A new variant in signal peptide of the human luteinizing hormone receptor (LHCGR) affects receptor biogenesis causing leydig cell hypoplasia.

The human luteinizing hormone/chorionic gonadotropin receptor (LHCGR) plays a fundamental role in male and female reproduction. In males, loss-of-function mutations in LHCGR have been associated with distinct degrees of impairment in pre- and postnatal testosterone secretion resulting in a variable phenotypic spectrum, classified as Leydig cell hypoplasia (LCH) type 1 (complete LH resistance and disorder of sex differentiation) and type 2 (partial LH resistance with impaired masculinization and fertility). Here, we report the case of an adolescent who came to the pediatric endocrinologist at the age of 12 years old for micropenis and cryptorchidism. Testis biopsy showed profound LCH and absent germinal line elements (Sertoli-only syndrome). The sequence analysis of the LHCGR gene showed the presence of a compound heterozygosity, being one variation, c.1847C>A p.S616Y, already described in association to Hypergonadotropic Hypogonadism, and the other, c.29 C>T p.L10P, a new identified variant in the putative signal peptide (SP) of LHCGR. Functional and structural studies provide first evidence that LHCGR have a functional and cleavable SP required for receptor biogenesis. Moreover, we demonstrate the pathogenic role of the novel p.L10P allelic variant, which has to be considered a loss-of-function mutation significantly contributing, in compound heterozygosity with p.S616Y, to the LCH type 2 observed in our patient.

A novel mutation in the NR0B1 gene in a family with monozygotic twin sisters and congenital adrenal hypoplasia affected children.

OBJECTIVE: Congenital adrenal hypoplasia (CAH) is a rare disorder that can be inherited in an X-linked or autosomal recessive pattern. CAH is frequently associated with hypogonadotropic hypogonadism (HHG) with absent or arrested puberty and impaired fertility caused by abnormalities in spermatogenesis. It is estimated that more than 50% of boys with idiopathic adrenal insufficiency have mutations in the NR0B1 gene product, DAX1. CASE REPORT: The proband is a young boy born after an uneventful pregnancy and delivery to non-consanguineous parents. At age 4 years and 4 months he came to our attention because of severe vomiting, abdominal pain, dehydration, and asthenia. The proband underwent a detailed clinical investigation including genetic testing. Sequencing analysis of the NR0B1 gene coding region from the affected child revealed a novel hemizygous deletion [c.385delC; p.(Leu129Cysfs*135)]. This mutation was also present in the heterozygous healthy mother and in her twin sister and in the first cousin of the proband. Monozygosity of the twin sisters was demonstrated. This suggests a de novo mutation and gonadal mosaicism for the deletion. CONCLUSIONS: Adrenal hypoplasia typically presents as adrenal insufficiency during the first few months of life, however, not necessarily as shown by our index case. HHG is thought to affect all NR0B1 mutated patients who reach puberty and, as understanding of the disease has improved, more of these patients survive while presenting different features of the disease, this emphasizing the value of genetic testing in boys with primary adrenal insufficiency and suspected X-linked CAH.

Progress in pediatrics in 2013: choices in allergology, endocrinology, gastroenterology, hypertension, infectious diseases, neonatology, neurology, nutrition and respiratory tract illnesses.

This review will provide new information related to pathophysiology and management of specific diseases that have been addressed by selected articles published in the Italian Journal of Pediatrics in 2013, focusing on allergology, endocrinology, gastroenterology, hypertension, infectious diseases, neonatology, neurology, nutrition and respiratory tract illnesses in children. Recommendations for interpretation of skin prick test to foods in atopic eczema, management of allergic conjunctivitis, hypertension and breastfeeding in women treated with antiepileptic drugs and healthy breakfast have been reported. Epidemiological studies have given emphasis to high incidence of autoimmune disorders in patients with Turner syndrome, increasing prevalence of celiac disease, frequency of hypertension in adolescents, incidence and risk factor for retinopathy of prematurity. Advances in prevention include elucidation of the role of probiotics in reducing occurrence of allergies and feeding intolerance, and events of foetal life that influence later onset of diseases. Mechanistic studies suggested a role for vitamin D deficiency in asthma and type 1 diabetes and for reactivation of Varicella-Zoster virus in aseptic meningitis. Regarding diagnosis, a new mean for the diagnosis of hyperbilirubinaemia in newborns, a score for recognition of impaired nutritional status and growth and criteria for early Dyke-Davidoff-Masson Syndrome have been suggested. New therapeutic approaches consist of use of etanercept for reducing insulin dose in type 1 diabetes, probiotics in atopic eczema, and melatonin in viral infections.

