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Cortical and Cytoplasmic Reorganizations (Ooplasmic Segregation)

 
Eggs of ascidians undergo 2 Major Phases of reorganization or Ooplasmic Segregation between fertilization and first cleavage which relocalize a cortical ER rich domain (in red) and a subcortical Mitochondria-rich Myoplasm domain (in green) first vegetally (1-3) and then posteriorly (5-7).

 

  

Two Major Phases

(1- 2): cortical contraction due to actomyosin microfilaments


(5- 6): cortical rotation due to microtubules

Many sub-phases

 (3-4): meiotic oscillations are periodic contractions due to repetitive calcium waves


(4-5): vegetal button formation is transient and due to actomyosin microfilaments

(7-8): vegetal cortical relaxation is due to actomyosin microfilaments

- Roegiers, F. et al. (1999). Development, 126, 3101-3117.