• Journal of Life Science
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• v.30 no.8
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• pp.713-721
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• 2020

Adipogenesis as a model system is needed to understand the molecular mechanisms of human adipocyte biology and the pathogenesis of obesity, diabetes, and other metabolic syndromes. Many relevant studies have been conducted with a focus on gene expression regulation and intracellular signaling relating to Peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα), which are master adipogenic transcription factors. However, epigenome regulation of adipogenesis by epigenomic modifiers or histone mutations is not fully understood. Histone methylation is one of the major epigenetic modifications on gene expression in mammals, and histone H3 lysine methylation (H3Kme) in particular implicates cell differentiation during various tissue and organ development. During adipogenesis, cell type-specific enhancers are marked by histone H3K4me1 with the active enhancer mark H3K27ac. Mixed-lineage leukemia 4 (MLL4) is a major H3K4 mono-methyltransferase on the adipogenic enhancers of PPARγ and C/EBPα loci. Thus, MLL4 is an important epigenomic modifier for adipogenesis. The repressive mark H3K27me3 is mediated by the enzymatic subunit Enhancer zeste homolog 2 (EZH2) of the polycomb repressive complex 2. EZH2-mediated H3K27 tri-methylation on the Wnt gene increases adipogenesis because WNT signaling is a negative regulator of adipogenesis. This review summarizes current knowledge about the epigenomic regulation of adipogenesis by histone H3 lysine methylation which fundamentally regulates gene expression.

• Journal of Interdisciplinary Genomics
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• v.5 no.1
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• pp.1-4
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• 2023

Kleefstra syndrome is caused by chromosome 9q34.3 deletion or heterozygous mutations in the Euchromatin Histone Methyl Transferase 1 (EHMT1) gene. The prevalence is estimated 1:25,000 to 1:35,000. Intellectual disability, distinctive facial features, hypotonia in childhood can be accompanied. The spectrum of Kleefstra syndrome includes behavioral/psychiatric problems, hearing and visual impairments, seizures, congenital heart defects, genitourinary defects, and obesity. Therefore, it is necessary to understand the pathophysiology and various manifestation of Kleefstra syndrome and discussing with a multidisciplinary team will help diagnose and treat Kleefstra syndrome patients.

• Genomics & Informatics
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• v.14 no.3
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• pp.78-84
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• 2016

Extranodal natural killer (NK)/T-cell lymphoma, nasal type (NKTCL), is a malignant disorder of cytotoxic lymphocytes of NK or T cells. It is an aggressive neoplasm with a very poor prognosis. Although extranodal NKTCL reportedly has a strong association with Epstein-Barr virus, the molecular pathogenesis of NKTCL has been unexplored. The recent technological advancements in next-generation sequencing (NGS) have made DNA sequencing cost- and time-effective, with more reliable results. Using the Ion Proton Comprehensive Cancer Panel, we sequenced 409 cancer-related genes to identify somatic mutations in five NKTCL tissue samples. The sequencing analysis detected 25 mutations in 21 genes. Among them, KMT2D, a histone modification-related gene, was the most frequently mutated gene (four of the five cases). This result was consistent with recent NGS studies that have suggested KMT2D as a novel driver gene in NKTCL. Mutations were also found in ARID1A, a chromatin remodeling gene, and TP53, which also recurred in recent NGS studies. We also found mutations in 18 novel candidate genes, with molecular functions that were potentially implicated in cancer development. We suggest that these genes may result in multiple oncogenic events and may be used as potential bio-markers of NKTCL in the future.

