Combinatorial clinically driven blood biomarker functional genomics significantly enhances genotype-phenotype resolution and diagnostics in neuromuscular disease

Abstract

Purpose50-60% of neuromuscular-disease patients remain undiagnosed even after extensive genetic testing that hinders precision-medicine/clinical-trial-enrollment. Importantly, those with DNA-based molecular diagnosis often remain without known molecular mechanism driving different degrees of disease severity that hinders patient stratification and trial-readiness. These are due to: a) clinical-genetic-heterogeneity (eg: limb-girdle-muscular-dystrophies(LGMDs)>30-subtypes); b) high-prevalence of variants-of-uncertain-significance (VUSs); (c) unresolved genotype-phenotype-correlations for patient stratification, and (d) lack of minimally-invasive biomarker-driven-assays. We therefore implemented a combinatorial phenotype-driven blood-biomarker functional-genomics approach to enhance diagnostics and trial-readiness by elucidating disease mechanisms of a neuromuscular-disease patient-cohort clinically-suspected of Dysferlinopathy/related-LGMD, the second-most-prevalent LGMD in the US.MethodsWe used CD14+monocyte protein-expression-assay on 364 Dysferlinopathy/related-LGMD-suspected patient-cohort without complete molecular-diagnosis or genotype-phenotype correlation; and then combined with blood-based targeted-transcriptome-sequencing (RNA-Seq) with tiered-analytical-algorithm correlating with clinical-measurements for a subset of patients.ResultsOur combinatorial-approach significantly increased the diagnostic-yield from 25% (N=326; 18%-27%; 95%CI) to 82% (N=38; 69.08% to 84.92%; 95% CI) by combining monocyte-assay with enhanced-RNA-Seq-analysis and clinical-correlation, following ACMG-AMP-guidelines. The tiered-analytical-approach detected aberrant-splicing, allele-expression-imbalance, nonsense-mediated-decay, and compound-heterozygosity without parental/offspring-DNA-testing, leading to VUS-reclassifications, identification of variant-pathomechanisms, and enhanced genotype-phenotype resolution including those with carrier-range Dysferlin-protein-expression and milder-symptoms, allowing patient-stratification for better trial-readiness. We identified uniform-distribution of pathogenic-variants across DYSF-gene-domains without any hotspot suggesting the relevance of upcoming gene-(full-DYSF-cDNA)-therapy trials.ConclusionOur results show the relevance of using a clinically-driven multi-tiered-approach utilizing a minimally-invasive biomarker-functional-genomic platform for precision-medicine-diagnostics, trial-recruitment/monitoring, elucidating pathogenic-mechanisms for patient stratification to enhance better trial outcomes, which in turn, will guide more rational use of current-therapeutics and development of novel-interventions for neuromuscular-disorders, and applicable to other genetic-disorders.

Targeted RNAseq Improves Clinical Diagnosis of Very Early-Onset Pediatric Immune Dysregulation

“…In large cohorts, transcript abundance can also be used to analyze downstream effects of some pathogenic variants and characterize pathways involved in disease [ 48 , 49 ]. Even where a likely pathogenic variant is identified by DNA analysis, RNAseq can provide supporting evidence that the transcript is affected, and may be used to establish that both alleles are affected in trans by different mutations [ 50 , 51 ]. Although peripheral blood is a mixture of dozens of cell types, so long as the defect is observed in one or more of the major leukocyte or monocyte populations, bulk RNAseq should be a useful source of clinically actionable information.…”