@article{ShkilnyyGraefHiebletal.2009,
  author    = {Shkilnyy, Andriy and Gr{\"a}f, Ralph and Hiebl, Bernhard and Neffe, Axel T. and Friedrich, Alwin and Hartmann, Juergen and Taubert, Andreas},
  title     = {Unprecedented, low cytotoxicity of spongelike calcium phosphate/poly(ethylene imine) hydrogel composites},
  issn      = {1616-5187},
  doi       = {10.1002/mabi.200800266},
  year      = {2009},
  abstract  = {Covalently crosslinked PEI hydrogels are efficient templates for calcium phosphate mineralization in SBF. In contrast to the PEI hydrogels, non-crosslinked PEI does not lead to calcium phosphate nucleation and growth in SBF. The precipitate is a mixture of brushite and hydroxyapatite. The PEI/calcium phosphate composite material exhibits a sponge like morphology and a chemical composition that is interesting for implants. Cytotoxicity tests using Dictyostelium discoideum amoebae show that both the non-mineralized and mineralized hydrogels have a very low cytotoxicity. This suggests that next generation PEI hydrogels, where also the degradation products are non-toxic, could be interesting for biomedical applications.},
  language  = {en}
}
@article{GraefGrafeMeyeretal.2021,
  author    = {Gr{\"a}f, Ralph and Grafe, Marianne and Meyer, Irene and Mitic, Kristina and Pitzen, Valentin},
  title     = {The dictyostelium centrosome},
  series = {Cells : open access journal},
  volume    = {10},
  journal   = {Cells : open access journal},
  number    = {10},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2073-4409},
  doi       = {10.3390/cells10102657},
  pages     = {26},
  year      = {2021},
  abstract  = {The centrosome of Dictyostelium amoebae contains no centrioles and consists of a cylindrical layered core structure surrounded by a corona harboring microtubule-nucleating gamma-tubulin complexes. It is the major centrosomal model beyond animals and yeasts. Proteomics, protein interaction studies by BioID and superresolution microscopy methods led to considerable progress in our understanding of the composition, structure and function of this centrosome type. We discuss all currently known components of the Dictyostelium centrosome in comparison to other centrosomes of animals and yeasts.},
  language  = {en}
}
@article{MuellerWindhofMaximovetal.2013,
  author    = {M{\"u}ller, Sara and Windhof, Indra M. and Maximov, Vladimir and Jurkowski, Tomasz and Jeltsch, Albert and F{\"o}rstner, Konrad U. and Sharma, Cynthia M. and Gr{\"a}f, Ralph and Nellen, Wolfgang},
  title     = {Target recognition, RNA methylation activity and transcriptional regulation of the dictyostelium discoideum Dnmt2-homologue (DnmA)},
  series = {Nucleic acids research},
  volume    = {41},
  journal   = {Nucleic acids research},
  number    = {18},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0305-1048},
  doi       = {10.1093/nar/gkt634},
  pages     = {8615 -- 8627},
  year      = {2013},
  abstract  = {Although the DNA methyltransferase 2 family is highly conserved during evolution and recent reports suggested a dual specificity with stronger activity on transfer RNA (tRNA) than DNA substrates, the biological function is still obscure. We show that the Dictyostelium discoideum Dnmt2-homologue DnmA is an active tRNA methyltransferase that modifies C38 in tRNA(Asp(GUC)) in vitro and in vivo. By an ultraviolet-crosslinking and immunoprecipitation approach, we identified further DnmA targets. This revealed specific tRNA fragments bound by the enzyme and identified tRNA(Glu(CUC/UUC)) and tRNA(Gly(GCC)) as new but weaker substrates for both human Dnmt2 and DnmA in vitro but apparently not in vivo. Dnmt2 enzymes form transient covalent complexes with their substrates. The dynamics of complex formation and complex resolution reflect methylation efficiency in vitro. Quantitative PCR analyses revealed alterations in dnmA expression during development, cell cycle and in response to temperature stress. However, dnmA expression only partially correlated with tRNA methylation in vivo. Strikingly, dnmA expression in the laboratory strain AX2 was significantly lower than in the NC4 parent strain. As expression levels and binding of DnmA to a target in vivo are apparently not necessarily accompanied by methylation, we propose an additional biological function of DnmA apart from methylation.},
