Discovery of a DNA methylation profile in individuals with Sifrim-Hitz-Weiss syndrome.

Pathogenic heterozygous variants in CHD4 cause Sifrim-Hitz-Weiss syndrome, a neurodevelopmental disorder associated with brain anomalies, heart defects, macrocephaly, hypogonadism, and additional features with variable expressivity. Most individuals have non-recurrent missense variants, complicating variant interpretation. A few were reported with truncating variants, and their role in disease is unclear. DNA methylation episignatures have emerged as highly accurate diagnostic biomarkers in a growing number of rare diseases. We aimed to study evidence for the existence of a CHD4-related DNA methylation episignature. We collected blood DNA samples and/or clinical information from 39 individuals with CHD4 variants, including missense and truncating variants. Genomic DNA methylation analysis was performed on 28 samples. We identified a sensitive and specific DNA methylation episignature in samples with pathogenic missense variants within the ATPase/helicase domain. The same episignature was observed in a family with variable expressivity, a de novo variant near the PHD domain, variants of uncertain significance within the ATPase/helicase domain, and a sample with compound heterozygous variants. DNA methylation data revealed higher percentages of shared probes with BAFopathies, CHD8, and the terminal ADNP variants encoding a protein known to form the ChAHP complex with CHD4. Truncating variants, as well as a sample with a recurrent pathogenic missense variant, exhibited DNA methylation profiles distinct from the ATPase/helicase domain episignature. These DNA methylation differences, together with the distinct clinical features observed in those individuals, provide preliminary evidence for clinical and molecular sub-types in the CHD4-related disorder.