scholarly journals Mechanisms for pattern formation leading to axis formation and lineage allocation in mammals: a marsupial perspective

Reproduction ◽  
2001 ◽  
pp. 677-683 ◽  
Author(s):  
L Selwood
Keyword(s):  
Cell Division ◽  
Early Embryogenesis ◽  
Boundary Effects ◽  
Axis Formation ◽  
Blastocyst Formation ◽  
Cell Type ◽  
Sperm Entry ◽  
Type Boundary ◽  
Point Gravity ◽  
Anterior Posterior

Developing patterns in early embryogenesis are analysed in conceptuses from several families, including Dasyuridae, Phalangeridae, Macropodidae and Didelphidae, in which cleavage has been examined in some detail. Features common to cleavage and blastocyst formation, and in some cases to hypoblast formation, are used to develop an outline of possible mechanisms leading to axis formation and lineage allocation. Relevant features that have been described only in some species are also included. It is suggested that certain features of marsupial cleavage establish patterns in the developing blastocyst epithelia, pluriblast, trophoblast and hypoblast that contribute to axis formation and lineage allocation. All marsupials examined had a polarized oocyte or conceptus, the polarity of which was related to the conceptus embryonic-abembryonic axis and, eventually, the conceptus dorsal-ventral axis and the formation of the pluriblast (future embryo) and trophoblast. The embryonic dorsal-ventral and anterior-posterior axes were established after the allocation of hypoblast and epiblast. Mechanisms that appear to result in patterning of the developing epithelia leading to axis formation and lineage allocation are discussed, and include sperm entry point, gravity, conceptus polarity, differentials in cell-zona, cell-cell and cell-type (boundary effects) contacts, cell division order during cleavage and signals external to the conceptus. A model of the patterning effects is included. The applicability of these mechanisms to other amniotes, including eutherian mammals, is also examined.

scholarly journals H3K9me2 orchestrates inheritance of spatial positioning of peripheral heterochromatin through mitosis

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Andrey Poleshko ◽  
Cheryl L Smith ◽  
Son C Nguyen ◽  
Priya Sivaramakrishnan ◽  
Karen G Wong ◽  
...  
Keyword(s):  
Cell Division ◽  
Spatial Organization ◽  
Nuclear Periphery ◽  
Nuclear Lamina ◽  
Positional Information ◽  
Specific Gene ◽  
Cell Type ◽  
Histone 3 ◽  
Spatial Positioning ◽  
Peripheral Heterochromatin

Cell-type-specific 3D organization of the genome is unrecognizable during mitosis. It remains unclear how essential positional information is transmitted through cell division such that a daughter cell recapitulates the spatial genome organization of the parent. Lamina-associated domains (LADs) are regions of repressive heterochromatin positioned at the nuclear periphery that vary by cell type and contribute to cell-specific gene expression and identity. Here we show that histone 3 lysine 9 dimethylation (H3K9me2) is an evolutionarily conserved, specific mark of nuclear peripheral heterochromatin and that it is retained through mitosis. During mitosis, phosphorylation of histone 3 serine 10 temporarily shields the H3K9me2 mark allowing for dissociation of chromatin from the nuclear lamina. Using high-resolution 3D immuno-oligoFISH, we demonstrate that H3K9me2-enriched genomic regions, which are positioned at the nuclear lamina in interphase cells prior to mitosis, re-associate with the forming nuclear lamina before mitotic exit. The H3K9me2 modification of peripheral heterochromatin ensures that positional information is safeguarded through cell division such that individual LADs are re-established at the nuclear periphery in daughter nuclei. Thus, H3K9me2 acts as a 3D architectural mitotic guidepost. Our data establish a mechanism for epigenetic memory and inheritance of spatial organization of the genome.

DNA methylation versus gene expression

Development ◽  
1984 ◽  
Vol 83 (Supplement) ◽  
pp. 31-40
Author(s):  
Adrian P. Bird
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Cell Division ◽  
Methylation Pattern ◽  
Current Evidence ◽  
Evolutionary Perspective ◽  
Cell Type ◽  
Versus Gene ◽  
Daughter Cells ◽  
The Relationship

Vertebrate DNA is methylated at a high proportion of cytosine residues in the sequence CpG, and it has been suggested that the distribution of methylated and non-methylated CpGs in a given cell type influences the pattern of gene expression in those cells. Since a DNA methylation pattern is normally transmitted faithfully to daughter cells via cell division, this idea suggests an origin for stable, clonally inherited patterns of gene expression. This article discusses some of the current evidence for a relationship between DNA methylation and gene expression. Although the evidence is incomplete, it appears already that the relationship is variable: transcription of some genes is repressed by the presence of 5-methylcytosine at certain CpGs, and may be controlled by methylation, while transcription of other genes is indifferent to methylation. In attempting to explain this variability it is helpful to adopt an evolutionary perspective.

