Biology subjects

Lee, H. K.

Publications and source records attributed to Lee, H. K..

52 records · Page 3Linked to original sources

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

Interferon-regulated genetic programs and JAK/STAT pathway activate the intronic promoter of the short ACE2 isoform in renal proximal tubules

Recently, a short, interferon-inducible isoform of Angiotensin-Converting Enzyme 2 (ACE2), dACE2 was identified. ACE2 is a SARS-Cov-2 receptor and changes in its renal expression have been linked to several human nephropathies. These changes were never analyzed in context of dACE2, as its expression was not investigated in the kidney. We used Human Primary Proximal Tubule (HPPT) cells to show genome-wide gene expression patterns after cytokine stimulation, with emphasis on the ACE2/dACE2 locus. Putative regulatory elements controlling dACE2 expression were identified using ChIP-seq and RNA-seq. qRT-PCR differentiating between ACE2 and dACE2 revealed 300- and 600-fold upregulation of dACE2 by IFN and IFN{beta}, respectively, while full length ACE2 expression was almost unchanged. JAK inhibitor ruxolitinib ablated STAT1 and dACE2 expression after interferon treatment. Finally, with RNA-seq, we identified a set of genes, largely immune-related, induced by cytokine treatment. These gene expression profiles provide new insights into cytokine response of proximal tubule cells.

genomics↗

bioRxiv2020

A neuroprotective locus modulates ischemic stroke infarction independent of collateral vessel anatomy

Ischemic stroke is caused by a disruption of the blood supply to the brain leading to neuronal cell death. Genetic studies of ischemic stroke have identified numerous gene variants that increase the risk to develop stroke. In stark contrast, genetic studies of stroke outcomes, such as the infarct territory size, are confounded by many uncontrollable variables, leading to a paucity of gene targets for treatment of an incipient stroke. Using genetically diverse inbred strains of mice and a surgically-induced model of ischemic stroke, we used quantitative trait locus mapping to identify novel gene targets modulating infarct size, which varies greatly across inbred strains. Although infarct size is largely determined by the extent of collateral vessel connection between arteries in the brain that enables reperfusion of the ischemic territory, we have identified strain pairs that do not vary in this phenotype, but which nonetheless exhibit large differences in infarct size. In this study we performed QTL mapping in mice from an intercross between two such strains, WSB/EiJ and C57BL/6J. We identified a strong locus on chromosome 8 that overlaps with a locus of similar direction and effect previously mapped in an intercross between C3H/HeJ and C57BL/6J strains. To identify causative genes within the overlapping genetic interval, we surveyed nonsynonymous coding SNPs and performed RNA sequencing data analysis for all three mapping strains. We identified Macrophage Scavenger Receptor 1 (Msr1) as a strong candidate gene that harbors multiple coding SNPs predicted to be damaging. Using Msr1-deficient mice, we demonstrated that cerebral infarct volume after stroke induction is dramatically increased in a strain background where reperfusion effects due to collateral vessels is blunted. Significantly, the identification of neuroprotective genes such as Msr1 provides new genes for future mechanistic studies of infarction following ischemic stroke and provides novel gene/protein targets for therapeutic development. Author summaryThe most common form of stroke arises when a blockage occurs in a blood vessel of the brain, thereby preventing delivery of oxygen and nutrients to areas supplied by the affected vessel, leading to tissue death. The main treatment for this form of stroke is medication to dissolve the blockage; however, more treatment options are required to better reduce the death and disability associated with stroke. In this study, we sought to identify genes that can decrease the amount of damage to brain tissue following a stroke, with a specific focus on examining genes that work to directly protect the neurons, rather than returning blood flow to the affected area. Since it is impossible to precisely control the nature of stroke and the genetic variability in humans, we used mice identify a genetic region that is associated with the amount of tissue damage following stroke. Within this genetic region, we identified a list of candidate genes, including the gene Msr1, which we found is important for controlling tissue damage in one genetic population of mice after stroke. The genes identified here require further follow-up to determine the impact on stroke outcomes and the usefulness of these candidates as therapeutic targets.

genetics↗

bioRxiv2020

Single cell transcriptomic re-analysis of immune cells in bronchoalveolar lavage fluids reveals the correlation of B cell characteristics and disease severity of patients with SARS-CoV-2 infection

