The Experts below are selected from a list of 5709 Experts worldwide ranked by ideXlab platform
Werner A Muller - One of the best experts on this subject based on the ideXlab platform.
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head formation at the basal end and mirror image pattern duplication in hydra vulgaris
The International Journal of Developmental Biology, 1996Co-Authors: Werner A MullerAbstract:Head and foot in Hydra are organizing centers and considered to be sources of long-range inhibitory morphogens that prevent head and foot formation elsewhere. In a previous study the apparent long-range head inhibition was shown to coincide with long-range foot promotion exerted by the head. Here it is shown that: (1) ring-shaped pieces of the body column taken from a near-foot position form feet - frequently circular - if inserted into the midgastric region; this ectopic foot formation is strongly dependent on assistance by the head. (2) Bisection causes a transient increase in Positional Value at the wounded basal end of the upper body column. This transient development in the head direction in turn promotes ectopic foot formation by transplants and thus has an effect as though the source of a foot-inhibiting morphogen were removed. The existence of long-range foot inhibition is open to question. (3) If a ring with low Positional Value is present in the midgastric region, the increase in Positional Value at the basal end is stable and results in mirror-image head formation instead of foot regeneration in up to 100% of cases. Even before the ring forms a foot it acts like a ligature and subdivides the body column into two developmental compartments. (4) The basal head in turn organizes a mirror-image duplication of the body pattern. In pattern regulation, Hydra follows rules of intercalation known from other organisms.
Maria A Ros - One of the best experts on this subject based on the ideXlab platform.
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intrinsic properties of limb bud cells can be differentially reset
Development, 2017Co-Authors: Patricia Saizlopez, Kavitha Chinnaiya, Matthew Towers, Maria A RosAbstract:ABSTRACT An intrinsic timing mechanism specifies the Positional Values of the zeugopod (i.e. radius/ulna) and then autopod (i.e. wrist/digits) segments during limb development. Here, we have addressed whether this timing mechanism ensures that patterning events occur only once by grafting GFP-expressing autopod progenitor cells to the earlier host signalling environment of zeugopod progenitor cells. We show by detecting Hoxa13 expression that early and late autopod progenitors fated for the wrist and phalanges, respectively, both contribute to the entire host autopod, indicating that the autopod Positional Value is irreversibly determined. We provide evidence that Hoxa13 provides an autopod-specific Positional Value that correctly allocates cells into the autopod, most likely through the control of cell-surface properties as shown by cell-cell sorting analyses. However, we demonstrate that only the earlier autopod cells can adopt the host proliferation rate to permit normal morphogenesis. Therefore, our findings reveal that the ability of embryonic cells to differentially reset their intrinsic behaviours confers robustness to limb morphogenesis. We speculate that this plasticity could be maintained beyond embryogenesis in limbs with regenerative capacity.
Shin Tochinai - One of the best experts on this subject based on the ideXlab platform.
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existence of gradient in cell adhesiveness along the developing xenopus hind limb bud shown by a cellular sorting out experiment in vitro
Development Growth & Differentiation, 1998Co-Authors: Nobutaka Koibuchi, Shin TochinaiAbstract:To examine the possibility of a difference in cell adhesiveness along the developing Xenopus hind limb bud axes, single mesenchymal cells from developing hind limb buds were cultured, allowing them to form an aggregate in a gyratory culture system. By observing the distribution of cells within aggregates, it was found that sorting-out occurred between cells from different positions and different stages. Cells derived from more distal positions tended to be situated interiorly in the aggregates. According to Steinberg's differential adhesion hypothesis, these results support the idea that there is a graded difference in cell adhesiveness along the proximo-distal axis of the developing limb, with adhesiveness increasing distally. Although similar sorting-out was observed between anterior and posterior cell populations, it could not be determined which cell populations were definitely more cohesive. These properties may be correlated with the experimentally demonstrated ‘Positional Value', which should be different among cells located at different positions along the axes of the developing vertebrate limb bud.
Monika Hassel - One of the best experts on this subject based on the ideXlab platform.
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signalling by the fgfr like tyrosine kinase kringelchen is essential for bud detachment in hydra vulgaris
Development, 2004Co-Authors: Stefanie Sudhop, Francois Coulier, Annette Bieller, Angelika Vogt, Tobias Hotz, Monika HasselAbstract:Signalling through fibroblast growth factors (FGFR) is essential for proper morphogenesis in higher evolved triploblastic organisms. By screening for genes induced during morphogenesis in the diploblastic Hydra , we identified a receptor tyrosine kinase ( kringelchen ) with high similarity to FGFR tyrosine kinases. The gene is dynamically upregulated during budding, the asexual propagation of Hydra . Activation occurs in body regions, in which the intrinsic Positional Value changes. During tissue displacement in the early bud, kringelchen RNA is transiently present ubiquitously. A few hours later – coincident with the acquisition of organiser properties by the bud tip – a few cells in the apical tip express the gene strongly. About 20 hours after the onset of evagination, expression is switched on in a ring of cells surrounding the bud base, and shortly thereafter vanishes from the apical expression zone. The basal ring persists in the parent during tissue contraction and foot formation in the young polyp, until several hours after bud detachment. Inhibition of bud detachment by head regeneration results in severe distortion, disruption or even complete loss of the well-defined ring-like expression zone. Inhibition of FGFR signalling by SU5402 or, alternatively, inhibition of translation by phosphorothioate antisense oligonucleotides inhibited detachment of buds, indicating that, despite the dynamic expression pattern, the crucial phase for FGFR signalling in Hydra morphogenesis lies in bud detachment. Although Kringelchen groups with the FGFR family, it is not known whether this protein is able to bind FGFs, which have not been isolated from Hydra so far.
Nobutaka Koibuchi - One of the best experts on this subject based on the ideXlab platform.
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existence of gradient in cell adhesiveness along the developing xenopus hind limb bud shown by a cellular sorting out experiment in vitro
Development Growth & Differentiation, 1998Co-Authors: Nobutaka Koibuchi, Shin TochinaiAbstract:To examine the possibility of a difference in cell adhesiveness along the developing Xenopus hind limb bud axes, single mesenchymal cells from developing hind limb buds were cultured, allowing them to form an aggregate in a gyratory culture system. By observing the distribution of cells within aggregates, it was found that sorting-out occurred between cells from different positions and different stages. Cells derived from more distal positions tended to be situated interiorly in the aggregates. According to Steinberg's differential adhesion hypothesis, these results support the idea that there is a graded difference in cell adhesiveness along the proximo-distal axis of the developing limb, with adhesiveness increasing distally. Although similar sorting-out was observed between anterior and posterior cell populations, it could not be determined which cell populations were definitely more cohesive. These properties may be correlated with the experimentally demonstrated ‘Positional Value', which should be different among cells located at different positions along the axes of the developing vertebrate limb bud.