A new insight into the molecular basis of 3beta-hydroxysteroid dehydrogenase deficiency

A CYP11A1 homozygous exonic variant inducing an alternative splicing, frameshift and truncation in a family with congenital adrenal hyperplasia

Background

Congenital adrenal hyperplasia (CAH) is a heterogeneous group of adrenal steroidogenesis disorders with variable degrees of glucocorticoid, mineralocorticoid and sex steroid deficiencies. CYP11A1 gene encodes the mitochondrial cholesterol side-chain cleavage enzyme (P450scc), which initiates the first reaction in steroidogenesis by converting cholesterol to pregnenolone. Variants in this gene are extremely rare but associated with severe forms of CAH due to its early and critical function in various steroid biosynthesis pathways. Here, we report a CYP11A1 exonic homozygous variant that, although exonic in location, affects splicing by creating an additional aberrant splicing site with frameshift and truncation of the gene.

Patients and methods

The proband is a 23-year old 46,XY patient raised as a girl. She was a product of normal pregnancy for first-degree relative parents. Soon after birth, she had vomiting, dehydration, hypotension, hyponatremia and hyperkalemia. She was started on glucocorticoids and mineralocorticoids with prompt recovery. Apart from a chronic need for these medications, her neonatal and childhood history was unremarkable. She sought medical advice at age 19 years for delayed puberty with primary amenorrhea and lack of breast development. On evaluation, she had normal external female genitalia, no breast development, undescended testes and absent uterus and ovaries. Her hormonal evaluation revealed very low estrogen, testosterone, cortisol, aldosterone, 17-hydroxyprogesterone, and androstenedione levels. ACTH, LH, FSH and renin were very high consistent with primary gonadal and adrenal failure. Her parents are healthy first-degree cousins. She has three sisters, all with 46,XX karyotype. One of them is clinically and biochemically normal while the other two sisters have normal female phenotype, normal uterus and ovaries, similar hormonal profile to the proband but different karyotype (46,XX) and absence of undescended testes. gDNA was used for whole exome sequencing (WES). Sanger sequencing was performed to confirm the detected variant and its segregation with the disease.

Results

WES identified a homozygous missense variant in CYP11A1 changing the second nucleotide (GCG > GTG) at position 189 in exon 3 and resulting in a change of Alanine to Valine (p.Ala189Val). This variant was confirmed by PCR and Sanger sequencing. It was found in a homozygous form in the proband and her two affected sisters and in a heterozygous form in the unaffected sister. In-silico analysis predicted this variant to create a new splicing site with frameshift and truncation of the gene transcript. This was confirmed by isolation of RNA, cDNA synthesis, gel electrophoresis and sequencing.

Conclusion

We describe a family with a very rare form of CAH due to a CYP11A1 variant leading to creation of a new splice site, frameshift and premature truncation of the protein.

Cocktails of NSAIDs and 17α Ethinylestradiol at Environmentally Relevant Doses in Drinking Water Alter Puberty Onset in Mice Intergenerationally

Non-steroidal anti-inflammatory drugs (NSAIDs) and 17α-ethinyl-estradiol (EE2) are among the most relevant endocrine-disrupting pharmaceuticals found in the environment, particularly in surface and drinking water due to their incomplete removal via wastewater treatment plants. Exposure of pregnant mice to NSAID therapeutic doses during the sex determination period has a negative impact on gonadal development and fertility in adults; however, the effects of their chronic exposure at lower doses are unknown. In this study, we investigated the impact of chronic exposure to a mixture containing ibuprofen, 2hydroxy-ibuprofen, diclofenac, and EE2 at two environmentally relevant doses (added to the drinking water from fetal life until puberty) on the reproductive tract in F1 exposed mice and their F2 offspring. In F1 animals, exposure delayed male puberty and accelerated female puberty. In post-pubertal F1 testes and ovaries, differentiation/maturation of the different gonad cell types was altered, and some of these modifications were observed also in the non-exposed F2 generation. Transcriptomic analysis of post-pubertal testes and ovaries of F1 (exposed) and F2 animals revealed significant changes in gene expression profiles and enriched pathways, particularly the inflammasome, metabolism and extracellular matrix pathways, compared with controls (non-exposed). This suggested that exposure to these drug cocktails has an intergenerational impact. The identified Adverse Outcome Pathway (AOP) networks for NSAIDs and EE2, at doses that are relevant to everyday human exposure, will improve the AOP network of the human reproductive system development concerning endocrine disruptor chemicals. It may serve to identify other putative endocrine disruptors for mammalian species based on the expression of biomarkers.