Expression pattern ofBrachyuryin the molluscPatella vulgatasuggests a conserved role in the establishment of the AP axis in Bilateria

Development ◽  
2002 ◽  
Vol 129 (6) ◽  
pp. 1411-1421 ◽  
Author(s):  
Nicolas Lartillot ◽  
Olivier Lespinet ◽  
Michel Vervoort ◽  
André Adoutte
Keyword(s):  
Expression Pattern ◽  
Bilateral Symmetry ◽  
Growth Zone ◽  
Posterior Pole ◽  
Axis Formation ◽  
Posterior Edge ◽  
Cell Stage ◽  
Posterior Growth Zone ◽  
Erk Activity ◽  
Anterior Posterior

We report the characterisation of a Brachyury ortholog (PvuBra) in the marine gastropod Patella vulgata. In this mollusc, the embryo displays an equal cleavage pattern until the 32-cell stage. There, an inductive event takes place that sets up the bilateral symmetry, by specifying one of the four initially equipotent vegetal macromeres as the posterior pole of all subsequent morphogenesis. This macromere, usually designated as 3D, will subsequently act as an organiser. We show that 3D expresses PvuBra as soon as its fate is determined. As reported for another mollusc (J. D. Lambert and L. M. Nagy (2001) Development128, 45-56), we found that 3D determination and activity also involve the activation of the MAP kinase ERK, and we further show that PvuBra expression in 3D requires ERK activity. PvuBra expression then rapidly spreads to neighbouring cells that cleave in a bilateral fashion and whose progeny will constitute the posterior edge of the blastopore during gastrulation, suggesting a role for PvuBra in regulating cell movements and cleavage morphology in Patella. Until the completion of gastrulation, PvuBra expression is maintained at the posterior pole, and along the developing anterior-posterior axis. Comparing this expression pattern with what is known in other Bilateria, we advocate that Brachyury might have a conserved role in the regulation of anterior-posterior patterning among Bilateria, through the maintenance of a posterior growth zone, suggesting that a teloblastic mode of axis formation might be ancestral to the Bilateria.

Patterning of the follicle cell epithelium along the anterior-posterior axis during Drosophila oogenesis

Development ◽  
1998 ◽  
Vol 125 (15) ◽  
pp. 2837-2846 ◽  
Author(s):  
A. Gonzalez-Reyes ◽  
D. St Johnston
Keyword(s):  
Follicle Cell ◽  
Cell Types ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Axis Formation ◽  
Main Body ◽  
Drosophila Oogenesis ◽  
Egfr Mutant ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

Gurken signals from the oocyte to the adjacent follicle cells twice during Drosophila oogenesis; first to induce posterior fate, thereby polarising the anterior-posterior axis of the future embryo and then to induce dorsal fate and polarise the dorsal-ventral axis. Here we show that Gurken induces two different follicle cell fates because the follicle cells at the termini of the egg chamber differ in their competence to respond to Gurken from the main-body follicle cells in between. By removing the putative Gurken receptor, Egfr, in clones of cells, we show that Gurken signals directly to induce posterior fate in about 200 cells, defining a terminal competence domain that extends 10–11 cell diameters from the pole. Furthermore, small clones of Egfr mutant cells at the posterior interpret their position with respect to the pole and differentiate as the appropriate anterior cell type. Thus, the two terminal follicle cell populations contain a symmetric prepattern that is independent of Gurken signalling. These results suggest a three-step model for the anterior-posterior patterning of the follicular epithelium that subdivides this axis into at least five distinct cell types. Finally, we show that Notch plays a role in both the specification and patterning of the terminal follicle cells, providing a possible explanation for the defect in anterior-posterior axis formation caused by Notch and Delta mutants.

scholarly journals Compartment-specific transcriptomics of ozone-exposed murine lungs reveals sex and cell type-associated perturbations relevant to mucoinflammatory lung diseases

2020 ◽  
Author(s):  
Ishita Choudhary ◽  
Thao Vo ◽  
Kshitiz Paudel ◽  
Sonika Patial ◽  
Yogesh Saini
Keyword(s):  
Gene Expression ◽  
Dna Repair ◽  
Cell Division ◽  
Mucous Cell ◽  
Ozone Exposure ◽  
Specific Gene ◽  
Cell Type ◽  
Distinct Cell Type ◽  
Airway Injury ◽  
Immunohistochemical Analyses

