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Context 46,XY Gonadal dysgenesis (GD) is a heterogeneous group of disorders with a wide phenotypic spectrum, including embryonic testicular regression syndrome (ETRS). Objective To report a gene for 46,XY GD etiology, especially for ETRS. Design Screening of familial cases of 46,XY GD using whole-exome sequencing and sporadic cases by target gene-panel sequencing. Setting Tertiary Referral Center for differences/disorders of sex development (DSD). Patients and Interventions We selected 87 patients with 46,XY DSD (17 familial cases from 8 unrelated families and 70 sporadic cases); 55 patients had GD (among them, 10 patients from 5 families and 8 sporadic cases had ETRS), and 32 patients had 46,XY DSD of unknown etiology. Results We identified four heterozygous missense rare variants, classified as pathogenic or likely pathogenic in the Asp-Glu-Ala-His-box (DHX) helicase 37 (DHX37) gene in five families (n = 11 patients) and in six sporadic cases. Two variants were recurrent: p.Arg308Gln (in two families and in three sporadic cases) and p.Arg674Trp (in two families and in two sporadic cases). The variants were specifically associated with ETRS (7/14 index cases; 50%). The frequency of rare, predicted-to-be-deleterious DHX37 variants in this cohort (14%) is significantly higher than that observed in the Genome Aggregation Database (0.4%; P < 0.001). Immunohistochemistry analysis in human testis showed that DHX37 is mainly expressed in germ cells at different stages of testis maturation, in Leydig cells, and rarely in Sertoli cells. Conclusion This strong genetic evidence identifies DHX37 as a player in the complex cascade of male gonadal differentiation and maintenance.

Molecular diagnosis is rarely established in 46,XX testicular (T) disorder of sex development (DSD) individuals with atypical genitalia. The Wilms' tumour factor‐1 (WT1) gene is involved in early gonadal development in both sexes. Classically, WT1 deleterious variants are associated with 46,XY disorders of sex development (DSD) because of gonadal dysgenesis. We report a novel frameshift WT1 variant identified in an SRY‐negative 46,XX testicular DSD girl born with atypical genitalia. Target massively parallel sequencing involving DSD‐related genes identified a novel heterozygous WT1 c.1453_1456del; p.Arg485Glyfs*14 variant located in the fourth zinc finger of the protein which is absent in the population databases. Segregation analysis and microsatellite analysis confirmed the de novo status of the variant that is predicted to be deleterious by in silico tools and to increase WT1 target activation in crystallographic model. This novel and predicted activating frameshift WT1 variant leading to the 46,XX testicular DSD phenotype includes the fourth zinc‐finger DNA‐binding domain defects in the genetic aetiology of 46,XX DSD.