Biology subjects

Wong, R. C.

Publications and source records attributed to Wong, R. C..

5 recordsLinked to original sources

bioRxiv2025

CNVPipe: An enhanced pipeline for accurate analysis of copy number variation from whole-genome sequencing

Copy number variations (CNVs) are critical contributors to the genetic architecture of complex diseases, yet many existing pipelines for whole-genome sequencing (WGS) data exhibit persistently high false discovery rates (FDR). Here, we introduce CNVPipe, an enhanced workflow that integrates widely used CNV-calling tools with a novel machine-learning framework to achieve lower FDR and higher sensitivity. CNVPipe also provides a specialised module for single-cell CNV analysis, featuring a new model that accurately estimates the ploidy of single cells to get integer copy number profile. Benchmark evaluations demonstrate that CNVPipe outperforms current pipelines in various genomic contexts. In addition to detecting recurrent CNVs in paediatric developmental disorders, CNVPipe enables large-scale functional genomics applications involving stem cell technologies. Moreover, its application to sparse single-cell DNA sequencing data provides a new aspect of research in cancer evolution. Collectively, these findings underscore the versatility and reliability of CNVPipe as a comprehensive solution for CNV detection in WGS-based research.

systems biology↗

bioRxiv2024

Using RNA-targeting CRISPR-Cas13 and engineered U1 systems to reduce ABCA4 splice variants in Stargardt disease

Dysregulation of the alternative splicing process results in aberrant mRNA transcripts, leading to dysfunctional proteins or nonsense-mediated decay that cause a wide range of mis-splicing diseases. Development of therapeutic strategies to target the alternative splicing process could potentially shift the mRNA splicing from disease isoforms to a normal isoform and restore functional protein. As a proof of concept, we focus on Stargardt disease (STGD1), an autosomal recessive inherited retinal disease caused by biallelic genetic variants in the ABCA4 gene. The splicing variants c.5461-10T>C and c.4773+3A>G in ABCA4 cause the skipping of exon 39-40 and exon 33-34 respectively. In this study, we compared the efficacy of different RNA-targeting systems to modulate these ABCA4 splicing defects, including four CRISPR-Cas13 systems (CASFx-1, CASFx-3, RBFOX1N-dCas13e-C and RBFOX1N-dPspCas13b-C) as well as an engineered U1 system (ExSpeU1). Using a minigene system containing ABCA4 variants in the human retinal pigment epithelium ARPE19, our results show that RBFOX1N-dPspCas13b-C is the best performing CRISPR-Cas system, which enabled up to 80% reduction of the mis-spliced ABCA4 c.5461-10T>C variants and up to 78% reduction of the ABCA4 c.4773+3A>G variants. In comparison, delivery of a single ExSpeU1 was able to effectively reduce the mis-spliced ABCA4 c.4773+3A>G variants by up to 84%. We observed that the effectiveness of CRISPR-based and U1 splicing regulation is strongly dependent on the sgRNA/snRNA targeting sequences, highlighting that optimal sgRNA/snRNA designing is crucial for efficient targeting of mis-spliced transcripts. Overall, our study demonstrated the potential of using RNA-targeting CRISPR-Cas technology and engineered U1 to reduce mis-spliced transcripts for ABCA4, providing an important step to advance the development of gene therapy to treat STGD1.

molecular biology↗

bioRxiv2022

Knockout of AMD-associated gene POLDIP2 reduces mitochondrial superoxide in human retinal pigment epithelial cells

Genetic and epidemiologic studies have significantly advanced our understanding of the genetic factors contributing to age-related macular degeneration (AMD). In particular, recent expression quantitative trait loci (eQTL) studies have highlighted POLDIP2 as a significant gene that confers risk of developing AMD. However, the role of POLDIP2 in retinal cells such as retinal pigment epithelium (RPE) and how it contributes to AMD pathology are unknown. Here we report the generation of a stable human RPE cell line with POLDIP2 knockout using CRISPR/Cas, providing an in vitro model to investigate the functions of POLDIP2. We conducted functional studies on the POLDIP2 knockout cell line and showed that they retained normal levels of cell proliferation, cell viability, phagocytosis and autophagy. Also, we performed RNA sequencing to profile the transcriptome of POLDIP2 knockout cells. Our results highlighted significant changes in genes involved in immune response, complement activation, oxidative damage and vascular development. We showed that loss of POLDIP2 causes a reduction in mitochondrial superoxide levels, which is consistent with the upregulation of the mitochondrial superoxide dismutase SOD2. In conclusion, this study demonstrates a novel link between POLDIP2 and SOD2, which supports a potential role of POLDIP2 in regulating oxidative stress in AMD pathology.

