Utility of Targeted RNA Analysis in Neurogenetic Disorders
Shoji Ichikawa1, Katie Yergert1, Brooklynn Gasser1
1From Ambry Genetics, Aliso Viejo, California.
Neurology. Genetics
|March 5, 2026
Summary
RNA analysis of whole blood effectively reclassified most variants of unknown significance (VUS) in neurologic genetic testing. This improves diagnostic accuracy for neurogenetic disorders by clarifying variant pathogenicity.
Area of Science:
- Genetics
- Molecular Biology
- Neuroscience
Background:
- Clinical genetic testing is crucial for diagnosing neurologic disorders but is limited by variants of unknown significance (VUS).
- Accurate classification of spliceogenic variants necessitates demonstrating splicing impact, often challenging due to limited access to disease-relevant tissues for RNA studies.
- Whole-blood RNA analysis offers a potential solution for assessing variants in neurogenetic conditions.
Purpose of the Study:
- To evaluate the effectiveness of whole-blood RNA studies in reclassifying potentially spliceogenic variants identified in clinical genetic testing for neurologic disorders.
- To determine if whole-blood RNA analysis can improve the diagnostic yield of genetic testing for neurogenetic conditions.
Main Methods:
- Identified 38 potentially spliceogenic variants (intronic and exonic) in patients with neurologic phenotypes undergoing genetic testing.
- Performed targeted RT-PCR sequencing on RNA isolated from whole blood of patients and controls.
- Assessed variant reclassification using ACMG/AMP standards and reviewed whole-blood gene expression data from the Genotype Tissue Expression (GTEx) Portal.
Main Results:
- RNA analysis reclassified 79% (30/38) of variants, with 18 VUS upgraded to pathogenic/likely pathogenic and 11 downgraded to likely benign.
- Whole blood demonstrated sufficient expression for targeted RNA analysis in 77% (164/212) of commonly tested neurodevelopmental genes.
- Diagnostic reclassifications provided genetic answers for patients, while downgrades resolved VUS, enhancing diagnostic clarity.
Conclusions:
- Targeted RNA analysis using whole blood provides molecular evidence to reclassify the majority of variants of unknown significance.
- This approach significantly improves the accuracy of genetic diagnoses for neurologic disorders.
- Whole-blood RNA studies are a valuable tool for clarifying variant pathogenicity in clinical neurogenetic testing.
