Background: 50-70% of inherited neuromuscular disease (NMD) patients remain undiagnosed even after DNA testing, a barrier for clinical trial enrolment. The major hurdles are: a) lack of genotype-phenotype correlation b) high prevalence (72%) of variants of uncertain significance (VUSs), c) >30% of all patients had pathogenic variant(s) or VUSs in ≥2 genes (multi-genic), and d) the lack of less-invasive biomarker-driven approaches.
Objectives: Our objective was to functionally resolve VUSs and multi-genic cases, by combining clinical and genetic data with different functional assays using minimally-invasive biomarker approach or target muscle biopsies, to enhance diagnostic yields and for better trial-readiness of patients by resolving genotype-phenotype correlations.
Results: We show in a cohort study of 394 Dysferlinopathy-suspected genetically unconfirmed NMD patients, a significant increase in diagnostic yield from 35% to 85% by using a combinatorial blood biomarker-driven CD14+ monocyte assay and whole blood targeted RNA-seq along with clinical correlation. Importantly, this further facilitated patient stratification, and mapping DYSF variant landscape. Moreover, in clinically-suspected Pompe cases (considered a monogenic disorder), we identified a high prevalence (72 cases) of one pathogenic variant or VUS each in GAA and another LGMD recessive gene, which are being functionally resolved using blood or muscle-based enzyme assays, immunoblotting, and RNA-Seq.
Conclusions: Using clinically driven-functional omics, we are resolving VUSs, and the nature of the defect in different pathways that lead to multi-genic contribution in NMDs, pointing towards their clinical utility. Our results show the importance of using a multi-tiered diagnostic approach that includes biomarkers, omics platforms and genotype-phenotype correlations not only for precision medicine diagnostics but also for testing clinical trial efficacy.