  language  = {en}
}
@misc{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 = {Potsprint der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Potsprint der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  number    = {682},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42597},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-425976},
  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}
}
@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}
}
@misc{BatsiosRenBaumannetal.2016,
  author    = {Batsios, Petros and Ren, Xiang and Baumann, Otto and Larochelle, Denis A. and Gr{\"a}f, Ralph},
  title     = {Src1 is a Protein of the Inner Nuclear Membrane Interacting with the Dictyostelium Lamin NE81},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-97033},
  pages     = {15},
  year      = {2016},
  abstract  = {The nuclear envelope (NE) consists of the outer and inner nuclear membrane (INM), whereby the latter is bound to the nuclear lamina. Src1 is a Dictyostelium homologue of the helix-extension-helix family of proteins, which also includes the human lamin-binding protein MAN1. Both endogenous Src1 and GFP-Src1 are localized to the NE during the entire cell cycle. Immuno-electron microscopy and light microscopy after differential detergent treatment indicated that Src1 resides in the INM. FRAP experiments with GFP-Src1 cells suggested that at least a fraction of the protein could be stably engaged in forming the nuclear lamina together with the Dictyostelium lamin NE81. Both a BioID proximity assay and mis-localization of soluble, truncated mRFP-Src1 at cytosolic clusters consisting of an intentionally mis-localized mutant of GFP-NE81 confirmed an interaction of Src1 and NE81. Expression GFP-Src11-646, a fragment C-terminally truncated after the first transmembrane domain, disrupted interaction of nuclear membranes with the nuclear lamina, as cells formed protrusions of the NE that were dependent on cytoskeletal pulling forces. Protrusions were dependent on intact microtubules but not actin filaments. Our results indicate that Src1 is required for integrity of the NE and highlight Dictyostelium as a promising model for the evolution of nuclear architecture.},
  language  = {en}
}
@article{BatsiosRenBaumannetal.2016,
  author    = {Batsios, Petros and Ren, Xiang and Baumann, Otto and Larochelle, Denis A. and Gr{\"a}f, Ralph},
  title     = {Src1 is a Protein of the Inner Nuclear Membrane Interacting with the Dictyostelium Lamin NE81},
  series = {Cells},
  volume    = {5},
  journal   = {Cells},
  number    = {1},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2073-4409},
  doi       = {10.3390/cells5010013},
  year      = {2016},
  abstract  = {The nuclear envelope (NE) consists of the outer and inner nuclear membrane (INM), whereby the latter is bound to the nuclear lamina. Src1 is a Dictyostelium homologue of the helix-extension-helix family of proteins, which also includes the human lamin-binding protein MAN1. Both endogenous Src1 and GFP-Src1 are localized to the NE during the entire cell cycle. Immuno-electron microscopy and light microscopy after differential detergent treatment indicated that Src1 resides in the INM. FRAP experiments with GFP-Src1 cells suggested that at least a fraction of the protein could be stably engaged in forming the nuclear lamina together with the Dictyostelium lamin NE81. Both a BioID proximity assay and mis-localization of soluble, truncated mRFP-Src1 at cytosolic clusters consisting of an intentionally mis-localized mutant of GFP-NE81 confirmed an interaction of Src1 and NE81. Expression GFP-Src11-646, a fragment C-terminally truncated after the first transmembrane domain, disrupted interaction of nuclear membranes with the nuclear lamina, as cells formed protrusions of the NE that were dependent on cytoskeletal pulling forces. Protrusions were dependent on intact microtubules but not actin filaments. Our results indicate that Src1 is required for integrity of the NE and highlight Dictyostelium as a promising model for the evolution of nuclear architecture.},
