Identification of an AR Mutation-Negative Class of Androgen Insensitivity by Determining Endogenous AR Activity

Abstract

Context:Only approximately 85% of patients with a clinical diagnosis complete androgen insensitivity syndrome and less than 30% with partial androgen insensitivity syndrome can be explained by inactivating mutations in the androgen receptor (AR) gene.Objective:The objective of the study was to clarify this discrepancy by in vitro determination of AR transcriptional activity in individuals with disorders of sex development (DSD) and male controls.Design:Quantification of DHT-dependent transcriptional induction of the AR target gene apolipoprotein D (APOD) in cultured genital fibroblasts (GFs) (APOD assay) and next-generation sequencing of the complete coding and noncoding AR locus.Setting:The study was conducted at a university hospital endocrine research laboratory.Patients:GFs from 169 individuals were studied encompassing control males (n = 68), molecular defined DSD other than androgen insensitivity syndrome (AIS; n = 18), AR mutation-positive AIS (n = 37), and previously undiagnosed DSD including patients with a clinical suspicion of AIS (n = 46).Intervention(s):There were no interventions.Main Outcome Measure(s):DHT-dependent APOD expression in cultured GF and AR mutation status in 169 individuals was measured.Results:The APOD assay clearly separated control individuals (healthy males and molecular defined DSD patients other than AIS) from genetically proven AIS (cutoff < 2.3-fold APOD-induction; 100% sensitivity, 93.3% specificity, P < .0001). Of 46 DSD individuals with no AR mutation, 17 (37%) fell below the cutoff, indicating disrupted androgen signaling.Conclusions:AR mutation-positive AIS can be reliably identified by the APOD assay. Its combination with next-generation sequencing of the AR locus uncovered an AR mutation-negative, new class of androgen resistance, which we propose to name AIS type II. Our data support the existence of cellular components outside the AR affecting androgen signaling during sexual differentiation with high clinical relevance.

Management of Gonads in Adults with Androgen Insensitivity: An International Survey

“…In men and women with partial AIS (PAIS), the phenotype is highly variable, depending on the degree of residual androgen activity and other modifying factors [1]. Whereas a likely pathogenic variant in AR can be identified in 85% of women who have CAIS, this is only the case in less than 30% of individuals who have clinical features suggestive of PAIS, suggesting that other mechanisms affect androgen signalling [2]. Providing care for individuals with AIS is best performed in a multidisciplinary setting and may be challenging [3-6].…”

Androgen-responsive non-coding small RNAs extend the potential of HCG stimulation to act as a bioassay of androgen sufficiency

“…A firm diagnosis of AIS requires the confirmation of a mutation in the androgen receptor gene (AR). However, recent studies suggest that the molecular genetic abnormality in AR may not necessarily reside in the conventional coding region within the gene (38). Whilst there is a school of thought that molecular genetic investigations can be performed in parallel with biochemical evaluation, the current study suggests that the utility of conventional biochemical investigations such as the hCG stimulation test, itself, can include a molecular genetic component that aids the diagnosis of androgen deficiency and perhaps, androgen resistance.…”

“…Although androgen-responsive circulating proteins such as SHBG have been measured previously (6), this test has not been considered to be sufficiently reliable to become common practice. More recently, another androgenresponsive protein in the genital skin fibroblasts has been reported to have a greater discriminant value for androgen sensitivity (38). Genital skin fibroblast studies have also previously reported an androgen-dependent transcriptome, which could differentiate between people with and without androgen sensitivity (3).…”

Improving Laboratory Assessment in Disorders of Sex Development through a Multidisciplinary Network

“…An example is the assay that uses DHT-dependent transcriptional induction of the androgen receptor (AR) target gene apolipoprotein D in genital skin fibroblasts to assess androgen action [Hornig et al, 2016]. This assay is able to discriminate between individuals with androgen insensitivity caused by an AR mutation and unaffected individuals.…”