Novel amino acid substitutional mutation, tyrosine-739-aspartic acid, in the androgen receptor gene in complete androgen insensitivity syndrome

Structural features discriminate androgen receptor N/C terminal and coactivator interactions

Human androgen receptor (AR) transcriptional activity involves interdomain and coactivator interactions with the agonist-bound AR ligand binding domain (LBD). Structural determinants of the AR NH(2)- and carboxyl-terminal interaction between the AR NH(2)-terminal FXXLF motif and activation function 2 (AF2) in the LBD were shown previously by crystallography. In this report, we provide evidence for a region in AR LBD helix 12 outside the AF2 binding cleft that facilitates interactions with the FXXLF and LXXLL motifs. Mutagenesis of glutamine 902 to alanine in AR LBD helix 12 (Q902A) disrupted AR FXXLF motif binding to AF2, but enhanced coactivator LXXLL motif binding. Functional compensation for defective FXXLF motif binding by AR-Q902A was suggested by the slower dissociation rate of bound androgen. Functional importance of glutamine 902 was indicated by the charged residue germline mutation Q902R that caused partial androgen insensitivity, and a similar somatic mutation Q902K reported in prostate cancer, both of which increased the androgen dissociation rate and decreased AR transcriptional activity. High affinity equilibrium androgen binding was retained by alanine substitution mutations at Tyr-739 in AR LBD helix 5 or Lys-905 in helix 12 structurally adjacent to AF2, whereas transcriptional activity decreased and the androgen dissociation increased. Deleterious effects of these loss of function mutations were rescued by the helix stabilizing AR prostate cancer somatic mutation H874Y. Sequence NH(2)-terminal to the AR FXXLF motif contributed to the AR NH(2)- and carboxyl-terminal interaction based on greater AR-2-30 FXXLF motif peptide binding to the agonist-bound AR LBD than a shorter AR-20-30 FXXLF motif peptide. We conclude that helix 12 residues outside the AF2 binding cleft modulate AR transcriptional activity by providing flexibility to accommodate FXXLF or LXXLL motif binding.

The fate of the duplicated androgen receptor in fishes: a late neofunctionalization event?

BACKGROUND

Based on the observation of an increased number of paralogous genes in teleost fishes compared with other vertebrates and on the conserved synteny between duplicated copies, it has been shown that a whole genome duplication (WGD) occurred during the evolution of Actinopterygian fish. Comparative phylogenetic dating of this duplication event suggests that it occurred early on, specifically in teleosts. It has been proposed that this event might have facilitated the evolutionary radiation and the phenotypic diversification of the teleost fish, notably by allowing the sub- or neo-functionalization of many duplicated genes.

RESULTS

In this paper, we studied in a wide range of Actinopterygians the duplication and fate of the androgen receptor (AR, NR3C4), a nuclear receptor known to play a key role in sex-determination in vertebrates. The pattern of AR gene duplication is consistent with an early WGD event: it has been duplicated into two genes AR-A and AR-B after the split of the Acipenseriformes from the lineage leading to teleost fish but before the divergence of Osteoglossiformes. Genomic and syntenic analyses in addition to lack of PCR amplification show that one of the duplicated copies, AR-B, was lost in several basal Clupeocephala such as Cypriniformes (including the model species zebrafish), Siluriformes, Characiformes and Salmoniformes. Interestingly, we also found that, in basal teleost fish (Osteoglossiformes and Anguilliformes), the two copies remain very similar, whereas, specifically in Percomorphs, one of the copies, AR-B, has accumulated substitutions in both the ligand binding domain (LBD) and the DNA binding domain (DBD).

CONCLUSION

The comparison of the mutations present in these divergent AR-B with those known in human to be implicated in complete, partial or mild androgen insensitivity syndrome suggests that the existence of two distinct AR duplicates may be correlated to specific functional differences that may be connected to the well-known plasticity of sex determination in fish. This suggests that three specific events have shaped the present diversity of ARs in Actinopterygians: (i) early WGD, (ii) parallel loss of one duplicate in several lineages and (iii) putative neofunctionalization of the same duplicate in percomorphs, which occurred a long time after the WGD.

