Taejoon Kwon

• BS, MS, MPhil, PhD
• Professor (Assistant) at Ulsan National Institute of Science and Technology

Triggering cancer cell death by inducing DNA damage is the primary aim of radiation therapy; however, normal cells are also damaged. Here, we showed that delivery of only four synthetic guide RNAs (sgRNAs) with Cas9 endonuclease efficiently induced simultaneous DNA double-strand breaks, resulting in efficient cell death in a cell type-specific mann...

Heterogeneity and the absence of a tumor microenvironment (TME) in traditional patient‐derived organoid (PDO) cultures limit their effectiveness for clinical use. Here, Embedded Bioprinting‐enabled Arrayed PDOs (Eba‐PDOs) featuring uniformly arrayed colorectal cancer (CRC) PDOs within a recreated TME is presented. This model faithfully reproduces c...

TNF receptor-associated protein1 (TRAP1) is a mitochondrial molecular chaperon with high homology with a cytosolic chaperon HSP90. It has been shown that TRAP1 functions as an inhibitor for apoptosis by preventing cytochrome-c release from mitochondria. In addition, TRAP1 seems to play critical roles in metabolic processes for energy production, su...

Drosophila establishes social clusters in groups, yet the underlying principles remain poorly understood. Here we performed a systemic analysis of social network behavior (SNB) that quantifies individual social distance (SD) in a group over time. The SNB assessment in 175 inbred strains from the Drosophila Genetics Reference Panel showed a tight as...

The actin-based cytoskeleton is considered a fundamental driving force for cell differentiation and development. Destrin (Dstn), a member of the actin-depolymerizing factor family, regulates actin dynamics by treadmilling actin filaments and increasing globular actin pools. However, the specific developmental roles of dstn have yet to be fully eluc...

Frogs are an ecologically diverse and phylogenetically ancient group of anuran amphibians that include important vertebrate cell and developmental model systems, notably the genus Xenopus. Here we report a high-quality reference genome sequence for the western clawed frog, Xenopus tropicalis, along with draft chromosome-scale sequences of three dis...

Perfluorooctanesulfonate (PFOS) is a ubiquitous environmental pollutant associated with increasing health concerns and environmental hazards. Toxicological analyses of PFOS exposure are hampered by large inter-species variations and limited studies on the mechanistic details of PFOS-induced toxicity. We investigated the effects of PFOS exposure on...

Multiciliated cells (MCCs) are epithelial cells that control body fluid flow and contribute to the clearance of pathogenic microbes and other particles from the airways, egg transport in oviducts, and circulation of cerebrospinal fluid in the central nervous system. Although MCCs have shared functions to control fluid flow via coordinated motility...

Background Gene knockout using the CRISPR/Cas (clustered regulatory interspaced short palindromic repeats/CRISPR-associated protein) system revolutionized reverse genetic (or targeted mutagenesis) studies in model and non-model organisms because almost all genetic elements can be targeted with few limitations. Although the CRISPR/Cas system incorpo...

The specialized cell types of the mucociliary epithelium (MCE) lining the respiratory tract enable continuous airway clearing, with its defects leading to chronic respiratory diseases. The molecular mechanisms driving cell fate acquisition and temporal specialization during mucociliary epithelial development remain largely unknown. Here, we profile...

Background Motile cilia in a vertebrate are important to sustaining activities of life. Fluid flow on the apical surface of several tissues, including bronchial epithelium, ependymal epithelium, and fallopian tubules is generated by the ciliary beating of motile cilia. Multi-ciliated cells in ependymal tissue are responsible for the circulation of...

Asymmetric localization of mRNAs is crucial for cell polarity and cell fate determination. By performing fractionation RNA-seq, we report here that a large number of maternal RNAs are associated with the ER in Xenopus oocytes but are released into the cytosol after oocyte maturation. We provide evidence that the majority of ER-associated RNA-bindin...

Pentachloronitrobenzene (PCNB) is an organochlorine fungicide commonly used to treat seeds against seedling infections and controlling snow mold on golf courses. PCNB has been demonstrated to be toxic to living organisms, including fish and several terrestrial organisms. However, only phenotypical deformities have been studied, and the effects of P...

