The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Elizabeth J Robertson - One of the best experts on this subject based on the ideXlab platform.
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tissue specific requirements for the proprotein convertase furin spc1 during embryonic turning and heart looping
Development, 2000Co-Authors: Daniel B Constam, Elizabeth J RobertsonAbstract:Furin, the mammalian prototype of a family of serine proteases, is required for ventral closure and axial rotation, and formation of the yolk sac vasculature. Here we show additionally that left-sided expression of pitx2 and lefty-2 are also perturbed in Furin-deficient embryos. These tissue abnormalities are preceded by a marked delay in the expansion of the definitive endoderm during gastrulation. Using a chimera approach, we show that Furin activity is required in epiblast derivatives, including the primitive heart, gut and Extraembryonic Mesoderm, whereas it is nonessential in the visceral endoderm. Thus, chimeric embryos, derived by injecting wild-type embryonic stem (ES) cells into fur(-/-) blastocysts, develop normally until at least 9.5 d.p.c. In contrast, Furin-deficient chimeras developing in the context of wild-type visceral endoderm fail to undergo ventral closure, axial rotation and yolk sac vascularization. Fur(-/-) cells are recruited into all tissues examined, including the yolk sac vasculature and the midgut, even though these structures fail to form in fur mutants. The presence of wild-type cells in the gut strikingly correlates with the ability of chimeric embryos to undergo turning. Overall, we conclude that Furin activity is essential in both Extraembryonic and precardiac Mesoderm, and in definitive endoderm derivatives.
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Tissue-specific requirements for the proprotein convertase furin/SPC1 during embryonic turning and heart looping.
Development (Cambridge England), 2000Co-Authors: Daniel B Constam, Elizabeth J RobertsonAbstract:Furin, the mammalian prototype of a family of serine proteases, is required for ventral closure and axial rotation, and formation of the yolk sac vasculature. Here we show additionally that left-sided expression of pitx2 and lefty-2 are also perturbed in Furin-deficient embryos. These tissue abnormalities are preceded by a marked delay in the expansion of the definitive endoderm during gastrulation. Using a chimera approach, we show that Furin activity is required in epiblast derivatives, including the primitive heart, gut and Extraembryonic Mesoderm, whereas it is nonessential in the visceral endoderm. Thus, chimeric embryos, derived by injecting wild-type embryonic stem (ES) cells into fur(-/-) blastocysts, develop normally until at least 9.5 d.p.c. In contrast, Furin-deficient chimeras developing in the context of wild-type visceral endoderm fail to undergo ventral closure, axial rotation and yolk sac vascularization. Fur(-/-) cells are recruited into all tissues examined, including the yolk sac vasculature and the midgut, even though these structures fail to form in fur mutants. The presence of wild-type cells in the gut strikingly correlates with the ability of chimeric embryos to undergo turning. Overall, we conclude that Furin activity is essential in both Extraembryonic and precardiac Mesoderm, and in definitive endoderm derivatives.
Daniel B Constam - One of the best experts on this subject based on the ideXlab platform.
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tissue specific requirements for the proprotein convertase furin spc1 during embryonic turning and heart looping
Development, 2000Co-Authors: Daniel B Constam, Elizabeth J RobertsonAbstract:Furin, the mammalian prototype of a family of serine proteases, is required for ventral closure and axial rotation, and formation of the yolk sac vasculature. Here we show additionally that left-sided expression of pitx2 and lefty-2 are also perturbed in Furin-deficient embryos. These tissue abnormalities are preceded by a marked delay in the expansion of the definitive endoderm during gastrulation. Using a chimera approach, we show that Furin activity is required in epiblast derivatives, including the primitive heart, gut and Extraembryonic Mesoderm, whereas it is nonessential in the visceral endoderm. Thus, chimeric embryos, derived by injecting wild-type embryonic stem (ES) cells into fur(-/-) blastocysts, develop normally until at least 9.5 d.p.c. In contrast, Furin-deficient chimeras developing in the context of wild-type visceral endoderm fail to undergo ventral closure, axial rotation and yolk sac vascularization. Fur(-/-) cells are recruited into all tissues examined, including the yolk sac vasculature and the midgut, even though these structures fail to form in fur mutants. The presence of wild-type cells in the gut strikingly correlates with the ability of chimeric embryos to undergo turning. Overall, we conclude that Furin activity is essential in both Extraembryonic and precardiac Mesoderm, and in definitive endoderm derivatives.
