Notes under development (notice removed when complete)
These notes are intended to introduce a number of mechanisms at the cellular level that form structures within the embryo. These cellular dynamic and physical interactions form basic tissue structures of epithelia, connective tissues and features such as tubes.
Epithelia during development often undergo folding or invagination, such that some of the epithelial cells are "pinched off" fron the existing epithelia to form a distinct structure. For example this process occurs in neural tube formation, sensory placode (otic and optic vesicles). Changes in cell shape require changes in the actin cytoskeleton and recent researh has shown Rho1 a small GTPase of the Rho subfamily (Rho, Rac and Cdc42) which acts as regulatory switch for actin cytoskeleton is activated in epithelial cells for invagination process initiation.
Simoes S, Denholm B, Azevedo D, Sotillos S, Martin P, Skaer H, Hombria JC, Jacinto A. Compartmentalisation of Rho regulators directs cell invagination during tissue morphogenesis. Development. 2006 Oct 4
Denholm B, Brown S, Ray RP, Ruiz-Gomez M, Skaer H, Hombria JC. rossveinless-c is a RhoGAP required for actin reorganisation during morphogenesis. Development. 2005 May;132(10):2389-400.
Cdc42 controls spindle orientation to position the apical surface during epithelial morphogenesis Aron B. Jaffe, Noriko Kaji, Joanne Durgan, and Alan Hall J. Cell Biol. 2008;183 625-633, Published online Nov 10 2008, 10.1083/jcb.200807121.
Epithelial cells (organised cellular layer) which loose their organisation and migrate/proliferate as a mesenchymal cells (disorganised cellular layers) are said to have undergone an Epithelial Mesenchymal Transition (EMT).
Mesenchymal cells, connective tissue-like, that have undergone this process may at a later time and under specific signaling can undergo the opposite process, mesenchyme to epithelia. In development, this process can be repeated several times during tissue differentiation.
Epithelial Mesenchymal Transition - gastrulation
Epithelial cells (organised cellular layer) and mesenchymal cells (disorganised cellular layers) or embryonic connective tissue interact together signaling back and forth by secreted signals or contact in the differentiation of many different organs, tissues and structures.
Morphodynamics refers to the biomechanical effects involved in development. There are several researchers who continue to build on concepts developed by Blechschmidt and others describing developmental events in terms of the physics involved in stresses and fluid movement within the embryo as important factors involved in establishing embryonic structures. (More? Morphodynamics)
Morphodynamics refers to the biomechanical effects involved in development. There are several researchers who continue to build on concepts developed by Blechschmidt and others describing developmental events in terms of the physics involved in stresses and fluid movement within the embryo as important factors involved in establishing embryonic structures.
(More? Tube Formation)