The COVID-19 pandemic (SARS-CoV-2) is a global infectious disease with rapid spread. Some patients have severe symptoms and clinical signs caused by an excessive inflammatory response, which increases the risk of mortality. In this study, we reanalyzed scRNA-seq data of cells from bronchoalveolar lavage fluids of patients with COVID-19 with mild and severe symptoms, focusing on antibody-producing cells. In patients with severe disease, B cells seemed to be more activated and expressed more immunoglobulin genes compared with cells from patients with mild disease, and macrophages expressed higher levels of the TNF superfamily member B-cell activating factor but not of APRIL (a proliferation-inducing ligand). In addition, macrophages from patients with severe disease had increased pro-inflammatory features and pathways associated with Fc receptor-mediated signaling, compared with patients with mild disease. CCR2-positive plasma cells accumulated in patients with severe disease, probably because of increased CCL2 expression on macrophages from patients with severe disease. Together, these results support that different characteristics of B cells might affect the severity of COVID-19 infection.

immunology↗

bioRxiv2020

Single cell RNA-seq reveals immunosuppressive gastric stem-like cancer cells as a poor prognostic factor

ObjectiveGastric cancer (GC) tumors are highly heterogenous with different subpopulations of epithelial cells. We employed single cell RNA sequencing (scRNA-seq) to dissect the heterogeneity and identified subpopulations of cancer cells with stem-like properties. We further investigated their resistance to oxaliplatin chemotherapy and their contribution to gastric cancer outcome. DesignWe performed scRNA-seq on FACS sorted epithelial and immune cells from paired samples of GC tumors and normal adjacent tissues. We identified two epithelial subpopulations (STMN1+IQGAP3+ and STMN1+IQGAP3-) with stem-like properties. We characterized and compared them to known healthy gastric stem cell populations. We also cultivated GC derived organoids to study the chemoresistance of similarly marked populations. Lastly, we employed immunohistochemistry (IHC) staining to ascertain the predicted immunosuppressive interactions. ResultsThe STMN1+IQGAP3+ subpopulation showed a higher tumor mutation burden, upregulated proliferative pathways and transcriptomically resembled proliferative healthy gastric isthmus stem cells. The STMN1+IQGAP3- subpopulation were comparatively quiescent and transcriptomically resembled enteroendocrine cells. Both transcriptomic signatures were associated with worse mortality than other epithelial subpopulations with the quiescent being associated with the poorest patient survival. GC tissue derived organoids were dominated by STMN1+IQGAP3+ cells but the STMN1+IQGAP3- compartment was more resistant to chemotherapy. We also verified the likely suppression of CD8 T cell cytotoxicity by STMN1+IQGAP3+ cells through the NECTIN2/TIGIT interaction. ConclusionsCancer cells with stem-like characteristics are associated with poor survival through chemoresistance and immunosuppression. Reactivating the immune system through checkpoint blockade is an opportunity to eliminate these cells. What is already known on this topicMultiple gastric stem cell populations have been identified and linked to tumor initiation in rodent-based studies. However, none of them have been conclusively proven in human tumors. Isolating and characterizing tumor cells with stem-like properties will help shed light on their possible origin and possible mitigation strategies. What this study addsHere we identified two sets of stem-like gastric cancer cells that are associated with poorer patient prognosis. One set is highly proliferative and exhibits oxaliplatin susceptibility. It also engages in immunosuppressive interactions such as NECTIN2/TIGIT. The other set is quiescent and highly resistant to oxaliplatin. How this study might affect research, practice or policyThe transcriptome signatures of the identified stem-like cells can aid in patient prognosis and identify patients who can benefit from checkpoint blockade therapy to reactivate their immune response towards gastric cancer cells.

immunology↗

bioRxiv2020

Activation of ACE2 and interferon-stimulated transcriptomes in human airway epithelium is curbed by Janus Kinase inhibitors

