Ingression is one of the many changes in the location or relative position of cells that takes place during the gastrulation stage of embryonic development. It produces an animal's mesenchymal cells at the onset of gastrulation. During the epithelial–mesenchymal transition (EMT), the primary mesenchyme cells (PMCs) detach from the epithelium and become internalized mesenchyme cells that can migrate freely.
While the mechanisms of ingression are not fully understood, studies using the sea urchin as a model organism have begun to shed light on this developmental process, and will be the focus here. There are three main changes that must occur within a cell to enable the process of ingression. The ingressing PMCs must first alter their affinity for the neighboring epithelial cells that will remain in the vegetal pole (vertebrate PMCs ingress from the primitive streak). During this time, these cells must lose their affinity for the hyaline layer to which their apical surface is attached. The ingressing cells will then apically constrict and alter their cellular architecture through a dramatic reorganization of their cytoskeleton. Lastly, these cells will modify their mode of motility and presumably gain affinity for the basal lamina which composes the lining of the blastocoel, the future migration substrate of the PMCs.
Changes in the adhesion properties of these cells are the best characterized and understood mechanism of ingression. In sea urchins, epithelial cells adhere to one another as well as the hyaline layer through classic cadherins and adherens junctions. Ingression is a very dynamic process however, and the first sign of an ingressing cell is seen when a future PMC loses its adhesion to hyaline, and cadherin, and increases its adhesion to a basal laminal substrate. These processes occur rapidly, over approximately 30 minutes. It is not understood how the PMCs penetrate the basal lamina. The basal lamina is a loose matrix, therefore it is possible that the ingressing cells squeeze through the matrix.
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This course will provide the fundamental knowledge in neuroscience required to
understand how the brain is organised and how function at multiple scales is
integrated to give rise to cognition and beh
This course will provide the fundamental knowledge in neuroscience required to
understand how the brain is organised and how function at multiple scales is
integrated to give rise to cognition and beh
This course will provide the fundamental knowledge in neuroscience required to
understand how the brain is organised and how function at multiple scales is
integrated to give rise to cognition and beh
The primitive streak is a structure that forms in the early embryo in amniotes. In amphibians the equivalent structure is the blastopore. During early embryonic development, the embryonic disc becomes oval shaped, and then pear-shaped with the broad end towards the anterior, and the narrower region projected to the posterior. The primitive streak forms a longitudinal midline structure in the narrower posterior (caudal) region of the developing embryo on its dorsal side.
In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell, (spermatozoon). Once fertilized, the ovum becomes a single diploid cell known as a zygote. The zygote undergoes mitotic divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to development of a multicellular embryo after passing through an organizational checkpoint during mid-embryogenesis.
Explores embryonic induction through Spemann and Mangold's experiments, highlighting organizer roles, neural plate formation, and Activin as a morphogen.
Explores embryonic induction, gastrulation, germ layer patterning, and signal transduction pathways in development.
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The emergence of multiple axes is an essential element in the establishment of the mammalian body plan. This process takes place shortly after implantation of the embryo within the uterus and relies on the activity of gene regulatory networks that coordina ...
Previous attempts to recapitulate embryogenesis in a developmentally relevant context started with aggregates composed of a few thousand ESCs, termed embryoid bodies (EB), that upon induction of differentiation reveal a surprising level of autonomous cell ...
Endoderm differentiation and movements are of fundamental importance not only for subsequent morphogenesis of the digestive tract but also to enable normal patterning and differentiation of mesoderm- and ectoderm-derived organs. This review defines the tis ...