Whole-genome and whole-exome sequencing of Mayer-Rokitansky-Küster-Hauser syndrome-discordant monozygotic twins.

PURPOSE: Mayer-Rokitansky-Küster-Hauser syndrome (MRKHS), characterized by congenital uterine and vaginal aplasia, lacks definitive etiology. Discordant monozygotic (MZ) twins provide a unique model to dissect postzygotic drivers of phenotypic divergence. This study aimed to identify postzygotic mutations (SNVs, Indels, CNVs, SVs) underlying MRKHS discordance and redefine its molecular etiology.

METHODS

Whole-genome and exome sequencing (WGS/WES) were performed on blood-derived DNA from MRKHS discordant MZ twins. Variant detection utilized VarScan2, GATK, BreakDancer, and CNVnator, with stringent filtering for somatic mutations. Putative discordant variants were validated via Sanger sequencing.

RESULTS

High-coverage sequencing (mean WGS: 66.2x-68.2x; WES: 94.5x-126.6x) revealed four low-quality discordant SNVs, none of which were validated by Sanger sequencing. No pathogenic CNVs/SVs were detected, including in genes critical to Müllerian development (e.g., WNT4, LHX1). Blood-derived DNA analysis failed to identify high-penetrance coding mutations or tissue-specific mosaicism.

CONCLUSIONS

The absence of validated postzygotic mutations challenges coding variants as primary MRKHS drivers. Findings implicate Müllerian-restricted somatic mosaicism or epigenetic dysregulation (e.g., WNT4/LHX1 methylation) during embryogenesis, undetectable in peripheral blood. This underscores limitations of blood-based genomics and highlights the need for non-invasive biomarkers (e.g., cfDNA methylation) and prenatal environmental risk mitigation (e.g., endocrine disruptor avoidance). The study advocates integrating tissue-specific multi-omics and patient derived organoids to resolve MRKHS mechanisms, guiding fertility preservation and personalized reproductive interventions.