Analysis of the steroidogenic acute regulatory protein (StAR) gene in Japanese patients with congenital lipoid adrenal hyperplasia

Steroidogenic acute regulatory protein (STAR) deficiency: Our experience and systematic review for phenotype-genotype correlation

OBJECTIVE

Lipoid congenital adrenal hyperplasia (LCAH) is caused by mutations in STAR. A systematic review of phenotype-genotype correlation and data on testicular histology in LCAH patients is unavailable. We aim to describe our experience and provide phenotype-genotype correlation. DESIGN, PATIENTS AND MEASUREMENTS: Retrospective review of three genetically proven LCAH patients from our centre and per-patient data analysis from a systematic review of 292 probands. The phenotypic subgroups of 46,XY were Group A (typical female genitalia), Group B (atypical genitalia) and Group C (typical male genitalia).

RESULTS

We report three new LCAH probands from India, all diagnosed post-infancy with preserved gonadal function and one novel variant. The systematic review reports 46,XY to 46,XX LCAH ratio of 1.1 (155:140). Patients with 46,XY LCAH in Group A were diagnosed in infancy (116/117) and had higher mineralocorticoid involvement than Group C (96.4% vs. 75%, p = 0.035), whereas Group C had preserved gonadal function. Hyperplastic adrenals are noted in ~60% of LCAH diagnosed with primary adrenal insufficiency in infancy. There was no report of gonadal germ cell cancer and rare reports of germ cell neoplasia in situ in adolescents, especially with intraabdominal gonads. Two-thirds of LCAH probands were East-Asian and 11/16 regional recurrent variants were from East Asia. There was minimal overlap between variants in Groups A (n = 55), B (n = 9) and C (n = 8). All nonsense and frameshift and most of the splice-site variants and deletion/insertions were present in Group A.

CONCLUSIONS

We report three new cases of LCAH from India. We propose a phenotype-derived genotypic classification of reported STAR variants in 46,XY LCAH.

Genetic and phenotypic spectrum of non-21-hydroxylase-deficiency primary adrenal insufficiency in childhood: data from 111 Chinese patients

BACKGROUND

Primary adrenal insufficiency (PAI) is a rare but life-threatening condition. Differential diagnosis of numerous causes of PAI requires a thorough understanding of the condition.

METHODS

To describe the genetic composition and presentations of PAI. The following data were collected retrospectively from 111 patients with non-21OHD with defined genetic diagnoses: demographic information, onset age, clinical manifestations, laboratory findings and genetic results. Patients were divided into four groups based on the underlying pathogenesis: (1) impaired steroidogenesis, (2) adrenal hypoplasia, (3) resistance to adrenocorticotropic hormone (ACTH) and (4) adrenal destruction. The age of onset was compared within the groups.

RESULTS

Mutations in the following genes were identified: NR0B1 (n=39), STAR (n=33), CYP11B1 (n=12), ABCD1 (n=8), CYP17A1 (n=5), HSD3B2 (n=4), POR (n=4), MRAP (n=2), MC2R (n=1), CYP11A1 (n=1), LIPA (n=1) and SAMD9 (n=1). Frequent clinical manifestations included hyperpigmentation (73.0%), dehydration (49.5%), vomiting (37.8%) and abnormal external genitalia (23.4%). Patients with adrenal hypoplasia typically presented manifestations earlier than those with adrenal destruction but later than those with impaired steroidogenesis (both p<0.01). The elevated ACTH (92.6%) and decreased cortisol (73.5%) were the most common laboratory findings. We generated a differential diagnosis flowchart for PAI using the following clinical features: 17-hydroxyprogesterone, very-long-chain fatty acid, external genitalia, hypertension and skeletal malformation. This flowchart identified 84.8% of patients with PAI before next-generation DNA sequencing.

CONCLUSIONS

STAR and NR0B1 were the most frequently mutated genes in patients with non-21OHD PAI. Age of onset and clinical characteristics were dependent on aetiology. Combining clinical features and molecular tests facilitates accurate diagnosis.

Lipoid Congenital Adrenal Hyperplasia With a Novel StAR Gene Mutation

Lipoid congenital adrenal hyperplasia (LCAH) is characterized by disturbance of adrenal and gonadal steroidogenesis (OMIM:201710). It is caused by mutation in the Steroidogenic Acute Regulatory Protein (StAR). We report a classic case of LCAH in a neonate (46, XY) with phenotypic female genitalia who presented with significant salt loss with a novel homozygous variant mutation c.745-1G>C p. in StAR gene.

New molecular insights into the A218V variant impact on the steroidogenic acute regulatory protein (STAR) associated with 46, XY disorders of sexual development

Disorders of sexual development (DSD) are an abnormal congenital conditions associated with atypical development of the urogenital tract and external genital structures. The steroidogenic acute regulatory (STAR) gene, associated with congenital lipoid adrenal hyperplasia (CLAH), is included in the targeted gene panel for the DSD diagnosis. Therefore, the genetic alterations of the STAR gene and their molecular effect were examined in the CLAH patients affected with DSD. Ten different Iranian families including twelve male pseudo-hermaphroditism patients with CLAH phenotype were studied using genetic linkage screening and STAR gene sequencing in the linked families to the STAR locus. Furthermore, the structural, dynamical, and functional impacts of the variants on the STAR in silico were analyzed. Sanger sequencing showed the pathogenic variant p.A218V in STAR gene, as the first report in Iranian population. Moreover, modeling and simulation analysis were performed using tools such as radius of gyration, root mean square deviation (RMSD), root mean square fluctuation (RMSF), and molecular docking showed that p.A218V variant affects the residues interaction in cholesterol-binding site and the proper folding of STAR through increasing H-bound and the amount of α-Helix, deceasing total flexibility and changing fluctuations in some residues, resulting in reduced steroidogenic activity of the STAR protein. The study characterized the structural and functional changes of STAR caused by pathogenic variant p.A218V. It leads to limited cholesterol-binding activity of STAR, ultimately leading to the CLAH disease. Molecular dynamics simulation of STAR variants could help explain different clinical manifestations of CLAH disease.

Clinical characteristics of a male child with non-classic lipoid congenital adrenal hyperplasia and literature review

BACKGROUND

Lipoid congenital adrenal hyperplasia (LCAH) is a rare and severe disorder that is caused by mutations in the steroidogenic acute regulatory protein (StAR). Non-classic LCAH is defined as late-onset glucocorticoid deficiency and even complete male external genitalia in 46,XY individuals. However, to date, few cases of non-classic LCAH have been reported.

METHODS

It was attempted to describe the clinical characteristics of a male child with complete male external genitalia in terms of age of onset, adrenal function, and biochemical indicators. Previously reported cases were also reviewed to investigate the relationship of age of onset with enzymatic activity in non-classic LCAH.

RESULTS

The patient with complete male external genitalia was diagnosed with non-classic LCAH, in which the reason for his referral to a local hospital at the of age 1.25 years was progressive skin hyperpigmentation, and plasma adrenocorticotropic hormone (ACTH) level was elevated to higher than 1,250 pg/ml. The compound heterozygous mutations c.772C>T/c.562C>T in STAR gene were identified via genetic testing. The literature review resulted in identification of 47 patients with non-classic LCAH from 36 families. The mutational analysis showed that c.562C>T mutation was prevalent in patients with non-classic LCAH, accounting for 37.2% of the total mutant alleles, which could reflect the founder effect on the non-classic LCAH population. In total, 28 46,XY patients were reported, including 22 (78.5%) cases with complete male external genitalia and six (21.5%) cases with different degrees of hypospadias.

CONCLUSION

The clinical phenotypes of non-classic LCAH are highly variable. Routine physical examination, laboratory measurement, genetic testing, and, importantly, enzymatic activity assay may facilitate the early diagnosis of non-classic LCAH. The age of primary adrenal insufficiency (PAI) onset may not be a diagnostic basis for non-classic LCAH, and enzymatic activity assay determination may be more effective.

Adrenal hyperplasias in childhood: An update

Pediatric adrenocortical hyperplasias are rare; they usually present with Cushing syndrome (CS); of them, isolated micronodular adrenal disease and its variant, primary pigmented adrenocortical disease are the most commonly encountered. Most cases are due to defects in the cyclic AMP/protein kinase A (cAMP/PKA) pathway, although a few cases remain without an identified genetic defect. Another cause of adrenal hyperplasia in childhood is congenital adrenal hyperplasia, a group of autosomal recessive disorders that affect steroidogenic enzymes in the adrenal cortex. Clinical presentation varies and depends on the extent of the underlying enzymatic defect. The most common form is due to 21-hydroxylase deficiency; it accounts for more than 90% of the cases. In this article, we discuss the genetic etiology of adrenal hyperplasias in childhood.

