Phenotypic variation and detection of carrier status in the partial androgen insensitivity syndrome.

The partial androgen insensitivity syndrome occurs in 46,XY subjects with phenotypes ranging from perineoscrotal hypospadias with cryptorchidism and micropenis (mild undervirilisation) to clitoromegaly and partial labial fusion (marked undervirilisation). Within an affected family, wide variation in the degree of genital ambiguity between individuals can be seen. Two cousins of a previously reported subject who had severe genital ambiguity and partial androgen insensitivity were investigated. Neither of the cousins had genital abnormalities as marked as the index case, who also had qualitatively abnormal androgen binding and two mutations of the androgen receptor gene. Despite marked phenotypic differences between the index case and his cousins, similar androgen binding and the same androgen receptor mutations were shown in the cousins. Furthermore, one of the androgen receptor gene mutations has been shown in the mother and sister of one of the boys indicating that they are carriers. Thus phenotypic variation in families affected by partial androgen insensitivity is dependent on factors other than abnormalities of the androgen receptor gene alone. Although carrier status in partial androgen insensitivity can be determined, the severity of genital abnormalities in an affected offspring cannot be reliably predicted.     

Phenotypic diversity in siblings with partial androgen insensitivity syndrome

The androgen insensitivity syndrome is a heterogeneous disorder with a wide spectrum of phenotypic abnormalities, ranging from complete female to ambiguous forms that more closely resemble males. The primary abnormality is a defective androgen receptor protein due to a mutation of the androgen receptor gene. This prevents normal androgen action and thus leads to impaired virilisation. A point mutation of the androgen receptor gene affecting two siblings with partial androgen insensitivity syndrome is described. One had cliteromegaly and labial fusion and was raised as a girl, whereas the other sibling had micropenis and penoscrotal hypospadias and was raised as a boy. Both were shown to have the arginine 840 to cysteine mutation. The phenotypic variation in this family is thus dependent on factors other than abnormalities of the androgen receptor gene alone.     

Phenotypic diversity in siblings with partial androgen insensitivity syndrome

Accepted 5 March 1997
The androgen insensitivity syndrome is a heterogeneous disorder with a wide spectrum of phenotypic abnormalities, ranging from complete female to ambiguous forms that more closely resemble males. The primary abnormality is a defective androgen receptor protein due to a mutation of the androgen receptor gene. This prevents normal androgen action and thus leads to impaired virilisation. A point mutation of the androgen receptor gene affecting two siblings with partial androgen insensitivity syndrome is described. One had cliteromegaly and labial fusion and was raised as a girl, whereas the other sibling had micropenis and penoscrotal hypospadias and was raised as a boy. Both were shown to have the arginine 840 to cysteine mutation. The phenotypic variation in this family is thus dependent on factors other than abnormalities of the androgen receptor gene alone.

     

Molecular characterization of the androgen receptor gene in boys with hypospadias

Development of male external genitalia is dependent on androgens, and karyotypic males lacking appropriate levels of androgens or functionally normal receptors may show abnormal virilization. Mutations in the androgen receptor gene cause abnormal receptor function and diverser mutations may be associated with heterogenous clinical signs of androgen insensitivity. In this study, we have searched for the existence of androgen receptor gene mutations carried by some patients with hypospadias. Genomic DNA samples from peripheral blood leucocytes from 21 patients with different degrees of hypospadias were studied. Analysis of the androgen receptor gene was performed by exon-specific amplification using polymerase chain reaction, single strand conformation polymorphism analysis, and direct genomic sequencing. Although a silent polymorphism was identified in exon 1 of the androgen receptor gene, the majority of patients studied (20/21) did not carry androgen receptor gene mutations. One patient with severe hypospadias and bilateral cryptorchidism was found to carry a point mutation in exon 8. We conclude that mutations in the androgen receptor gene may be carried by subset of patients with genital ambiguity presenting primarily with hypospadias, but this is not the underlying cause in the majority of cases. Characterization of this genetic defect may be important for classification and subsequent conservative therapeutic approaches for these patients.     

A novel point mutation in the hormone binding domain of the androgen receptor associated with partial and minimal androgen insensitivity syndrome

Mutations in the coding sequence of the androgen receptor (AR) gene result in a wide range of androgen insensitivity syndromes (AIS). We report an extended family in which at least five male individuals in different generations suffer from partial AIS. The index patient presented at birth with ambiguous genitalia; the karyotype was 46,XY and subsequent sex assignment male. Elevated stimulated testosterone (T) and normal baseline gonadotropins were found. Family history revealed four additional adult males affected with various abnormalities of their external genitalia. Molecular analysis of the coding sequence of the AR gene revealed in all a novel point mutation in exon 6, changing threonine to isoleucine at codon position 800 in the hormone-binding domain. We conclude that phenotypic variations in mild AR defects are striking and can remain undetected even until late in life.     

