Biomedical subjects

June Ho Shin

Publications and source records attributed to June Ho Shin.

5 recordsLinked to original sources

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↗

PubMed2006

Stem cell therapy for hearing loss: Math1 overexpression in VOT-E36 cells.

HYPOTHESIS: VOT-E36 cells acquire mechanosensitivity after mammalian atonal homolog 1 (Math1) overexpression. BACKGROUND: VOT-E36 cells are derived from a population of epithelial cells in the ventral region of the otocyst at embryonic Day 10.5, before hair cell differentiation. These cells express a number of specific molecular markers for hair cells under both proliferation and differentiation states. Overexpression of Math1 can convert nonsensory epithelial cells into hair cells in the cochlea. Based on this information, we tested whether VOT-E36 cells can be converted into hair cells by Math1 overexpression. METHODS: Using reverse transcriptase-polymerase chain reaction-based analysis, we first compared the expression patterns of various molecular markers for hair cell development in VOT-E36 cells between proliferation and differentiation states, and also before and after overexpression of Math1. Subsequently, with a standard calcium imaging method, we examined whether VOT-E36 cells overexpressing Math1 could detect mechanical vibrations and activate spiral ganglion neurons in a coculture model. In addition, using confocal and scanning electron microscopes, we examined morphologic changes of VOT-E36 cells after Math1 overexpression. RESULTS: Consistent with previous reports, this study has shown that VOT-E36 cells express a number of specific molecular markers for hair cells in both proliferation and differentiation states. Under appropriate culture conditions, Math1 is transiently expressed in this cell line during conditional differentiation. In VOT-E36 cells overexpressing Math1, the normal expression pattern of certain molecular markers for mature hair cells is partially restored. Interestingly, after coculture with spiral ganglion neurons, VOT-E36 cells overexpressing Math1 are able to respond to mechanical vibrations and activate spiral ganglion neurons. Possible molecular mechanisms underlying this novel finding have been explored. CONCLUSION: Math1 overexpression can partially restore presumably downstream signaling cascades for normal hair cell differentiation in VOT-E36 cells, which are able to detect mechanical vibrations after being cocultured with spiral ganglion neurons.

Animals↗

PubMed2006

Preferentially enhanced gene expression from a synthetic human telomerase reverse transcriptase promoter in human cancer cells.

Although the human telomerase reverse transcriptase (hTERT) promoter can regulate cancer-specific genes, it is generally too weak to be effective. We therefore attempted to improve the potency of synthetic hTERT promoters by fusing the core element (E) of the hTERT promoter (H) and the tripartite leader sequence (T) from human adenovirus 5 in a combinatorial manner. To determine the potential as cancer-specific promoters, we measured luciferase activity driven by the chimeric hTERT promoters in human cancer cells. Among various constructs, the E3-H-T promoter induced the strongest luciferase activity in all the tested cancer cells. SK-Hep1 and Hela cells experienced 1000- and 11-fold higher expression than the basic hTERT promoter, respectively. Relative to the SV40 universal promoter, the E3-H-T promoter led to higher levels of gene expression. Using EMSA, we found that the hTERT enhancer region was specifically bound to c-Myc and Sp1. Thus, the data suggest that the E3-H-T promoter with up-regulated cancer-specific gene expression could be useful in cancer gene therapy.

Adenoviruses, Human↗

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↗

PubMedDate not supplied

Development of artificial chimerical gene regulatory elements specific for cancer gene therapy.

To achieve satisfactory outcome by the expression of therapeutic genes, it is of great importance to obtain efficient and high level of gene expression as well as minimizing inappropriate gene expression in non-target cells. To accomplish this goal for cancer gene therapy, we have evaluated the potential of cancer specific gene expression of functional promoter/enhancer elements in six putative cancer-specific genes (Tcf1alpha, C-Ha-Ras, CyclinE, Cdc25A, HK II, and hTert) using a luciferase reporter assay. Most of the reporter constructs showed higher activity in HepG2 cells than in non-transformed or stem cells, and, in particular, the hTert (E) or Tcf1alpha (T) regulatory element showed significantly higher activity. We have also constructed a series of artificial chimerical regulatory elements by combinatorial linking of E promoter and T enhancer. A dramatic decrease of activity was observed as the copy number of concatenated T/E regulatory elements increased. In contrast, in chimerical constructs containing two or three copies of regulatory elements of T/E, cell type preferential expression profiles were changed. Thus, both pGL3-TE and -TEE showed higher activity specifically in MCF7 breast cancer cells, whereas pGL3-TET showed moderate activity in several cancer cell lines of different origins. Our results demonstrate that although the transcriptional activities of synthetic promoters are weak, some cancer-specific regulatory elements are useful in developing optimized and systemic cancer-specific regulatory regions with potential application in targeted cancer cell therapy.

Amino Acid Motifs↗