A novel nonsense mutation of the glucocorticoid receptor gene causing glucocorticoid resistance with infertility

Area of Science:

• Endocrinology
• Molecular Biology
• Genetics

Background:

• Chrousos syndrome is a rare genetic disorder caused by inactivating mutations in the NR3C1 gene, encoding the human glucocorticoid receptor (GR).
• This study focuses on a male patient with Chrousos syndrome presenting with oligospermia and infertility, lacking other typical clinical features.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the unique clinical manifestations, specifically infertility, in a patient with Chrousos syndrome.
• To elucidate how a novel NR3C1 mutation (c.1839T > A, p. Tyr613Ter) affects glucocorticoid receptor (GR) function and expression.

Main Methods:

• Transfection of mutant GR plasmids into HEK293T and HeLa cells to assess glucocorticoid sensitivity and GR expression.
• Utilized proteomic analysis and cellular experiments to determine the mechanism behind GR expression changes induced by the mutation.

Main Results:

• The identified mutation (GR Y613*) results in the deletion of the GR ligand-binding region, leading to decreased affinity for dexamethasone, reduced nuclear translocation, and impaired transactivation.
• GR Y613* exhibited decreased protein levels but unchanged gene expression, with E3 ligase STUB1 identified as a regulator of its ubiquitin-proteasome degradation.
• Expression of STUB1 was found to be significantly lower in human testis and Sertoli cells compared to other tissues.

Conclusions:

• The GR Y613* mutation confers reduced sensitivity to glucocorticoids.
• STUB1 facilitates the ubiquitination and degradation of the mutant GR Y613*.
• The low expression of STUB1 in the testis may lead to the accumulation of GR Y613*, potentially explaining the observed infertility in this Chrousos syndrome patient.