Ozone is known to cause lung injury and resident cells of the respiratory tract, i.e., epithelial cells and macrophages, respond to inhaled ozone in a variety of ways that affect their survival, morphology, and functioning. However, a complete understanding of the sex-associated and the cell type-specific gene expression changes in response to ozone exposure is still limited. Through transcriptomics, we aimed to analyze gene expression alterations and associated enrichment of biological pathways enrichment in three distinct cell type-enriched compartments of ozone-exposed murine lungs. We sub-chronically exposed adult males and females to 0.8ppm ozone or filtered air. RNA-Seq was performed on airway epithelium-enriched airways, parenchyma, and purified airspace macrophages. Differential gene expression and biological pathway analyses were performed and supported by cellular and immunohistochemical analyses. While a majority of differentially expressed genes (DEGs) in ozone-exposed versus air-exposed groups were common between both sexes, sex-specific DEGs were also identified in all the three tissue compartments. As compared to ozone-exposed males, ozone-exposed females had significant alterations in gene expression in three compartments. Pathways relevant to cell division and DNA repair were enriched in the ozone-exposed airways indicating ozone-induced airway injury and repair which was further supported by immunohistochemical analyses. In addition to cell division and DNA repair pathways, inflammatory pathways were also enriched within the parenchyma supporting contribution by both epithelial and immune cells. Finally, immune response and cytokine-cytokine receptor interactions were enriched in macrophages, indicating ozone-induced macrophage activation. Lastly, our analyses also revealed ozone-induced upregulation of mucoinflammation- and mucous cell metaplasia-associated pathways.

scholarly journals Determination of cell division axes in the early embryogenesis of Caenorhabditis elegans.

1987 ◽  
Vol 105 (5) ◽  
pp. 2123-2135 ◽  
Author(s):  
A A Hyman ◽  
J G White
Keyword(s):  
Cell Division ◽  
Caenorhabditis Elegans ◽  
Early Embryogenesis ◽  
The Other ◽  
Nuclear Complex ◽  
Centrosome Separation

The establishment of cell division axes was examined in the early embryonic divisions of Caenorhabditis elegans. It has been shown previously that there are two different patterns of cleavage during early embryogenesis. In one set of cells, which undergo predominantly determinative divisions, the division axes are established successively in the same orientation, while division axes in the other set, which divide mainly proliferatively, have an orthogonal pattern of division. We have investigated the establishment of these axes by following the movement of the centrosomes. Centrosome separation follows a reproducible pattern in all cells, and this pattern by itself results in an orthogonal pattern of cleavage. In those cells that divide on the same axis, there is an additional directed rotation of pairs of centrosomes together with the nucleus through well-defined angles. Intact microtubules are required for rotation; rotation is prevented by inhibitors of polymerization and depolymerization of microtubules. We have examined the distribution of microtubules in fixed embryos during rotation. From these and other data we infer that microtubules running from the centrosome to the cortex have a central role in aligning the centrosome-nuclear complex.

scholarly journals Blastomere movement post first cell division correlates with embryonic compaction and subsequent blastocyst formation

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Kazuki Ohata ◽  
Kenji Ezoe ◽  
Tetsuya Miki ◽  
Hirofumi Morita ◽  
Ryoma Tsuchiya ◽  
...  
Keyword(s):  
Cell Division ◽  
Blastocyst Formation

Consistency of constructions for cell division processes

2015 ◽  
Vol 47 (3) ◽  
pp. 640-651 ◽  
Author(s):  
Werner Nagel ◽  
Eike Biehler
Keyword(s):  
Cell Division ◽  
Euclidean Space ◽  
Wide Class ◽  
Boundary Effects ◽  
Bounded Set ◽  
Spatial Consistency ◽  
Division Process

For a class of cell division processes in the Euclidean space ℝd, spatial consistency is investigated. This addresses the problem whether the distribution of the generated structures, restricted to a bounded set V, depends on the choice of a larger region W ⊃ V where the construction of the cell division process is performed. This can also be understood as the problem of boundary effects in the cell division procedure. It is known that the STIT tessellations are spatially consistent. In the present paper it is shown that, within a reasonable wide class of cell division processes, the STIT tessellations are the only ones that are consistent.

A role for Drosophila LKB1 in anterior–posterior axis formation and epithelial polarity

Nature ◽  
2003 ◽  
Vol 421 (6921) ◽  
pp. 379-384 ◽  
Author(s):  
Sophie G. Martin ◽  
Daniel St Johnston
Keyword(s):  
Axis Formation ◽  
Epithelial Polarity ◽  
Anterior Posterior ◽  
Anterior Posterior Axis
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