and the second exon, and the catalytic domain in the fourth exon. The promoter for 11 beta-HSD K gene lacks a TATA box and has a high GC base content, suggesting that the gene may be transcriptionally regulated by factors that recognize GC-rich sequences. Fluorescent in situ hybridization of metaphase chromosomes with a positive bacteriophage P1 genomic 11 beta-HSD K clone localized the gene to chromosome 16q22. In contrast, the 11 beta-HSD L gene is located on chromosome 1 and contains 6 exons; the coding sequences of these genes are only 21% identical. Different transcriptional start sites are utilized in kidney and placenta.

The human type II 17 beta-hydroxysteroid dehydrogenase gene encodes two alternatively spliced mRNA species

The isozymes of the 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) gene family are responsible for the formation of the 17 beta-hydroxysteroids delta 5-androstene-3 beta,17 beta-diol, testosterone, 17 beta-estradiol, and dihydrotestosterone from their corresponding 17-ketosteroid precursors, thus playing a pivotal role in the formation of active sex steroids in both steroidogenic and peripheral target tissues. To clone the type II 17 beta-HSD gene, the full-length cDNA type II 17 beta-HSD was used as probe to screen a human leukocyte genomic DNA library. The type II 17 beta-HSD gene contains seven exons and spans > 40 kbp. The type II 17 beta-HSD gene encodes two alternatively spliced mRNAs that give rise to the previously identified type IIA 17 beta-HSD protein of 387 amino acids, as well as to a related 291-amino-acid type IIB 17 beta-HSD protein of unknown function. RNA blot analysis revealed the presence of a major 1.45-kb transcript that is abundant in placenta and endometrium. The mRNA cap site has been localized in a region between 179 and 167 nucleotides upstream of the ATG start codon by RNase protection and S1 nuclease mapping analyses. Cloning of the 17 beta-HSD type II gene provides us with the tools to study its transcriptional expression.