Jeong Ho-chang

The future of safe cell-based therapy rests on overcoming teratoma/tumor formation, in particular when using human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs). Because the presence of a few remaining undifferentiated hPSCs can cause undesirable teratomas after transplantation, complete removal of these cells with no/minimal damage to differentiated cells is a prerequisite for clinical application of hPSC-based thera

Dyskeratosis congenita (DC) is a pediatric bone marrow failure syndrome caused by germline mutations in telomere biology genes. Mutations in DKC1 (the most commonly mutated gene in DC), the 3' region of TERC, and poly(A)-specific ribonuclease (PARN) cause reduced levels of the telomerase RNA component (TERC) by reducing its stability and accelerating TERC degradation. We have previously shown that depleting wild-type DKC1 levels by RNA interference or expression of the disease-associated A353V m

Mutations in the 3' to 5' RNA exonuclease USB1 cause hematopoietic failure in poikiloderma with neutropenia (PN). Although USB1 is known to regulate U6 small nuclear RNA maturation, the molecular mechanism underlying PN remains undetermined, as pre-mRNA splicing is unaffected in patients. We generated human embryonic stem cells harboring the PN-associated mutation c.531_delA in USB1 and show that this mutation impairs human hematopoiesis. Dysregulated microRNA (miRNA) levels in USB1 mutants duri

Basic fibroblast growth factor (bFGF) supplementation is critical to maintain the pluripotency of human pluripotent stem cells (hPSCs) through activation of PI3K/AKT, rather than MEK/ERK pathway. Thus, elaborate molecular mechanisms that preserve PI3K/AKT signaling upon bFGF stimulation may exist in hPSCs. Protein arginine methyltransferase 8 (PRMT8) was expressed and then its level gradually decreased during spontaneous differentiation of human embryonic stem cells (hESCs). PRMT8 loss- or gain-

Small molecules to selectively induce cell death of undifferentiated human pluripotent stem cells (hPSCs) have been developed with the aim of lowering the risk of teratoma formation during hPSC-based cell therapy. In this context, we have reported that Quercetin (QC) induces cell death selectively in hESCs via p53 mitochondrial localization. However, the detailed molecular mechanism by which hESCs undergo selective cell death induced by QC remains unclear. Herein, we demonstrate that mitochondri

Stem-toxic small molecules have been developed to induce selective cell death of pluripotent stem cells (PSCs) to lower the risk of teratoma formation. However, despite their high efficacies, chemical-based approaches may carry unexpected toxicities on specific differentiated cell types. Herein, we took advantage of KillerRed (KR) as a suicide gene, to selectively induce phototoxicity using visible light via the production of reactive oxygen species. PSCs in an undifferentiated state that exclus

The selective survival advantage of culture-adapted human embryonic stem cells (hESCs) is a serious safety concern for their clinical application. With a set of hESCs with various passage numbers, we observed that a subpopulation of hESCs at late passage numbers was highly resistant to various cell death stimuli, such as YM155, a survivin inhibitor. Transcriptome analysis from YM155-sensitive (YM155S) and YM155-resistant (YM155R) hESCs demonstrated that BCL2L1 was highly expressed in YM155R hESC

Wip1 belongs to the protein phosphatase C (PP2C) family, of which expression is up-regulated by a number of external stresses, and serves as a stress modulator in normal physiological conditions. When overexpressed, premature dephosphorylation of stress-mediators by Wip1 results in abrogation of tumor surveillance, thus Wip1 acts as an oncogene. Previously, the functional regulation of Wip1 in cell-cycle progression by counteracting cellular G1 and G2/M checkpoint activity in response to DNA dam

BACKGROUND AND AIMS: Telomere attrition is a major risk factor for end-stage liver disease. Due to a lack of adequate models and intrinsic difficulties in studying telomerase in physiologically relevant cells, the molecular mechanisms responsible for liver disease in patients with telomere syndromes remain elusive. To circumvent that, we used genome editing to generate isogenic human embryonic stem cells (hESCs) harboring clinically relevant mutations in telomerase and subjected them to an in vi

It is well established that short telomeres activate an ATM-driven DNA damage response that leads to senescence in terminally differentiated cells. However, technical limitations have hampered our understanding of how telomere shortening is signaled in human stem cells. Here, we show that telomere attrition induces ssDNA accumulation (G-strand) at telomeres in human pluripotent stem cells (hPSCs), but not in their differentiated progeny. This led to a unique role for ATR in the response of hPSCs