@article{SchweigelBatsiosMuellerTaubenbergeretal.2022,
  author    = {Schweigel, Ulrike and Batsios, Petros and M{\"u}ller-Taubenberger, Annette and Gr{\"a}f, Ralph and Grafe, Marianne},
  title     = {Dictyostelium spastin is involved in nuclear envelope dynamics during semi-closed mitosis},
  series = {Nucleus},
  volume    = {13},
  journal   = {Nucleus},
  number    = {1},
  publisher = {Taylor \& Francis Group},
  address   = {Philadelphia},
  issn      = {1949-1034},
  doi       = {10.1080/19491034.2022.2047289},
  pages     = {144 -- 154},
  year      = {2022},
  abstract  = {Dictyostelium amoebae perform a semi-closed mitosis, in which the nuclear envelope is fenestrated at the insertion sites of the mitotic centrosomes and around the central spindle during karyokinesis. During late telophase the centrosome relocates to the cytoplasmic side of the nucleus, the central spindle disassembles and the nuclear fenestrae become closed. Our data indicate that Dictyostelium spastin (DdSpastin) is a microtubule-binding and severing type I membrane protein that plays a role in this process. Its mitotic localization is in agreement with a requirement for the removal of microtubules that would hinder closure of the fenestrae. Furthermore, DdSpastin interacts with the HeH/ LEM-family protein Src1 in BioID analyses as well as the inner nuclear membrane protein Sun1, and shows subcellular co-localizations with Src1, Sun1, the ESCRT component CHMP7 and the IST1-like protein filactin, suggesting that the principal pathway of mitotic nuclear envelope remodeling is conserved between animals and Dictyostelium amoebae.},
  language  = {en}
}
@article{GrafeHofmannBatsiosetal.2020,
  author    = {Grafe, Marianne and Hofmann, Phillip and Batsios, Petros and Meyer, Irene and Gr{\"a}f, Ralph},
  title     = {In vivo assembly of a Dictyostelium lamin mutant induced by light, mechanical stress, and pH},
  series = {Cells : open access journal},
  volume    = {9},
  journal   = {Cells : open access journal},
  number    = {8},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2073-4409},
  doi       = {10.3390/cells9081834},
  pages     = {14},
  year      = {2020},
  abstract  = {We expressedDictyosteliumlamin (NE81) lacking both a functional nuclear localization signal and a CAAX-box for C-terminal lipid modification. This lamin mutant assembled into supramolecular, three-dimensional clusters in the cytosol that disassembled at the onset of mitosis and re-assembled in late telophase, thus mimicking the behavior of the endogenous protein. As disassembly is regulated by CDK1-mediated phosphorylation at serine 122, we generated a phosphomimetic S122E mutant called GFP-NE81-S122E-Delta NLS Delta CLIM. Surprisingly, during imaging, the fusion protein assembled into cytosolic clusters, similar to the protein lacking the phosphomimetic mutation. Clusters disassembled again in the darkness. Assembly could be induced with blue but not green or near ultraviolet light, and it was independent of the fusion tag. Assembly similarly occurred upon cell flattening. Earlier reports and own observations suggested that both blue light and cell flattening could result in a decrease of intracellular pH. Indeed, keeping the cells at low pH also reversibly induced cluster formation. Our results indicate that lamin assembly can be induced by various stress factors and that these are transduced via intracellular acidification. Although these effects have been shown in a phosphomimetic CDK1 mutant of theDictyosteliumlamin, they are likely relevant also for wild-type lamin.},
  language  = {en}
}
@article{GrafeHofmannBatsiosetal.2020,
  author    = {Grafe, Marianne and Hofmann, Phillip and Batsios, Petros and Meyer, Irene and Gr{\"a}f, Ralph},
  title     = {In vivo assembly of a Dictyostelium lamin mutant induced by light, mechanical stress, and pH},
  series = {Cells},
  volume    = {9},
  journal   = {Cells},
  number    = {8},
  publisher = {MDPI},
  address   = {Basel},
  pages     = {14},
  year      = {2020},
  abstract  = {We expressed Dictyostelium lamin (NE81) lacking both a functional nuclear localization signal and a CAAX-box for C-terminal lipid modification. This lamin mutant assembled into supramolecular, three-dimensional clusters in the cytosol that disassembled at the onset of mitosis and re-assembled in late telophase, thus mimicking the behavior of the endogenous protein. As disassembly is regulated by CDK1-mediated phosphorylation at serine 122, we generated a phosphomimetic S122E mutant called GFP-NE81-S122E-∆NLS∆CLIM. Surprisingly, during imaging, the fusion protein assembled into cytosolic clusters, similar to the protein lacking the phosphomimetic mutation. Clusters disassembled again in the darkness. Assembly could be induced with blue but not green or near ultraviolet light, and it was independent of the fusion tag. Assembly similarly occurred upon cell flattening. Earlier reports and own observations suggested that both blue light and cell flattening could result in a decrease of intracellular pH. Indeed, keeping the cells at low pH also reversibly induced cluster formation. Our results indicate that lamin assembly can be induced by various stress factors and that these are transduced via intracellular acidification. Although these effects have been shown in a phosphomimetic CDK1 mutant of the Dictyostelium lamin, they are likely relevant also for wild-type lamin.},
  language  = {en}
}
@article{GrafeBatsiosMeyeretal.2019,
  author    = {Grafe, Marianne and Batsios, Petros and Meyer, Irene and Lisin, Daria and Baumann, Otto and Goldberg, Martin W. and Gr{\"a}f, Ralph},
  title     = {Supramolecular Structures of the Dictyostelium Lamin NE81},
  series = {Cells},
  volume    = {8},
  journal   = {Cells},
  number    = {2},
  publisher = {Molecular Diversity Preservation International},
  address   = {Basel},
  issn      = {2073-4409},
  doi       = {10.3390/cells8020162},
  pages     = {17},
  year      = {2019},
  abstract  = {Nuclear lamins are nucleus-specific intermediate filaments (IF) found at the inner nuclear membrane (INM) of the nuclear envelope (NE). Together with nuclear envelope transmembrane proteins, they form the nuclear lamina and are crucial for gene regulation and mechanical robustness of the nucleus and the whole cell. Recently, we characterized Dictyostelium NE81 as an evolutionarily conserved lamin-like protein, both on the sequence and functional level. Here, we show on the structural level that the Dictyostelium NE81 is also capable of assembling into filaments, just as metazoan lamin filament assemblies. Using field-emission scanning electron microscopy, we show that NE81 expressed in Xenopous oocytes forms filamentous structures with an overall appearance highly reminiscent of Xenopus lamin B2. The in vitro assembly properties of recombinant His-tagged NE81 purified from Dictyostelium extracts are very similar to those of metazoan lamins. Super-resolution stimulated emission depletion (STED) and expansion microscopy (ExM), as well as transmission electron microscopy of negatively stained purified NE81, demonstrated its capability of forming filamentous structures under low-ionic-strength conditions. These results recommend Dictyostelium as a non-mammalian model organism with a well-characterized nuclear envelope involving all relevant protein components known in animal cells.},
  language  = {en}
}