Symmetry breaking in biology is the process by which uniformity is broken, or the number of points to view invariance are reduced, to generate a more structured and improbable state.
[2] In a biological perspective, the more complex an organism is, the higher number of symmetry-breaking events can be found.
[6][7] However, there is also evidence that earlier asymmetries in serotonin distribution and ion-channel mRNA and protein localization occur in zebrafish, chicken and Xenopus development,[8][9][10] and similar to observations of intrinsic chirality generated by the cytoskeleton[11][12] leading to organ and whole organism asymmetries in Arabidopsis[13][14][15][16] this itself seems to be controlled from the macromolecular level by the cytoskeleton.
Another example that involves symmetry breaking is the establishment of dendrites and axon during neuron development, and the PAR protein network in C. elegans.
[20] Another study also revealed that mutant phenotype could be rescued (returned to normal) by physically turning the embryo, thus mimicking cortical rotation and demonstrating that microtubules were not the determinant of dorsal development.
To identify these elements, researchers looked for mRNA and protein that demonstrated localization to either the vegetal pole or the dorsal side of the embryo to find candidates.
The Dsh protein was fused to a GFP and tracked during cortical rotation, it was observed to be in vesicles that were couriered along microtubules to the dorsal side.
[24] VegT, a T-box transcription factor, is localized to the vegetal cortex and upon cortical rotation is released in a gradient fashion into the embryo to regulate mesoderm development.