Tsikolia, Nikoloz

[["dc.bibliographiccitation.artnumber","4"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","EvoDevo"],["dc.bibliographiccitation.volume","9"],["dc.contributor.author","Kremnyov, Stanislav"],["dc.contributor.author","Viebahn, Christoph"],["dc.contributor.author","Tsikolia, Nikoloz"],["dc.contributor.author","Henningfeld, Kristine A."],["dc.date.accessioned","2018-04-18T14:43:20Z"],["dc.date.accessioned","2021-10-27T13:21:04Z"],["dc.date.available","2018-04-18T14:43:20Z"],["dc.date.available","2021-10-27T13:21:04Z"],["dc.date.issued","2018-01-31"],["dc.date.updated","2018-04-18T14:43:20Z"],["dc.description.abstract","Abstract Background The notochord has organizer properties and is required for floor plate induction and dorsoventral patterning of the neural tube. This activity has been attributed to sonic hedgehog (shh) signaling, which originates in the notochord, forms a gradient, and autoinduces shh expression in the floor plate. However, reported data are inconsistent and the spatiotemporal development of the relevant shh expression domains has not been studied in detail. We therefore studied the expression dynamics of shh in rabbit, chicken and Xenopus laevis embryos (as well as indian hedgehog and desert hedgehog as possible alternative functional candidates in the chicken). Results Our analysis reveals a markedly divergent pattern within these vertebrates: whereas in the rabbit shh is first expressed in the notochord and its floor plate domain is then induced during subsequent somitogenesis stages, in the chick embryo shh is expressed in the prospective neuroectoderm prior to the notochord formation and, interestingly, prior to mesoderm immigration. Neither indian hedgehog nor desert hedgehog are expressed in these midline structures although mRNA of both genes was detected in other structures of the early chick embryo. In X. laevis, shh is expressed at the beginning of gastrulation in a distinct area dorsal to the dorsal blastopore lip and adjacent to the prospective neuroectoderm, whereas the floor plate expresses shh at the end of gastrulation. Conclusions While shh expression patterns in rabbit and X. laevis embryos are roughly compatible with the classical view of “ventral to dorsal induction” of the floor plate, the early shh expression in the chick floor plate challenges this model. Intriguingly, this alternative sequence of domain induction is related to the asymmetrical morphogenesis of the primitive node and other axial organs in the chick. Our results indicate that the floor plate in X. laevis and chick embryos may be initially induced by planar interaction within the ectoderm or epiblast. Furthermore, we propose that the mode of the floor plate induction adapts to the variant topography of interacting tissues during gastrulation and notochord formation and thereby reveals evolutionary plasticity of early embryonic induction."],["dc.identifier.doi","10.1186/s13227-017-0090-x"],["dc.identifier.pmid","29423139"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/15170"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/91992"],["dc.language.iso","en"],["dc.language.rfc3066","en"],["dc.notes.intern","Migrated from goescholar"],["dc.relation.issn","2041-9139"],["dc.relation.orgunit","Universitätsmedizin Göttingen"],["dc.rights","CC BY 4.0"],["dc.rights.holder","The Author(s)"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0"],["dc.subject.ddc","610"],["dc.title","Divergent axial morphogenesis and early shh expression in vertebrate prospective floor plate"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","957211"],["dc.bibliographiccitation.journal","Frontiers in Cell and Developmental Biology"],["dc.bibliographiccitation.volume","10"],["dc.contributor.affiliation","Negretti, Maria Isabella; \r\n1\r\nAnatomy and Embryology, University Medical Center Göttingen, Göttingen, Germany"],["dc.contributor.affiliation","Böse, Nina; \r\n1\r\nAnatomy and Embryology, University Medical Center Göttingen, Göttingen, Germany"],["dc.contributor.affiliation","Petri, Natalia; \r\n2\r\nDepartment of Embryology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia"],["dc.contributor.affiliation","Kremnyov, Stanislav; \r\n2\r\nDepartment of Embryology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia"],["dc.contributor.affiliation","Tsikolia, Nikoloz; \r\n1\r\nAnatomy and Embryology, University Medical Center Göttingen, Göttingen, Germany"],["dc.contributor.author","Negretti, Maria Isabella"],["dc.contributor.author","Böse, Nina"],["dc.contributor.author","Petri, Natalia"],["dc.contributor.author","Kremnyov, Stanislav"],["dc.contributor.author","Tsikolia, Nikoloz"],["dc.date.accessioned","2022-10-04T10:21:48Z"],["dc.date.available","2022-10-04T10:21:48Z"],["dc.date.issued","2022"],["dc.date.updated","2022-11-11T13:13:24Z"],["dc.description.abstract","Development