Single-molecule enzymology of steroid transforming enzymes: Transient kinetic studies and what they tell us

Structure-function studies on steroid transforming enzymes often use site-directed mutagenesis to inform mechanisms of catalysis and effects on steroid binding, and data are reported in terms of changes in steady state kinetic parameters kcat, Km and kcat/Km. However, this dissection of function is limited since kcat is governed by the rate-determining step and Km is a complex macroscopic kinetic constant. Often site-directed mutagenesis can lead to a change in the rate-determining step which cannot be revealed by just reporting a decrease in kcat alone. These issues are made more complex when it is considered that many steroid transforming enzymes have more than one substrate and product. We present the case for using transient-kinetics performed with stopped-flow spectrometry to assign rate constants to discrete steps in these multi-substrate reactions and their use to interpret enzyme mechanism and the effects of disease and engineered mutations. We demonstrate that fluorescence kinetic transients can be used to measure ligand binding that may be accompanied by isomerization steps, revealing the existence of new enzyme intermediates. We also demonstrate that single-turnover reactions can provide a klim for the chemical step and Ks for steroid-substrate binding and that when coupled with kinetic isotope effect measurements can provide information on transition state intermediates. We also demonstrate how multiple turnover experiments can provide evidence for either "burst-phase" kinetics, which can reveal a slow product release step, or linear-phase kinetics, in which the chemical step can be rate-determining. With these assignments it becomes more straightforward to analyze the effects of mutations. We use examples from the hydroxysteroid dehydrogenases (AKR1Cs) and human steroid 5β-reductase (AKR1D1) to illustrate the utility of the approach, which are members of the aldo-keto reductase (AKR) superfamily.

A Combination of Culture Conditions and Gene Expression Analysis Can Be Used to Investigate and Predict hES Cell Differentiation Potential towards Male Gonadal Cells

Human embryonic stem cell differentiation towards various cell types belonging to ecto-, endo- and mesodermal cell lineages has been demonstrated, with high efficiency rates using standardized differentiation protocols. However, germ cell differentiation from human embryonic stem cells has been very inefficient so far. Even though the influence of various growth factors has been evaluated, the gene expression of different cell lines in relation to their differentiation potential has not yet been extensively examined. In this study, the potential of three male human embryonic stem cell lines to differentiate towards male gonadal cells was explored by analysing their gene expression profiles. The human embryonic stem cell lines were cultured for 14 days as monolayers on supporting human foreskin fibroblasts or as spheres in suspension, and were differentiated using BMP7, or spontaneous differentiation by omitting exogenous FGF2. TLDA analysis revealed that in the undifferentiated state, these cell lines have diverse mRNA profiles and exhibit significantly different potentials for differentiation towards the cell types present in the male gonads. This potential was associated with important factors directing the fate of the male primordial germ cells in vivo to form gonocytes, such as SOX17 or genes involved in the NODAL/ACTIVIN pathway, for example. Stimulation with BMP7 in suspension culture resulted in up-regulation of cytoplasmic SOX9 protein expression in all three lines. The observation that human embryonic stem cells differentiate towards germ and somatic cells after spontaneous and BMP7-induced stimulation in suspension emphasizes the important role of somatic cells in germ cell differentiation in vitro.

