Moraga Biotech Blog http://moragabiotech.com/nucleus/ en-us Nucleus CMS v3.23 © Weblog http://backend.userland.com/rss http://moragabiotech.com/nucleus//nucleus/nucleus2.gif Moraga Biotech Blog http://moragabiotech.com/nucleus/ Efficient Generation of Induced Pluripotent Stem Cells from Adult Mouse Adipose Tissue-Derived and Neural Stem Cells http://moragabiotech.com/nucleus/index.php?itemid=982 Cell Transplantation, Australian scientists P. A. Tat et al. from the Monash institute of Medical Research (Melbourne) reported their experimental results on the transduction/reprogramming efficiencies in either mouse neural stem cells (NSCs), adipose tissue-derived cells (ADCs), or mouse embryonic fibroblasts (mEFs) for generating induced pluripotent stem (iPS) cells. With a retroviral vector encoding for the DNA sequence of Oct4, Sox2, Klf4, and c-Myc, the investigators transduced NSCs, ADCs, and mEFs and analyzed GFP expression as an indicator of reprogramming (GFP transgene was under the control of the Oct4 promoter). Although the transduction efficiencies were similar for all 3 cell types, the investigators found that reprogramming efficiencies in the number of GFP-positive colonies for both NSCs and ADCs were greater than control mEFs. Additionally, the experimental results revealed that ADCs had an 8- and 38-fold increase in reprogramming efficiencies compared to NSCs and mEFs, respectively. In vitro and in vivo experiments showed that iPS cells from ADCs were found to be pluripotent by their ability to differentiate into cell lineages representing all 3 germ layers. The authors concluded from their study results "that ADCs are an ideal candidate as a readily accessible somatic cell type for high efficiency and establishment of iPS cell lines."]]> Reprogramming http://moragabiotech.com/nucleus/index.php?itemid=982 Mon, 26 Jul 2010 07:38:00 -0700 Nanog Regulates Primordial Germ Cell Migration Through CXCR-4b http://moragabiotech.com/nucleus/index.php?itemid=981 Stem Cells, A. V. Sánchez-Sánchez et al. from the Universidad de Valencia (Spain) published their study results on genes responsible for specification and migration of primordial germ cells (PGCs) during gonadal development in vertebrates. The investigators found that the pluripotency gene, medaka Nanog (Ol-Nanog), is expressed in developing PGCs and regulates the expression of CXCR-4b by binding to its promoter region. PGC migration is guided by CXCR-4b receptor expression and binding to its ligand SDF-1a. The experimental data revealed that depletion of the Ol-Nanog protein results in aberrant migration of PGCs as well as downregulating the expression of CXCR-4b. Similarily, overexpression of CXCR-4b and depletion of Ol-Nanog protein can rescue defective migration, whereas, overexpression of SDF-1a cannot restore proper PGC migration. The authors concluded that their results "indiciate that Ol-Nanog mediates PGC migration by regulating CXCR-4b expression."]]> Signaling and Pathways http://moragabiotech.com/nucleus/index.php?itemid=981 Tue, 13 Jul 2010 10:38:00 -0700 Reversal of Hyperglycemia in Diabetic Mouse Models with iPS-Derived Panceatic β-like Cells http://moragabiotech.com/nucleus/index.php?itemid=980 reported their proof of concept studies in which they were able to reprogram mouse somatic cells and differentiate the induced pluripotent stem cells (iPSCs) into insulin-secreting β-like cells. The investigators demonstrated in vitro that iPSC-derived β-like cells, similar to endogenous insulin-secreting mouse cells, were able to secrete insulin in response to the presence of glucose. When the iPSC-derived β-like cells were transplanted into type 1 and 2 diabetic mice, the differentiated β-like cells were able to secrete insulin and with normal gylcemic controls in glucose tolerance experiments. Hemoglobin A1c and blood glucose levels were found to be at normal levels 3 months after transplantation; illustrating long-term correction of hyperglycemia by the β-like cells . The authors concluded that the data from their study illustrate the "potential clinical application of reprogrammed somatic cells in the treatment of diabetes type 1 and 2." ]]> Reprogramming http://moragabiotech.com/nucleus/index.php?itemid=980 Mon, 12 Jul 2010 10:33:00 -0700 Aberrant Epigenetic Silencing of Tumor Suppressor Genes is Reversed by Direct Reprogramming http://moragabiotech.com/nucleus/index.php?itemid=979 Stem Cells, S. Ron-Bigger et al from The Hebrew University of Jerusalem conducted a study on reprogramming somatic cells which took some of the air out of using induced pluripotent stem cells (iPSCs) as an alternative to embryonic stem cells for future cell-based therapeutic applications. The investigators published their study results demonstrating that resetting the epigenetic memory of somatic cells can lead to abnormal epigenetic changes and pathological conditions. Studying the fate of the silenced tumor suppressor gene, p16 (CDKN2A), during reprogramming. Surprisingly, the researchers reported that reprogramming restored p16 expression, irrespective of whether the cells were induced to differentiate. Large scale methylation profiling of donor cells identified hundreds of aberrant methylation sites. On the positive side, many of these sites had restored normal methylation patterns following reprogramming. The authors concluded that "reprogramming approaches may be applied to repair the epigenetic lesions associated with cancer."]]