  language  = {en}
}
@misc{GraefSecklerHagemannetal.2012,
  author    = {Gr{\"a}f, Ralph and Seckler, Robert and Hagemann, Alfred and D'Aprile, Iwan-Michelangelo and Schulte, Christoph and Zimmermann, Matthias and Blom, Hans and Horn-Conrad, Antje and Kampe, Heike and J{\"a}ger, Sophie and Haase, Jana and Eckardt, Barbara and Priebs-Tr{\"o}ger, Astrid and Walz, Bernd},
  title     = {Portal Wissen = Raum},
  number    = {01/2012},
  organization    = {Universit{\"a}t Potsdam, Referat f{\"u}r Presse- und {\"O}ffentlichkeitsarbeit},
  issn      = {2194-4237},
  doi       = {10.25932/publishup-44078},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-440785},
  pages     = {98},
  year      = {2012},
  abstract  = {Mit „Portal Wissen" laden wir Sie ein, die Forschung an der Universit{\"a}t Potsdam zu entdecken und in ihrer Vielfalt kennenzulernen. In der ersten Ausgabe dreht sich alles um „R{\"a}ume". R{\"a}ume, in denen geforscht wird, solche, die es zu erforschen gilt, andere, die durch Wissenschaft zug{\"a}nglich oder erschlossen werden, aber auch R{\"a}ume, die Wissenschaft braucht, um sich entfalten zu k{\"o}nnen. Forschung vermisst R{\"a}ume: „Wissenschaft wird von Menschen gemacht", schrieb der Physiker Werner Heisenberg. Umgekehrt l{\"a}sst sich sagen: Wissenschaft macht Menschen, widmet sich ihnen, beeinflusst sie. Dieser Beziehung ist „Portal Wissen" nachgegangen. Wir haben Wissenschaftler getroffen, sie gefragt, wie aus ihren Fragen Projekte entstehen, haben sie auf dem oft verschlungenen Weg zum Ziel begleitet. Ein besonderes Augenmerk dieses Heftes gilt den „Kulturellen Begegnungsr{\"a}umen", denen ein eigener Profilbereich der Forschung an der Universit{\"a}t Potsdam gewidmet ist. Forschung hat R{\"a}ume: Labore, Bibliotheken, Gew{\"a}chsh{\"a}user oder Archive - hier ist Wissenschaft zu Liebe Leserinnen und Leser, Hause. All diese Orte sind so einzigartig wie die Wissenschaftler, die in ihnen arbeiten, oder die Untersuchungen, die hier stattfinden. Erst die Vision davon, wie ein Problem zu l{\"o}sen ist, macht aus einfachen Zimmern „Laborr{\"a}ume". Wir haben ihre T{\"u}ren ge{\"o}ffnet, um zu zeigen, was - und wer - sich dahinter befindet. Forschung er{\"o}ffnet R{\"a}ume: Wenn Wissenschaft erfolgreich ist, bewegt sie uns, bringt uns voran. Auf dem Weg einer wissenschaftlichen Erkenntnis aus dem Labor in den Alltag stehen mitunter H{\"u}rden, die meist nicht auf den ersten Blick zu erkennen sind. Auf jeden Fall aber ist ihre Anwendung erster Ausgangspunkt von Wissenschaft, Antrieb und Motivation jedes Forschers. „Portal Wissen" zeigt, welche „Praxisr{\"a}ume" sich aus der {\"U}bersetzung von Forschungsresultaten ergeben. Dort, wo wir es unbedingt erwarten, und dort, wo vielleicht nicht. Forschung erschließt R{\"a}ume: Bei Expeditionen, Feldversuchen und Exkursionen wird nahezu jede Umgebung zum mobilen Labor. So er{\"o}ffnet Wissenschaft Zug{\"a}nge auch zu Orten, die auf vielfach andere Weise verschlossen oder unzug{\"a}nglich scheinen. Wir haben uns in Forscher- Reisetaschen gemogelt, um bei Entdeckungsreisen dabei zu sein, die weit weg - vor allem nach Afrika - f{\"u}hren. Zugleich haben wir beobachtet, wie „Entwicklungsr{\"a}ume" sich auch von Potsdam aus erschließen lassen oder zumindest ihre Vermessung in Potsdam beginnen kann. Forschung braucht R{\"a}ume: Wissenschaft hat zwei Geschlechter, endlich. Noch nie waren so viele Frauen in der Forschung t{\"a}tig wie derzeit. Ein Grund zum Ausruhen ist dies gleichwohl nicht. Deutschlandweit ist aktuell nur jede f{\"u}nfte Professur von einer Frau besetzt. „Portal Wissen" schaut, welche „Entwicklungsr{\"a}ume" Frauen sich in der Wissenschaft, aber auch dar{\"u}ber hinaus geschaffen haben. Und wo sie ihnen verwehrt werden. Wir w{\"u}nschen Ihnen eine anregende Lekt{\"u}re und dass auch Sie einen Raum finden, der Sie inspiriert. Prof. Dr. Robert Seckler Vizepr{\"a}sident f{\"u}r Forschung und wissenschaftlichen Nachwuchs},
