Diagnosing Cornelia de Lange syndrome and related neurodevelopmental disorders using RNA-sequencing

Abstract

ABSTRACTPurposeNeurodevelopmental phenotypes represent major indications for children undergoing clinical exome sequencing. However, 50% of cases remain undiagnosed even upon exome reanalysis. Here we show RNA sequencing (RNA-seq) on human B lymphoblastoid cell lines (LCL) is highly suitable for neurodevelopmental Mendelian gene testing and demonstrate the utility of this approach in suspected cases of Cornelia de Lange syndrome (CdLS).MethodsGenotype-Tissue Expression project transcriptome data for LCL, blood, and brain was assessed for neurodevelopmental Mendelian gene expression. Detection of abnormal splicing and pathogenic variants in these genes was performed with a novel RNA-seq diagnostic pipeline and using a validation CdLS-LCL cohort (n=10) and test cohort of patients who carry a clinical diagnosis of CdLS but negative genetic testing (n=5).ResultsLCLs share isoform diversity of brain tissue for a large subset of neurodevelopmental genes and express 1.8-fold more of these genes compared to blood (LCL, n=1706; whole blood, n=917). This enables testing of over 1000 genetic syndromes. The RNA-seq pipeline had 90% sensitivity for detecting pathogenic events and revealed novel diagnoses such as abnormal splice products in NIPBL and pathogenic coding variants in BRD4 and ANKRD11.ConclusionThe LCL transcriptome enables robust frontline and/or reflexive diagnostic testing for neurodevelopmental disorders.