Biomedical subjects

Yoon Shin Cho

Publications and source records attributed to Yoon Shin Cho.

7 recordsLinked to original sources

PubMed2006

Jak2 and Tyk2 are necessary for lineage-specific differentiation, but not for the maintenance of self-renewal of mouse embryonic stem cells.

As the LIF-induced Jak1/STAT3 pathway has been reported to play a crucial role in self-renewal of mESCs, we sought to determine if Jak2, which is also expressed in mESCs, might also be involved in the pathway. By employing an RNAi strategy, we established both Jak2 and Jak2/Tyk2 knockdown mESC clones. Both Jak2 and Jak2/Tyk2 knockdown clones maintained the undifferentiated state as wild-type controls, even in a very low concentration of LIF. However, we observed not only faster onset of differentiation but also differential expression of tissue-specific lineage genes for ectodermal and mesodermal, but not endodermal origins from embryoid bodies generated from both types of knockdown clones compared to the wild-type. Furthermore, the reduced level of Jak2 caused differentiation of mESCs in the presence of LIF when the Wnt pathway was activated by LiCl treatment. Taken together, we demonstrated that Jak2 and Tyk2 are not involved in LIF-induced STAT3 pathway for self-renewal of mESCs, but play a role in early lineage decision of mESCs to various differentiated cell types.

Animals↗

PubMed2006

Profiling of differentially expressed genes in human stem cells by cDNA microarray.

Stem cells are unique cell populations with the ability to undergo both self-renewal and differentiation, although a wide variety of adult stem cells as well as embryonic stem cells have been identified and stem cell plasticity has recently been reported. To identify genes implicated in the control of the stem cell state as well as the characteristics of each stem cell line, we analyzed the expression profiles of genes in human embryonic, hematopoietic (CD34+ and CD133+), and mesenchymal stem cells using cDNA microarrays, and identified genes that were differentially expressed in specific stem cell populations. In particular we were able to identify potential hESC signature-like genes that encode transcription factors (TFAP2C and MYCN), an RNA binding protein (IMP-3), and a functionally uncharacterized protein (MAGEA4). The overlapping sets of 22 up-regulated and 141 down-regulated genes identified in this study of three human stem cell types may also provide insight into the developmental mechanisms common to all human stem cells. Furthermore, our comprehensive analyses of gene expression profiles in various adult stem cells may help to identify the genetic pathways involved in self-renewal as well as in multi-lineage specific differentiation.

Adult↗

PubMed2005

Microarray profiling of genes differentially expressed during erythroid differentiation of murine erythroleukemia cells.

Murine erythroleukemia (MEL) cells are widely used to study erythroid differentiation thanks to their ability to terminally differentiate in vitro in response to chemical induction. At the molecular level, not much is known of their terminal differentiation apart from activation of adult-type globin gene expression. We examined changes in gene expression during the terminal differentiation of these cells using microarray-based technology. We identified 180 genes whose expression changed significantly during differentiation. The microarray data were analyzed by hierarchical and k-means clustering and confirmed by semi-quantitative RT-PCR. We identified several genes including H1f0, Bnip3, Mgl2, ST7L, and Cbll1 that could be useful markers for erythropoiesis. These genetic markers should be a valuable resource both as potential regulators in functional studies of erythroid differentiation, and as straightforward cell type markers.

Acetamides↗

PubMed2005

Meiotic messenger RNA and noncoding RNA targets of the RNA-binding protein Translin (TSN) in mouse testis.

In postmeiotic male germ cells, TSN, formerly known as testis brain-RNA binding protein, is found in the cytoplasm and functions as a posttranscriptional regulator of a group of genes transcribed by the transcription factor CREM-tau. In contrast, in pachytene spermatocytes, TSN is found predominantly in nuclei. Tsn-null males show a reduced sperm count and high levels of apoptosis in meiotic cells, suggesting a critical function for TSN during meiosis. To identify meiotic target RNAs that associate in vivo with TSN, we reversibly cross-linked TSN to RNA in testis extracts from 17-day-old and adult mice and immunoprecipitated the complexes with an affinity-purified TSN antibody. Extracts from Tsn-null mice were used as controls. Cloning and sequencing the immunoprecipitated RNAs, we identified four new TSN target mRNAs, encoding diazepam-binding inhibitor-like 5, arylsulfatase A, a tetratricopeptide repeat structure-containing protein, and ring finger protein 139. In contrast to the population of postmeiotic translationally delayed mRNAs that bind TSN, these four mRNAs are initially expressed in pachytene spermatocytes. In addition, anti-TSN also precipitated a nonprotein-coding RNA (ncRNA), which is abundant in nuclei of pachytene spermatocytes and has a putative polyadenylation signal, but no open reading frame. A second similar ncRNA is adjacent to a GGA repeat, a motif frequently associated with recombination hot spots. RNA gel-shift assays confirm that the four new target mRNAs and the ncRNA specifically bind to TSN in testis extracts. These studies have, for the first time, identified both mRNAs and a ncRNA as TSN targets expressed during meiosis.

