Summary Overlapping clinical phenotypes and an expanding breadth and complexity of genomic associations are a growing challenge in the diagnosis and clinical management of Mendelian disorders. The functional consequences and clinical impacts of genomic variation may involve unique, disorder-specific, genomic DNA methylation episignatures. In this study, we describe 19 novel episignature disorders and compare the findings alongside 38 previously established episignatures for a total of 57 episignatures associated with 65 genetic syndromes. We demonstrate increasing resolution and specificity ranging from protein complex, gene, sub-gene, protein domain, and even single nucleotide-level Mendelian episignatures. We show the power of multiclass modeling to develop highly accurate and disease-specific diagnostic classifiers. This study significantly expands the number and spectrum of disorders with detectable DNA methylation episignatures, improves the clinical diagnostic capabilities through the resolution of unsolved cases and the reclassification of variants of unknown clinical significance, and provides further insight into the molecular etiology of Mendelian conditions.

Data availabilitySummary statistics generated by COVID-19 Host Genetics Initiative are available online (https://www.covid19hg.org/results/r6/). The analyses described here use the freeze 6 data. The COVID-19 Host Genetics Initiative continues to regularly release new data freezes. Summary statistics for samples from individuals of non-European ancestry are not currently available owing to the small individual sample sizes of these groups, but the results for 23 loci lead variants are reported in Supplementary Table 3. Individual-level data can be requested directly from the authors of the contributing studies, listed in Supplementary Table 1.

Double minutes (dmin), homogeneously staining regions, and ring chromosomes are vehicles of gene amplification in cancer. The underlying mechanism leading to their formation as well as their structure and function in acute myeloid leukemia (AML) remain mysterious. We combined a range of high-resolution genomic methods to investigate the architecture and expression pattern of amplicons involving chromosome band 8q24 in 23 cases of AML (AML-amp). This revealed that different MYC-dmin architectures can coexist within the same leukemic cell population, indicating a step-wise evolution rather than a single event origin, such as through chromothripsis. This was supported also by the analysis of the chromothripsis criteria, that poorly matched the model in our samples. Furthermore, we found that dmin could evolve toward ring chromosomes stabilized by neocentromeres. Surprisingly, amplified genes (mainly PVT1) frequently participated in fusion transcripts lacking a corresponding DNA template. We also detected a significant overexpression of the circular RNA of PVT1 (circPVT1) in AML-amp cases versus AML with a normal karyotype. Our results show that 8q24 amplicons in AML are surprisingly plastic DNA structures with an unexpected association to novel fusion transcripts and circular RNAs.

Kabuki syndrome is a rare autosomal dominant condition characterized by facial features, various organs malformations, postnatal growth deficiency and intellectual disability. The discovery of frequent germline mutations in the histone methyltransferase KMT2D and the demethylase KDM6A revealed a causative role for histone modifiers in this disease. However, the role of missense mutations has remained unexplored. Here, we expanded the mutation spectrum of KMT2D and KDM6A in KS by identifying 37 new KMT2D sequence variants. Moreover, we functionally dissected 14 KMT2D missense variants, by investigating their impact on the protein enzymatic activity and the binding to members of the WRAD complex. We demonstrate impaired H3K4 methyltransferase activity in 9 of the 14 mutant alleles and show that this reduced activity is due in part to disruption of protein complex formation. These findings have relevant implications for diagnostic and counseling purposes in this disease.