A Novel Intronic Splice-Site Mutation of the CYP11A1 Gene Linked to Adrenal Insufficiency with 46,XY Disorder of Sex Development

A novel CYP11A1: c.1236 + 5G > A was identified, expanding the mutation spectrum of the congenital adrenal insufficiency with 46,XY sex reversal. In a now 17-year-old girl delivered full-term (G2P2, parents unrelated), adrenal failure was diagnosed in the first year of life based on clinical picture of acute adrenal crisis with vomiting, dehydration, weight loss, hypotension, and electrolyte disturbances. At the time, hormonal tests revealed primary adrenocortical insufficiency and steroid profiles showed lack of products of steroidogenesis, and since then the patient has been treated with substitution doses of hydrocortisone and fludrocortisone. At the age of 14, considering the absence of puberty symptoms, extended diagnostic tests revealed elevated LH levels (26.5 mIU/mL) with pre-puberty FSH levels (4.9 mIU/mL), low estradiol (28 pmol/L), testosterone (<2.5 ng/mL), and extremely high levels of ACTH (4961 pg/mL). A cytogenetic study revealed a 46 XY karyotype. A molecular examination confirmed the missense mutation and a novel splice-site mutation of CYP11A1 gene. Compound heterozygosity for the CYP11A1 gene with a known pathogenic variant in one allele and a novel splice site mutation in the second allele is most probably responsible for congenital adrenal insufficiency with 46,XY sex reversal. We discuss the necessity of cytogenetic test in the case of early onset of adrenal failure in the absence of steroidogenesis metabolites in the steroid profile.

Novel STAR gene variant in a patient with classic lipoid congenital adrenal hyperplasia and combined pituitary hormone deficiency

We report the first case of classic lipoid congenital adrenal hyperplasia and combined pituitary hormone deficiency. We identified pathogenic variants in the STAR gene: a novel variant of c.126_127delCCinsG, namely, p.Thr44Profs*2 and an already reported variant of c.634C>T, namely, p.Gln212*. The association with combined pituitary hormone deficiency might be just a coincidence.

Clinical and molecular characterization of thirty Chinese patients with congenital lipoid adrenal hyperplasia

Congenital lipoid adrenal hyperplasia (LCAH), as the most severe form of congenital adrenal hyperplasia (CAH), is caused by mutations in the steroidogenic acute regulatory protein (STAR). Affected patients were typically characterized by adrenal insufficiency in the first year of life and present with female external genitalia regardless of karyotype. Non-classic LCAH patients usually present from 2 to 4 years old with glucocorticoid deficiency and mild mineralocorticoid deficiency, even develop naturally masculinized external genitalia at birth when they have 46,XY karyotype. We described thirty patients from unrelated Chinese families, including three non-classic LCAH ones. Four novel mutations were reported, including c.556A > G, c.179-15G > T, c.695delG and c.306 + 3_c.306 + 6delAAGT. The c.772C > T is the most common STAR mutation in Chinese population, suggesting a possibility of founder effect. Enzymatic activity assay combined with clinical characteristics showed a good genotype-phenotype correlation in this study. Residual STAR activity more than 20 % may be correlated with non-classic LCAH phenotype. We support the perspective that onset age may be affected by multiple factors and masculinization should be the main weighting factor for diagnosis of non-classic LCAH. Compared with 46,XX LCAH patients, less 46,XY ones were found in our report. A less comprehensive inspection and an easy diagnosis due to classical phenotype both would reduce the possibility of 46,XY LCAH patients to be referred to specialists or geneticists.

Reference values for the external genitalia of full-term and pre-term female neonates

BACKGROUND AND OBJECTIVES

Identifying virilisation of the genitalia in female newborns early during the neonatal period is important to diagnose pathologies. However, there is no clear threshold for clitoromegaly or for the anogenital ratio. The objective of this study was to define reference values for the external genitalia of full-term and pre-term female neonates.

DESIGN

This was a prospective study of all females born in the study centre between May 2014 and July 2016. Clitoral length and anogenital ratio were measured in 619 newborns with a gestational age of 24+2 to 41+3 weeks during their first 3 days of life. Associations between the values at day 3 and gestational age, birth weight and other newborn characteristics were examined by linear regression.

RESULTS

The mean clitoral length at day 3 of life was 3.69±1.53 mm (n=551; 95th percentile, 6.5 mm; maximum, 8 mm), and the mean anogenital ratio was 0.42±0.09 (95th percentile, 0.58). There was no significant variation with gestational age or birth weight, and no significant difference between the results at day 0 and day 3.

CONCLUSION

These results suggest that clitoromegaly can be defined as a clitoral length >6.5 mm. Values ≥8 mm should prompt further investigations. An anogenital ratio >0.6 should be considered a sign of virilisation. Since clitoral size does not vary with gestational age or birth weight, clitoromegaly should not be attributed to prematurity.

Clinical Features of 57 Patients with Lipoid Congenital Adrenal Hyperplasia: Criteria for Nonclassic Form Revisited

CONTEXT

Lipoid congenital adrenal hyperplasia (LCAH) is caused by mutations in STAR. Classic (CLCAH) and nonclassic (NCLCAH) forms were reported as total and partial deficiencies, respectively, of adrenal and gonadal steroid hormones. The rarity of LCAH has precluded large-scale epidemiological and clinical investigations.

OBJECTIVE

To determine the epidemiological and clinical characteristics of 2 forms of LCAH.

DESIGN

A multicenter cross-sectional cohort study in Japan on December 1, 2017.

PARTICIPANTS

Fifty-seven patients with LCAH (median age, 23.7 years; range, 0.0-47.5 years).

MAIN OUTCOME MEASURES

Patient demographics, STAR genotype, Quigley grade, endocrinological and imaging data, treatment, and prognosis.

RESULTS

Fifty-three and 4 patients fulfilled definite and probable diagnostic criteria for LCAH, respectively. When NCLCAH was defined as either Quigley grade 1 in XY karyotype, no episode of salt losing or requirement of fludrocortisone, or onset of primary adrenal insufficiency (PAI) at 1 year or older, patients were divided into groups of 43 patients with CLCAH (75.4%), 11 with NCLCAH (19.3%), and 3 with unclassified LCAH (5.3%). All of the patients with CLCAH and 7/11 NCLCAH (63.6%) were treated with fludrocortisone. CLCAH was diagnosed at a significantly younger age than NCLCAH (median, 0.0 vs 4.0 years). STAR-Arg272Cys or -Met225Thr was identified only in NCLCAH (8/11, 72.7%).

CONCLUSIONS

We demonstrated the relative proportions and clinical and molecular characteristics of NCLCAH and CLCAH in Japan. These criteria for NCLCAH correspond to all previously published cases and our cases whose masculinization of the external genitalia, ability of mineralocorticoid production, and onset of PAI were described.

Characterization of Two Novel Variants of the Steroidogenic Acute Regulatory Protein Identified in a Girl with Classic Lipoid Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) consists of several autosomal recessive disorders that inhibit steroid biosynthesis. We describe a case report diagnosed with adrenal insufficiency due to low adrenal steroids and adrenocorticotropic hormone excess due to lack of cortisol negative feedback signaling to the pituary gland. Genetic work up revealed two missense variants, p.Thr204Arg and p.Leu260Arg in the STAR gene, inherited by both parents (non-consanguineous). The StAR protein supports CYP11A1 enzyme to cleave the side chain of cholesterol and synthesize pregnenolone which is metabolized to all steroid hormones. We used bioinformatics to predict the impact of the variants on StAR activity and then we performed functional tests to characterize the two novel variants. In a cell system we tested the ability of variants to support cholesterol conversion to pregnenolone and measured their mRNA and protein expression. For both variants, we observed loss of StAR function, reduced protein expression and categorized them as pathogenic variants according to guidelines of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. These results fit the phenotype of the girl during diagnosis. This study characterizes two novel variants and expands the list of missense variants that cause CAH.

Nonclassic congenital lipoid adrenal hyperplasia diagnosed at 17 months in a Korean boy with normal male genitalia: emphasis on pigmentation as a diagnostic clue

Congenital lipoid adrenal hyperplasia (CLAH) is one of the most fatal conditions caused by an abnormality of adrenal and gonadal steroidogenesis. CLAH results from loss-of-function mutations of the steroidogenic acute regulatory (STAR) gene; the disease manifests with electrolyte imbalances and hyperpigmentation in neonates or young infants due to adrenocortical hormone deficiencies, and 46, XY genetic male CLAH patients can be phenotypically female. Meanwhile, some patients with STAR mutations develop hyperpigmentation and mild signs of adrenal insufficiency, such as hypoglycemia, after infancy. These patients are classified as having nonclassic CLAH (NCCLAH) caused by STAR mutations that retain partial activity of STAR. We present the case of a Korean boy with normal genitalia who was diagnosed with NCCLAH. He presented with whole-body hyperpigmentation and electrolyte abnormalities, which were noted at the age of 17 months after an episode of sepsis with peritonitis. The compound heterozygous mutations p.Gly221Ser and c.653C&gt;T in STAR were identified by targeted gene-panel sequencing. Skin hyperpigmentation should be considered an important clue for diagnosing NCCLAH.

