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Embryonic Pattern Formation (embryonic + pattern_formation)

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Life Sciences100%

Selected Abstracts

Embryonic pattern formation without morphogens

BIOESSAYS, Issue 5 2008
Hamid Bolouri
One of the earliest and most-fundamental pattern- formation events in embryonic development is endoderm and mesoderm specification. In sea urchin embryos, this process begins with blimp1 and wnt8 gene expression at the vegetal pole as soon as embryonic transcription begins. Shortly afterwards, wnt8/blimp1 expression spreads to the adjacent ring of mesoderm progenitor cells and is extinguished in the vegetal-most cells. A little later, the ring of wnt8/blimp1 activity moves out of the mesoderm progenitors and into the neighboring endoderm cells. Remarkably, this moving ring of gene expression has now been shown to be controlled entirely by transcriptional cis -regulatory logic.1. BioEssays 30:412,417, 2008. © 2008 Wiley Periodicals, Inc. [source]

Re-organisation of the cytoskeleton during developmental programmed cell death in Picea abies embryos

THE PLANT JOURNAL, Issue 5 2003
Andrei P. Smertenko
Summary Cell and tissue patterning in plant embryo development is well documented. Moreover, it has recently been shown that successful embryogenesis is reliant on programmed cell death (PCD). The cytoskeleton governs cell morphogenesis. However, surprisingly little is known about the role of the cytoskeleton in plant embryogenesis and associated PCD. We have used the gymnosperm, Picea abies, somatic embryogenesis model system to address this question. Formation of the apical,basal embryonic pattern in P. abies proceeds through the establishment of three major cell types: the meristematic cells of the embryonal mass on one pole and the terminally differentiated suspensor cells on the other, separated by the embryonal tube cells. The organisation of microtubules and F-actin changes successively from the embryonal mass towards the distal end of the embryo suspensor. The microtubule arrays appear normal in the embryonal mass cells, but the microtubule network is partially disorganised in the embryonal tube cells and the microtubules disrupted in the suspensor cells. In the same embryos, the microtubule-associated protein, MAP-65, is bound only to organised microtubules. In contrast, in a developmentally arrested cell line, which is incapable of normal embryonic pattern formation, MAP-65 does not bind the cortical microtubules and we suggest that this is a criterion for proembryogenic masses (PEMs) to passage into early embryogeny. In embryos, the organisation of F-actin gradually changes from a fine network in the embryonal mass cells to thick cables in the suspensor cells in which the microtubule network is completely degraded. F-actin de-polymerisation drugs abolish normal embryonic pattern formation and associated PCD in the suspensor, strongly suggesting that the actin network is vital in this PCD pathway. [source]

Controlling the stem cell niche: right time, right place, right strength

BIOESSAYS, Issue 1 2006
Catherin Niemann
Wnt signalling through ,-catenin plays a pivotal role during embryonic pattern formation, cell fate determination and tissue homeostasis in the adult organism. In the skin, as in many other tissues, Wnt/,-catenin signalling can control lineage determination and differentiation. However, it was not known whether Wnt/,-catenin signalling is an immediate regulator of the stem cell niche in skin tissue. A recent publication now provides evidence that Wnt/,-catenin signalling exerts a direct effect on the stem cell compartment by inducing quiescent stem cells to enter the cell cycle during early stages of hair follicle regeneration. In addition, the authors demonstrate that ,-catenin is required for maintenance of the stem cell pool in the tissue.1 The data suggest that a gradient in Wnt/,-catenin activity levels can induce different responses within distinct cell populations reflected by activation of distinct transcriptional profiles. BioEssays 28:1,5, 2006. © 2005 Wiley Periodicals, Inc. [source]

Turning it up a Notch: cross-talk between TGF, and Notch signaling

BIOESSAYS, Issue 2 2005
Michael Klüppel
Signaling through both the transforming growth factor , (TGF,) superfamily of growth factors and Notch play crucial roles during embryonic pattern formation and cell fate determination. Although both pathways are able to exert similar biological responses in certain cell types, a functional interaction between these two signaling pathways has not been described. Now, three papers provide evidence of both synergy and antagonism between TGF, and Notch signaling.1,3 These reports describe a requirement for Notch signal transducers in TGF,- and BMP-induced expression of Notch target genes, as well as in BMP-controlled cell differentiation and migration. These papers uncover a direct link between the Notch and TGF, pathways and suggest a critical role for Notch in some of the biological responses to TGF, family signaling. BioEssays 27:115,118, 2005. © 2005 Wiley Periodicals, Inc. [source]