Novel point mutations in complete androgen insensitivity syndrome with incomplete müllerian regression: two Taiwanese patients

Complete androgen insensitivity syndrome (CAIS) is a relatively rare X-linked disorder caused by androgen receptor gene (AR) mutations that result in complete impairment of genital virilisation. In these individuals, no müllerian derivatives are usually found; however, several sporadic cases of CAIS with müllerian remnants have been reported. In this paper, we report two novel point mutations of the AR gene resulting in two cases of CAIS with incomplete müllerian regression. Molecular studies of cases 1 and 2 showed novel missense mutations of the AR gene, with a methionine to threonine substitution at codon 749 (base 2608 TC) in exon 5 and a methionine to lysine substitution at codon 787 (base 2722 TA) in exon 6. Both patients received bilateral gonadectomy and inguinal hernia repair. The excised gonads proved to be testes with incomplete regression of the müllerian structures. Conclusion:müllerian structures can be present in androgen insensitivity syndrome and the presence of a uterus therefore does not exclude this disorder. Further study of these patients may promote a better understanding of the pathogenesis.Abbreviations AIS androgen insensitivity syndrome - AR androgen receptor - CAIS complete androgen insensitivity syndrome - hAR human androgen receptor - MIS müllerian inhibiting substance - PAIS partial androgen insensitivity syndrome     

Expression of two functionally different androgen receptors in a patient with androgen insensitivity

Recently, we demonstrated a previously unknown high rate of de novo mutations of the androgen receptor (AR) gene in androgen insensitivity syndrome (AIS) with some resulting in somatic mosaicism of mutant and wild type AR alleles. However, data on the genotype-phenotype relationship in the latter patients are sparse. We present here a 46,XY newborn with ambiguous genitalia carrying a mosaic of an 866 GTG (Val) → ATG (Met) mutation with the wild type AR gene. This mutation has usually been associated with complete AIS. Accordingly, we found markedly impaired transactivation due to the mutant Met⁸⁶⁶ AR. Essential information arose from Scatchard analysis of methyltrienolone binding on cultured genital skin fibroblasts. We demonstrated for the first time the expression of two functionally different ARs (K_d1: 5.58 nM = mutant, K_d2: 0.06 nM = wild type) in one AIS individual. This finding not only represents an important confirmation for the presence of the somatic mosaicism in the patient, it also indicates the most likely molecular mechanism responsible for the unexpectedly strong virilization of the patient: Androgen action through the wild type AR expressed by part of the somatic cells. Conclusions The present case clearly demonstrates the molecular mechanism by which somatic mosaicism of the androgen receptor gene can modulate in vivo androgen action. It underlines the importance of particular notice on somatic mosaicism in all androgen insensitivity syndrome patients carrying de novo mutations of the androgen receptor gene. Received: 24 August 1998 / Accepted in revised form: 5 January 1999     

Incomplete androgen insensitivity syndrome. Difficulties of diagnosis and management

A familial form of incomplete androgen insensitivity syndrome (AIS) is reported. The index case was first seen at 9 months of age for ambiguous genitalia. Diagnosis of AIS, suspected but first discarded on the basis of an androgen sensitivity test, was finally made at puberty on the discordance between poor virilization and elevated levels of both testosterone and LH, a florid gynecomastia, and the exclusion of any enzymatic defect in testosterone biosynthesis of 5 alpha-reductase deficiency. Androgen receptors in public skin were within the limits of normal for total number, with normal affinity. Familial occurrence included 2 first cousins born 7 and 10 years later, a maternal grand-uncle with similar ambiguous genitalia, and a maternal uncle with the gynecomastia-preserved fertility syndrome. This case report illustrates the heterogeneity of AIS in a given family and the difficulty of and early positive diagnosis in a newborn presenting with sexual ambiguity.     