Animals↗

PubMed2005

Erythroid cell-specific alpha-globin gene regulation by the CP2 transcription factor family.

We previously demonstrated that ubiquitously expressed CP2c exerts potent erythroid-specific transactivation of alpha-globin through an unknown mechanism. This mechanism is reported here to involve specific CP2 splice variants and protein inhibitor of activated STAT1 (PIAS1). We identify a novel murine splice isoform of CP2, CP2b, which is identical to CP2a except that it has an additional 36 amino acids encoded by an extra exon. CP2b has an erythroid cell-specific transcriptional activation domain, which requires the extra exon and can form heteromeric complexes with other CP2 isoforms, but lacks the DNA binding activity found in CP2a and CP2c. Transcriptional activation of alpha-globin occurred following dimerization between CP2b and CP2c in erythroid K562 and MEL cells, but this dimerization did not activate the alpha-globin promoter in nonerythroid 293T cells, indicating that an additional erythroid factor is missing in 293T cells. PIAS1 was confirmed as a CP2 binding protein by the yeast two-hybrid screen, and expression of CP2b, CP2c, and PIAS1 in 293T cell induced alpha-globin promoter activation. These results show that ubiquitously expressed CP2b exerts potent erythroid cell-specific alpha-globin gene expression by complexing with CP2c and PIAS1.

Alternative Splicing↗

PubMed2004

The relative levels of translin-associated factor X (TRAX) and testis brain RNA-binding protein determine their nucleocytoplasmic distribution in male germ cells.

Testis brain RNA-binding protein (TB-RBP), the mouse orthologue of human translin, is an RNA and single-stranded DNA-binding protein abundant in testis and brain. Translin-associated factor X (TRAX) was identified as a protein that interacts with TB-RBP and is dependent upon TB-RBP for stabilization. Using immunohistochemistry to investigate the subcellular locations of TB-RBP and TRAX during spermatogenesis, both proteins localize in nuclei in meiotic pachytene spermatocytes and in the cytoplasm of subsequent meiotic and post-meiotic cells. An identical subcellular distribution is seen in female germ cells. Western blot analysis of germ cell protein extracts reveals an increased ratio of TRAX to TB-RBP in meiotic pachytene spermatocytes compared with the post-meiotic round and elongated spermatids. Using COS-1 cells and mouse embryonic fibroblasts derived from TB-RBP null mice as model systems to examine the shuttling of TB-RBP and TRAX, we demonstrate that TRAX contains a functional nuclear localization signal and TB-RBP contains a functional nuclear export signal. Coexpression of both proteins in COS-1 cells and TB-RBP-deficient mouse embryonic fibroblasts reveals that the ratio of TRAX to TB-RBP determines their subcellular locations, i.e. increased TRAX to TB-RBP ratios lead to nuclear localizations, whereas TRAX remains in the cytoplasm when TB-RBP levels are elevated. These subcellular distributions require interaction between TB-RBP and TRAX. We propose that the subcellular locations of TB-RBP and TRAX in male germ cells are modulated by the relative ratios of TRAX and TB-RBP.

Animals↗

PubMed2004

Translin-associated factor X is post-transcriptionally regulated by its partner protein TB-RBP, and both are essential for normal cell proliferation.

To determine the functions of the DNA/RNA-binding protein TB-RBP in somatic cells, we examined cultured primary mouse embryonic fibroblasts (MEFs) derived from TB-RBP-deficient mice. The TB-RBP-deficient MEFs exhibit a reduced growth rate compared with MEFs from littermates. Reintroduction of TB-RBP remedies this defect. A partner protein of TB-RBP, Translin-associated factor X (TRAX), was absent in TB-RBP-deficient MEFs, despite normal TRAX mRNA levels. TRAX is dependent upon the presence of TB-RBP and is removed from null MEFs following ubiquitination. Re-introduction of TB-RBP, but not TB-RBP lacking an oligomerization domain, into null MEFs stabilized TRAX protein without changing TRAX mRNA levels. The coordinated expression of TB-RBP and TRAX is also seen in synchronized cells, where the amount of TRAX protein but not TRAX RNA closely parallels TB-RBP levels throughout the cell cycle. In transgenic mice overexpressing TRAX in testis, total TB-RBP and TRAX levels are constant with reductions of endogenous TRAX compensating for exogenous TRAX. Using RNA interference, reductions of either TB-RBP or TRAX (without affecting TB-RBP) slow cell growth rates. We conclude that TRAX is post-transcriptionally stabilized by TB-RBP and both proteins are needed for normal cell proliferation.

Animals↗