A novel variant in the 5’ UTR of the androgen receptor gene without coding region alterations in three patients with complete androgen insensitivity syndrome

A syndrome-causing androgen receptor ( AR) gene variant is identified in > 95% of 46,XY individuals with a female phenotype due to complete androgen insensitivity syndrome (CAIS). Here, we describe three patients (two adults, 37 and 32 years of age, and a 14-year-old teenager) with CAIS harboring a new 5’UTR variant of AR . Sanger sequencing of the AR coding region did not identify any known syndrome-causing variant. Massive parallel sequencing of genes, known to be involved in differences in sexual development, and their regulatory regions identified a novel c.-829C > T variant in the 5’UTR sequence of AR in all three patients. The ORF Finder software predicted the use of a new AUG codon located 296 bp downstream of the transcription start site (not confirmed by western blotting). Luciferase activity was slightly decreased in U2SO cells after transfection of the AR 5’UTR-c.-829C > T construct, but this could not explain the CAIS phenotype. Western blotting with an anti-AR antibody showed increased expression of a high molecular weight band and a decrease of the native AR protein. Aberrant splicing and mRNA level alterations were not detected. This study identified the c.-829C > T AR variant in three unrelated patients with CAIS. The functional analysis suggests that a posttranslational modification in AR may increase its molecular weight. The reduced bioavailability of the native AR protein could explain CAIS in these three patients. This second 5’UTR-coding sequence variant highlights the need to analyze AR exons and non-coding regions in all patients with CAIS.