The gap junction complex functions as a transport channel across the membrane. Among gap junction subunits, gap junction protein α1 (GJA1) is the most commonly expressed subunit. A recent study showed that GJA1 is necessary for the maintenance of motile cilia; however, the molecular mechanism and function of GJA1 in ciliogenesis remain unknown. Her...

Progressive iron accumulation in the substantia nigra in the aged human brain is a major risk factor for Parkinson's disease and other neurodegenerative diseases. Heavy metals, such as iron, produce reactive oxygen species and consequently oxidative stress in cells. It is unclear, however, how neurons in the substantia nigra are protected against t...

Significance The targeted killing of cancer cells without affecting surrounding normal cells is the most desirable approach for cancer therapy; however, it cannot be easily achieved, owing to the shared properties of normal and cancer cells. Using CRISPR-Cas9 targeting multiple cancer-specific mutations, we developed an innovative approach called c...

The current diagnosis of bacteremia mainly relies on blood culture, which is inadequate for the rapid and quantitative determination of most bacteria in blood. Here, a quantitative, multiplex, microfluidic fluorescence in situ hybridization method (μFISH) is developed, which enables early and rapid (3‐h) diagnosis of bacteremia without the need for...

Chondrocytes secrete massive extracellular matrix (ECM) molecules that are produced, folded, and modified in the endoplasmic reticulum (ER). Thus, the ER-associated degradation (ERAD) complex—which removes misfolded and unfolded proteins to maintain proteostasis in the ER— plays an indispensable role in building and maintaining cartilage. Here, we...

Frogs are an ecologically diverse and phylogenetically ancient group of living amphibians that include important vertebrate cell and developmental model systems, notably the genus Xenopus . Here we report a high-quality reference genome sequence for the western clawed frog, Xenopus tropicalis , along with draft chromosome-scale sequences of three d...

Glutathione peroxidase 1 (Gpx1) and peroxiredoxin 2 (Prdx2) belong to the thiol peroxidase family of antioxidants, and have been studied for their antioxidant functions and roles in cancers. However, the physiological significance of Gpx1 and Prdx2 during vertebrate embryogenesis are lacking. Currently, we investigated the functional roles of Gpx1...

Background Explanted tissues from vertebrate embryos reliably develop in culture and have provided essential paradigms for understanding embryogenesis, from early embryological investigations of induction, to the extensive study of Xenopus animal caps, to the current studies of mammalian gastruloids. Cultured explants of the Xenopus dorsal marginal...

Glutathione peroxidase 3 (GPx3) belongs to the glutathione peroxidase family of selenoproteins and is a key antioxidant enzyme in multicellular organisms against oxidative damage. Downregulation of GPx3 affects tumor progression and metastasis and is associated with liver and heart disease. However, the physiological significance of GPx3 in vertebr...

The gap junction complex functions as a transport channel across the membrane. Among gap junction subunits, gap junction protein alpha 1 (GJA1) is the most commonly expressed subunit. However, the roles of GJA1 in the formation and function of cilia remain unknown. Here, we examined GJA1 functions during ciliogenesis in vertebrates. GJA1 was locali...

The dopamine system in the midbrain is essential for volitional movement, action selection, and reward-related learning. Despite its versatile roles, it contains only a small set of neurons in the brainstem. These dopamine neurons are especially susceptible to Parkinson’s disease and prematurely degenerate in the course of disease progression, whil...

The extracellular matrix is a critical component of every human tissue. ECM not only functions as a structural component but also regulates a variety of cellular processes such as cell migration, differentiation, proliferation, and cell death. In addition, current studies suggest that ECM is critical for the pathophysiology of various human disease...

Exposure to particulate matter (PM) in ambient air is known to increase the risk of cardiovascular disorders and mortality. The cytotoxicity of PM is mainly due to the abnormal increase of reactive oxygen species (ROS), which damage cellular components such as DNA, RNA, and proteins. The correlation between PM exposure and human disorders, includin...

Motile cilia of multiciliated epithelial cells have important roles in animal development and cell homeostasis. Although several studies have identified and reported proteins localized in this complex organelle and the related immotile primary cilia from various cell types, it is still challenging to isolate high quantities of ciliary proteins for...

The Western clawed frog Xenopus tropicalis is a diploid model system for both frog genetics and developmental biology, complementary to the paleotetraploid X. laevis. Here we report a chromosome-scale assembly of the X. tropicalis genome, improving the previously published draft genome assembly through the use of new assembly algorithms, additional...