Progress in Pediatrics in 2012: choices in allergy, endocrinology, gastroenterology, hematology, infectious diseases, neurology, nutrition and respiratory tract illnesses.

In this review, we summarize the progresses in allergy, endocrinology, gastroenterology, hematology, infectious diseases, neurology, nutrition and respiratory tract illnesses that have been published in The Italian Journal of Pediatrics in 2012. The induction of Treg activity by probiotics might be effective for promoting tolerance towards food allergens. Nasal cytology is useful in patients with rhinitis for diagnosing chronic non-allergic non-infectious diseases. Atopic eczema is associated both with an aberrant skin matrix and impaired systemic immune response. Therefore, isolated topical treatment may have suboptimal effect. Diagnostic work-up of exercise-induced anaphylaxis, including exercise challenge test, is necessary to reach a diagnosis. Studies may support a role for nutrition on prevention of asthma and cardiovascular diseases. Clinicians need to early identify adolescent menstrual abnormalities to minimize sequelae, and to promote health information. In Multiple Endocrine Neoplasia type 2B investigations include acetylcholinesterase study of rectal mucosa followed by the molecular analysis of RET mutation. Low adherence to gluten-free diet and osteopenia are common problems in children with diabetes mellitus type 1 and celiac disease. In infantile colic, laboratory tests are usually unnecessary and the treatment is based on reassurance. Prevalence of obesity and stunting is elucidated by several studies. Evidences are growing that dietetic measures are needed to prevent obesity in children with acute leukemia. Treatment studies for infectious diseases show promise for probiotics along with standard triple therapy in children with Helicobacter pilori infection, while zinc has no effect on pneumonia. Educational programs about the proper management of the febrile child are warranted. A new hour-specific total serum bilirubin nomogram has been shown to be able to predict newborns without hyperbilirubinemia after 48 to 72 hours of life. Newborns with hypoxic-ischemic encephalopathy present ECG and cardiac enzymes alterations leading to reduced neonatal survival. Rehabilitation programs including sensory integration therapy and motor performance, may improve activities of daily life in children with developmental coordination disorder. Aerobic exercise training in addition to chest physiotherapy might be useful in children with cystic fibrosis. Studies on effectiveness of leukotriene receptor antagonists, alone or with other drugs in preschool wheezing are needed.

New aspects of the physiology of the GH-IGF-1 axis.

Growth hormone (GH) secretion from the pituitary is regulated by a complex network of CNS and peripheral inputs. Circulating GH binds to its receptor and initiates a cascade of signaling events which involve the JAK2-STAT pathway, the PI3K/Akt pathway and the RAS/MAPK pathway, leading to the transcription of several genes, including insulin-like growth factor 1 (IGF-1), IGFBP3, ALS, and others. Recent findings indicate that nutrition plays an important role in GH secretion and action. Furthermore, data are emerging which suggest that the RAS-MAPK pathway as well as epigenetic regulation of transcription may be important in determining both circulating and locally produced IGF-1.

Relationship of CYP21A2 genotype and serum 17-hydroxyprogesterone and cortisol levels in a large cohort of Italian children with premature pubarche.

