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Articles by S. H Song
Total Records ( 3 ) for S. H Song
  T. H Lee , S. H Song , K. L Kim , J. Y Yi , G. H Shin , J. Y Kim , J Kim , Y. M Han , S. H Lee , S. H Shim and W. Suh
 

Rationale: Generation of induced pluripotent stem (iPS) cells has been intensively studied by a variety of reprogramming methods, but the molecular and functional properties of the cells differentiated from iPS cells have not been well characterized.

Objective: To address this issue, we generated iPS cells from human aortic vascular smooth muscle cells (HASMCs) using lentiviral transduction of defined transcription factors and differentiated these iPS cells back into smooth muscle cells (SMCs).

Methods and Results: Established iPS cells were shown to possess properties equivalent to human embryonic stem cells, in terms of the cell surface markers, global mRNA and microRNA expression patterns, epigenetic status of OCT4, REX1, and NANOG promoters, and in vitro/in vivo pluripotency. The cells were differentiated into SMCs to enable a direct, comparative analysis with HASMCs, from which the iPS cells originated. We observed that iPS cell–derived SMCs were very similar to parental HASMCs in gene expression patterns, epigenetic modifications of pluripotency-related genes, and in vitro functional properties. However, the iPS cells still expressed a significant amount of lentiviral transgenes (OCT4 and LIN28) because of partial gene silencing.

Conclusions: Our study reports, for the first time, the generation of iPS cells from HASMCs and their differentiation into SMCs. Moreover, a parallel comparative analysis of human iPS cell–derived SMCs and parental HASMCs revealed that iPS-derived cells possessed representative molecular and in vitro functional characteristics of parental HASMCs, suggesting that iPS cells hold great promise as an autologous cell source for patient-specific cell therapy.

  D. H Ko , S. H Jun , H. D Park , S. H Song , K. U Park , J. Q Kim , Y. H Song and J. Song
 

Background: Galactosemia is one of the most important inherited disorders detected by newborn screening tests. Abnormal results in screening tests should be confirmed by enzyme activity assays, but existing methods are time and labor intensive. We developed a novel multiplex enzyme assay for galactosemia using ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS).

Methods: [13C6]-galactose, [13C2]-galactose-1-phosphate, and UDP-glucose were used as substrates for 3 galactose-metabolizing enzymes. The end products from the combined reaction mixtures, [13C6]-galactose-1-phosphate, UDP-[13C2]-galactose, and UDP-galactose, were simultaneously measured using UPLC-MS/MS. Linearity, imprecision, ion suppression, and the effects of substrate were evaluated to determine assay performance. Enzyme activities from 35 healthy individuals, 8 patients with enzyme deficiency, and 18 mutant cells were analyzed.

Results: Substrates, products, and internal standards from the mixture of 3 enzyme reactions were clearly separated by using UPLC-MS/MS, with an injection cycle time of 10 min. Ion suppression was 0.1%–2.5%, the interassay imprecision of UPLC-MS/MS was 3.3%–10.6% CV, and the linearity of each system was good (R2 = 0.994–0.999). Patient samples and mutated cells showed consistently low enzyme activities compared with those of normal individuals and wild-type cells.

Conclusions: This method allows for a high-throughput and reproducible multiplex enzyme assay for galactosemia in erythrocytes.

  L Li , J. Y Lee , J Gross , S. H Song , A Dean and P. E. Love
 

During erythrocyte development, the nuclear cofactor Lim domain binding protein 1 (Ldb1) functions as a core subunit of multiprotein DNA binding complexes that include the transcription factors Scl and Gata-1 and the Lim-only adapter Lmo2. Scl, Gata-1, and Lmo2 are each required for erythropoiesis, suggesting that Ldb1-nucleated transcription complexes regulate key steps during erythropoiesis. We documented a requirement for Ldb1 in erythropoiesis in mice. Analysis of ldb1–/– embryos revealed a critical requirement for Ldb1 during primitive erythropoiesis, and conditional inactivation of ldb1 at later stages of gestation and in adult mice demonstrated that Ldb1 is continuously required for both definitive erythropoiesis and megakaryopoiesis. Down-regulation of Ldb1 in erythroblasts inhibited the expression of multiple erythroid-specific and prosurvival genes. These results represent the first unequivocal demonstration of a role for Ldb1 in erythropoiesis in vivo and establish a critical function for Ldb1-nucleated complexes in regulating the erythroid/megakaryocyte transcriptional program.

 
 
 
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