ESPE Abstracts

Introduction: Steroidogenic factor1 (SF1/NR5A1) regulates adrenal and sex development and function. SF1 mutations manifest with a broad phenotype; generally in 46,XY individuals with disorders of sex development (DSD) and in women with ovarian insufficiency. So far, no genotype–phenotype correlation has been found. We hypothesized that the broad phenotype of SF1 mutations may be due to a second hit in a gene with similar function. Liver receptor homolog-1 (LRH1/NR5A2), from the same family, was thought a good candidate. Thus, we studied the role of LRH1 in SF1 deficiency in vitro and in vivo.

Methods and patients: In vitro, we assessed the interplay between DAX1, SF1 and LRH1 in non-steroidogenic HEK293 cells. V20L SF1 (present in a severely-affected 46,XY DSD subject and his healthy father) was chosen for comparative studies. We investigated the effect of WT SF1 and V20L SF1 combined with LRH1 isoforms on SF1 regulated promoter-luciferase-reporter-constructs (CYP17A1 and HSD3B2) in transfection experiments. We also assessed the expression of these factors (including LRH1 isoforms) in human steroidogenic tissues. In vivo, we searched for NR5A2 mutations in 21 subjects harboring heterozygous NR5A1 mutations.

Results: In vitro assays showed that all LRH1 isoforms were able to transactivate the CYP17A1 and the HSD3B2 promoters. When SF1 activity was lost, all LRH1 isoforms transactivated the HSD3B2 promoter. DAX1 inhibited SF1 and LRH1 mediated transactivation. Gene profiles revealed that LRH1 isoforms are all expressed in both human adult and fetal adrenals and testis. However, we found no mutations in NR5A2 in our cohort of SF1 patients.

Conclusions: In vitro, LRH1 can regulate transcription of steroidogenic genes similarly to SF1. LRH1 can (partially) replace SF1 in case of deficiency. However, there were no mutations in NR5A2 in heterozygote NR5A1 patients with a severe phenotype of SF1 deficiency. Thus the variability in phenotype with SF1 genotype remains elusive.