@article{9495,
  abstract     = {RNA interference is a conserved process in which double-stranded RNA is processed into 21–25 nucleotide siRNAs that trigger posttranscriptional gene silencing. In addition, plants display a phenomenon termed RNA-directed DNA methylation (RdDM) in which DNA with sequence identity to silenced RNA is de novo methylated at its cytosine residues. This methylation is not only at canonical CpG sites but also at cytosines in CpNpG and asymmetric sequence contexts. In this report, we study the role of the DRM and CMT3 DNA methyltransferase genes in the initiation and maintenance of RdDM. Neither drm nor cmt3 mutants affected the maintenance of preestablished RNA-directed CpG methylation. However, drm mutants showed a nearly complete loss of asymmetric methylation and a partial loss of CpNpG methylation. The remaining asymmetric and CpNpG methylation was dependent on the activity of CMT3, showing that DRM and CMT3 act redundantly to maintain non-CpG methylation. These DNA methyltransferases appear to act downstream of siRNAs, since drm1 drm2 cmt3 triple mutants show a lack of non-CpG methylation but elevated levels of siRNAs. Finally, we demonstrate that DRM activity is required for the initial establishment of RdDM in all sequence contexts including CpG, CpNpG, and asymmetric sites.},
  author       = {Cao, Xiaofeng and Aufsatz, Werner and Zilberman, Daniel and Mette, M.Florian and Huang, Michael S. and Matzke, Marjori and Jacobsen, Steven E.},
  issn         = {1879-0445},
  journal      = {Current Biology},
  number       = {24},
  pages        = {2212--2217},
  publisher    = {Elsevier},
  title        = {{Role of the DRM and CMT3 methyltransferases in RNA-directed DNA methylation}},
  doi          = {10.1016/j.cub.2003.11.052},
  volume       = {13},
  year         = {2003},
}

@article{4169,
  abstract     = {Background: During vertebrate gastrulation, cell polarization and migration are core components in the cellular rearrangements that lead to the formation of the three germ layers, ectoderm, mesoderm, and endoderm. Previous studies have implicated the Wnt/planar cell polarity (PCP) signaling pathway in controlling cell morphology and movement during gastrulation. However, cell polarization and directed cell migration are reduced but not completely abolished in the absence of Wnt/PCP signals; this observation indicates that other signaling pathways must be involved. Results: We show that Phosphoinositide 3-Kinases (PI3Ks) are required at the onset of zebrafish gastrulation in mesendodermal cells for process formation and cell polarization. Platelet Derived Growth Factor (PDGF) functions upstream of PI3K, while Protein Kinase B (PKB), a downstream effector of PI3K activity, localizes to the leading edge of migrating mesendodermal cells. In the absence of PI3K activity, PKB localization and cell polarization are strongly reduced in mesendodermal cells and are followed by slower but still highly coordinated and directed movements of these cells. Conclusions: We have identified a novel role of a signaling pathway comprised of PDGF, PI3K, and PKB in the control of morphogenetic cell movements during gastrulation. Furthermore, our findings provide insight into the relationship between cell polarization and directed cell migration at the onset of zebrafish gastrulation.},
  author       = {Montero, Juan and Kilian, Beate and Chan, Joanne and Bayliss, Peter and Heisenberg, Carl-Philipp J},
  issn         = {1879-0445},
  journal      = {Current Biology},
  number       = {15},
  pages        = {1279 -- 1289},
  publisher    = {Cell Press},
  title        = {{Phosphoinositide 3-kinase is required for process outgrowth and cell polarization of gastrulating mesendodermal cells}},
  doi          = {10.1016/S0960-9822(03)00505-0},
  volume       = {13},
  year         = {2003},
}