Androgen receptor abnormalities

The human androgen receptor is a member of the superfamily of steroid hormone receptors. Proper functioning of this protein is a prerequisite for normal male sexual differentiation and development. The cloning of the human androgen receptor cDNA and the elucidation of the genomic organization of the corresponding gene has enabled us to study androgen receptors in subjects with the clinical manifestation of androgen insensitivity and in a human prostate carcinoma cell line (LNCaP). Using PCR amplification, subcloning and sequencing of exons 2–8, we identified a G → T mutation in the androgen receptor gene of a subject with the complete form of androgen insensitivity, which inactivates the splice donor site at the exon 4/intron 4 boundary. This mutation causes the inactivation of a cryptic splice donor site in exon 4, which results in the deletion of 41 amino acids from the steroid binding domain. In two other independently arising cases we identified two different nucleotide alterations in codon 686 (GAC; aspartic acid) located in exon 4. One mutation (G → C) results in an aspartic acid → histidine substitution (with negligible androgen binding), whereas the other mutation (G → A) leads to an aspartic acid → asparagine substitution (normal androgen binding, but a rapidly dissociating androgen receptor complex). Sequence analysis of the androgen receptor in human LNCaP-cells (lymph node carcinoma of the prostate) revealed a point mutation (A → G) in codon 868 in exon 8 resulting in the substitution of threonine by alanine. This mutation is the cause of the altered steroid binding specificity of the LNCaP-cell androgen receptor. The functional consequences of the observed mutations with respect to protein expression, specific ligand binding and transcriptional activation, were established after transient expression of the mutant receptors in COS and HeLa cells. These findings illustrate that functional error

Genomic variants reducing expression of two endocytic receptors in 46,XY differences of sex development

Transporter-dependent steroid hormone uptake into target cells was demonstrated in genetically engineered mice and fruit flies. We hypothesized that mutations in such transporters may cause differences in sex development (DSD) in humans. Exome sequencing was performed in 16 genetically unsolved cases of 46,XY DSD selected from an anonymized collection of 708 lines of genital fibroblasts (GF) that were taken from individuals with incomplete virilization. Selection criteria were based on available biochemical characterization of GF compatible with reduced androgen uptake. Two unrelated individuals were identified with mutations in LDL receptor related protein 2 (LRP2), a gene previously associated with partial sex steroid insensitivity in mice. Like Lrp2(-/-) mice, affected individuals had non-descended testes. Western blots on GF confirmed reduced LRP2 expression, and endocytosis of sex hormone binding globulin was reduced. In three unrelated individuals, with inguinal testes, mutations in another endocytic receptor gene, limb development membrane protein 1 like (LMBR1L), were detected. Two of these individuals had mutations affecting the same codon. In a transfected cell model, mutated LMBR1L showed reduced cell surface expression. Our findings suggest that endocytic androgen uptake in complex with sex hormone binding globulin is relevant in human. LMBR1L may play a similar role in androgen uptake

Epigenetic Repression of Androgen Receptor Transcription in Mutation-Negative Androgen Insensitivity Syndrome (AIS Type II).

Item does not contain fulltextContext: Inactivating mutations within the AR-gene are present in only around 40% of individuals with clinically and hormonally diagnosed androgen insensitivity syndrome (AIS). Previous studies revealed the existence of an AR-gene mutation negative group of AIS-individuals with compromised AR-function (AIS type II). Objective: To investigate if AIS type II can be due to epigenetic repression of AR-transcription. Design: Quantification of AR-mRNA and AR proximal promoter CpG-methylation levels in genital skin derived fibroblasts (GF) derived from AIS type II individuals and control individuals. Setting: University Hospital endocrine research laboratory. Patients: GF from control individuals (N=11) and AIS type II individuals (N=14). Intervention(s): None. Main Outcome Measure(s): Measurement of AR-mRNA and AR promoter CpG-methylation as well as activity of AR proximal promoter in vitro. Results: 57% of individuals with AIS type II (N=8) show a reduced AR-mRNA expression in their GF. A significant inverse correlation exists between AR-mRNA abundance and methylation at two consecutive CpGs within the proximal AR promoter. Methylation of a 158bp long region containing these CpGs is sufficient to severely reduce reporter gene expression. This region is bound by the Runt Related transcription factor1 (RUNX1). Ectopic expression of RUNX1 in HEK293T cells is able to inhibit reporter gene expression through this region. Conclusions: Aberrant CpGs methylation within the proximal AR promoter plays an important role in the control of AR-gene expression and may result in AIS type II. We suggest that transcriptional modifiers, like RUNX1, could play roles therein offering new perspectives for understanding androgen-mediated endocrine diseases