of visceral left–right asymmetry in bilateria is based on initial symmetry breaking followed by subsequent asymmetric molecular patterning. An important step is the left-sided expression of transcription factor\r\n pitx2\r\n which is mediated by asymmetric expression of the\r\n nodal\r\n morphogen in the left lateral plate mesoderm of vertebrates. Processes leading to emergence of the asymmetric\r\n nodal\r\n domain differ depending on the mode of symmetry breaking. In\r\n Xenopus laevis\r\n and mouse embryos, the leftward fluid flow on the ventral surface of the left–right organizer leads through intermediate steps to enhanced activity of the nodal protein on the left side of the organizer and subsequent asymmetric\r\n nodal\r\n induction in the lateral plate mesoderm. In the chick embryo, asymmetric morphogenesis of axial organs leads to paraxial\r\n nodal\r\n asymmetry during the late gastrulation stage. Although it was shown that hedgehog signaling is required for initiation of the\r\n nodal\r\n expression, the mechanism of its asymmetry remains to be clarified. In this study, we established the activation of hedgehog signaling in early chick embryos to further study its role in the initiation of asymmetric\r\n nodal\r\n expression. Our data reveal that hedgehog signaling is sufficient to induce the\r\n nodal\r\n expression in competent domains of the chick embryo, while treatment of\r\n Xenopus\r\n embryos led to moderate\r\n nodal\r\n inhibition. We discuss the role of symmetry breaking and competence in the initiation of asymmetric gene expression."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2022"],["dc.identifier.doi","10.3389/fcell.2022.957211"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/114505"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-600"],["dc.publisher","Frontiers Media S.A."],["dc.relation.eissn","2296-634X"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Nodal asymmetry and hedgehog signaling during vertebrate left–right symmetry breaking"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1010"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Journal of Anatomy"],["dc.bibliographiccitation.lastpage","1022"],["dc.bibliographiccitation.volume","238"],["dc.contributor.author","Schäfer, Tobias"],["dc.contributor.author","Stankova, Viktoria"],["dc.contributor.author","Viebahn, Christoph"],["dc.contributor.author","Bakker, Bernadette"],["dc.contributor.author","Tsikolia, Nikoloz"],["dc.date.accessioned","2021-04-14T08:31:28Z"],["dc.date.available","2021-04-14T08:31:28Z"],["dc.date.issued","2020"],["dc.description.abstract","Abstract Bilaterally symmetrical primordia of visceral organs undergo asymmetrical morphogenesis leading to typical arrangement of visceral organs in the adult. Asymmetrical morphogenesis within the upper abdomen leads, among others, to the formation of the omental bursa dorsally to the rotated stomach. A widespread view of this process assumes kinking of thin mesenteries as a main mechanism. This view is based on a theory proposed already by Johannes Müller in 1830 and was repeatedly criticized, but some of the most plausible alternative views (initially proposed by Swaen in 1897 and Broman in 1904) still remain to be proven. Here, we analyzed serial histological sections of human embryos between stages 12 and 15 at high light microscopical resolution to reveal the succession of events giving rise to the development of the omental bursa and its relation to the emerging stomach asymmetry. Our analysis indicates that morphological symmetry breaking in the upper abdomen occurs within a wide mesenchymal plate called here mesenteric septum and is based on differential behavior of the coelomic epithelium which causes asymmetric paragastric recess formation and, importantly, precedes initial rotation of stomach. Our results thus provide the first histological evidence of breaking the symmetry of the early foregut anlage in the human embryo and pave the way for experimental studies of left‐right symmetry breaking in the upper abdomen in experimental model organisms."],["dc.description.sponsorship","De Snoo – van ’t Hoogerhuijs Foundation"],["dc.identifier.doi","10.1111/joa.13344"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/83606"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-399"],["dc.relation.eissn","1469-7580"],["dc.relation.issn","0021-8782"],["dc.rights","This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made."],["dc.title","Initial morphological symmetry breaking in the foregut and development of the omental bursa in human