The angiotensin-converting enzyme 2 (ACE2) receptor is the gateway for SARS-CoV-2 to airway epithelium1,2 and the strong inflammatory response after viral infection is a hallmark in COVID-19 patients. Deciphering the regulation of the ACE2 gene is paramount for understanding the cell tropism of SARS-CoV-2 infection. Here we identify candidate regulatory elements in the ACE2 locus in human primary airway cells and lung tissue. Activating histone and promoter marks and Pol II loading characterize the intronic dACE2 and define novel candidate enhancers distal to the genuine ACE2 promoter and within additional introns. dACE2, and to a lesser extent ACE2, RNA levels increased in primary bronchial cells treated with interferons and this induction was mitigated by Janus kinase (JAK) inhibitors that are used therapeutically in COVID-19 patients. Our analyses provide insight into regulatory elements governing the ACE2 locus and highlight that JAK inhibitors are suitable tools to suppress interferon-activated genetic programs in bronchial cells.

genomics↗

bioRxiv2020

The transcription factor STAT5 binds to distinct super-enhancer sites and controls Lrrc32 expression in a prominent autoimmune and allergic disease risk locus

Genetic variants associated with diseases are enriched in genomic sequences linked to regulatory regions, such as enhancers, super-enhancers and possibly repressors, that control nearby and distant genes. A known allergic and autoimmune risk locus at chromosome 11q13.51,2 is associated with the LRRC32 gene, which encodes GARP, a protein critical for TGF-{beta} delivery3. This region coincides with a candidate enhancer that was predicted by the presence of activating chromatin marks and contains a polymorphism significantly associated with GARP expression on CD4+CD127-CD25+ Treg cells4. In the mouse, binding of the cytokine-induced transcription factor STAT5 was detected at two sites within the expansive candidate enhancer region and a 2.3 kb deletion resulted in reduced Lrrc32 expression4. However, a clear definition of the enhancer units controlled by STAT5 and a functional understanding of STAT5 in the regulation of Lrrc32 are needed. Here we use high-resolution ChIP-seq and identify three STAT5 binding sites within the Lrrc32 super-enhancer, one shared between Treg cells and mammary epithelium and one specific to each respective cell type. Using mice that express only 10% of normal STAT5 levels we demonstrate the defining contribution of STAT5 in the activation of the Lrrc32 super-enhancer.

genetics↗

bioRxiv2020

Regulatory plasticity within a complex cytokine-sensing mammary enhancer during lactation

Enhancers are transcription factor platforms that synergize with promoters to activate gene expression up to several-thousand-fold. While genome-wide structural studies are used to predict enhancers, the in vivo significance is less clear. Specifically, the biological importance of individual transcription factors within enhancer complexes remains to be understood. Here we investigate the structural and biological importance of individual transcription factor binding sites and redundancy among transcription components within a complex enhancer in vivo. The Csn1s2b gene is expressed exclusively in mammary tissue and activated several thousand-fold during pregnancy and lactation. Using ChIP-seq we identified a complex lactation-specific candidate enhancer that binds multiple transcription factors and coincides with activating histone marks. Using experimental mouse genetics, we determined that deletion of canonical binding motifs for the transcription factors NFIB and STAT5, individually and combined, had a limited biological impact. Loss of these sites led to a shift of transcription factor binding to juxtaposed sites, suggesting exceptional plasticity that does not require direct protein-DNA interactions. Additional deletions revealed the critical importance of a non-canonical STAT5 binding site for enhancer activity. Our data also suggest that enhancer RNAs are not required for the activity of this specific enhancer. While ChIP-seq experiments predicted an additional candidate intronic enhancer, its deletion did not adversely affect gene expression, emphasizing the limited biological information provided by structural data. Our study provides comprehensive insight into the anatomy and biology of a composite mammary enhancer that activates its target gene several hundred-fold during lactation.

genomics↗

bioRxiv2020

Activation of the SARS-CoV-2 receptor Ace2 by cytokines through pan JAK-STAT enhancers

