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

N C Hornig, M Ukat, H U Schweikert, O Hiort, R Werner, S L S Drop, M Cools, I A Hughes, L Audi, S F Ahmed, J Demiri, P Rodens, L Worch, G Wehner, A E Kulle, D Dunstheimer, E Müller-Roßberg, T Reinehr, A T Hadidi, A K Eckstein, C van der Horst, C Seif, R Siebert, O Ammerpohl, P-M Holterhus

Only about 85% of patients with clinical diagnosis complete androgen insensitivity syndrome (CAIS) and less than 30% with partial androgen insensitivity syndrome (PAIS) can be explained by inactivating mutations in the androgen receptor (AR) gene. To clarify this discrepancy by in-vitro determination of AR transcriptional activity in individuals with disorders of sex development (DSD) and male controls. Quantification of dihydrotestosterone (DHT)-dependent transcriptional induction of the AR target gene apolipoprotein D (APOD) in cultured genital fibroblasts (GF) (APOD-assay) and next generation sequencing (NGS) of the complete coding - and non-coding AR-locus. University Hospital Endocrine research laboratory Patients: GF from 169 individuals were studied encompassing control males (N=68), molecular defined DSD other than AIS (N=18), AR-mutation positive AIS (N=37) and previously undiagnosed DSD including patients with clinical suspicion of AIS (N=46). None. DHT-dependent APOD-expression in cultured GF and AR-mutation status in 169 individuals. 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<0.0001). Of 46 DSD-individuals with no AR-mutation, 17 (37%) fell below the cutoff indicating disrupted androgen signaling. AR-mutation positive AIS can be reliably identified by the APOD-assay. Its combination with NGS 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.