Asymmetrical localization and segregation of Paracentrotus lividus Bep4 maternal protein.

Asymmetric divisions that produce two distinct cells play a fundamental role in generating different cell types during development. Here we investigate the role of the cortex region and mitotic apparatus in asymmetrical localization and segregation of Bep4 protein in Paracentrotus lividus egg. By centrifugation of eggs with or without drugs we established an involvement of the cortex region in localization of Bep4 protein, con®rmed by immunohistochemistry of isolated cortex. Association with the mitotic apparatus during cell division permits selective partitioning of Bep4 protein into the daughter cells. Direct association with spindle was also demonstrated both by Western blot and immunohistochemestry after isolation of the mitotic apparatus.