ESPE Abstracts

Patients with Disorders of sex development (DSD) can present with a large phenotypic spectrum and caused by a number of different genetic defects. Therefore, it is difficult to reach a specific diagnosis using traditional approaches including biochemical analysis and single gene sequencing in a number of patients with DSD. Recently, next-generation sequencing technologies have revolutionized the identification of causative genes with diseases with genetic heterogeneity using massive parallel sequencing of multiple samples simultaneously.

Objective and hypotheses: This study was performed to investigate the genetic etiology of DSD patients using targeted exome sequencing of 67 known human DSD associated genes.

Method: This study included 39 patients with 46,XY DSD and eight patients with 46,XX DSD. Exomes were captured using SureSelect kit (Agilent Technologies) and sequenced on the Miseq platform (Illumina, Inc.), which includes 2914 probes targeting a 152.953 kbp region spanning 67 genes. Mean coverage was over 150X for each sample, and approximately 99.46% of the targeted bases were read. We classified variants into five main categories (pathogenic, likely pathogenic, uncertain significance, likely benign, and benign) according to the American College of Medical Genetics and Genomics guidelines.

Results: We identified known pathogenic mutations or deletion in 11 (23.4%) in the AR, CYP17A1, POR, and DMRT1/2 genes. Novel variants were identified in 10 patients (21.3%) in the AR, ATRX, CHD7, FGFR1, MAP3K1, NR5A1, PROP1, and WWOX genes. Of these, three patients harbored pathogenic or likely pathogenic variants, while the remaining 6 patients had variants of uncertain significance.

Conclusion: Whole exome sequencing is expensive and laborious. Thus, targeted strategies provide efficient methods for identification of the genetic causes in DSD patients. This approach allows for early diagnosis of a genetic cause, which could influence clinical management and genetic counseling. In vitro analysis is needed to verify functional implications of the novel variants.