Epigenetic modifier lysine demethylase 3a (Kdm3a) specifically demethylates mono- and di-methylated ninth lysine of histone 3 and belongs to the Jumonji domain-containing group of demethylases. Kdm3a serves roles during various biological and pathophysiological processes, including spermatogenesis and metabolism, determination of sex, androgen rece...

Background Lysine-specific histone demethylase 5C (KDM5C) belongs to the jumonji family of demethylases and is specific for the di- and tri-demethylation of lysine 4 residues on histone 3 (H3K4 me2/3). KDM5C is expressed in the brain and skeletal muscles of humans and is associated with various biologically significant processes. KDM5C is known to...

Determining how size is controlled is a fundamental question in biology that is poorly understood at the organismal, cellular, and subcellular levels. The Xenopus species, X. laevis and X. tropicalis differ in size at all three of these levels. Despite these differences, fertilization of X. laevis eggs with X. tropicalis sperm gives rise to viable...

Nuclear to cell size relationships post-zygotic genome activation in injected X. laevis embryos. (A) Nuclear diameter vs. cell diameter in Ventx2-injected X. laevis embryos at stage 10 and 21. Analysis of covariance at stage 10 gave a p-value of 0.865 and at stage 21 of 0.016. (B) Nuclear diameter vs. cell diameter in Hes7-injected X. laevis embryo...

Protein sequence alignments of Xenopus Ventx2 and Hes7. (A) Ventx2 protein sequences of X. tropicalis, X. laevis L, and S copies aligned using Clustal Omega. (B) Hes7 protein sequences of X. tropicalis, X. laevis L, and S copies aligned using Clustal Omega. For (A,B), identities and similarities were calculated using EMBOSS Needle.

Characterization of haploid X. laevis embryo development. X. laevis vs. haploid X. laevis. X. laevis eggs were fertilized with X. laevis (left) or irradiated X. laevis sperm (right) and simultaneously imaged in separate dishes. The video plays 20 h in 12 s (rate of 120 fps) and the scale bar corresponds to 200 μm.

Significantly differentially expressed transcripts in le × ts hybrids compared to X. laevis embryos.

Characterization of le × ts hybrid embryo development. X. laevis vs. le × ts X. laevis eggs were fertilized with X. laevis (left) or X. tropicalis sperm (right). and simultaneously imaged in separate dishes. The video plays 20 h in 12 s (rate of 120 fps) and the scale bar corresponds to 200 μm.

Developing and mature chondrocytes constantly interact with and remodel the surrounding extracellular matrix (ECM). Recent research indicates that integrin-ECM interaction is differentially regulated during cartilage formation (chondrogenesis). Integrin signaling is also a key source of the catabolic reactions responsible for joint destruction in b...

Aims: Peroxiredoxin5 (Prdx5) - a thioredoxin peroxidase is an antioxidant enzyme that is widely studied for its antioxidant properties and protective roles in neurological and cardiovascular disorders. The present study is aimed to investigate the functional significance of Prdx5 in mitochondria and to analyze its roles in ciliogenesis during the...

Determining how size is controlled is a fundamental question in biology that is poorly understood at the organismal, cellular and subcellular levels. The Xenopus species, X. laevis and X. tropicalis differ in size at all three of these levels. Despite these differences, fertilization of X. laevis eggs with X. tropicalis sperm gives rise to viable h...

The lysine-specific histone demethylase 1A (KDM1A) was the first demethylase to challenge the concept of the irreversible nature of methylation marks. KDM1A, containing a flavin adenine dinucleotide (FAD)-dependent amine oxidase domain, demethylates histone 3 lysine 4 and histone 3 lysine 9 (H3K4me1/2 and H3K9me1/2). It has emerged as an epigenetic...

The airway epithelium in human plays a central role as the first line of defense against environmental contaminants. Most respiratory diseases such as chronic obstructive pulmonary disease (COPD), asthma, and respiratory infections, disturb normal muco-ciliary functions by stimulating the hypersecretion of mucus. Several muco-active agents have bee...