OBJECTIVE: Premature pubarche (PP) is the most frequent sign of nonclassic congenital adrenal hyperplasia (NCCAH) due to 21-hydroxylase deficiency in childhood. The aim of this study was to assess the relationship between the CYP21A2 genotype and baseline and ACTH-stimulated 17-hydroxyprogesterone (17-OHP) and cortisol serum levels in patients presenting with PP. PATIENTS AND METHODS: A total of 152 Italian children with PP were studied. Baseline and ACTH-stimulated 17-OHP and cortisol serum levels were measured and CYP21A2 gene was genotyped in all subjects. RESULTS: Baseline and ACTH-stimulated serum 17-OHP levels were significantly higher in NCCAH patients than in both heterozygotes and children with idiopathic PP (IPP). Of the patient population, four NCCAH patients (7.3%) exhibited baseline 17-OHP values <2 ng/ml (6 nmol/l). An ACTH-stimulated 17-OHP cutoff level of 14 ng/ml (42 nmol/l) identified by the receiver-operating characteristics curves showed the best sensitivity (90.9%) and specificity (100%) in distinguishing NCCAH patients. This value, while correctly identifying all unaffected children, missed 9% of affected individuals. Cortisol response to ACTH stimulation was <18.2 µg/dl (500 nmol/l) in 14 NCCAH patients (28%) and none of the heterozygotes or IPP children. Among the 55 NCCAH patients, 54.5% were homozygous for mild CYP21A2 mutations, 41.8% were compound heterozygotes for one mild and one severe CYP21A2 gene mutations, and 3.6% had two severe CYP21A2 gene mutations. CONCLUSION: In children with PP, baseline 17-OHP levels are not useful to rule out the diagnosis of NCCAH, which is accomplished by means of ACTH testing only. The different percentages of severe and mild CYP21A2 gene mutations found in PP children compared with adult NCCAH patients is an indirect evidence that the enzyme defect is under-diagnosed in childhood, and it might not lead to the development of hyperandrogenic symptoms in adulthood. Stress-dose glucocorticoids should be considered in patients with suboptimal cortisol response to ACTH stimulation.

Mitochondrial dysfunction in patients with primary congenital insulin resistance.

Mitochondrial dysfunction is associated with insulin resistance and type 2 diabetes. It has thus been suggested that primary and/or genetic abnormalities in mitochondrial function may lead to accumulation of toxic lipid species in muscle and elsewhere, impairing insulin action on glucose metabolism. Alternatively, however, defects in insulin signaling may be primary events that result in mitochondrial dysfunction, or there may be a bidirectional relationship between these phenomena. To investigate this, we examined mitochondrial function in patients with genetic defects in insulin receptor (INSR) signaling. We found that phosphocreatine recovery after exercise, a measure of skeletal muscle mitochondrial function in vivo, was significantly slowed in patients with INSR mutations compared with that in healthy age-, fitness-, and BMI-matched controls. These findings suggest that defective insulin signaling may promote mitochondrial dysfunction. Furthermore, consistent with previous studies of mouse models of mitochondrial dysfunction, basal and sleeping metabolic rates were both significantly increased in genetically insulin-resistant patients, perhaps because mitochondrial dysfunction necessitates increased nutrient oxidation in order to maintain cellular energy levels.

Prevalence of pathogenetic MC4R mutations in Italian children with early onset obesity, tall stature and familial history of obesity.

BACKGROUND: Melanocortin-4-receptor (MC4R) mutations represent the most frequent genetic cause of non-syndromic early onset obesity. Children carrying MC4R mutations seem to show a particular phenotype characterized by early onset, severe obesity and high stature. To verify whether MC4R mutations are associated with this particular phenotype in the Italian pediatric population, we decided to screen the MC4R gene in a group of obese children selected on the basis of their phenotype. METHODS: To perform this study, a multicentric approach was designed. Particularly, to be enrolled in the study subjects needed to meet the following criteria: Body mass index > or = 3 deviation scores according to age and sex, familiar history of obesity (at least one parent obese), obesity onset before the 10 years old, height > or = 2 deviation scores. The coding region of MC4R gene was screened in 240 obese children (mean age 8.3 +/- 3.1, mean BMI 30.8 +/- 5.4) and in 200 controls (mean age 8.1 +/- 2.8; mean BMI 14.2 +/- 2.5). RESULTS: Three mutations have been found in five obese children. The S127L (C380T), found in three unrelated children, had been described and functionally characterized previously. The Q307X (C919T) and the Y332H (T994C) mutations were found in two patients. Functional studies showed that only Q307X impaired protein function. CONCLUSION: The low prevalence of MC4R mutations (1.6%) in this group of obese children selected according to the obesity degree, the tall stature and the family history of obesity was similar to the prevalence observed in previous screenings performed in obese adults and in not phenotypically selected obese children.

Postreceptor insulin resistance contributes to human dyslipidemia and hepatic steatosis.