Molecular regulation of steroidogenesis in endocrine Leydig cells

Steroid hormones regulate essential physiological processes and inadequate levels are associated with various pathological conditions. Consequently, the process of steroid hormone biosynthesis is finely regulated. In the testis, the main steroidogenic cells are the Leydig cells. There are two distinct populations of Leydig cells that arise during development: fetal and adult Leydig cells. Fetal Leydig cells are responsible for masculinizing the male urogenital tract and inducing testis descent. These cells atrophy shortly after birth and do not contribute to the adult Leydig cell population. Adult Leydig cells derive from undifferentiated precursors present after birth and become fully steroidogenic at puberty. The differentiation of both Leydig cell populations is controlled by locally produced paracrine factors and by endocrine hormones. In fully differentially and steroidogenically active Leydig cells, androgen production and hormone-responsiveness involve various signaling pathways and downstream transcription factors. This review article focuses on recent developments regarding the origin and function of Leydig cells, the regulation of their differentiation by signaling molecules, hormones, and structural changes, the signaling pathways, kinases, and transcription factors involved in their differentiation and in mediating LH-responsiveness, as well as the fine-tuning mechanisms that ensure adequate production steroid hormones.

CCAAT/enhancer-binding protein β is involved in the breed-dependent transcriptional regulation of 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4)-isomerase in adrenal gland of preweaning piglets

The enzyme 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4)-isomerase (3β-HSD) catalyzes the biosynthesis of all steroid hormones. The molecular mechanisms regulating porcine adrenal 3β-HSD expression in different breeds are still poorly understood. In this study, we aimed to compare the expression of 3β-HSD between preweaning purebred Large White (LW) and Erhualian (EHL) piglets and to explore the potential factors regulating 3β-HSD transcription. EHL had significantly higher serum levels of cortisol (P<0.01) and testosterone (P<0.01), which were associated with significantly higher expression of 3β-HSD mRNA (P<0.01) and protein (P<0.05) in the adrenal gland, compared with LW piglets. The 5' flanking region of the porcine 3β-HSD gene showed significant sequence variations between breeds, and the sequence of EHL demonstrated an elevated promoter activity (P<0.05) in luciferase reporter gene assay. Higher adrenal expression of 3β-HSD in EHL was accompanied with higher CCAAT/enhancer binding protein β (C/EBPβ) expression (P<0.05), enriched histone H3 acetylation (P<0.05) and C/EBPβ binding to 3β-HSD promoter (P<0.05). In addition, higher androgen receptor (AR) (P=0.06) and lower glucocorticoid receptor (GR) (P<0.05) were detected in EHL. Co-immunoprecipitation analysis revealed interactions of C/EBPβ with both AR and GR. These results indicate that the C/EBPβ binding to 3β-HSD promoter is responsible, at least in part, for the breed-dependent 3β-HSD expression in adrenal gland of piglets. The sequence variations of 3β-HSD promoter and the interactions of AR and/or GR with C/EBPβ may also participate in the regulation.

Transcripts of testicular gonadotropin-releasing hormone, steroidogenic enzymes, and intratesticular testosterone levels in infertile men

OBJECTIVE

To investigate the expressions of testicular GnRH and steroidogenic enzymes and their correlations with intratesticular T levels (ITT) and serum hormonal parameters in infertile men.

DESIGN

Prospective case study.

SETTING

University reproductive laboratory and clinics.

PATIENT(S)

Thirty-four azoospermic men.

INTERVENTION(S)

The mRNA transcript levels of GnRH-I, GnRH-II, GnRH-R, and five steroidogenic enzymes in the testes of azoospermic men were determined by quantitative real time polymerase chain reaction. The ITT level was determined by radioimmunoassay.

MAIN OUTCOME MEASURE(S)

Transcript levels of genes and ITT determination.