Hybridization of eggs and sperm from closely related species can give rise to genetic diversity, or can lead to embryo inviability owing to incompatibility. Although central to evolution, the cellular and molecular mechanisms underlying post-zygotic barriers that drive reproductive isolation and speciation remain largely unknown. Species of the Afr...

Peroxiredoxin1 (Prdx1) is an antioxidant enzyme belonging to the peroxiredoxin family of proteins. Prdx1 catalyzes the reduction of H2O2 and alkyl hydroperoxide and plays an important role in different biological processes. Prdx1 also participates in various age-related diseases and cancers. In this study, we investigated the role of Prdx1 in prone...

The inner mitochondrial membrane (IMM) proteome plays a central role in maintaining mitochondrial physiology and cellular metabolism. Various important biochemical reactions such as oxidative phosphorylation, metabolite production, and mitochondrial biogenesis are conducted by the IMM proteome and mitochondria-targeted therapeutics have been develo...

More than five thousand genes annotated in the recently published Xenopus laevis and Xenopus tropicalis genomes do not have a candidate orthologous counterpart in other vertebrate species. To determine whether these sequences represent genuine amphibian-specific genes or annotation errors, it is necessary to analyze them alongside sequences from ot...

To explore the origins and consequences of tetraploidy in the African clawed frog, we sequenced the Xenopus laevis genome and compared it to the related diploid X. tropicalis genome. We characterize the allotetraploid origin of X. laevis by partitioning its genome into two homoeologous subgenomes, marked by distinct families of 'fossil' transposabl...

Mammalian target of rapamycin (mTOR) signaling is a core pathway in cellular metabolism, and control of the mTOR pathway by rapamycin shows potential for the treatment of metabolic diseases. In this study, we employed a new proximity biotin-labeling method using promiscuous biotin ligase (pBirA) to identify unknown elements in the rapamycin-induced...

During early vertebrate embryogenesis, cell fate specification is often coupled with cell acquisition of specific adhesive, polar and/or motile behaviors. In Xenopus gastrulae, tissues fated to form different axial structures display distinct motility. The cells in the early organizer move collectively and directionally toward the animal pole and c...

For a long time it has been assumed that the only role of sperm at fertilization is to introduce the male genome into the egg. Recently, ideas have emerged that the epigenetic state of the sperm nucleus could influence transcription in the embryo. However conflicting reports have challenged the existence of epigenetic marking of sperm genes, and th...

Unlabelled: Antimicrobial-resistant bacteria pose a serious threat in the clinic. This is particularly true for opportunistic pathogens that possess high intrinsic resistance. Though many studies have focused on understanding the acquisition of bacterial resistance upon exposure to antimicrobials, the mechanisms controlling intrinsic resistance ar...

There are six members of the tubulin superfamily in eukaryotes [1]. Alpha- and beta-tubulin form a heterodimer that polymerizes to form microtubules, and gamma-tubulin nucleates microtubules as a component of the gamma-tubulin ring complex. Alpha-, beta-, and gamma-tubulin are conserved in all eukaryotes. In contrast, delta- and epsilon-tubulin are...

Xenopus is an important model organism for the study of genome duplication in vertebrates. With the full genome sequence of diploid Xenopus tropicalis available, and that of allotetraploid X. laevis close to being finished, we will be able to expand our understanding of how duplicated genes have evolved. One of the key features in the study of the...

Genome duplication creates redundancy in proteins and their interaction networks, and subsequent smaller-scale gene duplication can further amplify genetic redundancy. Mutations then lead to the loss, maintenance or functional divergence of duplicated genes. Genome duplication occurred many times in African clawed frogs (genus Xenopus), and almost...

Recently, using the frog Xenopus laevis as a model system, we showed that transcription factor Rfx2 coordinates many genes involved in ciliogenesis and cell movement in multiciliated cells (Chung et al., 2014). To our knowledge, it was the first paper to utilize the genomic resources, including genome sequences and interim gene annotations, from th...

Recent studies have shown that the concentrations of proteins expressed from orthologous genes are often conserved across organisms and to a greater extent than the abundances of the corresponding mRNAs. However, such studies have not distinguished between evolutionary (e.g., sequence divergence) and environmental (e.g., growth condition) effects o...

911 genes corresponding to the directly regulated downstream target genes of Rfx2.DOI: http://dx.doi.org/10.7554/eLife.01439.005