Identification of Differentially Expressed Genes in Prostatic Epithelium in Relation to Androgen Receptor CAG Repeat Length

Size Matters: The CAG Repeat Length of the Androgen Receptor Gene, Testosterone, and Male Adolescent Depression Severity

There is a distinct increase in the prevalence of depression with the onset of puberty. The role of peripubertal testosterone levels in boys in this context is insufficiently understood and may be modulated by a functional polymorphism of the androgen receptor gene (AR), a variable number of CAG repeats. Moreover, there is preliminary evidence that the relationship between testosterone, CAG repeat length, and the severity of depressive symptoms may differ between subclinical and overt depression, but this has neither been studied in a clinical sample of adolescents with depression nor compared between subclinical and overt depression in an adequately powered study. To investigate the relationship between free testosterone, CAG repeat length of the AR, depression status (subclinical vs. overt), and the severity of depressive symptoms, 118 boys treated as in- or daycare patients at a single psychiatric hospital were studied. Of these, 73 boys had at least mild depressive symptoms according to the Beck Depression Inventory-II (BDI-II > 13). Higher-order moderation analysis in the multiple regression framework revealed a constant relationship between free testosterone and depression severity irrespective of the number of CAG repeats in adolescents with a BDI-II score ≤ 13. In adolescents with a BDI-II score > 13, however, there was a significant negative relationship between free testosterone and BDI-II score in patients with <19 CAG repeats and a significant positive relationship regarding free testosterone and BDI-II score in those with more than 28 CAG repeats, even when considering important covariates. These results suggest that the effects of testosterone on mood in male adolescents with depression depend on the genetic make-up of the AR as well as on depression status. This complex relationship should be considered by future studies addressing mental health issues against an endocrine background and may, moreover, contribute to tailored treatment concepts in psychiatric medicine, especially in adults.

Inactivation of X-linked tumor suppressor genes in human cancer

Cancer cells silence autosomal tumor suppressor genes by Knudson's two-hit mechanism in which loss-of-function mutations and then loss of heterozygosity occur at the tumor suppressor gene loci. However, the identification of X-linked tumor suppressor genes has challenged the traditional theory of 'two-hit inactivation' in tumor suppressor genes, introducing the novel concept that a single genetic hit can cause loss of tumor suppressor function. The mechanism through which these genes are silenced in human cancer is unclear, but elucidating the details will greatly enhance our understanding of the pathogenesis of human cancer. Here, we review the identification of X-linked tumor suppressor genes and discuss the potential mechanisms of their inactivation. In addition, we also discuss how the identification of X-linked tumor suppressor genes can potentially lead to new approaches in cancer therapy.

ATRX in chromatin assembly and genome architecture during development and disease

The regulation of genome architecture is essential for a variety of fundamental cellular phenomena that underlie the complex orchestration of mammalian development. The ATP-dependent chromatin remodeling protein ATRX is emerging as a key regulatory component of nucleosomal dynamics and higher order chromatin conformation. Here we provide an overview of the role of ATRX at chromatin and during development, and discuss recent studies exposing a repertoire of ATRX functions at heterochromatin, in gene regulation, and during mitosis and meiosis. Exciting new progress on several fronts suggest that ATRX operates in histone variant deposition and in the modulation of higher order chromatin structure. Not surprisingly, dysfunction or absence of ATRX protein has devastating consequences on embryonic development and leads to human disease.

Pharmacogenetics of testosterone replacement therapy

Variable phenotypes of androgen insensitivity exist in humans, mainly owing to defective, mutated androgen receptors. A more subtle modulation of androgen effects is related to the CAG repeat polymorphism ([CAG]n) in exon 1 of the androgen receptor gene, in vitro, transcription of androgen-dependent target genes is attenuated with increasing length of triplets. As a clinical entity, the CAG repeat polymorphism can relate to variations of androgenicity in (apparently) eugonadal men in various tissues and psychological traits, the longer the (CAG)n, the less prominent the androgen effect when individuals with similar testosterone concentrations are compared. A strictly defined threshold to hypogonadism is likely to be replaced by a continuum spanned by genetics as well as symptom specificity. In addition, effects of externally applied testosterone can be markedly influenced by the (CAG)n and respective pharmacogenetic implications are likely influence indications as well as modalities of testosterone treatment of hypogonadal men.

Mechanisms of Disease: pharmacogenetics of testosterone therapy in hypogonadal men

A defective, mutated androgen receptor may lead to variable phenotypes of androgen insensitivity in humans. Also, the CAG repeat polymorphism in exon 1 of the androgen receptor gene modulates androgen effects; in vitro, transcription of androgen-dependent target genes is attenuated with increasing length of triplet residues. Clinically, the CAG repeat polymorphism causes significant modulations of androgenicity in various tissues and psychological traits in healthy eugonadal men: the longer the repeat tracts, the less pronounced is the androgen effect when individuals with similar testosterone concentrations are compared. Furthermore, as effects of testosterone substitution are markedly influenced by the number of CAG repeats, the pharmacogenetic implications of this polymorphism are likely to have a significant role in future testosterone treatment of hypogonadal men. Thresholds at which testosterone treatment should be initiated, as well as androgen dosage, might be tailored according to the receptor polymorphism.