Metabolic dyslipidemia is characterized by high circulating triglyceride (TG) and low HDL cholesterol levels and is frequently accompanied by hepatic steatosis. Increased hepatic lipogenesis contributes to both of these problems. Because insulin fails to suppress gluconeogenesis but continues to stimulate lipogenesis in both obese and lipodystrophic insulin-resistant mice, it has been proposed that a selective postreceptor defect in hepatic insulin action is central to the pathogenesis of fatty liver and hypertriglyceridemia in these mice. Here we show that humans with generalized insulin resistance caused by either mutations in the insulin receptor gene or inhibitory antibodies specific for the insulin receptor uniformly exhibited low serum TG and normal HDL cholesterol levels. This was due at least in part to surprisingly low rates of de novo lipogenesis and was associated with low liver fat content and the production of TG-depleted VLDL cholesterol particles. In contrast, humans with a selective postreceptor defect in AKT2 manifest increased lipogenesis, elevated liver fat content, TG-enriched VLDL, hypertriglyceridemia, and low HDL cholesterol levels. People with lipodystrophy, a disorder characterized by particularly severe insulin resistance and dyslipidemia, demonstrated similar abnormalities. Collectively these data from humans with molecularly characterized forms of insulin resistance suggest that partial postreceptor hepatic insulin resistance is a key element in the development of metabolic dyslipidemia and hepatic steatosis.

Ghrelin inhibits steroid biosynthesis by cultured granulosa-lutein cells.

CONTEXT: Growing evidence indicates that ghrelin may participate in the regulation of different aspects of reproductive function. The genes encoding for this peptide and its receptor are expressed in the human ovary, but their functional role is still unknown. OBJECTIVE: The aim of our study was to assess whether ghrelin has any effect on steroid synthesis by human granulosa-lutein cells and to identify the receptor isoform through which this potential effect is exerted. DESIGN, PATIENTS, AND METHODS: Thirty-five women with spontaneous ovulatory cycles undergoing in vitro fertilization for infertility due to uni- or bilateral tubal impatency or male factor were studied. Granulosa-lutein cells obtained from follicular fluid were incubated with increasing amounts of human acylated ghrelin (10(-11) to 10(-7) mol/liter) either alone or together with a 1:500 concentration of a specific anti-ghrelin receptor antibody [GH secretagogue receptor 1a (GHS-R1a)]. Culture media were tested for estradiol (E(2)) and progesterone (P(4)). The expression of GHS-R1a and GHS-R1b in human granulosa-lutein cells was also studied by real-time quantitative PCR. RESULTS: E(2) and P(4) concentrations in the culture media were significantly reduced by ghrelin in a dose-dependent fashion. The maximal decrease in E(2) (25%) and P(4) (20%) media concentrations was obtained with the 10(-7) and 10(-8) mol/liter ghrelin concentrations, respectively. The inhibitory effect of all ghrelin concentrations used was antagonized by the specific anti-ghrelin receptor-1a antibody added to the culture media and not by the specific anti-ghrelin receptor-1b antibody. Both 1a and 1b isoforms of the GHS-R were expressed in human granulosa-lutein cells, with the latter exceeding the former's expression (GHS-R1b/GHS-R1a ratio, 143.23 +/- 28.15). CONCLUSIONS: Ghrelin exerts an inhibitory effect on granulosa-lutein cells steroidogenesis by acting through its functional GHS-R1a. This suggests that ghrelin may serve an autocrine-paracrine role in the control of gonadal function and be part of a network of molecular signals responsible for the coordinated control of energy homeostasis and reproduction.

Clinical significance of the parental origin of the X chromosome in turner syndrome.

CONTEXT: The phenotype in Turner syndrome (TS) is variable, even in patients with a supposedly nonmosaic karyotype. Previous work suggested that there were X-linked parent-of-origin effects on the phenotype. HYPOTHESIS: The TS phenotype is influenced by the parental origin of the missed X chromosome. DESIGN: This was a multicenter prospective study of TS patients and both their parents, determining parental origin of the X-chromosome, and characterizing the clinical phenotype. PATIENTS AND METHODS: Eighty-three TS patients and their parents were studied. Inclusion criteria were TS with karyotype 45,X or 46Xi(Xq). Four highly polymorphic microsatellite markers on the X-chromosome DMD49, DYSII, DXS1283, and the androgen receptor gene and three Y chromosome markers, SRY, DYZ1, and DYZ3. OUTCOME MEASURES: The study determined the correlation between the parental origin of the X chromosome and the unique phenotypic traits of TS including congenital malformations, anthropometry and growth pattern, skeletal defects, endocrine traits, education, and vocation. RESULTS: Eighty-three percent of 45,X retained their maternal X (X(m)), whereas 64% 46Xi(Xq) retained their paternal X (X(p), P < 0.001). Kidney malformations were exclusively found in X(m) patients (P = 0.030). The X(m) group had lower total and low-density lipoprotein cholesterol (P < 0.003), and higher body mass index sd score (P = 0.030) that was not maintained after GH treatment. Response to GH therapy was comparable. Ocular abnormalities were more common in the paternal X group (P = 0.017), who also had higher academic achievement. CONCLUSIONS: The parental origin of the missing short arm of the X chromosome has an impact on overweight, kidney, eye, and lipids, which suggests a potential effect of an as-yet-undetermined X chromosome gene imprinting.

