• International Journal of Stem Cells
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• v.16 no.1
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• pp.27-35
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• 2023

Background and Objectives: Spermatogonial stem cells (SSCs) are the most primitive cells in spermatogenesis and are the only adult stem cells capable of passing on the genome of a given species to the next generation. SSCs are the only adult stem cells known to exhibit high Oct4 expression and can be induced to self-reprogram into pluripotent cells depending on culture conditions. Epigenetic modulation is well known to be involved in the induction of pluripotency of somatic cells. However, epigenetic modulation in self-reprogramming of SSCs into pluripotent cells has not been studied. Methods and Results: In this study, we examined the involvement of epigenetic modulation by assessing whether selfreprogramming of SSCs is enhanced by treatment with epigenetic modulators. We found that second-generation selective class I HDAC inhibitors increased SSC reprogramming efficiency, whereas non-selective HDAC inhibitors had no effect. Conclusions: We showed that pluripotent stem cells derived from adult SSCs by treatment with small molecules with epigenetic modulator functions exhibit pluripotency in vitro and in vivo. Our results suggest that the mechanism of SSC reprogramming by epigenetic modulator can be used for important applications in epigenetic reprogramming research.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.3
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• pp.67-75
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• 2010

Network reprogramming is a technology that allows several sensor nodes deployed in sensor field to be repaired remotely. Unlike general communication in sensor network where small amount of data is transferred, network reprogramming requires reliable transfer of large amount of data. The existing network reprogramming techniques suffers high cost and large energy consumption to recover data loss in node communication. In this paper, a cluster based network reporgramming scheme is proposed for sensor network. It divides sensor field into several clusters and chooses a cluster header in charge of data relay to minimize duplicated transmission and unnecessary competition. It increases reliability by effective error recovery through status table.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.181-183
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• 2005

Network Reprogramming 에서는 코드 전파가 완료되기까지 걸리는 시간과 에너지 소모가 문제가 된다. 지금까지의 연구들은 에너지 소모를 줄이기 위해서 완료시간을 줄이는 방법에 초점을 두었지만 제한된 에너지를 사용해야 하는 센서 네트워크에서는 전송된 메시지에 의한 에너지 소모도 고려해야 한다. 본 논문에서는 코드 전파 시 전송 메시지 개수를 최소로 하는 DANP를 제시한다. DANP는 각 노드가 이웃 노드에 대한 정보를 이용하여 advertisement 주기를 적절히 늘려서 모든 경우의 Density에 대해서 코드 전파의 효율성을 높인다.

• Development and Reproduction
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• v.15 no.3
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• pp.187-195
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• 2011

X chromosome inactivation (XCI) is a process that enables mammalian females to ensure the dosage compensation for X-linked genes. Investigating the mechanism of XCI might provide deeper understandings of chromosomal silencing, epigenetic regulation of gene expressions, and even the course of evolution. Studies on mammalian XCI conducted with mice have revealed many fundamental findings on XCI. However, difference of murine and human XCI necessitates the further investigation in human XCI. Recent success in reprogramming of differentiated cells into pluripotent stem cells showed the reversibility of XCI in vitro, X chromosome reactivation (XCR), which provides another tool to study the change in X chromosome status. This review summarizes the current knowledge of XCI during early embryonic development and describes recent achievements in studies of XCI in reprogramming process.

• BMB Reports
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• v.50 no.9
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• pp.435-436
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• 2017

Primed human pluripotent stem cells (hPSCs) are highly dependent on glycolysis rather than oxidative phosphorylation, which is similar to the metabolic switch that occurs in cancer cells. However, the molecular mechanisms that underlie this metabolic reprogramming in hPSCs and its relevance to pluripotency remain unclear. Cha et al. (2017) recently revealed that downregulation of SIRT2 by miR-200c enhances acetylation of glycolytic enzymes and glycolysis, which in turn facilitates cellular reprogramming, suggesting that SIRT2 is a key enzyme linking the metabolic switch and pluripotency in hPSCs.

• Biomolecules & Therapeutics
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• v.25 no.4
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• pp.362-366
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• 2017

Direct conversion by trans-differentiation is of growing interest in cell therapy for incurable diseases. The efficiency of cell reprogramming and functionality of converted cells are important considerations in cell transplantation therapy. Here, we compared two representative protocols for the generation of induced-oligodendrocyte progenitor cells (iOPCs) from mouse and rat fibroblasts. Then, we showed that induction of Nkx6.2, Olig2, and Sox10 (NOS) was more effective in mouse fibroblasts and that induction of Olig2, Sox10, and Zfp536 (OSZ) was more effective at reprogramming iOPCs from rat fibroblasts. However, OSZ-iOPCs did not show greater proliferation than NOS-induced cells. Because the efficiency of iOPCs generation appears to differ between cell species depending on transcription factors and culture conditions, it is important to select appropriate methods for efficient reprogramming.

