Biology subjects

de Bruijn, S. E.

Publications and source records attributed to de Bruijn, S. E..

6 recordsLinked to original sources

bioRxiv2026

Deep-intronic variants in USH2A: the importance of model selection in variant interpretation and pathogenicity assessment

Interpreting splice-altering USH2A variants is challenging when these result in the alteration of splicing in only a fraction of transcripts. We investigated two deep-intronic USH2A variants from a single case, the inherited variant c.5573-834A>G and the de novo variant c.11047+345A>G, using a minigene splice assay and transcript analysis in patient-derived photoreceptor precursor cells and nasal epithelial cells. The minigene assay revealed the inclusion of a pseudoexon in the presence of the c.11047+345A>G variant, but did not reproduce previously reported aberrant splicing for c.5573-834A>G. In patient-derived cells, c.5573-834A>G resulted in the inclusion of a pseudoexon in part of the transcripts, whereas c.11047+345A>G did not result in detectable levels of aberrantly spliced transcripts. To assess the impact of residual wildtype transcripts on retinal function, we used the previously developed humanized ush2aPE40+M1 knock-in zebrafish model which allows the modeling of the impact of mixed wildtype and pseudoexon-containing ush2a transcripts. This model demonstrated that detectable levels of usherin expression are maintained even when only a fraction of wildtype transcripts lacking pseudoexon inclusion remain. Collectively, these findings advocate for a more nuanced classification of partially splice-altering USH2A variants. The mere presence of alternative transcripts should not be considered sufficient evidence for pathogenicity. Within this framework, data on the c.5573-834A>G variant do not support a (likely) pathogenic classification, and findings related to the c.11047+345A>G variant are consistent with a likely benign classification.

genetics↗

bioRxiv2026

Genome sequencing reveals novel pathogenic deep-intronic PCDH15 variants, amenable to antisense oligonucleotide-based splice correction

Despite substantial advances in diagnostic testing, 10-15% of Usher syndrome patients remain without a genetic diagnosis, having significant implications for genetic counseling and potential future therapeutic interventions. In this study, genome sequencing data from probands clinically presenting with Usher syndrome were analyzed. Two novel deep-intronic variants were identified in PCDH15, c.3983+3635A>G and c.3123-1728A>G, in two independent patients. Both deep-intronic variants were classified as likely pathogenic and predicted to alter PCDH15 pre-mRNA splicing. Using a minigene splice assay and iPSC-derived photoreceptor precursor cells from patients, we confirmed that both variants lead to the inclusion of a pseudoexon in the PCDH15 transcript introducing a stop codon and subsequent premature termination of protein translation. We designed and evaluated antisense oligonucleotides (ASOs) with the purpose of redirecting aberrant pre-mRNA splicing caused by both deep-intronic variants. For both variants, designed ASOs were successful in restoring normal splicing patterns, highlighting their potential as a future therapeutic intervention strategy to halt the progression of retinitis pigmentosa caused by these novel variants. Overall, these findings contribute to the understanding of Usher syndrome caused by deep-intronic pathogenic variants in PCDH15 and describe for the first time the use of an ASO-mediated splice correction strategy for individuals diagnosed with these variants.

genetics↗

bioRxiv2025

Deep learning-based prediction of tissue-specific splice sites in the human neural retina

Splice prediction tools can be used to identify splice-altering variants in patients with inherited diseases. Since splicing is tissue-specific, a predicted splice defect may vary depending on the tissue of interest. Current splice prediction tools often neglect splice junctions from the human neural retina, which can lead to the misinterpretation of benign and pathogenic variants in patients with inherited retinal diseases (IRDs). To address this issue, we developed a retina-specific splice prediction tool based on the model architecture of SpliceAI. In addition to retraining the existing model using splice junctions derived from retina RNA-sequencing data, we also improved the models generalization through hyperparameter optimizations such as dropout. The resulting retina-specific model was validated on retina-enriched exons and variants known to cause retina-specific splicing defects. Although the retina model correctly identified five more retina-enriched splice sites than the GTEx model, it did not enhance predictions for variants with tissue-specific splicing defects nor did it identify novel pathogenic variants in a set of genetically unexplained IRD cases. Despite these limitations, the retina-specific SpliceAI model shows promising results and should be applied to a larger patient cohort to uncover novel splice-altering variants in IRD patients.

