Subcortical Rotation:

Role of Microtubules

The micrographs below show that in normal embryo aligned microtubules are present in the vegetal hemisphere at the interface between cortex and subcortical regions of the fertilized egg. In addition, the micrographs show the drastic effects on subsequent development when the organization of these microtubules is pertubed using two different sorts of drugs. Nocodazole causes the eventual depolymerization of microtubules, i.e., they "fall apart". Taxol, which has received some notoreity of late as a treatment for breast cancer, results in excessive stabilization of microtubules. The two drugs have contrasting effects, nocodazole results in loss of anterior structures like eyes, cement gland, etc, whereas taxol results in "hyperdorsalization", with the production of an excess of eye and mouth structures in a radially symmetric pattern (talking about having "eyes in the back of your head"!). How can you account for the different effects of the drugs, assuming that their effects relate to the process of subcortical rotation?