Congenital Adrenal Hyperplasias Presenting in the Newborn and Young Infant

Congenital adrenal hyperplasia includes autosomal recessive conditions that affect the adrenal cortex steroidogenic enzymes (cholesterol side-chain cleavage enzyme; 3β-hydroxysteroid dehydrogenase; 17α-hydroxylase/17,20 lyase; P450 oxidoreductase; 21-hydroxylase; and 11β-hydroxylase) and proteins (steroidogenic acute regulatory protein). These are located within the three major pathways of the steroidogenic apparatus involved in the production of mineralocorticoids, glucocorticoids, and androgens. Many countries have introduced newborn screening program (NSP) based on 17-OH-progesterone (17-OHP) immunoassays on dried blood spots, which enable faster diagnosis and treatment of the most severe forms of 21-hydroxylase deficiency (21-OHD). However, in several others, the use of this diagnostic tool has not yet been implemented and clinical diagnosis remains challenging, especially for males. Furthermore, less severe classic forms of 21-OHD and other rarer types of CAHs are not identified by NSP. The aim of this mini review is to highlight both the main clinical characteristics and therapeutic options of these conditions, which may be useful for a differential diagnosis in the neonatal period, while contributing to the biochemical evolution taking place in the steroidogenic field. Currently, chromatographic techniques coupled with tandem mass spectrometry are gaining attention due to an increase in the reliability of the test results of NPS for detecting 21-OHD. Furthermore, the possibility of identifying CAH patients that are not affected by 21-OHD but presenting elevated levels of 17-OHP by NSP and the opportunity to include the recently investigated 11-oxygenated androgens in the steroid profiles are promising tools for a more precise diagnosis and monitoring of some of these conditions.

A novel mutation of the StAR gene with congenital adrenal hyperplasia and its association with heterochromia iridis: a case report

BACKGROUND

We report a novel mutation within the StAR gene, causing congenital adrenal hyperplasia, with the so far unreported association with heterochromia iridis.

CASE PRESENTATION

In a now 15-year-old girl (born at 41 + 6 weeks of gestation) adrenal failure was diagnosed in the neonatal period based on the clinical picture with spontaneous hypoglycaemia, hyponatremia and an extremely elevated concentration of ACTH (3381 pmol/l; ref. level 1,1-10,1 pmol/l), elevated renin (836 ng/l; ref. level 5-308 ng/l), and a decreased concentration of aldosterone (410 pmol/l; ref. level 886-3540 pmol/l). In addition to hyperpigmented skin the patient exhibited sectorial heterochromia iridis. Sequence analysis of the steroidogenic acute regulatory protein (StAR) gene showed a novel homozygous mutation (c.652G > A (p.Ala218Thr), which was predicted in-silico to be possibly damaging. Under daily steroid substitution her electrolyte levels are balanced while she became obese. Puberty occurred spontaneously.

CONCLUSION

A novel mutation in the StAR gene was identified in a patient with severe adrenal hypoplasia and sectorial heterochromia iridis. We discuss a causal relationship between these two rare phenotypes, i.e. whether very high levels of ACTH and alpha-MSH during early development might have disturbed early differentiation and distribution of uveal melanocytes. If confirmed in additional cases, discolorization of the iris might be considered as an additional phenotypical feature in the differential diagnosis of congenital adrenal insufficiency.

The biological basis of sexual orientation: How hormonal, genetic, and environmental factors influence to whom we are sexually attracted

Humans develop relatively stable attractions to sexual partners during maturation and present a spectrum of sexual orientation from homosexuality to heterosexuality encompassing varying degrees of bisexuality, with some individuals also displaying asexuality. Sexual orientation represents a basic life phenomenon for humans. However, the molecular mechanisms underlying these diverse traits of sexual orientation remain highly controversial. In this review, we systematically discuss recent advancements in sexual orientation research, including those related to measurements and associated brain regions. Current findings regarding sexual orientation modulation by hormonal, genetic, maternal immune system, and environmental factors are summarized in both human and model systems. We also emphasize that future studies should recognize the differences between males and females and pay more attention to minor traits and the epigenetic regulation of sexual orientation. A comprehensive view of sexual orientation may promote our understanding of the biological basis of sex, and that of human reproduction, and evolution.

Steroidogenic Acute Regulatory Protein: Structure, Functioning, and Regulation

Steroidogenesis takes place mainly in adrenal and gonadal cells that produce a variety of structurally similar hormones regulating numerous body functions. The rate-limiting stage of steroidogenesis is cholesterol delivery to the inner mitochondrial membrane, where it is converted by cytochrome P450scc into pregnenolone, a common precursor of all steroid hormones. The major role of supplying mitochondria with cholesterol belongs to steroidogenic acute regulatory protein (STARD1). STARD1, which is synthesized de novo as a precursor containing mitochondrial localization sequence and sterol-binding domain, significantly accelerates cholesterol transport and production of pregnenolone. Despite a tremendous interest in STARD1 fueled by its involvement in hereditary diseases and extensive efforts of numerous laboratories worldwide, many aspects of STARD1 structure, functioning, and regulation remain obscure and debatable. This review presents current concepts on the structure of STARD1 and other lipid transfer proteins, the role of STARD1 in steroidogenesis, and the mechanism of its functioning, as well as identifies the most controversial and least studied questions related to the activity of this protein.

Pubertal and Adult Testicular Functions in Nonclassic Lipoid Congenital Adrenal Hyperplasia: A Case Series and Review

Lipoid congenital adrenal hyperplasia (LCAH) is caused by mutations in STAR and characterized by a defect in steroidogenesis and lipid droplet accumulation in steroidogenic cells. Patients with 46,XY and classic LCAH will typically present with female-type external genitalia. However, those with nonclassic LCAH will have masculinized external genitalia. The rarity of the nonclassic form has precluded the clarification of the long-term outcomes of testicular function in nonclassic LCAH. We report the cases of three adult males with nonclassic LCAH in whom primary adrenal insufficiency had been diagnosed at 5 days, 4 years, and 5 years of age. All exhibited complete male external genitalia and had completed pubertal development without androgen replacement. The endocrinological data showed preserved gonadal function in patients 1 and 2 and hypergonadotropic hypogonadism in patient 3. Semen analyses showed normozoospermia in patient 1 and mild oligozoospermia in patient 2. Electron microscopic analysis of a testicular biopsy specimen from patient 2 at 13 years of age revealed prominent lipid accumulation in the cytosol of Leydig cells. Patients 1 and 2 shared the same compound heterozygous mutations in STAR (p.Glu258* and p.Arg272Cys). Patient 3 possessed a heterozygous dominant-negative mutation in STAR (p.Gly22_Leu59del). A functional assay of a variant STAR-Arg272Cys determined the residual activity as 35% of the wild-type STAR. The results from the present case series and a review of four previously reported adult cases indicate that testosterone synthesis can be preserved in most males with nonclassic LCAH to complete pubertal development and induce germ cell maturation despite lipid accumulation in the Leydig cells.

Pubertal Development and Pregnancy Outcomes in 46,XX Patients With Nonclassic Lipoid Congenital Adrenal Hyperplasia

CONTEXT

Lipoid congenital adrenal hyperplasia (LCAH) is characterized by a disorder of steroidogenesis in both adrenal glands and gonads. 46,XX patients with classic LCAH usually have thelarche and menarche but show anovulatory menstruations and subsequent premature menopause. Only three patients with classic LCAH have been reported to successfully achieve delivery with the aid of assisted reproductive therapies for conception and progesterone replacement therapy during early pregnancy. In contrast, pubertal development and pregnancy outcomes in patients with nonclassic LCAH have not been fully elucidated.

CASE DESCRIPTION

We report four Japanese women who had a diagnosis of primary adrenal insufficiency during infancy or childhood and carried compound heterozygous STAR mutations (p.Gln258* and p.Arg188His, p.Gln258* and p.Met225Thr, and p.Gln258* and p.Arg272Cys). In all four patients, thelarche and menarche spontaneously occurred from 10 to 11 years of age and from 12 to 14 years of age, respectively. Subsequently, their menstruation cycles were regular at almost 1-month intervals. Patient 1 conceived naturally twice, and patient 2 conceived with the use of clomiphene citrate for ovulation induction. These two patients maintained the pregnancies without progesterone replacement therapy and successfully delivered children.

