Prioritizing disease-associated missense variants with chemoproteomic-detected amino acids

Missense variants are the most common type of protein-altering genetic variation. Due to their wide-ranging potential functional consequences, missense variants are challenging to interpret and, as a result, are often classified as unknown pathogenicity or as variants of uncertain significance (VUSs). Genomic-based predictive tools have made significant inroads into the challenge of accurately pinpointing functional missense variants by providing genome-wide assessments of deleteriousness or potential pathogenicity. Complementary to these tools, here we provide an initial study into the utility of harnessing protein-based measures of amino acid reactivity to delineate functionally significant missense variants. These reactivity measurements, which are generated using mass spectrometry-based chemoproteomic methods, have already proved capable of pinpointing functional sites on proteins, which provide the added value of delineating potential sites suitable for drug-development efforts. Here, using published chemoproteomic datasets for three specific privileged amino acids, cysteine, lysine, and tyrosine, we assessed the utility of proteomic reactivity measurements to identify clinically important variants and regions within monogenic-disease-associated genes. We found that genes where amino acids are detected via chemoproteomics are enriched for monogenic-disease phenotypes, indicative of functional importance. Chemoproteomic-detected amino acids (CpDAAs) are enriched at and around sites with known pathogenic missense variants when assessed with either one- or three-dimensional protein structures. To further illustrate the utility of our findings, we found that regions at or around CpDAAs in fumarate hydratase (FH) were enriched for VUSs and pathogenic variants, which we validate through demonstration of an altered FH oligomerization state. Collectively, our study highlights the potential of chemoproteomic and genetic data integration for enhancing the identification of functional genetic variants and protein sites with potential value for drug-development efforts.