Primary ciliary dyskinesia (PCD) is a primarily autosomal recessive disease. Despite genetic testing contributing to the disease confirmation, in 30% of the cases a complete genetic diagnosis remains unsolved due to variants of unknown significance or failure of identifying biallelic pathogenic variants.

This work aims to improve PCD diagnostics through transcriptome analysis focusing on deleterious RNA splicing events. RNA splicing is a mechanism whereby the non-coding introns, located in between protein-coding exons, are removed and the coding exons ligated together, resulting in a mature mRNA molecule.

Nasal epithelial cells obtained from 27 PCD patients were obtained for transcriptome analysis to either assess the impact of a previously identified genetic variant, or to assess whether the missing second pathogenic variant could be identified. Cells were grown at an air-liquid-interface for 21 days followed with RNA isolation. Bulk RNA-seq of the total RNA was performed followed with an in-house bioinformatic data analysis pipeline.

For 22% of the patients recruited more diagnostic insights were obtained through identifying deleterious RNA splicing with or without gene downregulation. These deleterious aberrant splicing events included exon skipping, mutually exclusive exon usage, novel splice site usage, and pseudoexon inclusion. The findings of the pseudoexon inclusion will be shown in detail illustrating the results which could be obtained only through transcriptome analysis.

Through applying transcriptome analysis additional diagnostic information was obtained by identifying disease causing variants and the underlying disease mechanism.