Biology subjects

Sung, W.-K.

Publications and source records attributed to Sung, W.-K..

5 recordsLinked to original sources

bioRxiv2023

SurVIndel2: improving local CNVs calling from next-generation sequencing using novel hidden information

Deletions and tandem duplications (commonly called CNVs) represent the majority of structural variations. They can be identified using short reads, but because they frequently occur in repetitive regions, existing methods fail to detect most of them. This is because CNVs in repetitive regions often do not produce the evidence needed by existing short reads-based callers (split reads, discordant pairs or read depth change). Here, we introduce a new CNV short reads-based caller named SurVIndel2. SurVindel2 builds on statistical techniques we previously developed, but also employs a novel type of evidence, hidden split reads, that can uncover many CNVs missed by existing algorithms. We use public benchmarks to show that SurVIndel2 outperforms other popular callers, both on human and non-human datasets. Then, we demonstrate the practical utility of the method by generating a catalogue of CNVs for the 1000g project that contains hundreds of thousands of CNVs missing from the most recent public catalogue. We also show that SurVIndel2 is able to complement small indels predicted by Google DeepVariant, and the two software used in tandem produce a remarkably complete catalogue of variants in an individual. Finally, we characterise how the limitations of current sequencing technologies contribute significantly to the missing CNVs.

bioinformatics↗

bioRxiv2022

An AI-assisted Tool For Efficient Prostate Cancer Diagnosis

Pathologists diagnose prostate cancer by core needle biopsy. For low-grade and low-volume cases, the pathologists look for the few malignant glands out of hundreds within a core. They may miss the few malignant glands, resulting in repeat biopsies or missed therapeutic opportunities. This study developed a multi-resolution deep learning pipeline detecting malignant glands in core needle biopsies to help pathologists effectively and accurately diagnose prostate cancer in low-grade and low-volume cases. The pipeline consisted of two stages: the gland segmentation model detected the glands within the sections and the multi-resolution model classified each detected gland into benign vs. malignant. Analyzing a gland at multiple resolutions provided the classification model to exploit both morphology information (of nuclei and glands) and neighborhood information (for architectural patterns), important in prostate gland classification. We developed and tested our pipeline on the slides of a local cohort of 99 patients in Singapore. The images were made publicly available, becoming the first digital histopathology dataset of prostatic carcinoma patients of Asian ancestry. Our pipeline successfully classified the core needle biopsy parts (81 parts: 50 benign and 31 malignant) into benign vs. malignant. It achieved an AUROC value of 0.997 (95% CI: 0.987 - 1.000). Moreover, it produced heatmaps highlighting the malignancy of each gland in core needle biopsies. Hence, our pipeline can effectively assist pathologists in core needle biopsy analysis.

cancer biology↗

bioRxiv2021

Obtaining Spatially Resolved Tumor Purity Maps Using Deep Multiple Instance Learning In A Pan-cancer Study

Tumor purity is the proportion of cancer cells in the tumor tissue. An accurate tumor purity estimation is crucial for accurate pathologic evaluation and for sample selection to minimize normal cell contamination in high throughput genomic analysis. We developed a novel deep multiple instance learning model predicting tumor purity from H&E stained digital histopathology slides. Our model successfully predicted tumor purity from slides of fresh-frozen sections in eight different TCGA cohorts and formalin-fixed paraffin-embedded sections in a local Singapore cohort. The predictions were highly consistent with genomic tumor purity values, which were inferred from genomic data and accepted as the golden standard. Besides, we obtained spatially resolved tumor purity maps and showed that tumor purity varies spatially within a sample. Our analyses on tumor purity maps also suggested that pathologists might have chosen high tumor content regions inside the slides during tumor purity estimation in the TCGA cohorts, which resulted in higher values than genomic tumor purity values. In short, our model can be utilized for high throughput sample selection for genomic analysis, which will help reduce pathologists workload and decrease inter-observer variability. Moreover, spatial tumor purity maps can help better understand the tumor microenvironment as a key determinant in tumor formation and therapeutic response.

cancer biology↗

bioRxiv2021

Tumour Suppressor Parafibromin/Hyrax Governs Cell Polarity and Centrosome Assembly in Neural Stem Cells

Neural stem cells (NSCs) divide asymmetrically to balance their self-renewal and differentiation, an imbalance in which can lead to NSC overgrowth and tumour formation. The functions of Parafibromin, a conserved tumour suppressor, in the nervous system are not established. Here, we demonstrate that Drosophila Parafibromin/Hyrax (Hyx) inhibits NSC overgrowth by governing cell polarity. Hyx is essential for the apicobasal polarization of NSCs, through its role in the asymmetric distribution of polarity proteins. hyx depletion results in the symmetric division of NSCs, leading to the formation of supernumerary NSCs in the larval brain. Importantly, we show that human Parafibromin can fully rescue NSC overgrowth and cell polarity defects in Drosophila hyx mutant brains. We have also discovered a novel role for Hyx in regulating the formation of interphase microtubule-organizing center and mitotic spindles in NSCs. Moreover, Hyx is required for the proper localization of a key centrosomal protein, Polo, and the microtubule-binding proteins Msps and D-TACC in dividing NSCs. Furthermore, Hyx directly regulates the polo expression in vitro. Altogether, our study provides the first evidence that the brain tumour suppressor-like role and polarity establishing functions of Hyx are mediated by its role in regulating microtubule growth and centrosomal assembly. The new paradigm that Parafibromin orchestrates cell polarization by regulating centrosomal assembly may be relevant to future studies on Parafibromin/HRPT2-associated cancers.

developmental biology↗

bioRxiv2019

HyPo: Super Fast & Accurate Polisher for Long Read Genome Assemblies

Efforts towards making population-scale long read genome assemblies (especially human genomes) viable have intensified recently with the emergence of many fast assemblers. The reliance of these fast assemblers on polishing for the accuracy of assemblies makes it crucial. We present HyPo-a Hybrid Polisher-that utilises short as well as long reads within a single run to polish a long read assembly of small and large genomes. It exploits unique genomic kmers to selectively polish segments of contigs using partial order alignment of selective read-segments. As demonstrated on human genome assemblies, Hypo generates significantly more accurate polished assemblies in about one-third time with about half the memory requirements in comparison to Racon (the widely used polisher currently).

bioinformatics↗