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Tissue-specific requirements for the proprotein convertase furin/SPC1 during embryonic turning and heart looping.
Development (Cambridge England), 2000Co-Authors: Daniel B Constam, Elizabeth J RobertsonAbstract:Furin, the mammalian prototype of a family of serine proteases, is required for ventral closure and axial rotation, and formation of the yolk sac vasculature. Here we show additionally that left-sided expression of pitx2 and lefty-2 are also perturbed in Furin-deficient embryos. These tissue abnormalities are preceded by a marked delay in the expansion of the definitive endoderm during gastrulation. Using a chimera approach, we show that Furin activity is required in epiblast derivatives, including the primitive heart, gut and Extraembryonic Mesoderm, whereas it is nonessential in the visceral endoderm. Thus, chimeric embryos, derived by injecting wild-type embryonic stem (ES) cells into fur(-/-) blastocysts, develop normally until at least 9.5 d.p.c. In contrast, Furin-deficient chimeras developing in the context of wild-type visceral endoderm fail to undergo ventral closure, axial rotation and yolk sac vascularization. Fur(-/-) cells are recruited into all tissues examined, including the yolk sac vasculature and the midgut, even though these structures fail to form in fur mutants. The presence of wild-type cells in the gut strikingly correlates with the ability of chimeric embryos to undergo turning. Overall, we conclude that Furin activity is essential in both Extraembryonic and precardiac Mesoderm, and in definitive endoderm derivatives.
Brigid L M Hogan - One of the best experts on this subject based on the ideXlab platform.
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Bone morphogenetic protein 4 in the Extraembryonic Mesoderm is required for allantois development and the localization and survival of primordial germ cells in the mouse
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Takeshi Fujiwara, N. Ray Dunn, Brigid L M HoganAbstract:Evidence suggests that the specification of primordial germ cells (PGCs) in the mammalian embryo does not depend on maternal determinants. Rather, previous genetic analysis in the mouse has shown that bone morphogenetic protein 4 (Bmp4) is required for the formation of both PGCs and allantois. Bmp4 is expressed in both the trophoblast-derived Extraembryonic ectoderm (ExE) and in the epiblast-derived Extraembryonic Mesoderm (ExM), in which the PGCs, allantois primordium, and angioblasts are first detected. We have shown that Bmp4 made in the ExE functions to induce precursors of PGCs and allantois in the adjacent epiblast, resulting in complete lack of both cell types in homozygous null mutants. However, the function of Bmp4 in the ExM is totally unknown. To address this question, we generated tetraploid (4N) chimeras by aggregating Bmp4 null ES cells with wild-type tetraploid embryos. In this combination, wild-type tetraploid cells contribute to the Extraembryonic trophoblast and primitive endoderm lineages but are excluded from the epiblast and its derivatives, including the ExM. Our results clearly demonstrate that Bmp4 made in the ExM does not affect the establishment of either PGC or allantois lineages, but is required for PGC localization and survival and for the differentiation of the allantois. These findings suggest that Bmp4 expressed in epiblast-derived tissues plays vital roles in reproduction by regulating both the development of the germ line and the vascular connection between the embryo and the placenta.
