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Gata2 provides an early anterior bias and uncovers a global positioning system for polarity in the amniote embryo.

ABSTRACT: The first axis to be specified during vertebrate development is that between the site where gastrulation will begin and the opposite pole of the embryo (dorsoventral axis in amphibians and fish, anteroposterior in amniotes). This relies on Nodal activity, but different vertebrates differ in how this activity is positioned. In chick, the earliest known asymmetry is posterior expression of the TGF?-related factor Vg1, close to the future Nodal expression domain. Here we show that the transcription factor Gata2 is expressed anteriorly before this stage. Gata2 influences the site of primitive streak formation and its role is independent from, and upstream of, Vg1 and Wnt. However, although Vg1 is required for streak formation, Gata2 does not act as an absolute anterior specifier, but provides an anterior bias. These findings point to previously unsuspected global determinants of polarity of the early amniote embryo.

SUBMITTER: Bertocchini F

PROVIDER: S-EPMC3565152 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Gata2 provides an early anterior bias and uncovers a global positioning system for polarity in the amniote embryo.

Bertocchini Federica F Stern Claudio D CD

Development (Cambridge, England) 20121101 22

The first axis to be specified during vertebrate development is that between the site where gastrulation will begin and the opposite pole of the embryo (dorsoventral axis in amphibians and fish, anteroposterior in amniotes). This relies on Nodal activity, but different vertebrates differ in how this activity is positioned. In chick, the earliest known asymmetry is posterior expression of the TGFβ-related factor Vg1, close to the future Nodal expression domain. Here we show that the transcription ...[more]

PMID: 23093427

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Project description:The tissue scale deformations (? 1 mm) required to form an amniote embryo are poorly understood. Here, we studied ?400 ?m-sized explant units from gastrulating quail embryos. The explants deformed in a reproducible manner when grown using a novel vitelline membrane-based culture method. Time-lapse recordings of latent embryonic motion patterns were analyzed after disk-shaped tissue explants were excised from three specific regions near the primitive streak: 1) anterolateral epiblast, 2) posterolateral epiblast, and 3) the avian organizer (Hensen's node). The explants were cultured for 8 hours-an interval equivalent to gastrulation. Both the anterolateral and the posterolateral epiblastic explants engaged in concentric radial/centrifugal tissue expansion. In sharp contrast, Hensen's node explants displayed Cartesian-like, elongated, bipolar deformations-a pattern reminiscent of axis elongation. Time-lapse analysis of explant tissue motion patterns indicated that both cellular motility and extracellular matrix fiber (tissue) remodeling take place during the observed morphogenetic deformations. As expected, treatment of tissue explants with a selective Rho-Kinase (p160ROCK) signaling inhibitor, Y27632, completely arrested all morphogenetic movements. Microsurgical experiments revealed that lateral epiblastic tissue was dispensable for the generation of an elongated midline axis- provided that an intact organizer (node) is present. Our computational analyses suggest the possibility of delineating tissue-scale morphogenetic movements at anatomically discrete locations in the embryo. Further, tissue deformation patterns, as well as the mechanical state of the tissue, require normal actomyosin function. We conclude that amniote embryos contain tissue-scale, regionalized morphogenetic motion generators, which can be assessed using our novel computational time-lapse imaging approach. These data and future studies-using explants excised from overlapping anatomical positions-will contribute to understanding the emergent tissue flow that shapes the amniote embryo.

Dataset Information

Gata2 provides an early anterior bias and uncovers a global positioning system for polarity in the amniote embryo.

Publications

Gata2 provides an early anterior bias and uncovers a global positioning system for polarity in the amniote embryo.

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