Functional effects of DAX-1 mutations identified in patients with X-linked adrenal hypoplasia congenita

X-linked adrenal hypoplasia congenita with hypogonadotropic hypogonadism and adrenal insufficiency is a rare disorder caused by mutations of DAX-1. In this study, we investigated the functional defects of DAX-1 caused by mutations identified in 3 unrelated Korean patients with adrenal hypoplasia congenita. The DAX-1 gene was directly sequenced using genomic DNA isolated from peripheral blood leukocytes. The functional defects of DAX-1 caused by mutations were evaluated using an in vitro promoter assay. After mutagenesis of DAX-1 complementary DNA in the pcDNA3.1 vector, steroidogenic factor 1 and the promoter region of steroidogenic acute regulatory protein (StAR) genes in pGL4.10[luc2] were transiently cotransfected into human embryonic kidney 293 cells, followed by luminometry measurements of the luciferase activity of StAR. Mutation analysis of 3 patients revealed p.L386delfsX2, p.W105X, and p.Q252X mutations of the DAX-1 gene. The mutant DAX-1 proteins showed lower repressive activity on the StAR gene promoter when compared with normal DAX-1. Nonsense and frameshift mutations of the DAX-1 gene partially eliminated the ability of DAX-1 to repress the transcription of StAR in an in vitro assay.