> Reprogramming http://moragabiotech.com/nucleus/index.php?itemid=979 Fri, 2 Jul 2010 11:01:46 -0700 Xenografts of Porcine Islets and Pancreatic Primordia in Nonimmune-Suppressed Diabetic Rats http://moragabiotech.com/nucleus/index.php?itemid=978 American J. of Pathology, S. A. Rogers et al. from Washington University School of Medicine reported the results of their study on xenotransplantation of procine islets and pig pancreatic primordia (embryonic day 28) into streptozotocin-treated diabetic rats. The investigators conducted experiments demonstrating normalization of glucose tolerance and without immune suppression. Porcine islets were engrafted into the renal capsule concomitant with pancreatic primordia transplanted into the mesentery. In situ hybridization analysis for porcine X chromosome revealed long-term donor cell engraftement. However, islet engraftment did not occur without transplantation of the E28 pig pancreatic primordia in the mesentery. The authors concluded from their study results that "tolerance induction to a cell component of porcine islets is induced by previous transplantation of E28 pig pancreatic primordia" in an immunocompetent animal.
]]> Tissue Regeneration http://moragabiotech.com/nucleus/index.php?itemid=978 Tue, 29 Jun 2010 10:55:00 -0700 Epithelial-Mesenchymal Transition-Derived Cells Exhibit Multi-Lineage Differentiation Potential Similar to Mesenchymal Stem Cells http://moragabiotech.com/nucleus/index.php?itemid=977 Stem Cells, V. L. Battula et al. from the University of Texas M.D. Anderson Cancer Center, reported their study on induction of epithelial-to-mesenchymal transition (EMT) in breast epithelial cells. The investigator noted that EMT normally is an embryonic process which is latent in normal adult tissues and diagnostic for aggressive metastatic breast cancers. The researchers conducted experiments in which ectotopic expression of Twist, Snail or TGF-β in immortalized human mammary epithelial cells can induced EMT and endow the cells with mesenchymal stem cell (MSC) traits. Similar to MSCs, these EMT-derived cells were CD44+, CD24-, CD45-, and CD140b+ (PDGFR-β). In vitro differentiation revealed EMT-derived cells could differentiate into adipocytes, chrondrocytes, and osteoblasts. Additionally, the investigators showed that EMT-derived homed in vivo toward wound sites and in vitro the cells migrated toward breast cancer cells, similar to MSCs. The authors concluded from their study results that "EMT-derived cells are similar to MSCs in gene expression, multilineage differentiation, and ability to migrate towards tumor cells and wound sites."
]]> Isolation and Characterization http://moragabiotech.com/nucleus/index.php?itemid=977 Mon, 28 Jun 2010 07:44:00 -0700 Wilms Tumor Chromatin Profiles Stem Cell Properties http://moragabiotech.com/nucleus/index.php?itemid=976 Cell Stem Cell, A. P. Aiden et al. from Harvard University reported their study results on identifying transcriptional and epigenetic mechanisms which give rise to Wilms tumor formation. With a comparison of genome-wide chromatin profiling of cells derived from Wilms tumors, embryonic stem cells (ESCs), and normal kidney, the investigators found that large active chromatin domains normally regulating gene expression in ESCs were also expressed in Wilms cells. These genes were associated with kidney development as well as maintaining the adult renal stem cell compartment. Interestingly, the Wilms cells expressing the embryonic-like chromatin regulators maintain stem cells in the kidney compartment by silencing p16. The experimental data revealed that these "bivalent promoters" in Wilms tumor correlated to silencing genes during early stages of differentiation in kidney progenitors. The authors concluded from their experimental results which they suggest that "Wilms cells share a transcriptional and epigenetic landscape with normal renal stem cells, which is inherently susceptible to transformation and my represent a cell of origin for this disease" (i.e. cancer stem cells).