embryos"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1339"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Journal of Morphology"],["dc.bibliographiccitation.lastpage","1361"],["dc.bibliographiccitation.volume","282"],["dc.contributor.author","Harmoush, Braah"],["dc.contributor.author","Tsikolia, Nikoloz"],["dc.contributor.author","Viebahn, Christoph"],["dc.date.accessioned","2021-08-12T07:45:15Z"],["dc.date.available","2021-08-12T07:45:15Z"],["dc.date.issued","2021"],["dc.description.abstract","Abstract The epiblast of the amniote embryo is of paramount importance during early development as it gives rise to all tissues of the embryo proper. In mammals, it emerges through segregation of the hypoblast from the inner cell mass and subsequently undergoes transformation into an epithelial sheet to create the embryonic disc. In rodents and man, the epiblast cell layer is covered by the polar trophoblast which forms the placenta. In mammalian model organisms (rabbit, pig, several non‐human primates), however, the placenta is formed by mural trophoblast whereas the polar trophoblast disintegrates prior to gastrulation and thus exposes the epiblast to the microenvironment of the uterine cavity. Both, polar trophoblast disintegration and epiblast epithelialization, thus pose special cell‐biological requirements but these are still rather ill‐understood when compared to those of gastrulation morphogenesis. This study therefore applied high‐resolution light and transmission electron microscopy and three‐dimensional (3D) reconstruction to 8‐ to 10‐days‐old pig embryos and defines the following steps of epiblast transformation: (1) rosette formation in the center of the ball‐shaped epiblast, (2) extracellular cavity formation in the rosette center, (3) epiblast segregation into two subpopulations ‐ addressed here as dorsal and ventral epiblast ‐ separated by a “pro‐amniotic” cavity. Ventral epiblast cells form between them a special type of desmosomes with a characteristic dense felt of microfilaments and are destined to generate the definitive epiblast. The dorsal epiblast remains a mass of non‐polarized cells and closely associates with the disintegrating polar trophoblast, which shows morphological features of both apoptosis and autophagocytosis. Morphogenesis of the definitive epiblast in the pig may thus exclude a large portion of bona fide epiblast cells from contributing to the embryo proper and establishes contact de novo with the mural trophoblast at the junction between the two newly defined epiblast cell populations."],["dc.description.abstract","Correlative light and electron microscopy revealed novel subcellular features as signs of unexpected morphogenetic processes in newly defined sub‐stages and sub‐regions during epiblast epithelialization and trophoblast re‐organization of the late pre‐gastrulation pig embryo (between 8 and 10 days post coitum). The results re‐emphasize the value of the pig as a well‐defined and accessible model organism for early mammalian development not least in the context of embryonic and extra‐embryonic stem cells, lineages and molecular programs. image"],["dc.identifier.doi","10.1002/jmor.21389"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/88406"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-448"],["dc.publisher","John Wiley \\u0026 Sons, Inc."],["dc.relation.eissn","1097-4687"],["dc.relation.issn","0362-2525"],["dc.rights","This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made."],["dc.title","Epiblast and trophoblast morphogenesis in the pre‐gastrulation blastocyst of the pig. A light‐ and electron‐microscopical study"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","77"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Cells Tissues Organs"],["dc.bibliographiccitation.lastpage","87"],["dc.bibliographiccitation.volume","201"],["dc.contributor.author","Schroeder, Silke S."],["dc.contributor.author","Tsikolia, Nikoloz"],["dc.contributor.author","Weizbauer, Annette"],["dc.contributor.author","Hue, Isabelle"],["dc.contributor.author","Viebahn, Christoph"],["dc.date.accessioned","2018-11-07T10:02:29Z"],["dc.date.available","2018-11-07T10:02:29Z"],["dc.date.issued","2015"],["dc.description.abstract","Nodal activity in the left lateral plate mesoderm is a conserved sign of irreversible left-right asymmetry at early somite stages of the vertebrate embryo. An earlier, paraxial nodal domain accompanies the emergence and initial extension of the notochord and is either left-sided, as in the chick and pig, or symmetrical, as in the mouse and rabbit; intriguingly, this interspecific dichotomy is mirrored by divergent morphological features of the posterior notochord (also known as the left-right organizer), which is ventrally exposed to the yolk sac cavity