  language  = {de}
}
@article{BatsiosGraefKoonceetal.2019,
  author    = {Batsios, Petros and Gr{\"a}f, Ralph and Koonce, Michael P. and Larochelle, Denis A. and Meyer, Irene},
  title     = {Nuclear envelope organization in Dictyostelium discoideum},
  series = {The international journal of developmental biology},
  volume    = {63},
  journal   = {The international journal of developmental biology},
  number    = {8-10},
  publisher = {UBC Pr},
  address   = {Bilbao},
  issn      = {0214-6282},
  doi       = {10.1387/ijdb.190184rg},
  pages     = {509 -- 519},
  year      = {2019},
  abstract  = {The nuclear envelope consists of the outer and the inner nuclear membrane, the nuclear lamina and the nuclear pore complexes, which regulate nuclear import and export.The major constituent of the nuclear lamina of Dictyostelium is the lamin NE81. It can form filaments like B-type lamins and it interacts with Sun 1, as well as with the LEM/HeH-family protein Src1. Sun 1 and Src1 are nuclear envelope transmembrane proteins involved in the centrosome-nucleus connection and nuclear envelope stability at the nucleolar regions, respectively. In conjunction with a KASH-domain protein, Sun 1 usually forms a so-called LINC complex.Two proteins with functions reminiscent of KASH-domain proteins at the outer nuclear membrane of Dictyostelium are known; interaptin which serves as an actin connector and the kinesin Kif9 which plays a role in the microtubule-centrosome connector. However, both of these lack the conserved KASH-domain. The link of the centrosome to the nuclear envelope is essential for the insertion of the centrosome into the nuclear envelope and the appropriate spindle formation. Moreover, centrosome insertion is involved in perm eabilization of the mitotic nucleus, which ensures access of tubulin dimers and spindle assembly factors. Our recent progress in identifying key molecular players at the nuclear envelope of Dictyostelium promises further insights into the mechanisms of nuclear envelope dynamics.},
  language  = {en}
}
@article{KraemerRavindranZaqoutetal.2015,
  author    = {Kr{\"a}mer, Nadine and Ravindran, Ethiraj and Zaqout, Sami and Neubert, Gerda and Schindler, Detlev and Ninnemann, Olaf and Gr{\"a}f, Ralph and Seiler, Andrea E. M. and Kaindl, Angela M.},
  title     = {Loss of CDK5RAP2 affects neural but not non-neural mESC differentiation into cardiomyocytes},
  series = {Cell cycle},
  volume    = {14},
  journal   = {Cell cycle},
  number    = {13},
  publisher = {Taylor \& Francis Group},
  address   = {Philadelphia},
  issn      = {1538-4101},
  doi       = {10.1080/15384101.2015.1044169},
  pages     = {2044 -- 2057},
  year      = {2015},
  abstract  = {Biallelic mutations in the gene encoding centrosomal CDK5RAP2 lead to autosomal recessive primary microcephaly (MCPH), a disorder characterized by pronounced reduction in volume of otherwise architectonical normal brains and intellectual deficit. The current model for the microcephaly phenotype in MCPH invokes a premature shift from symmetric to asymmetric neural progenitor-cell divisions with a subsequent depletion of the progenitor pool. The isolated neural phenotype, despite the ubiquitous expression of CDK5RAP2, and reports of progressive microcephaly in individual MCPH cases prompted us to investigate neural and non-neural differentiation of Cdk5rap2-depleted and control murine embryonic stem cells (mESC). We demonstrate an accumulating proliferation defect of neurally differentiating Cdk5rap2-depleted mESC and cell death of proliferative and early postmitotic cells. A similar effect does not occur in non-neural differentiation into beating cardiomyocytes, which is in line with the lack of non-central nervous system features in MCPH patients. Our data suggest that MCPH is not only caused by premature differentiation of progenitors, but also by reduced propagation and survival of neural progenitors.},
  language  = {en}
}