A novel androgen receptor gene splice site mutation induces aberrant mRNA splicing and internal in-frame deletion in androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is a disorder caused by pathogenic mutations in the androgen receptor (AR) gene, leading to androgen resistance and impaired sex differentiation in 46,XY individuals. Despite increasing recognition of AR mutations, the pathogenic mechanisms and genotype–phenotype correlations of many variants remain incompletely characterized. In this study, we identified a novel splice site mutation in the AR gene, c.2450-1G > A, in a 46,XY patient presenting with a female phenotype, including primary amenorrhea and classical features of AIS, confirmed by chromosomal analysis and ultrasonography. Functional validation using minigene splicing assays demonstrated that this variant disrupts normal splicing, leading to an aberrant transcript lacking 6 bp at the 5′ end of exon 7. This results in an aberrant in-frame transcript, c.2450_2455del, encoding a mutant protein with a three-amino acid deletion and a methionine insertion (p.Ile817_Val819delinsMet), while preserving the reading frame. In silico structural modeling suggested that this alteration may disturb the ligand-binding domain (LBD) conformation and receptor functionality. These findings highlight the pathogenic significance of splice-site variants in AR and provide mechanistic insight into AIS diagnosis and management.