neuroscience↗

bioRxiv2020

Comparison of CRISPR/Cas endonucleases for in vivo retinal gene editing.

CRISPR/Cas has opened the prospect of direct gene correction therapy for some inherited retinal diseases. Previous work has demonstrated the utility of adeno-associated virus (AAV) mediated delivery to retinal cells in vivo; however, with the expanding repertoire of CRISPR/Cas endonucleases, it is not clear which of these are most efficacious for retinal editing in vivo. We sought to compare CRISPR/Cas endonuclease activity using both single and dual AAV delivery strategies for gene editing in retinal cells. Plasmids of a dual vector system with SpCas9, SaCas9, Cas12a, CjCas9 and sgRNA targeting YFP and a single vector system with SaCas9/YFP sgRNA were generated and validated in YFP-expressing HEK293A cell by flow cytometry and T7E1 assay. Paired CRISPR/Cas endonuclease and its best performing sgRNA was then packaged into an AAV2 capsid derivative, AAV7m8, and injected intravitreally into CMV-Cre::Rosa26-YFP mice. SpCas9 and Cas12a achieved better knockout efficiency than SaCas9 and CjCas9. Moreover, no significant difference in YFP gene editing was found between single and dual CRISPR/SaCas9 vector systems. With a marked reduction of YFP-positive retinal cells, AAV7m8 delivered SpCas9 was found to have the highest knockout efficacy among all investigated endonucleases. We demonstrate that the AAV7m8-mediated delivery of CRISPR/SpCas9 construct achieves the most efficient gene modification in neurosensory retinal cells in vitro and in vivo.

bioengineering↗

bioRxiv2018

Efficacy and dynamics of self-targeting CRISPR/Cas constructs for gene editing in the retina.

Safe delivery of CRISPR/Cas endonucleases remains one of the major barriers to the widespread application of in vivo genome editing including the anticipatory treatment of monogenic retinal diseases. We previously reported the utility of adeno-associated virus (AAV)-mediated CRISPR/Cas genome editing in the retina; however, with this type of viral delivery system, active endonucleases will remain in the retina for an extended period, making genotoxicity a significant consideration in clinical applications. To address this issue, we have designed a self-destructing \"kamikaze\" CRISPR/Cas system that disrupts the Cas enzyme itself following expression. Four guide RNAs (sgRNAs) were designed to target Streptococcus pyogenes Cas9 (SpCas9), after in situ validation, the selected sgRNAs were cloned into a dual AAV vector. One construct was used to deliver SpCas9 and the other delivered sgRNAs directed against SpCas9 and the target locus (yellow fluorescent protein, YFP), in the presence of mCherry. Both constructs were packaged into AAV2 vector and intravitreally administered in C57BL/6 and Thy1-YFP transgenic mice. After 8 weeks the expression of SpCas9, the efficacy of YFP gene disruption was quantified. A reduction of SpCas9 mRNA was found in retinas treated with AAV2-mediated-YFP/SpCas9 targeting CRISPR/Cas compared to those treated with YFP targeting CRISPR/Cas alone. We also show that AAV2-mediated delivery of YFP/SpCas9 targeting CRISPR/Cas significantly reduced the number of YFP fluorescent cells among mCherry-expressing cells (~85.5% reduction compared to LacZ/SpCas9 targeting CRISPR/Cas) in transfected retina of Thy1-YFP transgenic mice. In conclusion, our data suggest that a self-destructive \"kamikaze\" CRISPR/Cas system can be used as a robust tool for refined genome editing in the retina, without compromising on-target efficiency.

genetics↗