Partial defects in transcriptional activity of two novel DAX-1 mutations in childhood onset adrenal hypoplasia congenita

LAISSUE P; COPELLI S; BERGADÁ I; BERGADA C; BARRIO G; KARABOGA S; WURTZ JM; FELLOUS M; LALLI E; VEITIA RA

CLINICAL ENDOCRINOLOGY

Lugar: Oxford; Año: 2006 vol. 63 p. 681 - 686

0300-0664

Objective. Mutations in DAX-1, an X-linked gene encoding an orphan nuclear receptor, have been associated with adrenal hypoplasia congenita and hypogonadotrophic hypogonadism. Here we describe two novel DAX-1 mutations, Y214X, and I361T, associated with childhood onset primary adrenal failure. We aimed at analyzing their effects on protein localization, transcriptional activity and propose a structural function relationship. Design. We have directly sequenced the DAX-1 gene from PCR amplified DNA. The effect of the pmutation on protein localization was assesed by immunocytochemistry in transfected cells.The impact of mutations on transcriptional activity was determined by transfection using a StAR promoter luciferase reporter system. Results.The mutation Y214X produces a protein lacking the C.terminal half of DAX-1. The other one, I361T, affects a highly conserved amino acid within the putative lignad binding domain. The mutant Y214X displayed a wild type subcellular localization while I361T was partially retained in the cytoplasm. Both mutants retained substantial transcriptional suppressive activity, compared to mutants producing early onset adrenal failure. Interestingly, I361T displayed similar in vitro transcriptional repressive activity to the mutant I439S previously described in a case of late onset AHC. This shows that molecular alterations of DAX-1 leading to similar in vitro activities may result in very different ages of onset of adrenal failure, which suggests that additional genetic and epigenetic factors are important in determining the clinical onset of AHC. Conclusions Our results help the understanding of structure function relationships in the DAX-1 molecule, suggesting that the N terminal domain is relatively autonomous and add credence to presumed molecular interactions within ligand binding domain of the protein.