CONCLUSION

Patients with nonclassic LCAH maintain ovarian function, which enables normal pubertal development and a successful pregnancy outcome without progesterone replacement therapy.

Translating genomics to the clinical diagnosis of disorders/differences of sex development

The medical and psychosocial challenges faced by patients living with Disorders/Differences of Sex Development (DSD) and their families can be alleviated by a rapid and accurate diagnostic process. Clinical diagnosis of DSD is limited by a lack of standardization of anatomical and endocrine phenotyping and genetic testing, as well as poor genotype/phenotype correlation. Historically, DSD genes have been identified through positional cloning of disease-associated variants segregating in families and validation of candidates in animal and in vitro modeling of variant pathogenicity. Owing to the complexity of conditions grouped under DSD, genome-wide scanning methods are better suited for identifying disease causing gene variant(s) and providing a clinical diagnosis. Here, we review a number of established genomic tools (karyotyping, chromosomal microarrays and exome sequencing) used in clinic for DSD diagnosis, as well as emerging genomic technologies such as whole-genome (short-read) sequencing, long-read sequencing, and optical mapping used for novel DSD gene discovery. These, together with gene expression and epigenetic studies can potentiate the clinical diagnosis of DSD diagnostic rates and enhance the outcomes for patients and families.

MECHANISMS IN ENDOCRINOLOGY: Rare defects in adrenal steroidogenesis

Congenital adrenal hyperplasia (CAH) is a group of genetic disorders of adrenal steroidogenesis that impair cortisol synthesis, with compensatory increases in ACTH leading to hyperplastic adrenals. The term 'CAH' is generally used to mean 'steroid 21-hydroxylase deficiency' (21OHD) as 21OHD accounts for about 95% of CAH in most populations; the incidences of the rare forms of CAH vary with ethnicity and geography. These forms of CAH are easily understood on the basis of the biochemistry of steroidogenesis. Defects in the steroidogenic acute regulatory protein, StAR, disrupt all steroidogenesis and are the second-most common form of CAH in Japan and Korea; very rare defects in the cholesterol side-chain cleavage enzyme, P450scc, are clinically indistinguishable from StAR defects. Defects in 3β-hydroxysteroid dehydrogenase, which also causes disordered sexual development, were once thought to be fairly common, but genetic analyses show that steroid measurements are generally unreliable for this disorder. Defects in 17-hydroxylase/17,20-lyase ablate synthesis of sex steroids and also cause mineralocorticoid hypertension; these are common in Brazil and in China. Isolated 17,20-lyase deficiency can be caused by rare mutations in at least three different proteins. P450 oxidoreductase (POR) is a co-factor used by 21-hydroxylase, 17-hydroxylase/17,20-lyase and aromatase; various POR defects, found in different populations, affect these enzymes differently. 11-Hydroxylase deficiency is the second-most common form of CAH in European populations but the retention of aldosterone synthesis distinguishes it from 21OHD. Aldosterone synthase deficiency is a rare salt-losing disorder. Mild, 'non-classic' defects in all of these factors have been described. Both the severe and non-classic disorders can be treated if recognized.

Monogenic Disorders of Adrenal Steroidogenesis

Disorders of adrenal steroidogenesis comprise autosomal recessive conditions affecting steroidogenic enzymes of the adrenal cortex. Those are located within the 3 major branches of the steroidogenic machinery involved in the production of mineralocorticoids, glucocorticoids, and androgens. This mini review describes the principles of adrenal steroidogenesis, including the newly appreciated 11-oxygenated androgen pathway. This is followed by a description of pathophysiology, biochemistry, and clinical implications of steroidogenic disorders, including mutations affecting cholesterol import and steroid synthesis, the latter comprising both mutations affecting steroidogenic enzymes and co-factors required for efficient catalysis. A good understanding of adrenal steroidogenic pathways and their regulation is crucial as the basis for sound management of these disorders, which in the majority present in early childhood.

Mutational analysis of rare subtypes of congenital adrenal hyperplasia in a highly inbred population

CONTEXT

Apart from 21 Hydroxylase deficiency, other subtypes of congenital adrenal hyperplasia (CAH) are rare. We studied the clinical features and molecular genetics of a relatively large series of patients with CYP17A1, HSD3β2 and StAR deficiencies.

PATIENTS AND METHODS

We studied 21 patients including 7 patients with CYP17A1, 10 patients with HSD3β2 and 4 patients with StAR deficiencies. For mutation detection, we isolated DNA from peripheral leucocytes, amplified genes of interest using polymerase chain reaction and directly sequenced the amplicons using Dideoxy Chain Termination method.

RESULTS

Regardless of their karyotype, patients with CYP17A1 deficiency presented with normally looking external female genitalia and were raised as females. Hypertension and hypokalemia were prominent features in 4 of 7 patients. Two missense (p.R416H, p.R239Q) and 2 non-sense (p.Y329X, p.Y329X) mutations were found in these 7 cases. In 3 unrelated families with 10 affected siblings with HSD3β2 mutations, two non-sense mutations were found (p.Q334X, p.R335X). 46XY patients with HSD3β2 deficiency presented with ambiguous genitalia while 46XX patients presented with normal female external genitalia. Adrenal crisis was common in patients with both karyotypes. In the 4 patients with StAR deficiency, both genetic male and female patients presented with normally looking female external genitalia and adrenal crisis. One previously reported missense mutation (p.R182H) was found in 3 unrelated patients and a novel non-sense mutation (p.Q264X) in the fourth patient.

CONCLUSIONS

These cases of rare subtypes of CAH illustrate the heterogeneous phenotypic and genetic features of these subtypes and add unique novel mutations to the previously known ones.

Measurement of Mitochondrial Cholesterol Import Using a Mitochondria-Targeted CYP11A1 Fusion Construct

All animal membranes require cholesterol as an essential regulator of biophysical properties and function, but the levels of cholesterol vary widely among different subcellular compartments. Mitochondria, and in particular the inner mitochondrial membrane, have the lowest levels of cholesterol in the cell. Nevertheless, mitochondria need cholesterol for membrane maintenance and biogenesis, as well as oxysterol, steroid, and hepatic bile acid production. Alterations in mitochondrial cholesterol have been associated with a range of pathological conditions, including cancer, hepatosteatosis, cardiac ischemia, Alzheimer's, and Niemann-Pick Type C Disease. The mechanisms of mitochondrial cholesterol import are not fully elucidated yet, and may vary in different cell types and environmental conditions. Measuring cholesterol trafficking to the mitochondrial membranes is technically challenging because of its low abundance; for example, traditional pulse-chase experiments with isotope-labeled cholesterol are not feasible. Here, we describe improvements to a method first developed by the Miller group at the University of California to measure cholesterol trafficking to the inner mitochondrial membrane (IMM) through the conversion of cholesterol to pregnenolone. This method uses a mitochondria-targeted, ectopically expressed fusion construct of CYP11A1, ferredoxin reductase and ferredoxin. Pregnenolone is formed exclusively from cholesterol at the IMM, and can be analyzed with high sensitivity and specificity through ELISA or radioimmunoassay of the medium/buffer to reflect mitochondrial cholesterol import. This assay can be used to investigate the effects of genetic or pharmacological interventions on mitochondrial cholesterol import in cultured cells or isolated mitochondria.

Genetic defects in pediatric-onset adrenal insufficiency in Japan

CONTEXT

Most patients with pediatric-onset primary adrenal insufficiency (PAI), such as 21-hydroxylase deficiency, can be diagnosed by measuring the urine or serum levels of steroid metabolites. However, the etiology is often difficult to determine in a subset of patients lacking characteristic biochemical findings.

OBJECTIVE

To assess the frequency of genetic defects in Japanese children with biochemically uncharacterized PAI and characterize the phenotypes of mutation-carrying patients.

METHODS

We enrolled 63 Japanese children (59 families) with biochemically uncharacterized PAI, and sequenced 12 PAI-associated genes. The pathogenicities of rare variants were assessed based on in silico analyses and structural modeling. We calculated the proportion of mutation-carrying patients according to demographic characteristics.

RESULTS

We identified genetic defects in 50 (85%) families: STAR in 19, NR0B1 in 18, SAMD9 in seven, AAAS in two, NNT in two, MC2R in one and CDKN1C in one. NR0B1 defects were identified in 78% of the male patients that received both glucocorticoid and mineralocorticoid replacement therapy and had normal male external genitalia. STAR defects were identified in 67% of female and 9% of male patients. Seven of the 19 patients with STAR defects developed PAI at age two or older, out of whom, five did not have mineralocorticoid deficiency.

