Identification of Novel and Known Variants in Epigenetic Genes Associated with Syndromic 46,XY Differences of Sex...

46,XY differences of sex development (DSD) are conditions with extreme phenotypic and genetic heterogeneity. Therefore, their diagnosis remains a major challenge for both clinicians and geneticists. In this study, we aimed to identify the underlying genetic causes of DSD in a series of 3 Moroccan patients with syndromic 46,XY DSD recruited in the BRO Biobank.

Methods: Karyotyping analysis was performed on peripheral blood samples using standard R banding techniques. SRY gene was analyzed using PCR amplification followed by Sanger sequencing. Whole exome sequencing (WES) was performed after unsuccessful conventional genetic analyses. Candidate variants were evaluated by segregation analysis and molecular modeling.

WES identified three pathogenic variants in genes encoding various components of the epigenetic machinery: in patient 1, a novel heterozygous frameshift variant c.4072dup (p.Glu1358GlyfsTer29) in the KAT6B gene associated with two clinically distinct syndromes (genitopatellar syndrome and Say-Barber-Biesecker-Young-Simpson syndrome) was detected; in patient 2, we identified a previously reported de novo heterozygous nonsense variant c.12943C>T (p.Gln4315Ter) in KMT2D responsible for Kabuki syndrome; in patient 3, WES revealed a novel heterozygous missense variant c.4056C>G (p.Phe1352Leu) in CHD7 responsible for CHARGE syndrome. We discuss the genotype-phenotype correlation in these syndromic 46,XY DSD and discuss the relevance of the epigenetic genes in sexual development.

Our findings highlight the utility of WES in discriminating clinically overlapping syndromic 46,XY DSD to provide an accurate diagnosis, thus allowing better follow-up and appropriate patient management. In addition, our study enriched the mutational spectrum of syndromic 46,XY DSD and confirmed the genotype-phenotype correlations.