RESULT(S)

The mRNA transcript levels of GnRH-I, GnRH-II, GnRH-R, cytochrome P450 side-chain cleavage (CYP11A1), and 3beta-hydroxy-steroid dehydrogenase type 2 enzyme (HSD3B2) as well as the ITT levels were significantly increased in patients with spermatogenic failure, especially in men with Sertoli cell-only syndrome. GnRH-I and -II mRNA transcript levels positively correlated with HSD3B2 mRNA transcript levels, ITT levels, and serum FSH levels.

CONCLUSION(S)

Increased testicular GnRH transcripts, steroidogenic enzyme transcripts, and ITT levels are associated with spermatogenic failure in infertile men. Testicular GnRH is involved in the regulation of human spermatogenesis and steroidogenesis.

A Case of 3β-Hydroxysteroid Dehydrogenase Type II (HSD3B2) Deficiency Picked up by Neonatal Screening for 21-Hydroxylase Deficiency: Difficulties and Delay in Etiologic Diagnosis

BACKGROUND

3beta-Hydroxysteroid dehydrogenase type II deficiency, a rare form of congenital adrenal hyperplasia, is characterized by varying degrees of salt loss and incomplete masculinization in males and mild virilization or normal external genitalia in females. The clinical signs may be difficult to recognize, increasing the risk of a neonatal adrenal crisis. In addition, elevated 17alpha-hydroxyprogesterone and androstenedione levels due to peripheral HSD3B1 activity may lead to a delay of the correct diagnosis and even to misdiagnosis as CYP21 deficiency.

METHOD

We report a patient who was detected on neonatal screening for 21-hydroxylase deficiency, in part because of cross-reactivity in the commonly used assay.

RESULTS

The diagnostic difficulties in this case were overcome by the use of more specific antibodies.

CONCLUSION

This case emphasizes the importance of confirming the etiological diagnosis with molecular genetic analyses.

New insights into the regulation of mammalian sex determination and male sex differentiation

In mammals, sex development is a genetically and hormonally controlled process that begins with the establishment of chromosomal or genetic sex (XY or XX) at conception. At approximately 6 to 7 weeks of human gestation or embryonic day e11.5 in the mouse, expression of the Y chromosome-linked sex determining gene called SRY (described in detail in this chapter) then initiates gonadal differentiation, which is the formation of either a testis (male) or an ovary (female). Male sex differentiation (development of internal and external reproductive organs and acquisition of male secondary sex characteristics) is then controlled by three principal hormones produced by the testis: Mullerian inhibiting substance (MIS) or anti-Mullerian hormone (AMH), testosterone, and insulin-like factor 3 (INSL3). In the absence of these critical testicular hormones, female sex differentiation ensues. This sequential, three-step process of mammalian sex development is also known as the Jost paradigm. With the advent of modern biotechnologies over the past decade, such as transgenics, array-based gene profiling, and proteomics, the field of mammalian sex determination has witnessed a remarkable boost in the understanding of the genetics and complex molecular mechanisms that regulate this fundamental biological event. Consequently, a number of excellent reviews have been devoted to this topic. The purpose of the present chapter is to provide an overview of selected aspects of mammalian sex determination and differentiation with an emphasis on studies that have marked this field of study.

[Rare forms of female pseudohermaphroditism: when to investigate?]

The congenital adrenal hyperplasia is the commonest cause of ambiguity of the external genitalia at birth, due to classic forms of 21-hydroxylase and 11beta-hydroxylase deficiencies. 3beta-hydroxysteroid dehydrogenase (3betaHSD) is a rare disorder that affects both sexes and female patients may have ambiguous genitalia. Familial glucocorticoid resistance is characterized by increased cortisol secretion without clinical evidence of hypercortisolism, but with manifestations of androgen and mineralocorticoid excess, caused by glucocorticoid receptor gene mutation, and rarely can lead to female pseudohermaphroditism. Placental aromatase deficiency is a rare disease characterized by a masculinized female fetus and a virilized mother, which should be considered in the absence of fetal adrenal hyperplasia and maternal androgen-secreting tumours. Finally, mutations of P450 oxidoreductase causes disordered steroidogenesis with ambiguous genitalia. The investigation of abnormal sexual development requires an initial karyotype analysis and serum 17OH progesterone, 11 deoxycortisol, 17 pregnenolone, and androgen measurements to assess the diagnosis of different forms of congenital adrenal hyperplasia.