CONCLUSIONS

Molecular testing elucidated the etiologies of most biochemically uncharacterized PAI patients. Genetic defects such as NR0B1 defects are presumed based on phenotypes, while others with broad phenotypic variability, such as STAR defects, are difficult to diagnose. Molecular testing is a rational approach to diagnosis in biochemically uncharacterized PAI patients.

Mutation Spectrum of STAR and a Founder Effect of the p.Q258* in Korean Patients with Congenital Lipoid Adrenal Hyperplasia

Congenital lipoid adrenal hyperplasia (CLAH) is the most severe form of congenital adrenal hyperplasia, caused by defects in the steroidogenic acute regulatory protein (STAR). The STAR p.Q258* mutation is the most common mutation in China, Japan, and Korea, suggesting a founder effect. This study aimed to investigate the phenotypic and mutation spectrum of STAR defects and identify a founder effect of the p.Q258* mutation in Korean patients with CLAH. For 45 patients from 42 independent pedigrees, haplotype analysis was performed in 10 unrelated trio families, including patients with the p.Q258* mutation whose DNA samples were available, using 1,972 single nucleotide polymorphism (SNP) and six short tandem repeat (STR) markers. An Illumina Infinium® Human Omni2.5-8 v1.3 performed the SNP genotyping. Among 84 alleles from 42 unrelated families, mutation p.Q258* was found in 74 alleles (88.1%) from 41 families. A shared haplotype was identified in 17 of 20 alleles from 10 patients (size, 198 kb). The age of the founder mutation was estimated as 4,875 years (95% credible set: 3,575-7,925 years) assuming an intergenerational time interval of 25 years. The STAR p.Q258* mutation is the most common in Korean patients with CLAH, suggesting a founder effect. The age of the mutation corresponded with the date when the Korean people settled in the Korean peninsula. The high prevalence of p.Q258* in Japan and China also suggests a founder effect in Asian countries.

Disorders in the initial steps of steroid hormone synthesis

Steroidogenesis begins with cellular internalization of low-density lipoprotein particles and subsequent intracellular processing of cholesterol. Disorders in these steps include Adrenoleukodystrophy, Wolman Disease and its milder variant Cholesterol Ester Storage Disease, and Niemann-Pick Type C Disease, all of which may present with adrenal insufficiency. The means by which cholesterol is directed to steroidogenic mitochondria remains incompletely understood. Once cholesterol reaches the outer mitochondrial membrane, its delivery to the inner mitochondrial membrane is regulated by the steroidogenic acute regulatory protein (StAR). Severe StAR mutations cause classic congenital lipoid adrenal hyperplasia, characterized by lipid accumulation in the adrenal, adrenal insufficiency, and disordered sexual development in 46,XY individuals. The lipoid CAH phenotype, including spontaneous puberty in 46,XX females, is explained by a two-hit model. StAR mutations that retain partial function cause a milder, non-classic disease characterized by glucocorticoid deficiency, with lesser disorders of mineralocorticoid and sex steroid synthesis. Once inside the mitochondria, cholesterol is converted to pregnenolone by the cholesterol side-chain cleavage enzyme, P450scc, encoded by the CYP11A1 gene. Rare patients with mutations of P450scc are clinically and hormonally indistinguishable from those with lipoid CAH, and may also present as milder non-classic disease. Patients with P450scc defects do not have the massive adrenal hyperplasia that characterizes lipoid CAH, but adrenal imaging may occasionally fail to distinguish these, necessitating DNA sequencing.

ACTH Action on StAR Biology

Adrenocorticotropin hormone (ACTH) produced by the anterior pituitary stimulates glucocorticoid synthesis by the adrenal cortex. The first step in glucocorticoid synthesis is the delivery of cholesterol to the mitochondrial matrix where the first enzymatic reaction in the steroid hormone biosynthetic pathway occurs. A key response of adrenal cells to ACTH is activation of the cAMP-protein kinase A (PKA) signaling pathway. PKA activation results in an acute increase in expression and function of the Steroidogenic Acute Regulatory protein (StAR). StAR plays an essential role in steroidogenesis- it controls the hormone-dependent movement of cholesterol across the mitochondrial membranes. Currently StAR's mechanism of action remains a major unanswered question in the field. However, some insight may be gained from understanding the mechanism(s) controlling the PKA-dependent phosphorylation of StAR at S194/195 (mouse/human StAR), a modification that is required for function. This mini-review provides a background on StAR's biology with a focus on StAR phosphorylation. The model for StAR translation and phosphorylation at the outer mitochondrial membrane, the location for StAR function, is presented to highlight a unifying theme emerging from diverse studies.

Thirty-Eight-Year Follow-Up of Two Sibling Lipoid Congenital Adrenal Hyperplasia Patients Due to Homozygous Steroidogenic Acute Regulatory (STARD1) Protein Mutation. Molecular Structure and Modeling of the STARD1 L275P Mutation

Objective: Review the impact of StAR (STARD1) mutations on steroidogenesis and fertility in LCAH patients. Examine the endocrine mechanisms underlying the pathology of the disorder and the appropriate therapy for promoting fertility and pregnancies.

Design: Published data in the literature and a detailed 38-year follow-up of two sibling LCAH patients. Molecular structure and modeling of the STARD1 L275P mutation.

Setting: University hospital.

Patients: Patient A (46,XY female phenotype) and patient B (46,XX female) with LCAH bearing the L275P mutation in STARD1.

Interventions: Since early-age diagnosis, both patients underwent corticoid replacement therapy. Patient A received estrogen therapy at pubertal age. Clomiphene therapy was given to Patient B to induce ovulation. Pregnancies were protected with progesterone administration.

Main Outcome Measures: Clinical and molecular assessment of adrenal and gonadal functions.

Results: Both patients have classic manifestations of corticosteroid deficiency observed in LCAH. Time of onset and severity were different. Patient A developed into a female phenotype due to early and severe damage of Leydig cells. Patient B started a progressive pubertal development, menarche and regular non-ovulatory cycle. She was able to have successful pregnancies.

Conclusions: Understanding the molecular structure and function of STARD1 in all steroidogenic tissues is the key for comprehending the heterogeneous clinical manifestations of LCAH, and the development of an appropriate strategy for the induction of ovulation and protecting pregnancies in this disease.

Identification of five novel STAR variants in ten Chinese patients with congenital lipoid adrenal hyperplasia

Congenital lipoid adrenal hyperplasia (CLAH) is a rare autosomal recessive disorder caused by defective synthesis of all steroids. This disorder is characterized by 46,XY sex reversal, skin hyperpigmentation, early-onset adrenal crisis and enlarged adrenal with fatty accumulation. CLAH is caused by mutations in the STAR gene. The clinical features and STAR gene mutation spectrum of a large cohort of Chinese patients with CLAH were not reported previously. We performed clinical retrospective review and genetic analysis of the STAR gene in ten unrelated Chinese phenotypic female patients who were clinically diagnosed with CLAH and followed up in our hospital from 2006 to 2015. All ten patients, including two 46,XY females and eight 46,XX females, presented skin hyperpigmentation and early salt-wasting episode, and showed normal growth and development after steroid replacement treatment. Totally 20 mutant alleles containing 11 different STAR gene mutations were identified in these ten patients, including five novel variants (two missense and three null variants), all predicted to be pathogenic in bioinformatics analysis, and six mutations described in previous literature. Among these 11 mutations, a reported mutation c.772C>T and a novel variant c.707_708delinsCTT were most frequent, accounting for 35% and 15% of the total mutant alleles, respectively. This is the first report of a large Chinese cohort with CLAH, presenting the mutation spectrum of the STAR gene and two possible founder mutations in the Chinese population, which may contribute to better genetic counseling and prenatal diagnosis.

Role of the steroidogenic acute regulatory protein in health and disease

Steroid hormones are an important class of regulatory molecules that are synthesized in steroidogenic cells of the adrenal, ovary, testis, placenta, brain, and skin, and influence a spectrum of developmental and physiological processes. The steroidogenic acute regulatory protein (STAR) predominantly mediates the rate-limiting step in steroid biosynthesis, i.e., the transport of the substrate of all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane. At the inner membrane, cytochrome P450 cholesterol side chain cleavage enzyme cleaves the cholesterol side chain to form the first steroid, pregnenolone, which is converted by a series of enzymes to various steroid hormones in specific tissues. Both basic and clinical evidence have demonstrated the crucial involvement of the STAR protein in the regulation of steroid biosynthesis. Multiple levels of regulation impinge on STAR action. Recent findings demonstrate that hormone-sensitive lipase, through its action on the hydrolysis of cholesteryl esters, plays an important role in regulating STAR expression and steroidogenesis which involve the liver X receptor pathway. Activation of the latter influences macrophage cholesterol efflux that is a key process in the prevention of atherosclerotic cardiovascular disease. Appropriate regulation of steroid hormones is vital for proper functioning of many important biological activities, which are also paramount for geriatric populations to live longer and healthier. This review summarizes the current level of understanding on tissue-specific and hormone-induced regulation of STAR expression and steroidogenesis, and provides insights into a number of cholesterol and/or steroid coupled physiological and pathophysiological consequences.