Mutational analysis of Hungarian patients with androgen insensitivity syndrome

OBJECTIVE: To support the clinical diagnosis of androgen insensitivity syndrome (AIS), we performed mutational analysis of the androgen receptor gene. DESIGN: Clinical, hormonal and molecular genetic data of ten undervirilized genetic male patients living in Hungary were recorded. METHODS: PCR-based single strand conformation polymorphism (SSCP) analysis was used to study the whole coding region of the androgen receptor gene. Direct fluorescent sequencing was applied when aberrant migration was detected by SSCP. RESULTS: Five different mutations were identified in five unrelated genetic male patients with abnormal sexual differentiation. One of these mutations was novel, while the other four mutations have been described previously in the literature. One of the mutations identified earlier in individuals with sporadic AIS showed a familial inheritance pattern in our study group. No abnormality of the androgen receptor gene was identified in three patients clinically suspected to have partial AIS. CONCLUSION: Application of molecular techniques helped to clarify the diagnosis in patients with disorders of male sexual differentiation.     

Case report: WT1 exon 6 truncation mutation and ambiguous genitalia in a patient with Denys-Drash syndrome

Denys-Drash syndrome is a rare genetic disorder featuring the triad of congenital nephropathy, Wilms tumor, and intersex disorders (XY under-virilization or XY female). Denys-Drash syndrome is associated with constitutional mutations in the Wilms tumor suppressor gene WT1. Unlike WAGR (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation) syndrome, with its complete deletion of one copy of WT1, Denys-Drash syndrome is generally caused by a dominant-negative mutation. We present a new case of Denys-Drash syndrome in a patient initially diagnosed with XY ambiguous genitalia/partial androgen insensitivity syndrome, who was found to have a novel nonsense mutation in exon 6 leading to a stop codon and hence a truncated protein. Based on lessons learned from this patient, the diagnosis of Denys-Drash syndrome should be considered in the presence of ambiguous genitalia and partial androgen insensitivity.     

Functional assessment and clinical classification of androgen sensitivity in patients with mutations of the androgen receptor gene

In the genetic male, mutations of the androgen receptor (AR) gene cause phenotypes ranging from female to subfertile male. Binding assays on genital skin fibroblasts and DNA analysis alone provide incomplete information about receptor function. We used the sex hormone-binding globulin (SHBG) response to stanozolol as a measure of AR function and correlated the results with phenotypes which were classified according to the degree of defective masculinization. Of the 34 patients investigated, 9 had complete, and 14 had partial androgen insensitivity syndrome (AIS) with predominantly female, ambiguous, or predominantly male phenotype. Eleven subjects served as controls. Mutations were characterized using polymerase chain reaction-single strand conformation polymorphism analysis and direct DNA sequencing. DNA analysis revealed two major deletions, two minor defects leading to premature stop codons in exon 1, and 19 point mutations in the DNA- and hormone-binding domains of the AR gene. After stanozolol, SHBG remained unchanged in patients with complete AIS (102.0 ± 3.8 [SE]%; range 92.4%–129% of the initial value). The SHBG decrease was diminished in partial AIS with predominantly female (83.8% ± 1.7%; range 81.3%–87.0%), ambiguous (80.4% ± 4.4%, range 68.4%–89.1%), and predominantly male (mean 65.9% ± 4.9%, range 48.6%– 80.8%) phenotypes, and normal in controls (51.4% ± 2.1%, range 35.6%–62.1%). Differences between controls and each AIS group were statistically significant (P< < 0.05 – < 0.0001). A close correlation was found between the degree of undermasculinization (AIS phenotype) and the SHBG response. Conclusions The SHBG test provides functional information about the severity of the receptor defect in vivo and hence adds to the structural information provided by DNA analysis. It detects receptor defects due to mutations within the entire gene, including the DNA-binding domain, and is a rapid, simple, and cost effective procedure. It may provide useful information for the diagnosis and management of affected children.     

Genetic studies in idiopathic short stature

Idiopathic short stature (ISS) refers to a heterogeneous group of children with marked growth failure of unknown cause, and encompasses familial short stature and constitutional delay of growth. It has been postulated that specific genetic mutations may explain certain cases of growth failure. Some patients with growth hormone (GH) deficiency have mutations in the GH-releasing hormone receptor or GH gene, whereas patients with GH insensitivity syndrome have mutations in the GH receptor or insulin-like growth factor-I gene. It appears that heterozygous mutations of the GH receptor may cause partial GH insensitivity in a subset of patients with ISS. Defects in the short stature homeobox-containing gene (SHOX) in the pseudoautosomal region of the sex chromosomes may cause the growth failure seen in the Leri-Weill and Turner syndromes, and in some familial cases of ISS. Further research into stature-related genes will likely contribute to our understanding of this population.     

