Endocrine Abstracts

Background: Differences/disorders of sex development (DSD) affect ~1% of live births and involve chromosomal, gonadal, or genital abnormalities. Diagnosis is often lengthy and inconclusive, with gonadal dysgenesis yielding a genetic diagnosis in only ~50% of cases. We aimed to increase DSD diagnostic yield by identifying causative DSD genes.

Methods: We report a 46,XY DSD patient presenting with perineal hypospadias, clitoromegaly, and cryptorchidism. Whole exome sequencing (WES) was performed, and variants were prioritized based on allele frequency, predicted pathogenicity, and relevance to sex development pathways, leading to the identification of a compound heterozygous DMRT3 variant. Functional effects were assessed using two luciferase reporter assays in HEK293T cells. An ESR1 promoter–luciferase construct was used to measure the impact of wild type and variant DMRT3 proteins on ESR1 transcription. A p4xDMRT luciferase reporter containing synthetic DMRT1 binding sites was used to evaluate how the DMRT3 variants influence DMRT1 mediated transcriptional activation.

Results: WES identified a compound heterozygous DMRT3 variant, which was prioritized as the most plausible genetic contributor. In the ESR1 promoter assay, both DMRT3 variants produced increased promoter activity compared with wild type DMRT3, indicating a potential gain of function effect on ESR1 regulation. Consistent with prior findings that DMRT1 preferentially forms heterodimers with DMRT3 rather than homodimers (Murphy, 2007), our p4xDMRT luciferase assay showed that DMRT3 suppressed DMRT1 driven transcriptional activation. Notably, the DMRT3 variants exhibited even stronger suppression than the wild type. Together, these results demonstrate that DMRT3 can inhibit DMRT1’s ability to bind and activate its target sites, and that the patient specific variants enhance this inhibitory effect.

Conclusions: These findings implicate DMRT3 variants as contributors to 46,XY DSD through dual disruption of sex determining pathways. By increasing ESR1 promoter activity while suppressing DMRT1 dependent transcription, the variants appear to shift the balance between pro testicular and pro ovarian signaling. This work highlights a previously unrecognized role for DMRT3 in human gonadal development and supports its relevance as a candidate gene in DSD, with potential implications for improved genetic diagnosis and future therapeutic strategies.