Asymmetrical distribution of microvilli in cytochalasin B-induced pseudocleavage of mouse oocytes

Abstract

CYTOCHALASIN B, a fungal alkaloid first described by Carter¹, has diverse effects on cultured cells, including inhibition of morphogenetic and movement processes, and interference with hormone mediated cellular response². It also induces various cultured mammalian cells to segregate the nucleus into an evagination of the plasma membrane which occasionally breaks away from the cell body³. Although some of the biological effects of cytochalasin B have been attributed to the disruption of microfilamentous structures found in cells, the mechanism of action of the drug remains unclear⁴. We have found that mouse oocytes cultured in the presence of cytochalasin B divide into two compartments; a process we called ‘pseudocleavage’⁵. We now report, using scanning electron microscopy, that although one of the oocyte compartments is covered with microvilli, the other is smooth. This suggests that cytochalasin B triggers a redistribution of cell surface elements in the mouse oocyte.