Functional assessment and clinical classification of androgen sensitivity in patients with mutations of the androgen receptor gene

In the genetic male, mutations of the androgen receptor (AR) gene cause phenotypes ranging from female to subfertile male. Binding assays on genital skin fibroblasts and DNA analysis alone provide incomplete information about receptor function. We used the sex hormone-binding globulin (SHBG) response to stanozolol as a measure of AR function and correlated the results with phenotypes which were classified according to the degree of defective masculinization. Of the 34 patients investigated, 9 had complete, and 14 had partial androgen insensitivity syndrome (AIS) with predominantly female, ambiguous, or predominantly male phenotype. Eleven subjects served as controls. Mutations were characterized using polymerase chain reaction-single strand conformation polymorphism analysis and direct DNA sequencing. DNA analysis revealed two major deletions, two minor defects leading to premature stop codons in exon 1, and 19 point mutations in the DNA- and hormone-binding domains of the AR gene. After stanozolol, SHBG remained unchanged in patients with complete AIS (102.0 ± 3.8 [SE]%; range 92.4%–129% of the initial value). The SHBG decrease was diminished in partial AIS with predominantly female (83.8% ± 1.7%; range 81.3%–87.0%), ambiguous (80.4% ± 4.4%, range 68.4%–89.1%), and predominantly male (mean 65.9% ± 4.9%, range 48.6%– 80.8%) phenotypes, and normal in controls (51.4% ± 2.1%, range 35.6%–62.1%). Differences between controls and each AIS group were statistically significant (P< < 0.05 – < 0.0001). A close correlation was found between the degree of undermasculinization (AIS phenotype) and the SHBG response. Conclusions The SHBG test provides functional information about the severity of the receptor defect in vivo and hence adds to the structural information provided by DNA analysis. It detects receptor defects due to mutations within the entire gene, including the DNA-binding domain, and is a rapid, simple, and cost effective procedure. It may provide useful information for the diagnosis and management of affected children. Received: 13 February 1996 / Accepted: 4 June 1996     

Androgen receptor genotyping in a large Australasian cohort with androgen insensitivity syndrome; identification of four novel mutations

We genotyped the androgen receptor (AR) gene in 31 Australasian patients with androgen insensitivity syndrome (AIS). The entire coding region of AR was examined including analysis of polymorphic CAG and GGN repeats in all patients. AR defects were found in 66.7% (6/9) of patients with complete AIS (CAIS) and 13.6% (3/22) of patients with partial AIS (PAIS). A novel deletion (N858delG) leading to a premature stop codon was found in CAIS patient P1. CAIS patient P2 has a novel deletion (N2676delGAGT) resulting in a stop at codon 787. These mutations would result in inactivation of AR protein. A novel insertion of a cysteine residue in the first zinc finger of the AR DNA-binding domain (N2045_2047dupCTG) was found in CAIS patient P3. PAIS patient P4 has a novel amino acid substitution (Arg760Ser) in the AR ligand binding domain, which may impair ligand binding. Five patients were found to have previously reported AR mutations and no mutations were identified in the remaining patients.     

Clinical and molecular spectrum of somatic mosaicism in androgen insensitivity syndrome

We recently found that postzygotic de novo mutations occur at the expected high rate of an X-linked recessive mutation in androgen insensitivity syndrome. The resulting somatic mosaicism can be an important molecular determinant of in vivo androgen action caused by expression of the wild-type androgen receptor (AR). However, the clinical relevance of this previously underestimated genetic condition in androgen insensitivity syndrome has not been investigated in detail as yet. Here, we present the clinical and molecular spectrum of somatic mosaicism considering all five patients with mosaic androgen insensitivity syndrome, whom we have identified since 1993: Patient 1 (predominantly female, clitoromegaly), 172 TTA(Leu)/TGA(Stop); patient 2 (ambiguous), 596 GCC(Ala)/ACC(Thr); patient 3 (ambiguous), 733 CAG(Gln)/ CAT(His); patient 4 (completely female), 774 CGC(Arg)/TGC (Cys); and patient 5 (ambiguous), 866 GTG(Val)/ATG(Met). Serum sex hormone binding globulin response to stanozolol, usually correlating well with in vivo AR function, was inconclusive for assessment of the phenotypes in all tested mosaic individuals. An unexpectedly strong virilization occurred in patients 1, 3, and 5 compared with phenotypes as published with corresponding inherited mutations and compared with the markedly impaired transactivation caused by the mutant ARs in cotransfection experiments. Only the prepubertal virilization of patients 2 and 4 matched appropriately with transactivation studies (patient 4) or the literature (patients 2 and 4). However, partial pubertal virilization in patient 4 caused by increasing serum androgens and subsequent activation of the wild-type AR could not be excluded. We conclude that somatic mosaicism is of particular clinical relevance in androgen insensitivity syndrome. The possibility of functionally relevant expression of the wild-type AR needs to be considered in all mosaic individuals, and treatment should be adjusted accordingly.     