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BMP4 IS REQUIRED FOR THE GENERATION OF PRIMORDIAL GERM CELLS IN THE MOUSE EMBRYO
Genes & development, 1999Co-Authors: Kirstie A. Lawson, Bernard A.j. Roelen, N. Ray Dunn, L. M. Zeinstra, A. M. Davis, Christopher V.e. Wright, J. P. W. F. M. Korving, Brigid L M HoganAbstract:Before gastrulation, the mouse embryo consists of three distinct cell lineages which were established in the blastocyst during the peri-implantation period, that is, epiblast, Extraembryonic endoderm, and trophectoderm. The epiblast, from which the entire fetus will form, as well as the Extraembryonic Mesoderm and amnion ectoderm, is a cup-shaped epithelium apposed on its open end to the Extraembryonic ectoderm, a trophectoderm derivative. Both epiblast and Extraembryonic ectoderm are covered by visceral endoderm, which is part of the Extraembryonic endoderm lineage (Hogan et al. 1994). The primordial germ cells (PGCs) of the mouse embryo are derived from part of the population of epiblast cells that will give rise mainly to the Extraembryonic Mesoderm. Precursors of the PGCs are located before gastrulation in the extreme proximal region of the epiblast adjacent to the Extraembryonic ectoderm, and have descendants not only in the germ line, but also in Extraembryonic structures, that is, the allantois, blood islands, and yolk sac Mesoderm, as well as both layers of the amnion. At embryonic day (E) 6.0, these precursors lie scattered in a ring that extends up to three cell diameters from the junction with the Extraembryonic ectoderm (Lawson and Hage 1994). Early in gastrulation, they converge toward the primitive streak in the posterior of the embryo and translocate through it. Allocation to the germ cell lineage is thought to occur in ∼45 cells around E7.2, after the precursors have passed through the streak and have come to reside in the Extraembryonic Mesoderm (Lawson and Hage 1994). This is about the time when the putative PGCs can first be identified morphologically in a cluster posterior to the primitive streak in a position that will later become the base of the allantois (Ginsburg et al. 1990). PGCs stain strongly in a characteristic pattern for alkaline phosphatase (AP) activity (Chiquoine 1954), which by this stage is due to tissue nonspecific AP (Hahnel et al. 1990; MacGregor et al. 1995). The PGCs continue to express AP during their proliferation in the developing hindgut and migration into the genital ridges (for review, see Buehr 1997). Transplantation studies have shown that genetically marked distal epiblast cells from pre- and early-primitive streak-stage embryos, which would normally contribute to neuroectoderm and never to the PGCs, can give rise to PGCs and Extraembryonic Mesoderm when grafted to the proximal epiblast (Tam and Zhou 1996). These results raise the possibility that PGC precursors are induced by extracellular factors and/or cell interactions present locally at the junction between the Extraembryonic ectoderm and epiblast. Candidate genes encoding putative germ cell precursor inducing factors are predicted to be expressed in the mouse embryo before and during gastrulation. One such factor is Bone Morphogenetic Protein 4 (Bmp4), a member of the TGFβ superfamily of intercellular signaling proteins (Hogan 1996; Waldrip et al. 1998). Most mouse embryos homozygous for a null mutation in Bmp4 die around gastrulation (∼E6.5) (Winnier et al. 1995). On some genetic backgrounds, however, a proportion of the mutant embryos survive until the early somite stage and show severe defects, particularly in the Extraembryonic Mesoderm (Winnier et al. 1995). In this paper, we exploit this late phenotype to show that PGC formation absolutely requires Bmp4 signaling. In addition, the size of the founding population of PGCs is significantly reduced in heterozygous mutant embryos. By using a Bmp4–lacZ reporter allele, we have definitively localized Bmp4 expression before gastrulation in the Extraembryonic ectoderm and in mid- to late- primitive streak stage embryos in the Extraembryonic Mesoderm. Thus, Bmp4 is expressed at the right time and in the right place to play a role both in the quantitative induction of PGC precursors in the proximal epiblast and in their allocation to the germ cell lineage in the Extraembryonic Mesoderm. Furthermore, by analyzing genetic chimeras, we have clearly established a role for Bmp4 in the induction of PGC precursors and demonstrate for the first time that a secreted signal from the Extraembryonic ectoderm is required for the normal development of the epiblast.
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Bone morphogenetic protein-4 is required for Mesoderm formation and patterning in the mouse
Genes and Development, 1995Co-Authors: G. Winnier, Michaela Blessing, Patricia A Labosky, Brigid L M HoganAbstract:Bone morphogenetic protein-4 (BMP-4) is a member of the TGF-beta superfamily of polypeptide signaling molecules, closely related to BMP-2 and to Drosophila decapentaplegic (DPP). To elucidate the role of BMP-4 in mouse development the gene has been inactivated by homologous recombination in ES cells. Homozygous mutant Bmp-4tm1blh embryos die between 6.5 and 9.5 days p.c., with a variable phenotype. Most Bmp-4tm1blh embryos do not proceed beyond the egg cylinder stage, do not express the Mesodermal marker T(Brachyury), and show little or no Mesodermal differentiation. Some homozygous mutants develop to the head fold or beating heart/early somite stage or beyond. However, they are developmentally retarded and have truncated or disorganized posterior structures and a reduction in Extraembryonic Mesoderm, including blood islands. These results provide direct genetic evidence that BMP-4 is essential for several different processes in early mouse development, beginning with gastrulation and Mesoderm formation. Moreover, in the presumed absence of zygotic ligand, it appears that homozygous mutants can be rescued partially by related proteins or by maternal BMP-4.
