MON-255 Whole Exome Sequencing of 46,XY DSD Patients with Gonadal Development Abnormalities

Abstract Disclosure: M.J. Chafloque Mesia: None. R. Loch Batista: None. J. Américo Pereira Batatinha: None. S. Alvarenga Galliano: None. M. Yumie Nishi: None. E.M. Frade Costa: None. S. Domenice: None. B.B. Mendonca: None. 46,XY Differences of Sex Development (46,XY DSD) encompasses a broad phenotypic spectrum, with molecular diagnosis being a persistent challenge, especially in cases of gonadal development abnormalities, where over 60% lack a molecular diagnosis. Pathogenic/likely pathogenic variants in NR5A1, MAP3K1, and SRY are the most common causes, but many cases remain unexplained.This study aims to analyze the molecular etiology of 46,XY DSD patients with gonadal development abnormalities using whole exome sequencing (WES).We studied 22 patients with isolated gonadal development abnormalities previously tested for NR5A1 and SRY variants with negative results. The cohort included 10 with complete gonadal dysgenesis (CGD), 7 with partial gonadal dysgenesis (PGD), and 5 with embryonic testicular regression syndrome (ETRS). Exome sequencing was performed, and SNV and CNV variants were submitted to an extensive in silico analysis.Variants in gonadal development-related genes were identified in 8 patients (36%). One CGD patient carried a known likely pathogenic variant in DHH (c.1004T>C, p.Leu335Pro). Three patients, with ETRS and PGD, carried variants of uncertain significance (VUS) in DHX37, including a previously reported missense variant (c.1496G>A, p.Arg499Gln) and a novel variant (c.3427A>G, p.Met1143Val) in two patients. One of these patients also carried a second VUS in ZFPM2 (c.2411C>T, p.Thr804Met). Additional VUS were identified in GATA4 (c.1223C>G, p.Pro408Arg) in one PGD patient and in ZEB2 (c.1472T>G, p.Met491Arg) in one CGD patient. Notably, two unrelated patients (ETRS and CGD) carried the same likely pathogenic variant in a novel possible candidate gene, ANKRD36 (c.2245+1G>A), with broad expression in testicular tissue. Additional CNV analysis did not identify any causative variants in this cohort.WES identified variants in gonadal development-related genes in 36% of patients with 46,XY DSD and gonadal abnormalities, including likely pathogenic variants in DHH and a novel candidate gene expressed in testicular tissue, ANKRD36. Variants of uncertain significance in genes such as DHX37, ZFPM2, GATA4, and ZEB2 highlight potential new targets for further investigation. No CNVs were identified as causative in this cohort, suggesting that CNVs may be rare in gonadal dysgenesis. These findings support an oligogenic model of gonadal abnormalities, with potential digenic interactions observed in some cases. Despite these advances, more than 50% of patients remain without a molecular diagnosis, emphasizing the importance of exploring non-coding regions through whole genome sequencing and conducting functional studies to validate novel candidate genes. Presentation: Monday, July 14, 2025