α-tubulin and acetylated α-tubulin during ovarian follicle differentiation in the lizard Podarcis sicula raf.

During most of the previtellogenic oocyte growth, the follicular epithelium of the lizard Podarcis sicula shows a polymorphic structure, due to the presence of different follicle cells. These include small cells which divide and move from the periphery of the follicle to the oocyte surface, intermediate cells which represent an initial step in the process of cell enlargement, and large pyriform cells engaged in the transport of different materials to the oocyte through intercellular bridges. We have studied, by immunolocalization and immunoblotting, the localization of alpha-tubulin and its acetylated form in different follicle cells and in the oocyte during the main steps of ovarian follicle differentiation. Our results indicate that alpha-tubulin is present in all follicle cells at different stages of ovarian follicle differentiation, while its acetylated form is detectable exclusively in the small proliferating and migrating follicle cells. In pyriforin cells, alpha-tubulin is localized around the nucleus, extends to the cell apex, and crosses the zona pellucida into the oocyte cortex. The presence of acetylated tubulin in the small follicle cells may be related to the proliferation and/or migration of these cells. The absence of acetylated tubulin form in the cytoplasm of intermediate and pyriform cells can be related to the colocalization of alpha-tubulin with the keratin cytoskeleton in these cells, as detected by confocal microscopy. We have also identified the colocalization of alpha-tubulin with keratin in the cortical region of the oocyte, in particular when the cortex is engaged in the uptake of the yolk proteins. (C) 2004 Wiley-Liss, Inc.