ACE2, in concert with the protease TMPRSS2, binds the novel coronavirus SARS-CoV-2 and facilitates its cellular entry. The ACE2 gene is expressed in SARS-CoV-2 target cells, including Type II Pneumocytes (Ziegler, 2020), and is activated by interferons. Viral RNA was also detected in breast milk (Wu et al., 2020), raising the possibility that ACE2 expression is under the control of cytokines through the JAK-STAT pathway. Here we show that Ace2 expression in mammary tissue is induced during pregnancy and lactation, which coincides with the establishment of a candidate enhancer. The prolactin-activated transcription factor STAT5 binds to tandem sites that coincide with activating histone enhancer marks and additional transcription components. The presence of pan JAK-STAT components in mammary alveolar cells and in Type II Pneumocytes combined with the autoregulation of both STAT1 and STAT5 suggests a prominent role of cytokine signaling pathways in cells targeted by SARS-CoV-2.

genomics↗

bioRxiv2020

Two groups of Arabidopsis receptor kinases preferentially regulate the growth of intraspecies pollen tubes in the female reproductive tract

In flowering plants, continuous cell-cell communication between the compatible male pollen grain/growing pollen tube and the female pistil is required for successful sexual reproduction. In Arabidopsis thaliana, the later stages of this dialogue are mediated by several peptide ligands and receptor kinases that guide pollen tubes to the ovules for the release of sperm cells. Despite a detailed understanding of these processes, a key gap remains on the nature of the regulators that function at the earlier stages. Here, we report on two groups of A. thaliana receptor kinases, the LRR-VIII-2 RK subclass and the SERKs, that function in the female reproductive tract to regulate the compatible pollen grains and early pollen tube growth, both essential steps for the downstream processes leading to fertilization. Multiple A. thaliana LRR-VIII-2 RK and SERK knockout mutant combinations were created, and several phenotypes were observed such as reduced wild-type pollen hydration and reduced pollen tube travel distances. As these mutant pistils displayed a wild-type morphology, the observed altered responses of the wild-type pollen are proposed to result from the loss of these receptor kinases leading to an impaired pollen-pistil dialogue at these early stages. Furthermore, using pollen from related Brassicaceae species, we also discovered that these receptor kinases are required in the female reproductive tract to establish a reproductive barrier to interspecies pollen. Thus, we propose that the LRR-VIII-2 RKs and the SERKs play a dual role in the preferential selection and promotion of intraspecies pollen over interspecies pollen.

plant biology↗

bioRxiv2019

Cytosine but not adenine base editor generates mutations in mice

Deaminase base editing has emerged as a tool to install or correct point mutations in the genomes of living cells in a wide range of organisms and its ultimate success therapeutically depends on its accuracy. Here we have investigated the fidelity of cytosine base editor 4 (BE4) and adenine base editor (ABE) in mouse embryos using unbiased whole genome sequencing of a family-based trio cohort. We demonstrate that BE4-edited mice carry an excess of single-nucleotide variants and deletions compared to ABE-edited mice and controls.

genomics↗

bioRxiv2019

Identification of a role for an E6-like 1 gene in early pollen-stigma interactions in Arabidopsis thaliana

In Arabidopsis, successful pollen-stigma interactions are dependent on rapid recognition of compatible pollen by the stigmatic papillae located on the surface of the pistil and the subsequent regulation of pollen hydration and germination, and followed by the growth of pollen tubes through the stigma surface. Here we have described the function of a novel gene, E6-like 1 (E6L1), that was identified through the analysis of transcriptome datasets, as one of highest-expressed genes in the stigma, and furthermore, its expression was largely restricted to the stigma and trichomes. The first E6 gene was initially identified as a highly-expressed gene during cotton fiber development, and related E6-like predicted proteins are found throughout the Angiosperms. To date, no orthologous genes have been assigned a biological function. Both the Arabidopsis E6L1 and cotton E6 proteins are predicted to be secreted, and this was confirmed using an E6L1:RFP fusion construct. To further investigate E6L1s function, one T-DNA and two independent CRISPR-generated mutants were analyzed for compatible pollen-stigma interactions, and pollen hydration, pollen adhesion and seed set were mildly impaired for the e6l1 mutants. This work identifies E6L1 as a novel stigmatic factor that plays a role during the early post-pollination stages in Arabidopsis.\n\nKey MessageWe describe a function for a novel Arabidopsis gene, E6-like 1 (E6L1), that was identified as a highly-expressed gene in the stigma and plays a role in early post-pollination stages.

