A novel ATP7A splice‑site variant with suspected maternal gonadal mosaicism in Menkes disease: functional validation and prenatal diagnosis

Abstract Menkes disease (MIM#309400) is a rare, fatal X-linked neurodegenerative disorder caused by ATP7A mutations. Delayed diagnosis due to clinical heterogeneity and limited data on mutational spectrum and reproductive risk remain challenges, with gonadal mosaicism being an often underestimated cause of disease recurrence. We performed whole-exome sequencing (WES) in the proband, and subsequently validated the identified variant in both parents by Sanger sequencing. Prenatal diagnosis via amniocentesis was offered in a subsequent pregnancy, and performed further validation using fetal skin tissue via RT-PCR and Western blot. A systematic literature review of Chinese Menkes cases was also conducted. We identified a novel hemizygous splice‑site variant, ATP7A c.2782-1G > T, absent from public population databases and globally unreported. Functional assays confirmed disrupted mRNA splicing and significantly reduced ATP7A protein expression, leading to reclassification as Pathogenic (PVS1 + PM2‑S+PP4). The mother showed low‑level somatic mosaicism (13.2%) in peripheral blood, and recurrence in two consecutive pregnancies strongly suggested gonadal mosaicism. Prenatal diagnosis identified an affected male fetus, and reproductive intervention followed genetic counselling. A review of 87 Chinese paediatric cases illustrated the phenotypic and mutational spectrum in this population. In conclusion, we report and functionally validate the first ATP7A c.2782-1G > T variant as causative for Menkes disease worldwide. Our findings highlight the value of WES and functional studies for accurate variant interpretation. Moreover, suspected maternal gonadal mosaicism can lead to unexpected familial recurrence, underscoring the need for comprehensive risk assessment in genetic counselling and prenatal diagnosis. These results expand the ATP7A mutational spectrum and provide a practical diagnostic paradigm for rare X‑linked disorders.