Association of the polymorphisms of genes involved in androgen metabolism and signaling pathways with familial prostate cancer risk in a Japanese population

BACKGROUND

Androgen plays a central role in the normal and malignant development of prostate glands. Genetic polymorphisms of genes involved in androgen metabolism and signaling might be associated with the risk of prostate cancer.

METHODS

One hundred and two patients with prostate cancer with a family history and 117 healthy age- and residence-matched male controls were enrolled. Genotypes of the CAG repeat length of androgen receptor (AR), CYP17, 5alpha-reductase type II (SRD5A2), UDG-glucuronosyltransferase (UGT) 2B15, PSA promoter genes were analyzed.

RESULTS

For single polymorphisms, the presence of Y alleles showed a significantly lower risk of prostate cancer in comparison with the D/D genotype in UGT2B15 (odds ratio [OR]=0.41, 95% confidence interval [CI]=1.40-4.28, p=0.0015), and the presence of A2 alleles showed a weak tendency to decrease prostate cancer risk in comparison with the A1/A1 genotype in CYP17 (OR=0.69, 95% CI=0.39-1.23, p=0.21). The stratification of cases according to clinical stage and pathological grade showed that the A2/A2 genotype was significantly associated with localized stage cancer in comparison with metastatic stage cancer (OR=5.18, 95% CI=1.49-17.95, p=0.007). The combination of UGT2B15 and CYP17 genotypes could identify higher risk subjects even in subjects with low-risk UGT2B15 genotypes, i.e., Y/Y+D/Y genotypes (OR=1.97, 95% CI=0.92-4.22, p=0.079).

CONCLUSION

Genetic polymorphisms of the genes involved in androgen metabolism and signaling were significantly associated with familial prostate cancer risk. Single nucleotide polymorphisms of low-penetrance genes could be targets to understand genetic susceptibility to familial prostate cancer.

Mutation analysis of five candidate genes in Chinese patients with hypospadias

Hypospadias is the displacement of the urethral meatus from the tip of the glans to the ventral side of the phallus. During fetal development, SRY, SOX9, WT1, SRD5A2 and AR are important at different stages in the differentiation and development of the male genital system. Mutations in these genes impair masculinization and may be associated with hypospadias. In order to explore these possibilities, we employed polymerase chain reaction and direct sequencing to analyze the coding regions of these five genes in 90 Chinese hypospadias patients. We found a total of 16 different mutations in SRD5A2, AR and WT1 in 24 of these 90 patients. Seven mutations are novel. No mutation was found in SRY or SOX9. SNP V89L found in SRD5A2 was statistically significant between patients and controls. Our results indicated that mutations in SRD5A2, AR and WT1 were associated with hypospadias. In conclusion, mutations are frequently found in genes that control androgen action and metabolism, but are seldom found in genes active in the early phase of sex determination and differentiation. Mutations in AR, SRD5A2 or WT1 seem to be associated not only with hypospadias but also with micropenis.

Mutation of the androgen receptor (R840S) in an Egyptian patient with partial androgen insensitivity syndrome: review of the literature on the clinical expression of different R840 substitutions

The X-linked androgen insensitivity syndrome (AIS) encompasses a heterogeneous group of defects in the androgen receptor (AR) that result in varying degrees of undermasculinization. In the current study, we characterize the R840S mutation on exon 7 of the AR ligand-binding domain. The Egyptian patient, who had been reared as female, presented ambiguous genitalia at 6.5 yr. Diagnosis of partial AIS (PAIS) was based on clinical phenotype and laboratory evidence of good testosterone response and normal testosterone/dihydrotestosterone (T/DHT) ratio. The therapeutic response to testosterone depot injections justified reassignment to male sex. To our knowledge, this mutation has been reported only once in two Brazilian brothers with PAIS. Three other mutations of this residue (R840C; R840G, nonconservative; and R840H, conservative) have been reported in patients with PAIS and, when expressed in vitro, they led to subnormal transactivation of a reporter gene. Each of these mutations was associated with a very diverse spectrum of phenotypes. These data highlight the role of the AR ligand-binding pocket (LBP) in the expression of transcriptional activity during prenatal sex differentiation.