Distribution of prosome proteins and their relationship with the cytoskeleton in oogenesis of Xenopus laevis.

The presence of prosome proteins (p25K and p27K) was shown and their distribution was studied in oogenesis of Xenopus laevis using immunoblotting and immunofluorescence. These proteins form numerous granular clusters of variable size all over the cell. At previtellogenic stages, the prosome antibodies homogeneously stain the oocyte nucleus and the evenly distributed relatively large clusters in the cytoplasm. As the oocyte grows, the pattern of distribution of the prosome proteins undergoes changes: animal-vegetal and cortical gradients appear in the cytoplasm. In the course of oocyte maturation the size of clusters diminishes. Artificial activation of the egg leads to a dorso-ventral gradient in distribution of the prosome proteins. In this way, specific localization of prosome proteins is first visualized during formation of the dorso-ventral polarity. Co-localization of prosome proteins and actin and myosin was found in the oocyte by double staining. Small clusters of prosomes dispersed in the cytoplasm acquire capability of movement (after artificial activation) due, in all likelihood, to persisting connection with the acto-myosin complex of the egg.