Final height in girls with central idiopathic precocious puberty treated with gonadotropin-releasing hormone analog and oxandrolone.

CONTEXT: GnRH analogs (GnRHa) are considered the treatment of choice for central precocious puberty (CPP). During GnRHa administration, the suppression of the pituitary-gonadal axis results in decreased rates of linear growth and skeletal maturation and in improved adult height. However, in some patients, the growth deceleration is so marked that the expected improvement in predicted adult height is not achieved. OBJECTIVE: The objective of this study was to assess whether the addition of oxandrolone (Ox) may affect the height outcome of patients with CPP and growth deceleration during GnRHa treatment. DESIGN: This was an open-label, clinical study. SETTING: The study was performed at a pediatric endocrinology referral clinic. PATIENTS: Twenty patients with CPP and marked growth deceleration during GnRHa treatment were studied. INTERVENTIONS: Treatment consisted of GnRHa (Leuprorelina, 3.75 mg im every 28 d) alone (10 patients) or in combination with Ox (0.06 mg/kg.d by mouth) (10 patients). MAIN OUTCOME MEASURE: The main outcome measure was the patients' adult height. RESULTS: The adult height of the patients treated with GnRHa plus Ox was significantly higher than pretreatment predicted adult height (162.6 +/- 2.3 vs. 154.8 +/- 1.7 cm, mean +/- sem; P < 0.05) and target height (162.6 +/- 2.3 vs. 158.0 +/- 1.9; P > 0.05). Patients treated with GnRHa alone reached an adult height similar to the pretreatment predicted adult height (151.9 +/- 1.2 vs. 155.4 +/- 2.1 cm) but significantly lower than target height (151.9 +/- 1.2 vs. 156.6 +/- 1.4 cm; P < 0.005). No side effects were recorded in either group of patients. CONCLUSIONS: Combined GnRHa and Ox therapy is a viable treatment option for children with CPP and marked growth deceleration during treatment with GnRHa alone.

The human glucocorticoid receptor (hGR) beta isoform suppresses the transcriptional activity of hGRalpha by interfering with formation of active coactivator complexes.

The human glucocorticoid receptor (hGR) beta, a splicing variant of the classic receptor hGRalpha, functions as a dominant-negative inhibitor of hGRalpha. We explored the mechanism(s) underlying this effect of hGRbeta by evaluating the interactions of this isoform with known steroid receptor coactivators. We found that hGRbeta suppressed the transcriptional activity of both activation function (AF)-1 and AF-2 of hGRalpha, indicating that hGRbeta may exert its dominant-negative effect by affecting the function of coactivators that are attracted to these transactivation domains. hGRbeta bound to one of the p160 coactivators, the glucocorticoid receptor-interacting protein 1 (GRIP1) via its preserved AF-1 but not via its defective AF-2 in vitro. In a chromatin immunoprecipitation assay, hGRbeta prevented coprecipitation of GRIP1 with hGRalpha tethered to glucocorticoid response elements of the endogenous tyrosine aminotransferase promoter, whereas deletion of the AF-1 of hGRbeta abolished this effect. In further experiments, overexpression of GRIP1 attenuated the suppressive effect of hGRbeta on hGRalpha-mediated transactivation of the mouse mammary tumor virus promoter. Competition for binding to glucocorticoid response elements or heterodimerization with hGRalpha via the D loop dimerization interface occurred, but they were not necessary for the suppressive effect of hGRbeta on the transcriptional activity of hGRalpha. Our findings suggest that hGRbeta suppresses the transcriptional activity of hGRalpha by competing with hGRalpha for binding to GRIP1, and possibly other p160 coactivators, through its preserved AF-1. These findings suggest that participation of hGRbeta in the formation of a coactivator complex renders this complex ineffective.

Spontaneous growth hormone (GH) secretion is not directly affected by ghrelin in either short normal prepubertal children or children with GH neurosecretory dysfunction.