plant biology↗

bioRxiv2019

Identification of novel neuroprotective loci modulating ischemic stroke volume in a cross between wild-derived inbred mouse strains

To identify genes involved in cerebral infarction we have employed a forward genetic approach in inbred mouse strains, using quantitative trait locus (QTL) mapping for cerebral infarct volume after middle cerebral artery occlusion. We had previously observed that infarct volume is inversely correlated with cerebral collateral vessel density in the strains. In this study, we expanded the pool of allelic variation among classical inbred mouse strains by utilizing the eight founder strains of the Collaborative Cross and found a wild-derived strain, WSB/EiJ, that breaks this general rule that collateral vessel density inversely correlates with infarct volume. WSB/EiJ and another wild-derived strain, CAST/EiJ, show the highest collateral vessel densities of any inbred strain, but infarct volume of WSB/EiJ mice is 8.7-fold larger than that of CAST/EiJ mice. QTL mapping between these strains identified four new neuroprotective loci modulating cerebral infarct volume while not affecting collateral vessel phenotypes. To identify causative variants in genes we surveyed non-synonymous coding SNPs between CAST/EiJ and WSB/EiJ and found 96 genes harboring coding SNPs predicted to be damaging and mapping within one of the four intervals. In addition, we performed RNA sequencing for brain tissue of CAST/EiJ and WSB/EiJ mice and identified 79 candidate genes mapping in one of the four intervals showing strain-specific differences in expression. The identification of the genes underlying these neuroprotective loci will provide new understanding of genetic risk factors of ischemic stroke which may provide novel targets for future therapeutic intervention of human ischemic stroke.

genetics↗

bioRxiv2017

Functional Difference of Mitochondrial Genome and Its Association with Traits of Common Complex Diseases in Humans

Recent evidence suggests that mitochondrial genomes harboring common mitochondrial DNA polymorphisms might have functional difference and could be associated with common complex human diseases such as metabolic syndrome and cancer that are related to mitochondrial dysfunction. However, there has been no report examining the functional difference of mitochondrial genome in the pathogenesis of such diseases at the cellular or molecular level. In order to examine the effect of mitochondrial genome on metabolic syndrome or cancer without interference from nuclear genes, we analyzed trans-mitochondrial cytoplasmic hybrid cells (cybrids) with common Asian mtDNA haplogroups A, B, D, and F from healthy volunteers. The mitochondrial oxygen consumption rates of cybrids were associated with multiple components of metabolic syndrome such as body mass index, waist circumference, serum triglyceride levels and high-density lipoprotein cholesterol levels. In addition, the cybrids showed varying degree of tumorigenicity both in vitro and in vivo. Especially, the cybrids harboring mtDNA haplogroup D had a significantly slower growth rate. These findings suggest that the phenotypes of common complex diseases in humans can be determined by their mitochondrial genomes. Therefore, not only nuclear genome but also mitochondrial genome should be considered in explaining the genetic pathogenesis of common complex human diseases.

genetics↗

bioRxiv2017

Daam2 Driven Degradation Of VHL Promotes Gliomagenesis

Von Hippel-Landau (VHL) protein is a potent tumor suppressor regulating numerous pathways that drive cancer, but mutations in VHL are restricted to limited subsets of malignancies. Here we identified a novel mechanism for VHL suppression in tumors that do not have inactivating mutations. Using developmental processes to uncover new pathways contributing to tumorigenesis, we found that Daam2 promotes glioma formation. Protein expression screening identified an inverse correlation between Daam2 and VHL expression across a host of cancers, including glioma. These in silico insights guided corroborating functional studies, which revealed that Daam2 promotes tumorigenesis by suppressing VHL expression. Furthermore, biochemical analyses demonstrate that Daam2 associates with VHL and facilitates its ubiquitination and degradation. Together, these studies are the first to define an upstream mechanism regulating VHL suppression in cancer and describe the role of Daam2 in tumorigenesis.\n\nStatement of SignificanceWe found that the glial developmental factor Daam2 promotes glioma tumorigenesis by suppressing VHL expression. Our studies show, for the first time, a regulatory mechanism that operates upstream of VHL in cancer and provides an explanation for how VHL expression is extinguished in tumors that do not have inactivating mutations.

cancer biology↗