Vertebrate Development
See also Embryogenesis and Embryonic development
The bodies of vertebrate animals are asymmetric along three axes: anterior-posterior (head to tail), dorsal-ventral (spine to stomach), and left-right (for example, our heart is on the left side of our body). These polarities arise within the developing embryo through a combination of several processes: 1) asymmetric cell division, in which two daughter cells receive different amounts of cellular material (e.g. mRNA, proteins), 2) asymmetric localization of specific proteins or RNAs within cells (which is often mediated by the cytoskeleton), 3) concentration gradients of secreted proteins across the embryo such as Wnt, Nodal, and Bone Morphogenic Proteins (BMPs), and 4) differential expression of membrane receptors and ligands that cause lateral inhibition, in which the receptor-expressing cell adopts one fate and its neighbors another.
In addition to defining asymmetric axes in the adult organism, cell polarity also regulates both individual and collective cell movements during embryonic development such as apical constriction, invagination, and epiboly. These movements are critical for shaping the embryo and creating the complex structures of the adult body.
Read more about this topic: Cell Polarity
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