• Journal of Korean Neurosurgical Society
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• v.61 no.3
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• pp.343-351
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• 2018

Diffuse intrinsic pontine glioma (DIPG) is a deadly paediatric brain cancer. Transient response to radiation, ineffective chemotherapeutic agents and aggressive biology result in rapid progression of symptoms and a dismal prognosis. Increased availability of tumour tissue has enabled the identification of histone gene aberrations, genetic driver mutations and methylation changes, which have resulted in molecular and phenotypic subgrouping. However, many of the underlying mechanisms of DIPG oncogenesis remain unexplained. It is hoped that more representative in vitro and preclinical models-using both xenografted material and genetically engineered mice-will enable the development of novel chemotherapeutic agents and strategies for targeted drug delivery. This review provides a clinical overview of DIPG, the barriers to progress in developing effective treatment, updates on drug development and preclinical models, and an introduction to new technologies aimed at enhancing drug delivery.

• Journal of Genetic Medicine
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• v.20 no.2
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• pp.70-74
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• 2023

CCCTC-binding factor (CTCF) is a transcriptional regulator that binds to a complex DNA motif in various orientations and plays a crucial role in regulating gene expression, chromatin restructuring, and developmental processes. Mutations in the CTCF are associated with neurodevelopmental disorders. Here we report the first Korean case with a de novo heterozygous variant in the CTCF (c.1025G>A; p.Arg342His). She showed global developmental delay, failure to thrive, and dysmorphic face, which are phenotypes consistent with previous reports in the autosomal dominant intellectual developmental disorder 21 (MIM 615502). She also showed clinical features not previously reported, such as antral web and tracheobronchomalacia. Our case follows suit and expands understanding of this rare disorder by reporting common features and, on the other hand, unreported concomitant congenital anomalies.

• Clinical and Experimental Pediatrics
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• v.56 no.8
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• pp.355-358
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• 2013

Kabuki syndrome (KS) is a rare genetic disease with a distinctive dysmorphic face, intellectual disability, and multiple congenital abnormalities. KS is inherited in an autosomal dominant manner. As the primary cause of KS, MLL2 mutations have been identified in 56-76% of affected individuals who have been tested, suggesting that there may be additional genes associated with KS. Recently, a few KS individuals have been found to have de novo partial or complete deletions of an X chromosome gene, KDM6A, which encodes a histone demethylase that interacts with MLL2. Nevertheless, mutations in MLL2 are the major cause of KS. Although there are a few reports of KS patients in Korea, none of these had been confirmed by genetic analysis. Here, we report a case of a Korean patient with clinical features of KS. Using direct sequencing, we identified a frameshift heterozygous mutation for MLL2 : (c.5256_5257delGA;p.Lys1753Alafs$^*34$). Clinically, the patient presented with typical facial features, and diagnosis of KS was based on the diagnostic criteria. While KS is a rare disease, other malformations that overlap with those found in individuals with KS are common. Hence, the diagnosis of KS by mutational analysis can be a valuable method for patients with KS-like syndromes. Furthermore, in the near future, other genes could be identified in patients with KS without a detectable MLL2 mutation.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.20 no.1
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• pp.1-13
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• 2020

Purpose: Gaucher disease (GD), which is the most prevalent lysosomal storage disorder worldwide, is caused by mutations in the glucocerebrosidase gene (GBA). GD is divided into three clinical subtypes based on the appearance of neurological symptoms. Type 1 GD is a chronic non-neuronopathic disease, and types 2 and 3 are acute neuronopathic and chronic neuronopathic forms, respectively. Neuronopathic GD types 2 and 3 are characterized by increased levels of glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph) in the brain, leading to massive loss of neurons. Methods: DNA damage and subsequent apoptosis of H4 cells were observed following neuroglioma H4 cell culture with GlcCer or GlcSph. Neuronal cell apoptosis was more prominent upon treatment with GlcSph. Results: When H4 cells were treated with GlcSph in the presence of tubacin, a histone deacetylase 6 inhibitor (HDAC6i), attenuation of both DNA damage and a reduction in the protein expression levels of GlcSph-induced apoptosis-associated factors were observed. Conclusion: These findings indicated that GlcSph played a prominent role in the pathogenesis of neuronopathic GD by inducing apoptosis, and that HDAC6i could be considered a therapeutic candidate for the treatment of neuronopathic GD.

