Jeong Beom Kim1,Vittorio Sebastiano1,Guangming Wu1,Marcos J. Araúzo-Bravo1,Philipp Sasse2,Luca Gentile1,Kinarm Ko1,David Ruau3,Mathias Ehrich4,Dirk van den Boom4,Johann Meyer5,Karin Hübner1,Christof Bernemann1,Claudia Ortmeier1,Martin Zenke3,Bernd K. Fleischmann2,Holm Zaehres1andHans R. Schöler1,Go To Corresponding Author,

1 Department of Cell and Developmental Biology, Max Planck Institute for Molecular Biomedicine, Röntgenstrasse 20, 48149 Münster, NRW, Germany
2 Institute of Physiology I, Life & Brain Center, University of Bonn, 53105 Bonn, NRW, Germany
3 Institute for Biomedical Engineering, Department of Cell Biology, RWTH Aachen University Medical School, Pauwelsstrasse 30, 52074 Aachen, NRW, Germany
4 SEQUENOM Inc., 3595 John Hopkins Court, San Diego, CA 92121, USA
5 Hannover Medical School, Department of Experimental Hematology, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
Corresponding author


Summary

The four transcription factors Oct4, Sox2, Klf4, and c-Myc can induce pluripotency in mouse and human fibroblasts. We previously described direct reprogramming of adult mouse neural stem cells (NSCs) by Oct4 and either Klf4 or c-Myc. NSCs endogenously express Sox2, c-Myc, and Klf4 as well as several intermediate reprogramming markers. Here we report that exogenous expression of the germline-specific transcription factor Oct4 is sufficient to generate pluripotent stem cells from adult mouse NSCs. These one-factor induced pluripotent stem cells (1F iPS) are similar to embryonic stem cells invitro and invivo. Not only can these cells can be efficiently differentiated into NSCs, cardiomyocytes, and germ cells invitro, but they are also capable of teratoma formation and germline transmission invivo. Our results demonstrate that Oct4 is required and sufficient to directly reprogram NSCs to pluripotency.

Cell, Volume 136, Issue 3, 411-419, 6 February 2009

Tags: Oct4, Stem Cell, Reprogramming, Pluripotency

Vascular development begins when mesodermal cells differentiate into endothelial cells, which then form primitive vessels. It has been hypothesized that endothelial-specific gene expression may be regulated combinatorially, but the transcriptional mechanisms governing specificity in vascular gene expression remain incompletely understood. Here, we identify a 44 bp transcriptional enhancer that is sufficient to direct expression specifically and exclusively to the developing vascular endothelium. This enhancer is regulated by a composite cis-acting element, the FOX:ETS motif, which is bound and synergistically activated by Forkhead and Ets transcription factors. We demonstrate that coexpression of the Forkhead protein FoxC2 and the Ets protein Etv2 induces ectopic expression of vascular genes in Xenopus embryos, and that combinatorial knockdown of the orthologous genes in zebrafish embryos disrupts vascular development. Finally, we show that FOX:ETS motifs are present in many known endothelial-specific enhancers and that this motif is an efficient predictor of endothelial enhancers in the human genome.

Cell, Volume 135, Issue 6, 1053-1064, 12 December 2008

The extracellular-regulated kinases ERK1 and ERK2 (commonly referred to as ERK1/2) have a crucial role in cardiac hypertrophy. ERK1/2 is activated by mitogen-activated protein kinase kinase-1 (MEK1) and MEK2 (commonly referred to as MEK1/2)-dependent phosphorylation in the TEY motif of the activation loop, but how ERK1/2 is targeted toward specific substrates is not well understood. Here we show that autophosphorylation of ERK1/2 on Thr188 directs ERK1/2 to phosphorylate nuclear targets known to cause cardiac hypertrophy. Thr188 autophosphorylation requires the activation and assembly of the entire Raf-MEK-ERK kinase cascade, phosphorylation of the TEY motif, dimerization of ERK1/2 and binding to G protein βγ subunits released from activated Gq. Thr188 phosphorylation of ERK1/2 was observed in isolated cardiomyocytes induced to undergo hypertrophic growth, in mice upon stimulation of Gq-coupled receptors or after aortic banding and in failing human hearts. Experiments using transgenic mouse models carrying mutations at the Thr188 phosphorylation site of ERK2 suggested a causal relationship to cardiac hypertrophy. We propose that specific phosphorylation events on ERK1/2 integrate differing upstream signals (Raf1-MEK1/2 or G protein–coupled receptor–Gq) to induce cardiac hypertrophy.

Nature Medicine aop, (7 December 2008) | doi:10.1038/nm.1893;

RNA polymerases are highly regulated molecular machines. We present a method (GRO-seq) that maps the position, amount, and orientation of transcriptionally engaged RNA polymerases genome-wide. In this method, nuclear run-on RNAs are subjected to large-scale parallel sequencing and mapped to the genome. Here, we show that peaks of promoter-proximal polymerase reside on ~30% of human genes, transcription extends beyond pre-mRNA 3’ cleavage, and antisense transcription is prevalent. Additionally, most promoters have an engaged polymerase upstream and in an orientation opposite to the annotated gene. This divergent polymerase is associated with active genes, but does not elongate effectively beyond the promoter. These results imply that the interplay between polymerases and regulators over broad promoter regions dictates the orientation and efficiency of productive transcription.

Published Online December 4, 2008
Science DOI: 10.1126/science.1162228