• Proceedings of the KSAR Conference
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• 2001.10a
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• pp.25-31
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• 2001

During early development, a dramatic reduction in methylation levels occurs in mouse (Monk et al., 1987). The process of epigenetic reprogramming in early embryos erases gamete-specific methylation patterns inherited from the parents (Howlett ＆ Reik 1991, Monk et al., 1987, Oswald et al., 2000, Sanford et al., 1984). This genome-wide demethylation process may be a prerequisite for the formation of pluripotent stem cells that are important for the later development (Reik ＆ Surani 1997). During post-implantation development, a wave of de novo methylation takes place; most of the genomic DNA is methylated at defined developmental timepoints, whereas tissue-specific genes undergo demethylation in their tissues of expression (Kafri et al., 1992, Razin ＆ Kafri 1994). Another demethylation-remethylation cycle of epigenetic reprogramming takes place during gametogenesis and is necessary for resetting of genomic imprinting (Solter 1988). The dynamic epigenetic reprogramming events appear to be basic and are probably conserved in eutherian mammals (see below). (omitted)

• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.1
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• pp.39-45
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• 2010

As wireless sensor network are being deployed in a wide variety of application areas, the number of sensor nodes in a sensor filed becomes larger and larger. In the past, ISP (In-System Programming) method have been generally used for code update but the large number of sensor nodes requires a new code update method called network reprogramming. There are many challenging issues for network reprogramming since it can make an impact on the network lifetime. In this paper, a new sender selection scheme for network reprogramming protocol is proposed to decrease energy consumption for code update by minimizing overlapped area between sender nodes and reducing data contention. Simulation results show that the proposed scheme can reduce the amount of message traffic and the overall data transmission time.

• Development and Reproduction
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• v.7 no.2
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• pp.61-68
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• 2003

Zygote genome should entail a complex process of epigenetic reprogramming including a global DNA demethylation to reach a totipotency or pluripotency during early mammalian development. In this study, we have analyzed methylation patterns in cloned bovine embryos to monitor the epigenetic reprogramming process of donor genomic DNA. Aberrant DNA methylation patterns were observed in various genomic regions of cloned embryos except single-copy gene sequences. The overall genomic methylation status of cloned embryos was quite different from that of normal embryos produced in viかo or in vivo. Abnormal methylation profiles were also specifically represented in trophectoderm cells of cloned embryos, which probably result in widespread gene dysregulation in extraembryonic region or placental dysfunction familiar to cloned animals. Our findings suggest that developmental failures of cloned embryos are due to incomplete epigenetic reprogramming of donor genomic DNA. Understanding the epigenetic reprogramming processes of donor genome will clearly define the faulty development of cloned embryos.

• Journal of Microbiology and Biotechnology
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• v.32 no.10
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• pp.1245-1252
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• 2022

Induced pluripotent stem cells (iPSCs) can be generated from somatic cells using Oct4, Sox2, Klf4, and c-Myc (OSKM). Small molecules can enhance reprogramming. Licochalcone D (LCD), a flavonoid compound present mainly in the roots of Glycyrrhiza inflata, acts on known signaling pathways involved in transcriptional activity and signal transduction, including the PGC1-α and MAPK families. In this study, we demonstrated that LCD improved reprogramming efficiency. LCD-treated iPSCs (LCD-iPSCs) expressed pluripotency-related genes Oct4, Sox2, Nanog, and Prdm14. Moreover, LCD-iPSCs differentiated into all three germ layers in vitro and formed chimeras. The mesenchymal-to-epithelial transition (MET) is critical for somatic cell reprogramming. We found that the expression levels of mesenchymal genes (Snail2 and Twist) decreased and those of epithelial genes (DSP, Cldn3, Crb3, and Ocln) dramatically increased in OR-MEF (OG2^+/+/ROSA26^+/+) cells treated with LCD for 3 days, indicating that MET effectively occurred in LCD-treated OR-MEF cells. Thus, LCD enhanced the generation of iPSCs from somatic cells by promoting MET at the early stages of reprogramming.