Androgen receptor CAGn repeat length influences phenotype of 47,XXY (Klinefelter) syndrome.
ABSTRACT Klinefelter syndrome (KS; 47,XXY karyotype and variants) is characterized by tall stature and testicular failure, with marked variation in severity of the phenotype. Previous studies have proposed that genetic factors including mosaicism, parental origin of the supernumerary X-chromosome, skewed X inactivation, and androgen receptor (AR) polyglutamine repeat length may contribute to phenotypic variability in KS.
The objective of this study was to investigate the roles of these genetic factors in the variability of the KS phenotype.
This was a cross-sectional study.
The study was performed at a pediatric endocrinology referral clinic.
Thirty-five KS boys and men, aged 0.1-39 yr, were studied. Interventions: There were no interventions.
Auxological measurements, biological indices of testicular function, and clinical assessment of muscle tone were the main outcome measures. Genetic studies included karyotyping to detect mosaicism, genotyping of microsatellite markers to determine parental origin of the supernumerary X-chromosome, and genotyping and methylation studies to measure AR polyglutamine (AR CAGn) repeat length and X inactivation ratio.
The only genetic factor that significantly influenced the KS phenotype was the AR CAGn repeat length, which was inversely correlated with penile length, a biological indicator of early androgen action. Mosaicism, imprinting, and skewed X inactivation did not account for the variability of the KS phenotype.
Normal genetic variation in the AR coding sequence may be clinically significant in the setting of early testicular failure and subnormal circulating testosterone levels, as occur in KS.
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ABSTRACT: Polycystic ovary syndrome (PCOS), one of the most common and complex endocrine disorders affecting up to 15 % of reproductive age women, is considered a predominantly hyperandrogenic syndrome according to the Androgen Excess Society. It is generally accepted that androgens determine the characteristic features of PCOS; in this context, a hyperactive androgen receptor (AR) at the levels of the GnRH pulse generator in the hypothalamus and at the granulosa cells in the ovary, skeletal muscle or adipocytes senses initially normal testosterone and dihydrotestosterone as biochemical hyperandrogenism and might be a crucial connection between the vicious circles of the PCOS pathogenesis. Polymorphism of the AR gene has been associated with different androgen pattern diseases. Several studies have demonstrated an association between AR with increased activity encoded by shorter CAG repeat polymorphism in the exon 1 of the AR gene and PCOS, although there are conflicting results in this field. The phenomenon is more complex because the AR activity is determined by the epigenetic effect of X chromosome inactivation (XCI). Moreover, we must evaluate the AR as a dynamic heterocomplex, with a large number of coactivators and corepressors that are essential to its function, thus mediating tissue-specific effects. In theory, any of these factors could modify the activity of AR, which likely explains the inconsistent results obtained when this activity was quantified by only the CAG polymorphism in PCOS.Journal of medicine and life 03/2013; 6(1):18-25.
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ABSTRACT: The phenotypic variation of Klinefelter syndrome (KS) is wide and may by caused by various genetic and epigenetic effects. Skewed inactivation of the supra-numerical X chromosome and polymorphism in the androgen receptor (AR) have been suggested as plausible causes. We wanted to describe X-chromosome inactivation patterns and the AR polymorphism and correlate these to clinical findings in KS in a cross-sectional study. To that end, we studied 70 KS patients enrolled from fertility clinics and endocrine clinics and 70 age-matched control subjects. The main outcome was X-chromosome inactivation pattern (skewX), AR polymorphism (CAGn - repeat length) and correlation to anthropometrical, hormonal, metabolic and bone-related variables. Forty-six of 70 KS men were heterozygous for CAGn. The shortest and the longest alleles were equally frequent inactivated and the mean CAGn of the two alleles did not differ significantly from the CAGn from either KS men, homozygous for the CAGn, or from the control subjects (22 vs. 23 vs. 21). SkewX was found in 12 of the 46 informative KS men (26%). In KS, height and arm span correlated positively to CAGn, whereas total cholesterol and haematocrit correlated negatively to CAGn. In controls, bone mineral density at the spine and hip correlated positively with CAGn, whereas adiponectin correlated negatively with CAGn. SkewX did not correlate to any of the investigated parameters. We conclude that CAGn polymorphism in AR explain some of the phenotypic variation in KS, whereas skewed X-chromosome inactivation did not. The impact of CAGn on final height may be caused by later reactivation of the pituitary-gonadal axis.International Journal of Andrology 12/2011; 34(6 Pt 2):e642-8. · 3.57 Impact Factor
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ABSTRACT: The effects of early androgen treatment on neurodevelopmental performance in pre-pubertal boys with 47,XXY have not been well investigated. The influence of hormones on brain development in humans suggests that a positive effect on neurodevelopmental outcome in young boys with XXY may be plausible with hormone replacement therapy. The aim of the study was to investigate retrospectively if an early course of androgen treatment (three injections of testosterone enanthate, 25 mg, each) had an impact on specific domains of neurodevelopmental function in boys with 47,XXY at 36 and 72 months of age. One hundred one boys with a karyotype of 47,XXY had neurodevelopmental assessments. The retrospective chart review resulted in one group (n = 34) who had received androgen treatment during infancy and the second group was untreated (N = 67). Statistical analysis was completed to determine if there was a positive effect from treatment observed at 36 and at 72 months on multiple domains of development. There were significant differences in multiple cognitive domains in the group who received androgen treatment, including multiple measures of language, intellectual, and neuromotor skills. Improved function was observed in neurodevelopmental outcome in boys with 47,XXY at 36 and 72 months who had been treated with a short course of androgen treatment in infancy. Continued research is underway to expand our understanding of the relationship of androgen, brain function, and neurobehavioral and neurodevelopmental outcome in boys with 47,XXY. © 2013 Wiley Periodicals, Inc.American Journal of Medical Genetics Part A 01/2013; · 2.30 Impact Factor