Resolving early mesoderm diversification through single-cell expression profiling.

In mammals, specification of the three major germ layers occurs during gastrulation, when cells ingressing through the primitive streak differentiate into the precursor cells of major organ systems. However, the molecular mechanisms underlying this process remain unclear, as numbers of gastrulating cells are very limited. In the mouse embryo at embryonic day 6.5, cells located at the junction between the extra-embryonic region and the epiblast on the posterior side of the embryo undergo an epithelial-to-mesenchymal transition and ingress through the primitive streak. Subsequently, cells migrate, either surrounding the prospective ectoderm contributing to the embryo proper, or into the extra-embryonic region to form the yolk sac, umbilical cord and placenta. Fate mapping has shown that mature tissues such as blood and heart originate from specific regions of the pre-gastrula epiblast, but the plasticity of cells within the embryo and the function of key cell-type-specific transcription factors remain unclear. Here we analyse 1,205 cells from the epiblast and nascent Flk1(+) mesoderm of gastrulating mouse embryos using single-cell RNA sequencing, representing the first transcriptome-wide in vivo view of early mesoderm formation during mammalian gastrulation. Additionally, using knockout mice, we study the function of Tal1, a key haematopoietic transcription factor, and demonstrate, contrary to previous studies performed using retrospective assays, that Tal1 knockout does not immediately bias precursor cells towards a cardiac fate.We thank M. de Bruijn, A. Martinez-Arias, J. Nichols and C. Mulas for discussion, the Cambridge Institute for Medical Research Flow Cytometry facility for their expertise in single-cell index sorting, and S. Lorenz from the Sanger Single Cell Genomics Core for supervising purification of Tal1−/− sequencing libraries. ChIP-seq reads were processed by R. Hannah. Research in the authors’ laboratories is supported by the Medical Research Council, Cancer Research UK, the Biotechnology and Biological Sciences Research Council, Bloodwise, the Leukemia and Lymphoma Society, and the Sanger-EBI Single Cell Centre, and by core support grants from the Wellcome Trust to the Cambridge Institute for Medical Research and Wellcome Trust - MRC Cambridge Stem Cell Institute and by core funding from Cancer Research UK and the European Molecular Biology Laboratory. Y.T. was supported by a fellowship from the Japan Society for the Promotion of Science. W.J. is a Wellcome Trust Clinical Research Fellow. A.S. is supported by the Sanger-EBI Single Cell Centre. This work was funded as part of Wellcome Trust Strategic Award 105031/D/14/Z ‘Tracing early mammalian lineage decisions by single-cell genomics’ awarded to W. Reik, S. Teichmann, J. Nichols, B. Simons, T. Voet, S. Srinivas, L. Vallier, B. Göttgens and J. Marioni.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1863

Epigenetic dysregulation of microRNA-9 in hepatocellular carcinoma (HCC)

The 21st Meeting of the European Association for Cancer Research (EACR 21), Oslo, Norway, 26-29 June 2010

SUV39H1 promotes HCC tumorigenesis and is targeted by tumor suppressive miRNA-125b

Poster Session 1 - Chromatin Regulators: abstract no. 1059Epigenetic alternation is a common dysregulated event in hepatocellular carcinoma (HCC) development. Through interrogating the expression of 90 major epigenetic regulating genes, we identified SUV39H1, the prototype histone methyltransferase as one of the most frequently up-regulated epigenetic regulators in human HCC (61%, 23/38). SUV39H1 is responsible for H3K9 trimethylation establishment and essentially involves in heterochromatin formation and transcriptional repression. We found that SUV39H1 up-regulation in human HCC was significantly associated with ...link_to_OA_fulltextThe Annual Meeting of the American Association for Cancer Research (AACR 2012), Chicago, IL., 31 March-4 April 2012

Annotaties bij de artikelen 734bis-sexies, 1253bus-octies, 1320-1322 en 1322bis-octies Ger. W.

Hepatocellular carcinoma (HCC) is a major liver malignancy. We previously demonstrated that deregulation of epigenetic regulators is a common event in human HCC. Suppressor of variegation 3-9 homolog 1 (SUV39H1), the prototype of histone methyltransferase, is the major enzyme responsible for histone H3 lysine 9 trimethylation, which, essentially, is involved in heterochromatin formation, chromosome segregation, and mitotic progression. However, the implication of SUV39H1 in hepatocarcinogenesis remains elusive. In this study, we found that SUV39H1 was frequently up-regulated in human HCCs and was significantly associated with increased Ki67 expression (P < 0.001) and the presence of venous invasion (P = 0.017). To investigate the role of SUV39H1 in HCC development, both gain- and loss-of-function models were established. SUV39H1 overexpression remarkably enhanced HCC cell clonogenicity, whereas knockdown of SUV39H1 substantially suppressed HCC cell proliferation and induced cell senescence. In addition, ectopic expression of SUV39H1 increased the migratory ability of HCC cells, whereas a reduced migration rate was observed in SUV39H1 knockdown cells. The significance of SUV39H1 in HCC was further demonstrated in a nude mice model; SUV39H1 knockdown drastically inhibited in vivo tumorigenicity and abolished pulmonary metastasis of HCC cells. We also identified microRNA-125b (miR-125b) as a post-transcriptional regulator of SUV39H1. Ectopic expression of miR-125b inhibited SUV39H1 3'-untranslated-region-coupled luciferase activity and suppressed endogenous SUV39H1 expression at both messenger RNA and protein levels. We have previously reported frequent down-regulation of miR-125b in HCC. Interestingly, miR-125b level was found to be inversely correlated with SUV39H1 expression (P = 0.001) in clinical specimens. Our observations suggested that miR-125b down-regulation may account for the aberrant SUV39H1 level in HCC. CONCLUSION: Our study demonstrated that SUV39H1 up-regulation contributed to HCC development and metastasis. The tumor-suppressive miR-125b served as a negative regulator of SUV39H1