Gastrulation
Gastrulation is a stage in early animal development marked by extensive cell migration[1]. When cells are reorganised in the gastrula they develop into distinct germ layers: the mesoderm, ectoderm and endoderm. Together they give the body the basis of its organs and create the external form of developing animals[2]. This positioning is controlled by Morphogens, secreted proteins which determine differentiation and result in a change in the cell shape.
Gastrulation can be divided into three main processes, which are morphogenetic and have been conserved evolutionarily: Ingression, Epiboly, and Convergence and Extension.
Ingression
Mesodermal and endodermal cells move via the primitive streak, a hollow sphere of cells which forms early in development[3]. Cells move downwards and outwards as individual cells to form the middle layer. Prior to this, mesodermal and endodermals cells are stored in the epithelium[4]. This process involves the cytoskeleton due to the formation of the intermediate filament network and rearrangement of microtubules to radiate from a centrosome.[5]
Epiboly
This is a thinning process whereby cell layers spread in the early embryo. Cells change the way they are arranged; this is achieved by Radial intercalation where cell layers merge and cells intermix as they move away from the blastula[6] . Actin is important in this process, with formation of rings of filamentation having been observed[7].
References
- ↑ Hartl, D. and Ruvolo, M. (2012) Genetics: Analysis of Genes and Genomes. pp 482-483 8th Edition. United States: Jones and Bartlett Publishers, Inc.
- ↑ Solnica-Krezel, L. and Sepich, D. (2012) ‘Gastrulation: Making and Shaping Germ Layers’, Annual Review of Cell and Developmental Biology, 28(1)
- ↑ Hartl and Ruvolo, 2012, pp. 482–483
- ↑ Solnica-Krezel and Sepich, 2012, pp. 687–71
- ↑ Thiery, J. P., Acloque, H., Huang, R. Y. J. and Nieto, A. (2009) ‘Epithelial-Mesenchymal Transitions in Development and Disease’, Cell, 139(5).
- ↑ Solnica-Krezel and Sepich, 2012, pp. 687–717
- ↑ Cheng, J., Miller, A. and Webb, S. (2004) ‘Organization and function of microfilaments during late epiboly in zebrafish embryos’, Developmental Dynamics, 231(2).