Transcriptional activation of LON Gene by a new form of mitochondrial stress: A role for the nuclear respiratory factor 2 in StAR overload response (SOR)

High output of steroid hormone synthesis in steroidogenic cells of the adrenal cortex and the gonads requires the expression of the steroidogenic acute regulatory protein (StAR) that facilitates cholesterol mobilization to the mitochondrial inner membrane where the CYP11A1/P450scc enzyme complex converts the sterol to the first steroid. Earlier studies have shown that StAR is active while pausing on the cytosolic face of the outer mitochondrial membrane while subsequent import of the protein into the matrix terminates the cholesterol mobilization activity. Consequently, during repeated activity cycles, high level of post-active StAR accumulates in the mitochondrial matrix. To prevent functional damage due to such protein overload effect, StAR is degraded by a sequence of three to four ATP-dependent proteases of the mitochondria protein quality control system, including LON and the m-AAA membranous proteases AFG3L2 and SPG7/paraplegin. Furthermore, StAR expression in both peri-ovulatory ovarian cells, or under ectopic expression in cell line models, results in up to 3-fold enrichment of the mitochondrial proteases and their transcripts. We named this novel form of mitochondrial stress as StAR overload response (SOR). To better understand the SOR mechanism at the transcriptional level we analyzed first the unexplored properties of the proximal promoter of the LON gene. Our findings suggest that the human nuclear respiratory factor 2 (NRF-2), also known as GA binding protein (GABP), is responsible for 88% of the proximal promoter activity, including the observed increase of transcription in the presence of StAR. Further studies are expected to reveal if common transcriptional determinants coordinate the SOR induced transcription of all the genes encoding the SOR proteases.

Clinical and molecular review of atypical congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is one of the most common inherited metabolic disorders. It comprises a group of autosomal recessive disorders caused by the mutations in the genes encoding for steroidogenic enzymes that involved cortisol synthesis. More than 90% of cases are caused by a defect in the enzyme 21-hydroxylase. Four other enzyme deficiencies (cholesterol side-chain cleavage, 17α-hydroxylase [P450c17], 11β-hydroxylase [P450c11β], 3β-hydroxysteroid dehydrogenase) in the steroid biosynthesis pathway, along with one cholesterol transport protein defect (steroidogenic acute regulatory protein), and one electrontransfer protein (P450 oxidoreductase) account for the remaining cases. The clinical symptoms of the different forms of CAH result from the particular hormones that are deficient and those that are produced in excess. A characteristic feature of CAH is genital ambiguity or disordered sex development, and most variants are associated with glucocorticoid deficiency. However, in the rare forms of CAH other than 21-hydroxylase deficiency so-called "atypical CAH", the clinical and hormonal phenotypes can be more complicated, and are not well recognized. This review will focus on the atypical forms of CAH, including the genetic analyses, and phenotypic correlates.

Congenital lipoid adrenal hyperplasia

Congenital lipoid adrenal hyperplasia (lipoid CAH) is the most fatal form of CAH, as it disrupts adrenal and gonadal steroidogenesis. Most cases of lipoid CAH are caused by recessive mutations in the gene encoding steroidogenic acute regulatory protein (StAR). Affected patients typically present with signs of severe adrenal failure in early infancy and 46,XY genetic males are phenotypic females due to disrupted testicular androgen secretion. The StAR p.Q258X mutation accounts for about 70% of affected alleles in most patients of Japanese and Korean ancestry. However, it is more prevalent (92.3%) in the Korean population. Recently, some patients have been showed that they had late and mild clinical findings. These cases and studies constitute a new entity of 'nonclassic lipoid CAH'. The cholesterol side-chain cleavage enzyme, P450scc (CYP11A1), plays an essential role converting cholesterol to pregnenolone. Although progesterone production from the fetally derived placenta is necessary to maintain a pregnancy to term, some patients with P450scc mutations have recently been reported. P450scc mutations can also cause lipoid CAH and establish a recently recognized human endocrine disorder.

The novel mutation p.Trp147Arg of the steroidogenic acute regulatory protein causes classic lipoid congenital adrenal hyperplasia with adrenal insufficiency and 46,XY disorder of sex development

BACKGROUND

The steroidogenic acute regulatory protein (StAR) is essential for steroidogenesis by mediating cholesterol transfer into mitochondria. Inactivating StAR mutations cause lipoid congenital adrenal hyperplasia.

OBJECTIVE AND METHODS

To identify causative mutations in a patient presenting with adrenal failure during early infancy. The objective was to study the functional and structural consequences of the novel StAR mutation p.Trp147Arg in a Turkish patient detected in compound heterozygosity with the p.Glu169Lys mutation.

RESULTS

Transient in vitro expression of the mutant proteins together with P450 side-chain cleavage enzyme, adrenodoxin, and adrenodoxin reductase yielded severely diminished cholesterol conversion of the p.Trp147Arg mutant. The previously described p.Glu169Lys mutant led to significantly lower cholesterol conversion than wild-type StAR protein. As derived from three-dimensional protein modeling, the residue W147 is stabilizing the C-terminal helix in a closed conformation hereby acting as gatekeeper of the ligand cavity of StAR.

CONCLUSIONS

The novel mutation p.Trp147Arg causes primary adrenal insufficiency and complete sex reversal in the 46,XY patient. Clinical disease, in vitro studies and three-dimensional protein modeling of the mutation p.Trp147Arg underscore the relevance of this highly conserved residue for StAR protein function.

STAR splicing mutations cause the severe phenotype of lipoid congenital adrenal hyperplasia: insights from a novel splice mutation and review of reported cases

OBJECTIVE

The steroidogenic acute regulatory protein (StAR) transports cholesterol to the mitochondria for steroidogenesis. Loss of StAR function causes lipoid congenital adrenal hyperplasia (LCAH) which is characterized by impaired synthesis of adrenal and gonadal steroids causing adrenal insufficiency, 46,XY disorder of sex development (DSD) and failure of pubertal development. Partial loss of StAR activity may cause adrenal insufficiency only.

PATIENT

A newborn girl was admitted for mild dehydration, hyponatremia, hyperkalemia and hypoglycaemia and had normal external female genitalia without hyperpigmentation. Plasma cortisol, 17OH-progesterone, DHEA-S, androstendione and aldosterone were low, while ACTH and plasma renin activity were elevated, consistent with the diagnosis of primary adrenal insufficiency. Imaging showed normal adrenals, and cytogenetics revealed a 46,XX karyotype. She was treated with fluids, hydrocortisone and fludrocortisone.

DESIGN, METHODS AND RESULTS

Genetic studies revealed a novel homozygous STAR mutation in the 3' acceptor splice site of intron 4, c.466-1G>A (IVS4-1G>A). To test whether this mutation would affect splicing, we performed a minigene experiment with a plasmid construct containing wild-type or mutant StAR gDNA of exons-introns 4-6 in COS-1 cells. The splicing was assessed on total RNA using RT-PCR for STAR cDNAs. The mutant STAR minigene skipped exon 5 completely and changed the reading frame. Thus, it is predicted to produce an aberrant and shorter protein (p.V156GfsX19). Computational analysis revealed that this mutant protein lacks wild-type exons 5-7 which are essential for StAR-cholesterol interaction.

CONCLUSIONS

STAR c.466-1A skips exon 5 and causes a dramatic change in the C-terminal sequence of the protein, which is essential for StAR-cholesterol interaction. This splicing mutation is a loss-of-function mutation explaining the severe phenotype of our patient. Thus far, all reported splicing mutations of STAR cause a severe impairment of protein function and phenotype.

