7644 Novel Candidate Genes for SRY-Negative 46,XX Differences of Sex Development with Testicular Differentiation

Abstract Disclosure: M.M. Ferrari: None. M.Y. Nishi: None. A.A. Jorge: None. A.F. Benedetti,: None. R.L. Batista: None. E.S. Silva: None. A. Martinez: None. V. Mericq: None. F.M. Carvalho: None. B.B. Mendonca: None. S. Domenice: None. Introduction: Gonadal development in mammals is a dynamic and complex process, which requires the interaction of multiple factors in a meticulous feedback control and self-regulation system. Defects in genes involved in this process may cause differences of sex development (DSD). In rare cases, the gonads of 46,XX individuals differentiate completely into testes (46,XX testicular DSD, 46,XX TDSD), or with the coexistence of testicular and ovarian tissues in the same individual (46,XX ovotesticular DSD, 46,XX OTDSD). Strategies of large-scale parallel sequencing have enabled the simultaneous analysis of known genes, as well as the identification of novel candidate genes contributing to molecular diagnosis of these conditions. Objective: To establish the molecular diagnosis of a cohort of SRY-negative 46,XX T/OTDSD patients using the whole exome sequencing (WES) technique. Patients and Methods: Twenty-three families (24 patients) were evaluated, 22 patients with sporadic disease, and one family with two affected siblings. Histological diagnosis of OTDSD was confirmed in all patients, except in two with the presumptive (non-histological) diagnosis of TDSD. WES was performed using the Illumina platform. The variants were classified according to ACMG criteria. Results: Six different candidate genes associated with the 46,XX DSD phenotype were identified in the 23 families (26%) studied; all in patients with OTDSD diagnosis. Two variants were classified as likely pathogenic in FLNB and SOX10 genes, and four as VUS in IMMP2L, SOX8, PRKACG, and CLASP1 genes. The unavailability of analysis of case-parent trio samples hampered the classification of some of the novel candidate allelic variants. All these candidate genes were selected as potential causes of OTDSD, based on evidence of direct or indirect interactions of these proteins with SOX9. In the two siblings with 46,XX OTDSD, the allelic variant c.397delT (p.Ser133Leufs*7) in IMMP2L was identified in a heterozygous state and was absent in the unaffected family members (mother and third XY sibling). A potential role of Immp2l had been previously associated with the etiology of XX female-to-male sex reversal in sheep lineage. Conclusion: Although establishing the genetic etiology of gonadal development abnormalities in individuals with 46,XX TDSD/OTDSD remains a challenge, the results of this study generated new information and perspectives on the mechanisms involved in gonadal development. Presentation: 6/3/2024