• BMB Reports
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• v.51 no.10
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• pp.500-507
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• 2018

Cell reprogramming has been considered a powerful technique in the regenerative medicine field. In addition to diverse its strengths, cell reprogramming technology also has several drawbacks generated during the process of reprogramming. Telomere shortening caused by the cell reprogramming process impedes the efficiency of cell reprogramming. Transcription factors used for reprogramming alter genomic contents and result in genetic mutations. Additionally, defective mitochondria functioning such as excessive mitochondrial fission leads to the limitation of pluripotency and ultimately reduces the efficiency of reprogramming. These problems including genomic instability and impaired mitochondrial dynamics should be resolved to apply cell reprograming in clinical research and to address efficiency and safety concerns. Sirtuin (NAD+-dependent histone deacetylase) has been known to control the chromatin state of the telomere and influence mitochondria function in cells. Recently, several studies reported that Sirtuins could control for genomic instability in cell reprogramming. Here, we review recent findings regarding the role of Sirtuins in cell reprogramming. And we propose that the manipulation of Sirtuins may improve defects that result from the steps of cell reprogramming.

• Molecules and Cells
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• v.45 no.4
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• pp.231-242
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• 2022

The neuromuscular junction (NMJ), which is a synapse for signal transmission from motor neurons to muscle cells, has emerged as an important region because of its association with several peripheral neuropathies. In particular, mutations in GARS that affect the formation of NMJ result in Charcot-Marie-Tooth disease and distal hereditary motor neuropathy. These disorders are mainly considered to be caused by neuronal axon abnormalities; however, no treatment is currently available. Therefore, in order to determine whether the NMJ could be targeted to treat neurodegenerative disorders, we investigated the NMJ recovery effect of HDAC6 inhibitors, which have been used in the treatment of several peripheral neuropathies. In the present study, we demonstrated that HDAC6 inhibition was sufficient to enhance movement by restoring NMJ impairments observed in a zebrafish disease model. We found that CKD-504, a novel HDAC6 inhibitor, was effective in repairing NMJ defects, suggesting that treatment of neurodegenerative diseases via NMJ targeting is possible.

• Molecules and Cells
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• v.43 no.5
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• pp.448-458
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• 2020

T-DNA insertional mutations in Arabidopsis genes have conferred huge benefits to the research community, greatly facilitating gene function analyses. However, the insertion process can cause chromosomal rearrangements. Here, we show an example of a likely rearrangement following T-DNA insertion in the Anti-Silencing Function 1B (ASF1B) gene locus on Arabidopsis chromosome 5, so that the phenotype was not relevant to the gene of interest, ASF1B. ASF1 is a histone H3/H4 chaperone involved in chromatin remodeling in the sporophyte and during reproduction. Plants that were homozygous for mutant alleles asf1a or asf1b were developmentally normal. However, following self-fertilization of double heterozygotes (ASF1A/asf1a ASF1B/asf1b, hereafter AaBb), defects were visible in both male and female gametes. Half of the AaBb and aaBb ovules displayed arrested embryo sacs with functional megaspore identity. Similarly, half of the AaBb and aaBb pollen grains showed centromere defects, resulting in pollen abortion at the bi-cellular stage of the male gametophyte. However, inheritance of the mutant allele in a given gamete did not solely determine the abortion phenotype. Introducing functional ASF1B failed to rescue the AaBb- and aaBb-mediated abortion, suggesting that heterozygosity in the ASF1B gene causes gametophytic defects, rather than the loss of ASF1. The presence of reproductive defects in heterozygous mutants but not in homozygotes, and the characteristic all-or-nothing pollen viability within tetrads, were both indicative of commonly-observed T-DNA-mediated translocation activity for this allele. Our observations reinforce the importance of complementation tests in assigning gene function using reverse genetics.