Kenneth L Audus - One of the best experts on this subject based on the ideXlab platform.
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tie 1 and tie 2 define another class of putative receptor tyrosine kinase genes expressed in early embryonic vascular system
Proceedings of the National Academy of Sciences of the United States of America, 1993Co-Authors: Thomas N Sato, Ying Qin, Christine A Kozak, Kenneth L AudusAbstract:We report the molecular cloning and characterization of two structurally related putative receptor tyrosine kinases, encoded by distinct genes (tie-1 and tie-2) on mouse chromosome 4. Both tie-1 and tie-2 encode receptor proteins possessing unique multiple extracellular domains: two immunoglobulin-like loop domains flanking three epidermal growth factor repeats followed by three fibronectin-type III repeats. Both genes are expressed in early embryonic vascular system and in maternal decidual vascular endothelial cells, where the vasculature undergoes an active angiogenesis. tie-2, but not tie-1, expression was also detected in Extraembryonic Mesoderm of the amnion. tie-1, but not tie-2, is expressed in an acute myelogenic cell line in vitro. tie-1 and tie-2 may form another class within the receptor tyrosine kinase gene family, and further characterization of these genes and identification of their putative ligands should define the nature of the signal-transduction cascades underlying early vascular system development, as well as their differential roles in Mesodermal cells of the amniotic and myeloid lineages.
E. N. Tolmacheva - One of the best experts on this subject based on the ideXlab platform.
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Skewed X-chromosome inactivation in human miscarriages
Cell and Tissue Biology, 2016Co-Authors: E. N. Tolmacheva, E. A. Sazhenova, S. A. Vasil’ev, D. I. Zhigalina, E. I. Grigorovich, T. V. Nikitina, A. A. Mel’nikov, E. S. Zhabina, T. V. Ivanova, I. D. EvtushenkoAbstract:The sex ratio in the first trimester of pregnancy shifts toward males due to increased elimination of female embryos. One reason for this phenomenon may be disruption of X chromosome inactivation. In this paper, we have analyzed the nature of the X chromosome inactivation in Extraembryonic tissues of induced and spontaneous abortuses with 46,XX karyotype. Both equiprobable and asymmetric inactivation have been found in chorionic cytotrophoblast from spontaneous and induced abortuses. In the Extraembryonic Mesoderm of the control group of embryos, only equiprobable inactivation has been found, whereas this parameter was shifted in 15% of spontaneous abortions. The highest incidence of the selective inactivation of one of the parent homologues was found in the group with a lack of development of embryos and embryos from women with recurrent miscarriages. One of the reasons for the observed results can be compartmentalization of cells in the blastocyst leading to the nonrandom redistribution of cells and the predominance in the inner mass of cells with an active X chromosome with aberrations incompatible with normal embryonic development.
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Methylation status of LINE-1 retrotransposon in chromosomal mosaicism during early stages of human embryonic development
Molecular Biology, 2015Co-Authors: S. A. Vasilyev, E. N. Tolmacheva, A. A. Kashevarova, E. A. Sazhenova, I. N. LebedevAbstract:Early stages of human embryonic development are characterized by spatio-temporal coincidence of events of total epigenetic genome reprogramming and elevated level of mosaic forms of numerical chromosome abnormalities. It is possible that the abnormal reprogramming of various regions of the genome can lead to violations of local epigenetic chromatin organization and gene expression, affecting the correct chromosome segregation during mitosis. In this study, a comparative analysis of the methylation index of LINE-1 retrotransposon, which is largely reflecting the methylation profile of the genome, is performed in placental tissues of spontaneous abortions with complete and mosaic forms of aneuploidy, and with a normal karyotype, as well as in the control group of induced abortions of the first trimester of pregnancy. It was shown that Extraembryonic Mesoderm and chorionic cytotrophoblast of spontaneous abortions with chromosomal mosaicism are characterized by the highest index of LINE-1 methylation among all groups studied. At the same time excessive hypomethylation of transposable genetic element recorded in spontaneous abortions with normal karyotype. It is suggested that violations of parental genomes demethylation during epigenetic reprogramming at preimplantation stages of development may be associated with an increased frequency of mitotic errors in chromosome segregation, leading to the formation of a mosaic karyotype.