Ghrelin, a specific endogenous ligand for the GH secretagogue receptor, stimulates GH secretion in humans when given in pharmacological amounts. Under physiological conditions, however, it is controversial whether ghrelin affects GH secretion and vice versa. No studies have reported on the relationship between daily ghrelin and GH secretion in children. Therefore, plasma ghrelin and GH concentrations over a 24-h period were studied in 10 prepubertal short normal children (five females and five males) to determine the potential relationship between the secretion of these two hormones. Furthermore, five prepubertal patients (two females and three males) with GH neurosecretory dysfunction (GHNSD) were studied in the same way to assess potential alterations in ghrelin secretion in a condition associated with distinct GH changes. No gender difference in ghrelin spontaneous secretion was detected in either short normal children or GHNSD patients, and in both male and female subjects, ghrelin was secreted in a pulsatile and circadian fashion, with a nocturnal surge. Twenty-four-hour secretion and daytime ghrelin secretion of short normal children were similar to those in GHNSD patients, whereas nighttime hormone secretion in the latter group was significantly greater than that in short normal children. The cross-correlation of 24-h ghrelin and GH levels revealed significant positive and negative correlations, which were similar in the two groups examined. The positive one, with GH leading ghrelin, might reflect a somatostatin (SMS)-mediated inhibitory effect on both GH and ghrelin secretion (low SMS levels are followed by high GH and ghrelin levels, and vice versa). The negative correlation, with ghrelin leading GH, might again reflect the positive effect of ghrelin on SMS, as shown in both animal and human studies. In conclusion, the results of the present study indicate that ghrelin secretion in prepubertal children is pulsatile and is not sexually dimorphic. Although the parallelism of ghrelin and GH dynamics hints at the potential relevance of endogenous ghrelin as a promoter of GH release, our data do not support this hypothesis. We suggest that the interactions of ghrelin and GH are the result of SMS action. SMS inhibits GH secretion not only by a direct effect on the pituitary and by inhibiting hypothalamic GHRH, but also through the suppression of ghrelin release.

Natural glucocorticoid receptor mutants causing generalized glucocorticoid resistance: molecular genotype, genetic transmission, and clinical phenotype.

Glucocorticoid resistance is a rare, familial, or sporadic condition characterized by partial end-organ insensitivity to glucocorticoids. The clinical spectrum of the condition ranges from completely asymptomatic to severe hyperandrogenism, fatigue, and/or mineralocorticoid excess. The molecular basis of glucocorticoid resistance in several families and sporadic cases has been ascribed to mutations in the human glucocorticoid receptor-alpha (hGRalpha) gene, which impair the ability of the receptor to transduce the glucocorticoid signal. We systematically investigated the molecular mechanisms through which natural, ligand-binding domain hGRalpha mutants, including hGRalphaI559N, hGRalphaV571A, hGRalphaD641V, hGRalphaV729I, and hGRalphaI747M, produce a defective signal and determined whether their differential effects on hGRalpha function might account for the type of genetic transmission of the disorder and the variable clinical phenotype of the affected subjects. Our findings suggest that all five mutant receptors studied have ligand-binding domains with decreased intrinsic transcriptional activity. Unlike hGRalphaI559N and I747M previously shown to exert a dominant negative effect upon the transcriptional activity of hGRalpha, hGRalphaV571A, D641V, and V729I do not have such an effect. All five mutants studied demonstrate varying degrees of decreased affinity for the ligand in a standard dexamethasone binding assay, but preserve their ability to bind DNA. The nondominant negative mutants, hGRalphaV571A, D641V, and V729I, show delayed translocation into the nucleus after exposure to ligand. Finally, hGRalphaI559N, V571A, D641V, and V729I display an abnormal interaction with the glucocorticoid receptor-interacting protein-1 coactivator in vitro, as this was previously shown also for hGRalphaI747M. We conclude that each of the above hGRalpha mutations imparts different functional defects upon the glucocorticoid signal transduction pathway, which explains the autosomal recessive or dominant transmission of the disorder, but might only explain in part its variable clinical phenotype.

Familial/sporadic glucocorticoid resistance syndrome and hypertension.