Glucocorticoids enhance activation of the human type II 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase gene

Glucocorticoids indirectly alter adrenocortical steroid output through the inhibition of ACTH secretion by the anterior pituitary. However, previous studies suggest that glucocorticoids can directly affect adrenocortical steroid production. Therefore, we have investigated the ability of glucocorticoids to affect transcription of adrenocortical steroid biosynthetic enzymes. One potential target of glucocorticoid action in the adrenal is an enzyme critical for adrenocortical steroid production: 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD). Treatment of the adrenocortical cell line (H295R) with the glucocorticoid agonist dexamethasone (DEX) increased cortisol production and 3beta-HSD mRNA levels alone or in conjunction with phorbol ester. This increase in 3beta-HSD mRNA was paralleled by increases in Steroidogenic Acute Regulatory Protein (StAR) mRNA levels. The human type II 3beta-HSD promoter lacks a consensus palindromic glucocorticoid response element (GRE) but does contain a Stat5 response element (Stat5RE) suggesting that glucocorticoids could affect type II 3beta-HSD transcription via interaction with Stat5. Transfection experiments show enhancement of human type II 3beta-HSD promoter activity by coexpression of the glucocorticoid receptor (GR) and Stat5A and treatment with 100nM dexamethasone. Furthermore, removal of the Stat5RE either by truncation of the 5' flanking sequence in the promoter or introduction of point mutations to the Stat5RE abolished the ability of DEX to enhance 3beta-HSD promoter activity. These studies demonstrate the ability of glucocorticoids to directly enhance the expression of an adrenal steroidogenic enzyme gene albeit independent of a consensus palindromic glucocorticoid response element.

Polymorphism in exon 4 of the human 3 beta-hydroxysteroid dehydrogenase type I gene (HSD3B1) and blood pressure

There is growing evidence to the effect that steroid hormones are associated with a complex phenotype of metabolic abnormalities usually referred to as the metabolic syndrome. The 3 beta-hydroxysteroid dehydrogenases/Delta(4,5)-isomerase (3 beta-HSD) is crucial to the biosynthesis of hormonal steroids, including aldosterone, cortisol, and testosterone. The objective of the present study was to examine the potential impact of a T-->C substitution at codon Leu(338) of the type I (HSD3B1) 3 beta-HSD gene on obesity, circulating hormones, and estimates of insulin, glucose, and lipid metabolism as well as blood pressure in 284 unrelated Swedish men born in 1944. The subjects were genotyped by using PCR amplification of exon 4 of the HSD3B1 gene followed by digestion with the restriction enzyme BglII. The frequency of allele T was 0.44 and that of allele C 0.56. Homozygotes for the C allele (n=75) had significantly (P<0.05) higher mean systolic and diastolic blood pressures compared to both heterozygotes (n=143) and homozygotes for the T allele (n=45). In addition, the C allele was significantly (P=0.018) more frequent among subjects with grade 1 hypertension (>140/90 mm Hg) compared to normotensive (<130/85 mm Hg) subjects. These results were all adjusted for the potential confounding effect of body mass index (BMI) and waist-to-hip ratio (WHR). Other measurements such as BMI, WHR, abdominal sagittal diameter, salivary cortisol, total testosterone, serum leptin, fasting insulin and glucose, and serum lipids were not different across the HSD3B1 genotype groups. In conclusion, a T-->C polymorphism at codon Leu(338) of exon 4 of the HSD3B1 gene is associated with elevated systolic and diastolic blood pressures. The pathogenic mechanism underlying this association is, however, uncertain from the present data and further studies are warranted.