Steroid hormone synthesis in mitochondria

Mitochondria are essential sites for steroid hormone biosynthesis. Mitochondria in the steroidogenic cells of the adrenal, gonad, placenta and brain contain the cholesterol side-chain cleavage enzyme, P450scc, and its two electron-transfer partners, ferredoxin reductase and ferredoxin. This enzyme system converts cholesterol to pregnenolone and determines net steroidogenic capacity, so that it serves as the chronic regulator of steroidogenesis. Several other steroidogenic enzymes, including 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase and aldosterone synthase also reside in mitochondria. Similarly, the mitochondria of renal tubular cells contain two key enzymes participating in the activation and degradation of vitamin D. The access of cholesterol to the mitochondria is regulated by the steroidogenic acute regulatory protein, StAR, serving as the acute regulator of steroidogenesis. StAR action requires a complex multi-component molecular machine on the outer mitochondrial membrane (OMM). Components of this machine include the 18 kDa translocator protein (TSPO), the voltage-dependent anion chanel (VDAC-1), TSPO-associated protein 7 (PAP7, ACBD3), and protein kinase A regulatory subunit 1α (PKAR1A). The precise fashion in which these proteins interact and move cholesterol from the OMM to P450scc, and the means by which cholesterol is loaded into the OMM, remain unclear. Human deficiency diseases have been described for StAR and for all the mitochondrial steroidogenic enzymes, but not for the electron transfer proteins or for the components of the cholesterol import machine.

Infarct-induced steroidogenic acute regulatory protein: a survival role in cardiac fibroblasts

Steroidogenic acute regulatory protein (StAR) is indispensable for steroid hormone synthesis in the adrenal cortex and the gonadal tissues. This study reveals that StAR is also expressed at high levels in nonsteroidogenic cardiac fibroblasts confined to the left ventricle of mouse heart examined 3 days after permanent ligation of the left anterior descending coronary artery. Unlike StAR, CYP11A1 and 3β-hydroxysteroid dehydrogenase proteins were not observed in the postinfarction heart, suggesting an apparent lack of de novo cardiac steroidogenesis. Work with primary cultures of rat heart cells revealed that StAR is induced in fibroblasts responding to proapoptotic treatments with hydrogen peroxide or the kinase inhibitor staurosporine (STS). Such induction of StAR in culture was noted before spontaneous differentiation of the fibroblasts to myofibroblasts. STS induction of StAR in the cardiac fibroblasts conferred a marked resistance to apoptotic cell death. Consistent with that finding, down-regulation of StAR by RNA interference proportionally increased the number of STS-treated apoptotic cells. StAR down-regulation also resulted in a marked increase of BAX activation in the mitochondria, an event known to associate with the onset of apoptosis. Last, STS treatment of HeLa cells showed that apoptotic demise characterized by mitochondrial fission, cytochrome c release, and nuclear fragmentation is arrested in individual HeLa cells overexpressing StAR. Collectively, our in vivo and ex vivo evidence suggests that postinfarction expression of nonsteroidogenic StAR in cardiac fibroblasts has novel antiapoptotic activity, allowing myofibroblast precursor cells to survive the traumatized event, probably to differentiate and function in tissue repair at the infarction site.

Identification of novel mutations in STAR gene in patients with lipoid congenital adrenal hyperplasia: a first report from India

Lipoid congenital adrenal hyperplasia (LCAH), a rare disorder of steroid biosynthesis, is the most severe form of CAH. We report novel molecular findings of three unrelated infants with LCAH diagnosed at our center. A known missense mutation c.653C>T (p.A218V) and two novel mutations [premature termination c.441G>A (or p.W147X) and frameshift deletion c.del815G (or p.R272PfsX35)] were identified after complete sequencing of the STAR gene. Prenatal diagnosis was carried out for the family with mutation c.815delG by molecular testing wherein the fetus was found to be homozygous for the mutation. This is the first report of molecular diagnosis and prenatal testing for LCAH from India.

STARD5 specific ligand binding: comparison with STARD1 and STARD4 subfamilies

We present herein a review of our recent results on the characterization of the binding sites of STARD1, STARD5 and STARD6 using NMR and other biophysical techniques. Whereas STARD1 and STARD6 bind cholesterol, no cholesterol binding could be detected for STARD5. However, titration of STARD5 with cholic acid and chenodeoxycholic acid led to specific binding. Using perturbation of the (1)H-(15)N-HSQC spectra and the sequence specific NMR assignments, we identified the amino acids in contact with those ligands. The most perturbed residues in presence of ligands are lining the internal cavity of the protein. Interestingly, these residues are not conserved in STARD1 and STARD6 and could therefore be key structural determinants of the specificity of START domains toward their ligands. We highlight three tissues expressing STARD5 that are affected by bile acids.

Distinguishing deficiencies in the steroidogenic acute regulatory protein and the cholesterol side chain cleavage enzyme causing neonatal adrenal failure

OBJECTIVES

To determine the genetic basis of disordered steroidogenesis in Kuwaiti siblings.

STUDY DESIGN

Two siblings (46,XX and 46,XY) had normal female external genitalia and severe glucocorticoid and mineralocorticoid deficiency presenting in the first month of life. Abdominal ultrasonography showed normal size adrenal glands, suggesting cholesterol side chain cleavage enzyme (P450scc) deficiency. The CYP11A1 gene encoding P450scc and the STAR gene encoding the steroidogenic acute regulatory protein (StAR) were directly sequenced from leukocyte DNA.

RESULTS

All exons and intron/exon boundaries of the CYP11A1 gene were normal; the STAR gene was homozygous for a novel 14-base deletion/frameshift in exon 4 (g.4643_4656del), so that no functional protein could be produced. Both parents and an unaffected sibling were heterozygous; zygosity was confirmed with a BsmF1 restriction fragment length polymorphism.

CONCLUSIONS

Unlike most patients with StAR deficiency, our patients did not have the massive adrenal hyperplasia typical of congenital lipoid adrenal hyperplasia. The distinction between StAR and P450scc deficiency may require gene sequencing.

Long-term clinical data and molecular defects in the STAR gene in five Greek patients

CONTEXT

Steroidogenic acute regulatory (STAR) gene mutations lead to adrenal and gonadal failure. Interesting, though as yet unexplained, features are the formation of ovarian cysts and the potential presence of CNS findings.

OBJECTIVE

To report biochemical, genetic, and long-term clinical data in five Greek patients from four different families with STAR gene defects (three 46,XX and two 46,XY).

METHODS AND RESULTS

All patients presented in early infancy with adrenal insufficiency. The STAR gene mutation c.834del11bp, detected in three of our patients, completely alters the carboxyl end of the STAR protein and has not thus far been described in other population groups. These three patients belong to three separate families, possibly genetically related, as they live in different villages located in a small region of a Greek island. However, their interrelationship has not been proven. A second mutation, p.W250X, detected in our fourth family, was previously described only in two Serbian patients. Ovarian cysts were detected ultrasonographically in our 46,XX patients and seemed to respond to a low dose of a contraceptive. The histology of an excised ovarian cyst was diagnosed as a corpus luteum (CL) cyst. In two out of the four patients who had undergone brain magnetic resonance imaging, asymptomatic Chiari-1 malformation was observed.

CONCLUSIONS

The occurrence of STAR gene mutation c.834del11bp in three families living in a restricted geographic region could indicate either a founder effect or simply reflect a spread of this defect in a highly related population. The ovarian histological findings suggest that ovarian cysts detected ultrasonographically in 46,XX individuals with STAR gene defects may be CL cysts. The Chiari-1 malformation in two of our patients may be part of the STAR gene mutation phenotype. Nevertheless, more data are needed to confirm or disprove the existence of specific CNS pathology in patients with STAR gene mutations.

StAR enhances transcription of genes encoding the mitochondrial proteases involved in its own degradation

Steroidogenic acute regulatory protein (StAR) is essential for steroid hormone synthesis in the adrenal cortex and the gonads. StAR activity facilitates the supply of cholesterol substrate into the inner mitochondrial membranes where conversion of the sterol to a steroid is catalyzed. Mitochondrial import terminates the cholesterol mobilization activity of StAR and leads to mounting accumulation of StAR in the mitochondrial matrix. Our studies suggest that to prevent mitochondrial impairment, StAR proteolysis is executed by at least 2 mitochondrial proteases, ie, the matrix LON protease and the inner membrane complexes of the metalloproteases AFG3L2 and AFG3L2:SPG7/paraplegin. Gonadotropin administration to prepubertal rats stimulated ovarian follicular development associated with increased expression of the mitochondrial protein quality control system. In addition, enrichment of LON and AFG3L2 is evident in StAR-expressing ovarian cells examined by confocal microscopy. Furthermore, reporter studies of the protease promoters examined in the heterologous cell model suggest that StAR expression stimulates up to a 3.5-fold increase in the protease gene transcription. Such effects are StAR-specific, are independent of StAR activity, and failed to occur upon expression of StAR mutants that do not enter the matrix. Taken together, the results of this study suggest the presence of a novel regulatory loop, whereby acute accumulation of an apparent nuisance protein in the matrix provokes a mitochondria to nucleus signaling that, in turn, activates selected transcription of genes encoding the enrichment of mitochondrial proteases relevant for enhanced clearance of StAR.