]]> Stem Cells and Cancer http://moragabiotech.com/nucleus/index.php?itemid=976 Fri, 25 Jun 2010 21:18:00 -0700 Members of H3K4 Trimethylation Complex Regulate Lifespan in a Germline-Dependent Manner in C. elegans http://moragabiotech.com/nucleus/index.php?itemid=975 Nature, scientists from Stanford University, E. L. Green et al., published their study on the relationship between histone methylation and longevity in round worms (C. elegans). The researchers noted that histone methylation is critically important in maintaining stem cell pluripotency in mammals, but not much is known regarding the mechanisms of methylation and aging. From their experimental results, the investigators identified ASH-2 tithorax complex as a key regulator of lifespan in C. elegans due to trimethylation of histone H3 at lysine 4 (H3K4). Additionally, the results revealed that deficiencies in members of the ASH-2 complex (either ASH-2, WDR-5, or methyltranferase SET-2) extended worm lifespan. It was also shown that H3K4 demethylase RBR-2 is required for normal lifespan, which supports the thesis that "excess H3K4 trimethylation is detrimental for longevity." Life extension by ASH-2 complex deficiencies also required an intact adult germline and the continuous production of mature eggs. The authors concluded from their experimental data that "ASH-2 and RBR-2 act in their germline, at least in part, to regulate lifespan and to control as sent of genes involved in lifespan determination." (It may also suggest that these complexes may also modulate the stem cell compartments in the worm?).
]]> General http://moragabiotech.com/nucleus/index.php?itemid=975 Thu, 24 Jun 2010 08:22:00 -0700 Long-term Self-Renewal of Human Pluripotent Stem Cells on Human Recombinant Laminin-511 http://moragabiotech.com/nucleus/index.php?itemid=974 Nature Biotechnology, S. Rodin et al. from the Karolinska Institute (Stockholm, Sweden) reported their study results in long-term propagation of human embryonic stem cells (ESCs) using a human recombinant protein, laminin-511 (α5, β1, γ1 chains) as a substrate, concomitant with defined medium supplemented with human albumin. The hESCS were propagated without feeder cells and the investigators were able to expand and passage (20) the cultures for at least 4 months without a loss in pluripotency. Following long-term cultivation, the scientists were able to differentiate the hESCs into cells all 3 germ layer lineages) as well as maintain the capacity to form teratomas. The researchers also reported that plating clumps of the hESCs onto laminin-511 allowed the cells to adhere to the substrate and form a monolayer culture while maintaining homogeneity in which the experimental results showed 97% of the cells were Oct4+. Adhesion to the substrate was dependent upon the hECC binding α6&beta1 integrin. The author noted that their recombinant substrate provides a novel approach for the generating a homogenous monolayer of hESCs or iPSCs cell cultures, which "provides more controllable conditions" for differentiating pluripotent stem cells down specific cell lineages for future therapeutic purposes.
]]> Embryonic Stem Cells http://moragabiotech.com/nucleus/index.php?itemid=974 Wed, 23 Jun 2010 10:14:00 -0700 Jarid2 Required for Multi-Lineage Differentiation of Embryonic Stem Cells http://moragabiotech.com/nucleus/index.php?itemid=973 Nature Cell Biology, D. Landiera et al. from the Imperial College School of Medicine (London, UK) reported in a letter their study results on identifying a novel subunit of the polycomb repressor complex 2 (PRC2), Jarid2, which regulates development/differentiation of mouse embryonic stem cells (ESCs). The investigators found that in Jarid2-deficient ESCs there were reduced histone methylation (HEK4me2/me3 and H3K27 me3) which mark recruitment of PRC1/PRC2. Additionally, lost of Jarid2 resulted in a reduced presence of phosphorlyated (Ser5P) RNA polymerase II (RNAP) at the target genes. This observation suggests that Jarid2 has role in also recruiting RNAP to the bivalent genes. The researchers also found ESCs lacking Jarid2 were severely compromised in their ability to differentiate into neural and mesodermal lineages. These mutant cells lack the ability to activated lineage-specific gene expression. The authors concluded from their observation "that transcriptional priming of bivalent genes in pluripotent ES cells is Jarid2-dependent, and suggests that priming is critical for subsequent multi-lineage differentiation."]]> Signaling and Pathways http://moragabiotech.com/nucleus/index.php?itemid=973 Tue, 22 Jun 2010 14:06:38 -0700
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