and carries motile cilia in the latter 2 species only. By introducing the cattle embryo as a new model organism for early left-right patterning, we present data to establish 2 groups of mammals characterized by both the morphology of the left-right organizer and the dynamics of paraxial nodal expression: presence and absence of a ventrally open surface of the early (plate-like) posterior notochord correlates with a symmetrical (in mice and rab-bits) versus an asymmetrical (in pigs and cattle) paraxial nodal expression domain next to the notochordal plate. High-resolution histological analysis reveals that the latter domain defines in all 4 mammals a novel 'parachordal' axial mesoderm compartment, the topography of which changes according to the specific regression of the similarly novel subchordal mesoderm during the initial phases of notochord development. In conclusion, the mammalian axial mesoderm compartment (1) shares critical conserved features despite the marked differences in early notochord morphology and early left-right patterning and (2) provides a dynamic topographical framework for nodal activity as part of the mammalian left-right organizer. (C) 2016 The Author(s) Published by S. Karger AG, Basel"],["dc.identifier.doi","10.1159/000440951"],["dc.identifier.isi","000372595000001"],["dc.identifier.pmid","26741372"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13230"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38232"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1422-6421"],["dc.relation.issn","1422-6405"],["dc.rights","CC BY-NC-ND 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by-nc-nd/4.0"],["dc.title","Paraxial Nodal Expression Reveals a Novel Conserved Structure of the Left-Right Organizer in Four Mammalian Species"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","496"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Developmental Dynamics"],["dc.bibliographiccitation.lastpage","508"],["dc.bibliographiccitation.volume","249"],["dc.contributor.author","Pieper, Tobias"],["dc.contributor.author","Carpaij, Meriam"],["dc.contributor.author","Reinermann, Johanna"],["dc.contributor.author","Surchev, Lachezar"],["dc.contributor.author","Viebahn, Christoph"],["dc.contributor.author","Tsikolia, Nikoloz"],["dc.date.accessioned","2019-12-16T11:15:39Z"],["dc.date.accessioned","2021-10-27T13:21:54Z"],["dc.date.available","2019-12-16T11:15:39Z"],["dc.date.available","2021-10-27T13:21:54Z"],["dc.date.issued","2019"],["dc.description.abstract","BACKGROUND: Hensen node of the amniote embryo plays a central role in multiple developmental processes, especially in induction and formation of axial organs. In the chick, it is asymmetrical in shape and has recently been considered to represent the left-right organizer. As mechanisms of breaking the initial left-right symmetry of the embryo are still ill-understood, analyzing the node's microarchitecture may provide insights into functional links between symmetry breaking and asymmetric morphology. RESULTS: In the course of a light- and electron-microscopic study addressing this issue we discovered novel intercellular matrix-filled cavities in the node of the chick during gastrulation and during early neurulation stages; measuring up to 45 μm, they are surrounded by densely packed cells and filled with nanoscale fibrils, which immunostaining suggests to consist of the basement membrane-related proteins fibronectin and perlecan. The cavities emerge immediately prior to node formation in the epiblast layer adjacent to the tip of the primitive streak and later, with emerging node asymmetry, they are predominantly located in the right part of the node. Almost identical morphological features of microcavities were found in the duck node. CONCLUSIONS: We address these cavities as \"nodal microcavities\" and propose their content to be involved in the function of the avian node by mediating morphogen signaling and storage."],["dc.identifier.doi","10.1002/dvdy.133"],["dc.identifier.eissn","1097-0177"],["dc.identifier.issn","1058-8388"],["dc.identifier.pmid","31729123"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16941"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/92053"],["dc.language.iso","en"],["dc.notes.intern","Migrated from goescholar"],["dc.publisher","John Wiley \\u0026 Sons, Inc."],["dc.relation.eissn","1097-0177"],["dc.relation.issn","1553-0795"],["dc.relation.issn","1058-8388"],["dc.relation.orgunit","Universitätsmedizin Göttingen"],["dc.rights","CC BY-NC 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by-nc/4.0"],["dc.subject.ddc","610"],["dc.title","Matrix‐filled microcavities in the emerging avian left‐right organizer"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]