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Methylation status of line-1 retrotransposon in chromosomal mosaicism during the early stages of human embryonic development
Molekuliarnaia biologiia, 2015Co-Authors: S A Vasil'ev, E. N. Tolmacheva, A. A. Kashevarova, E. A. Sazhenova, I. N. LebedevAbstract:Early stages of human embryonic development are characterized by spatio-temporal coincidence of events of total epigenetic genome reprogramming and elevated level of mosaic forms of numerical chromosome abnormalities. It is possible that the abnormal reprogramming of various regions of the genome can lead to violations of local epigenetic chromatin organization and gene expression, affecting the correct chromosome segregation during mitosis. In this study, a comparative analysis of the methylation index of LINE-1 retrotransposon, which is largely reflecting the methylation profile of the genome, is performed in placental tissues of spontaneous abortions with complete and mosaic forms of aneuploidy, and with a normal karyotype, as well as in the control group of induced abortions of the first trimester of pregnancy. It was shown that Extraembryonic Mesoderm and chorionic cytotrophoblast of spontaneous abortions with chromosomal mosaicism are characterized by the highest index of LINE-1 methylation among all groups studied. At the same time excessive hypomethylation of transposable genetic element recorded in spontaneous abortions with normal karyotype. It is suggested that violations of parental genomes demethylation during epigenetic reprogramming at preimplantation stages of development may be associated with an increased frequency of mitotic errors in chromosome segregation, leading to the formation of a mosaic karyotype.
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Epigenetic effects of trisomy 16 in human placenta
Molecular Biology, 2013Co-Authors: E. N. Tolmacheva, A. A. Kashevarova, N. A. Skryabin, I. N. LebedevAbstract:The methylation profiles of the placental tissues of human embryos with normal karyotype and trisomy 16 were compared using an Infinium HumanMethylation27 BeadChip array (Illumina, United States). Numerous differences between the Extraembryonic tissues with diploid and aneuploid karyotypes were observed. The Extraembryonic Mesoderm of embryos with trisomy 16 appeared to be less methylated than the diploid tissue, whereas the cytotrophoblast of aneuploid embryos was hypermethylated. The presence of the supernumerary chromosome was shown to influence the epigenetic profile of the genome by changing the level of methylation of CpG sites of all chromosomes. However, the largest number of differentially methylated loci was found on chromosome 16. Furthermore, more often, the epimutations were tissuespecific. In both tissues, the hypomethylated genes belong to the groups of genes responsible for different metabolic processes, whereas the hypermethylated genes control the processes of development, cell adhesion, immune response, and response to stimulus.
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DNA methylation profile in human placental tissues
Molecular Biology, 2011Co-Authors: E. N. Tolmacheva, A. A. Kashevarova, N. A. Skryabin, I. N. LebedevAbstract:For the first time, DNA methylation patterns in the human cytotrophoblast and the Extraembryonic Mesoderm were determined using a genome-wide Infinium HumanMethylation27 BeadChip Array (Illumina, United States). These tissues are derivatives of the trophectoderm and the inner cell mass of the blastocyst and have substantial differences in the dynamics of epigenetic genome reprogramming during early stages of differentiation. It was shown that the genome of the Extraembryonic Mesoderm cells was more methylated than that of the cytotrophoblast, similarly to the findings in other mammalian species. There were differences in the methylation patterns of single CpG dinucleotides and dinucleotides located within promoter CpG islands: in both tissues most single CpG dinucleotides were methylated, promoters CpG island sites were not. A comparative analysis revealed 202 differentially methylated genes in the Extraembryonic Mesoderm and 40 such genes in the cytotrophoblast. These genes are responsible for a number of diverse biological processes. However, in the Extraembryonic Mesoderm, a majority of genes identified were responsible for DNA binding and transcriptional factor activity, whereas those identified in the cytotrophoblast were responsible for transport and protein and cytokine secretion.