Phenotypic variation in a family with partial androgen insensitivity syndrome

A family with partial androgen insensitivity syndrome exhibited considerable variation in phenotypic expression of their androgen resistance. One subject died at 2 1/2 years of age of a Wilms' tumor. In the two living members, one had a micropenis with otherwise normal genitalia, while the other had a small phallus, perineoscrotal hypospadias, bifid scrotum, and persistence of a vaginoutricular pouch. At puberty, plasma androgens and serum gonadotropins increased to normal or elevated values. However, despite adequate endogenous plasma testosterone levels and testosterone therapy, these patients showed poor virilization and were sterile. Studies of cultured sexual skin fibroblasts showed adequate 5 alpha-reductase activity and normal receptor affinity and capacity for dihydrotestosterone. An X-linked mode of inheritance is postulated, although autosomal dominance cannot be ruled out.     

The androgen resistance syndromes: Clinical and biochemical aspects

The genetic, biochemical, clinical and endocrinological features of syndromes associated with androgen resistance (insensitivity) are described. The clinical appearance of these syndromes covers the whole spectrum of phenotypically female patients to normal appearing men with infertility. In these disorders testosterone formation and regression of the Müllerian duct derivates are normal, but male development is absent or impaired as a result of total or partial resistance to androgen action in the target cell. Based on studies with cultured genital skin fibroblasts three defects on the level of the androgen target organ can be differentiated in these syndromes: 1. Defective testosterone metabolism, 2. anomalies of the androgen receptor and 3. a postreceptor defect.The original work cited in this paper was supported by The Deutsche Forschungsgemeinschaft     

Signal transduction defects in growth hormone insensitivity

Growth hormone (GH) insensitivity is a heterogeneous condition that can result from mutations within the GH receptor (GHR) and that can be inherited as both an autosomal recessive and a dominant trait. However, evidence from a small number of growth hormone binding protein (GHBP)-positive families indicates that their GH insensitivity is independent of GHR mutations. Two of these families appear to have distinct abnormalities in GH signal transduction. Studies suggest that one family (classic Laron syndrome phenotype; designated family H) have a signalling defect close to the GHR, preventing activation of both the STAT and MAPK pathways, whereas the other family (less marked phenotype; family M) have a defect in activating MAPK but not the STAT pathway. The children studied here are specifically insensitive to GH and their defect must be exclusive to this signalling system. Thus, families with GHBP-positive GH insensitivity without GHR mutations are likely to be important models in which to study the specificity of GH signal transduction and the relationship between GH insensitive phenotype and signalling defect.     

Abnormality of intracellular 5 alpha-dihydrotestosterone binding in simple hypospadias: studies on equilibrium steroid binding in sonicates of genital skin fibroblasts

A method was developed for the measurement of the binding of [3H]5 alpha-dihydrotestosterone, [3H]DHT and other steroids at equilibrium with intracellular androgen receptor of genital skin fibroblasts. This method utilized 0.2 M Na2MoO4 to stabilize the receptor and Sephadex G-25 chromatography to eliminate steroid metabolism. This binding protein showed the expected limited capacity, high affinity, and specificity of an androgen receptor. Using this method, penile skin cultures from 26 infants with simple hypospadias (HS) were compared with 18 controls. The [3H]DHT binding capacity (Bmax) was 10.1 +/- 1.3 (+/- SE) fmol/mg protein for controls and 6.1 +/- 1.7 for HS. The two populations were significantly different by Mann-Whitney test (P less than 0.001). Equilibrium dissociation constant was similar for both groups. Surprisingly, there was no correlation between Bmax and the severity of the anatomic defect. Bmax was below the values seen in HS for two of three infants with male pseudohermaphroditism. In complete androgen insensitivity, DHT binding was unmeasurable. A subgroup exists in HS with an abnormality of intracellular androgen receptors. The lack of correlation between severity of hypospadias and Bmax suggests that additional factors, such as differences in physicochemical properties of the receptor or factors present in utero, contribute to the development of HS.