Delayed diagnosis of adrenal insufficiency in a patient with severe penoscrotal hypospadias due to two novel P450 side-change cleavage enzyme (CYP11A1) mutations (p.R360W; p.R405X)

CONTEXT

Cytochrome P450 side-chain cleavage enzyme (CYP11A1) catalyses the first and rate-limiting step of steroidogenesis, the conversion of cholesterol to pregnenolone. CYP11A1 deficiency is commonly associated with adrenal insufficiency, and in 46,XY individuals, with variable degrees of disorder of sex development (DSD).

PATIENT AND METHODS

The patient was born with hyperpigmentation, micropenis, penoscrotal hypospadias, and mild cryptorchidism. Biochemical and hormonal findings were normal except for low testosterone and low-borderline cortisol. However, no short synacthen test was undertaken. Development was unremarkable apart from an episode labeled as sepsis with documented hyperkalemia and elevated C-reactive protein at age 15 days. Diagnosis of 46,XY DSD was made at age 2.5 months. Progression of hyperpigmentation prompted further investigations and the diagnosis of adrenal insufficiency was established at 2 years with raised ACTH, normal renin activity, and failure of cortisol to respond to short synacthen test. Genetic analyses were performed. The novel CYP11A1 mutations were characterized in vitro and in silico.

RESULTS

The patient was compound heterozygous for two novel CYP11A1 mutations, p.R360W and p.R405X. p.R360W retained 30-40% of wild-type activity. In silico analyses confirmed these findings and indicated that p.R405X is severe.

CONCLUSIONS

This study demonstrates the pathogenicity of two novel CYP11A1 mutations found in a patient with delayed diagnosis of CYP11A1 deficiency. Patients with partial deficiencies of steroidogenic enzymes are at risk to be misdiagnosed if adrenal function is not assessed. The adrenocortical function should be routinely assessed in all patients with DSD including severe hypospadias of unknown origin to prevent life-threatening adrenal crises.

StAR-related lipid transfer domain protein 5 binds primary bile acids

Steroidogenic acute regulatory-related lipid transfer (START) domain proteins are involved in the nonvesicular intracellular transport of lipids and sterols. The STARD1 (STARD1 and STARD3) and STARD4 subfamilies (STARD4-6) have an internal cavity large enough to accommodate sterols. To provide a deeper understanding on the structural biology of this domain, the binding of sterols to STARD5, a member of the STARD4 subfamily, was monitored. The SAR by NMR [(1)H-(15)N heteronuclear single-quantum coherence (HSQC)] approach, complemented by circular dichroism (CD) and isothermal titration calorimetry (ITC), was used. Titration of STARD5 with cholic (CA) and chenodeoxycholic acid (CDCA), ligands of the farnesoid X receptor (FXR), leads to drastic perturbation of the (1)H-(15)N HSQC spectra and the identification of the residues in contact with those ligands. The most perturbed residues in presence of ligands are lining the internal cavity of the protein. Ka values of 1.8·10-(4) M(-1) and 6.3·10(4) M(-1) were measured for CA and CDCA, respectively. This is the first report of a START domain protein in complex with a sterol ligand. Our original findings indicate that STARD5 may be involved in the transport of bile acids rather than cholesterol.

Congenital lipoid adrenal hyperplasia (a rare form of adrenal insufficiency and ambiguous genitalia) caused by a novel mutation of the steroidogenic acute regulatory protein gene

Congenital lipoid adrenal hyperplasia (lipoid CAH) is a rare autosomal recessive disorder of adrenal and gonadal steroidogenesis. It is most frequently caused by mutations in the steroidogenic acute regulatory protein (StAR) gene. Patients with lipoid CAH typically present with adrenal crisis in early infancy, and those with a 46,XY karyotype have female genitalia. However, it has been recently recognized that the phenotype can be quite variable, in that adrenal insufficiency is detected later in life and patients may have partially masculinized or even normal male genitalia. We report a patient assigned and reared as a female with a 46,XY karyotype and with a homozygous intron 2 (c.178+1G>C) splice site mutation of the StAR gene, which is a novel mutation that causes lipoid CAH. Her clinical presentation was somewhat atypical for a patient with classic lipoid CAH, marked by mild masculinization of the genitalia, detectable adrenal steroids at baseline, and ability to tolerate the stress of a surgical procedure with anesthesia without receiving glucocorticoid treatment.

CONCLUSION

There is significant phenotypic variability among patients with lipoid CAH. While splice site mutations in the StAR gene lead to premature translational termination, resulting in truncated and non-functional proteins, there is phenotypic variability among patients with such mutations. Our patient appears to have the more atypical phenotype compared to reported patients with similar mutations. The molecular mechanism underlying this heterogeneity remains unclear.

Prenatal diagnosis of congenital lipoid adrenal hyperplasia (CLAH) by molecular genetic testing in Korean siblings

Congenital lipoid adrenal hyperplasia (CLAH) is caused by mutations to the steroidogenic acute regulatory protein (StAR) gene associated with the inability to synthesize all adrenal and gonadal steroids. Inadequate treatment in an infant with this condition may result in sudden death from an adrenal crisis. We report a case in which CLAH developed in Korean siblings; the second child was prenatally diagnosed because the first child was affected and low maternal serum estriol was detected in a prenatal screening test. To our knowledge, this is the first prenatal diagnosis of the Q258X StAR mutation, which is the only consistent genetic cluster identified to date in Japanese and Korean populations.

High allele frequency of the p.Q258X mutation and identification of a novel mis-splicing mutation in the STAR gene in Korean patients with congenital lipoid adrenal hyperplasia

OBJECTIVE

Steroidogenic acute regulatory (STAR) protein plays a crucial role in steroidogenesis, and mutations in the STAR gene cause congenital lipoid adrenal hyperplasia (CLAH). This study investigated the STAR mutation spectrum and functionally analyzed a novel STAR mutation in Korean patients with CLAH.

METHODS

Mutation analysis of STAR was carried out in 25 unrelated Korean CLAH patients. A region of STAR comprising exons 4-7 was cloned from human genomic DNA into an expression vector, followed by site-directed mutagenesis and transient expression in COS7 cells. The splicing pattern was analyzed by in vitro transcription, and each transcript was functionally characterized by measuring pregnenolone production in COS7 cells cotransfected with the cholesterol side chain cleavage system.

RESULTS

Mutation p.Q258X was identified in 46 of 50 alleles (92%); mutation c.653C>T was detected in two alleles (4%); and mutations p.R182H and c.745-6_810del were found in one allele (2%). Reverse transcriptase-PCR products amplified from a patient heterozygous for compound c.653C>T and c.745-6_810del mutation revealed multiple alternatively spliced mRNAs. In vitro expression analysis of a minigene consisting of exons 4-7 containing the c.653C>T yielded two transcripts in which exon 6 or exons 5 and 6 were skipped. The encoded proteins exhibited defective pregnenolone-producing ability. The c.745-6_810del mutation led to full and partial intron retention.

CONCLUSIONS

p.Q258X is the most common STAR mutation in Korea. A previously reported c.653C>T variant was found to cause aberrant splicing at the mRNA level, resulting in perturbation of STAR function. The c.745-6_810del mutation also resulted in aberrant splicing.

Early steps in steroidogenesis: intracellular cholesterol trafficking

Steroid hormones are made from cholesterol, primarily derived from lipoproteins that enter cells via receptor-mediated endocytosis. In endo-lysosomes, cholesterol is released from cholesterol esters by lysosomal acid lipase (LAL; disordered in Wolman disease) and exported via Niemann-Pick type C (NPC) proteins (disordered in NPC disease). These diseases are characterized by accumulated cholesterol and cholesterol esters in most cell types. Mechanisms for trans-cytoplasmic cholesterol transport, membrane insertion, and retrieval from membranes are less clear. Cholesterol esters and "free" cholesterol are enzymatically interconverted in lipid droplets. Cholesterol transport to the cholesterol-poor outer mitochondrial membrane (OMM) appears to involve cholesterol transport proteins. Cytochrome P450scc (CYP11A1) then initiates steroidogenesis by converting cholesterol to pregnenolone on the inner mitochondrial membrane (IMM). Acute steroidogenic responses are regulated by cholesterol delivery from OMM to IMM, triggered by the steroidogenic acute regulatory protein (StAR). Chronic steroidogenic capacity is determined by CYP11A1 gene transcription. StAR mutations cause congenital lipoid adrenal hyperplasia, with absent steroidogenesis, potentially lethal salt loss, and 46,XY sex reversal. StAR mutations initially destroy most, but not all steroidogenesis; low levels of StAR-independent steroidogenesis are lost later due to cellular damage, explaining the clinical findings. Rare P450scc mutations cause a similar syndrome. This review addresses these early steps in steroid biosynthesis.