bioinformatics↗

bioRxiv2024

Pushing the limits of single molecule transcript sequencing to uncover the largest disease-associated transcript isoforms in the human neural retina

Sequencing technologies have long limited the comprehensive investigation of large transcripts associated with inherited retinal diseases (IRDs) like Usher syndrome, which involves 11 associated genes with transcripts up to 19.6 kb. To address this, we used PacBio long-read mRNA isoform sequencing (Iso-Seq) following standard library preparation and an optimized workflow to enrich for long transcripts in the human neural retina. While our workflow achieved sequencing of transcripts up to 15 kb, this was insufficient for Usher syndrome-associated genes USH2A and ADGRV1, with transcripts of 18.9 kb and 19.6 kb, respectively. To overcome this, we employed the Samplix Xdrop System for indirect target enrichment of cDNA, a technique typically used for genomic DNA capture. This method facilitated the successful capture and sequencing of ADGRV1 transcripts as well as the full-length 18.9 kb USH2A transcripts. By combining algorithmic analysis with detailed manual curation of sequenced reads, we identified novel isoforms and alternative splicing events across the 11 Usher syndrome-associated genes, with implications for diagnostics and therapy development. Our findings demonstrate the Xdrop systems adaptability for cDNA capture and the advantages of integrating computational and manual transcript analyses. The full neural retina sequencing dataset is available via EGA under identifier EGAD50000000720.

genetics↗

bioRxiv2024

A proteogenomic atlas of the human neural retina

The human neural retina is a complex tissue with abundant alternative splicing and more than 10% of genetic variants linked to inherited retinal diseases (IRDs) alter splicing. Traditional short-read RNA-sequencing methods have been used for understanding retina-specific splicing but have limitations in detailing transcript isoforms. To address this, we generated a proteogenomic atlas that combines PacBio long-read RNA-sequencing data with mass spectrometry and whole genome sequencing data of three healthy human neural retina samples. We identified nearly 60,000 transcript isoforms, of which approximately one-third are novel. Additionally, ten novel peptides confirmed novel transcript isoforms. For instance, we identified a novel IMPDH1 isoform with a novel combination of known exons that is supported by peptide evidence. Our research underscores the potential of in-depth tissue-specific transcriptomic analysis to enhance our grasp of tissue-specific alternative splicing. The data underlying the proteogenomic atlas are available via EGA with identifier EGAD50000000101, via ProteomeXchange with identifier PXD045187, and accessible through the UCSC genome browser. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=149 SRC="FIGDIR/small/595273v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1e0810org.highwire.dtl.DTLVardef@1a382b6org.highwire.dtl.DTLVardef@1da7d9eorg.highwire.dtl.DTLVardef@16d29a3_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2019

A RIPOR2 in-frame deletion is a frequent and highly penetrant cause of adult-onset hearing loss

Hearing loss is one of the most prevalent disabilities worldwide, and has a significant impact on quality of life. The adult-onset type of the condition is highly heritable but the genetic causes are largely unknown, which is in contrast to childhood-onset hearing loss. We identified an in-frame deletion of 12 nucleotides in RIPOR2 as a highly penetrant cause of adult-onset progressive hearing loss that segregated as an autosomal dominant trait in 12 families from the Netherlands. Hearing loss associated with the deletion in 63 subjects displayed variable audiometric characteristics and an average age of onset of 30.6 years (SD 14.9 years, range 0-70 years). A functional effect of the RIPOR2 variant was demonstrated by aberrant localization of the mutant RIPOR2 in the stereocilia of cochlear hair cells and failure to rescue morphological defects in RIPOR2-deficient hair cells, in contrast to the wildtype protein. Strikingly, the RIPOR2 variant is present in 18 of 22,952 individuals not selected for hearing loss in the Southeast Netherlands. Collectively, these data demonstrate that an inherited form of adult-onset hearing loss is relatively common, with potentially thousands of individuals at risk in the Netherlands and beyond, which makes it an attractive target for developing a (genetic) therapy.

genetics↗