Glucocorticoids regulate diverse functions important for the maintenance of central nervous system, cardiovascular, metabolic, and immune homeostasis. The actions of these hormones are mediated by the specific intracellular glucocorticoid receptors (GRs). Pathologic conditions associated with changes of tissue sensitivity to these hormones have been described. The syndrome of familial/sporadic glucocorticoid resistance is characterized by hypercortisolism without Cushing syndrome stigmata. Many of the patients present with hypertension, with or without hypokalemic alkalosis, as a result of elevated concentrations of cortisol and other salt-retaining steroids. The molecular defects of 4 kindreds and one sporadic case have been elucidated as inactivating mutations in the ligand-binding domain of the GR. In two patients in whom the GR was mutated at amino acid isoleucine 559 to aspartic acid (GRalphaI559N) and isoleucine 747 to methionine (GRalphaI747M), respectively, glucocorticoid resistance developed at the heterozygous state, with transdominant negative activity of each of the mutant receptors upon the wild-type protein. Retention of the wild-type receptor in the cytoplasm by the mutant receptor was found in the former, while inappropriate accumulation of p160-type coactivators on the promoter region of glucocorticoid-responsive genes, because of a defective interaction between the AF2 region of the mutant receptor and the LXXLL motif of the coactivators, was determined in the latter. These results suggest that the pathologic mechanisms of glucocorticoid resistance is quite broad, and this is reflected in the wide variability of the clinical picture in patients with the syndrome.

Increased glucocorticoid receptor Beta expression converts mouse hybridoma cells to a corticosteroid-insensitive phenotype.

Glucocorticoid (GC) insensitivity is a challenging clinical problem associated with many chronic inflammatory disorders and life-threatening disease progression. The molecular basis of GC insensitivity, however, is unknown. Alternative splicing of the GC receptor (GCR) pre-mRNA generates a second GCR, termed GCRbeta, which does not bind GC but antagonizes the transactivating activity of the classic GCR, termed GCRalpha. GC-insensitive conditions have been associated with increased GCRbeta expression. Whether or not increased GCRbeta expression can contribute to GC insensitivity, however, remains controversial. To more precisely demonstrate the effect of GCRbeta on steroid responsiveness, we virally transduced GCRbeta cDNA into mouse DO-11.10 hybridoma cells, as mice are known to be deficient in the GCRbeta gene. We demonstrate that viral transduction of GCRbeta cDNA into mouse hybridoma cells to induce stable expression of GCRbeta results in GC insensitivity of these cells. Furthermore, in such cells GCRalpha is complexed with GCRbeta. Such heterodimer formation may account for the reduced effectiveness of GC action in cells overexpressing GCRbeta.

A novel, C-terminal dominant negative mutation of the GR causes familial glucocorticoid resistance through abnormal interactions with p160 steroid receptor coactivators.

Primary cortisol resistance is a rare, inherited or sporadic form of generalized end-organ insensitivity to glucocorticoids. Here, we report a kindred in which affected members had a heterozygous T to G base substitution at nucleotide 2373 of exon 9alpha of the GR gene, causing substitution of Ile by Met at position 747. This mutation was located close to helix 12, at the C terminus of the ligand-binding domain, which has a pivotal role in the formation of activation function (AF)-2, a subdomain that interacts with p160 coactivators. The affinity of the mutant GR for dexamethasone was decreased by about 2-fold, and its transcriptional activity on the glucocorticoid-responsive mouse mammary tumor virus promoter was compromised by 20- to 30-fold. In addition, the mutant GR functioned as a dominant negative inhibitor of wild-type receptor-induced transactivation. The mutant GR through its intact AF-1 domain bound to a p160 coactivator, but failed to do so through its AF-2 domain. Overexpression of a p160 coactivator restored the transcriptional activity and reversed the negative transdominant activity of the mutant GR. Interestingly, green fluorescent protein (GFP)-fused GRalphaI747M had a slight delay in its translocation from the cytoplasm into the nucleus and formed coarser nuclear speckles than GFP-fused wild-type GRalpha. Similarly, a GFP-fused p160 coactivator had a distinctly different distribution in the nucleus in the presence of mutant vs. wild-type receptor, presenting also as coarser speckling. We conclude that the mutation at amino acid 747 of the GR causes familial, autosomal dominant glucocorticoid resistance by decreasing ligand binding affinity and transcriptional activity, and by exerting a negative transdominant effect on the wild-type receptor. The mutant receptor has an ineffective AF-2 domain, which leads to an abnormal interaction with p160 coactivators and a distinct nuclear distribution of both.