α‐Tubulin and acetylated α‐tubulin during ovarian follicle differentiation in the lizard Podarcis sicula Raf.

Abstract

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 pyriform 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.

Vasa protein is localized in the germ cells and in the oocyte-associated pyriform follicle cells during early oogenesis in the lizard Podarcis sicula

“…Using immunostaining and light microscopy, we reported the presence of a cytokeratin network in the cytoplasm of pyriform cells which crosses their apex and extends through the intercellular bridges and into the oocyte cortex (Maurizii et al 2000). We have also reported that the tubulin cytoskeleton is involved in the interaction between the somatic follicle cells and the growing oocyte (Maurizii et al 2004). The morphology of the previtellogenic oogenesis of the lizard P. sicula is illustrated in Fig.…”

Hormonal Regulation of Ovarian Function in Reptiles

“…Such activity often occurs seasonally, particularly in temperate reptilian species (Guraya, 1989). These pyriform cells differentiate from small somatic follicular cells early in follicular development via the intermediate cell stage to become 'nurse cells,' in direct contact with the developing oocyte (Maurizii, Alibardi, & Taddei, 2004). Some features of follicular development vary among squamate, chelonian, and crocodilian reptiles.…”

“…Most reptilian oocytes are telolecithal, and so follicular development is typically associated with extensive vitellogenesis. The pyriform cells are connected to the oocyte via intercellular bridges containing a cytoskeleton of a-tubulin and cytokeratin microtubules (Maurizii et al, 2004). In squamates, the follicular epithelium, or granulosa, initially consists of small cuboidal cells, but differentiates during the pre-vitellogenic phase to become multi-layered and polymorphic.…”

Reproductive pattern and sex hormones of Calotes emma Gray 1845 andCalotes versicolor Daudin 1802 (Squamata; Agamidae)

“…Uribe et al (1996) stated that in squamates the follicular epithelium or granulosa initially consists of small cuboidal cells, but differentiates during the previtellogenic phase and becomes multilayered and polymorphic by the presence of unique flask-shaped pyriform cells, intermediate cells, and small cells. These pyriform cells differentiate from small somatic follicular cells early in follicular development via the intermediate-cell stage to become nurse cells, in direct contact with the developing oocytes (Maurizii et al, 2004). Differentiation of the small cells into pyriform cells appears to be linked to the progressive appearance of glycoproteins with terminal α-N-acetylgalactosamine residues on the cell surface, which may be involved in fusion between the oocyte and the follicle cell membranes as well as maintenance of the differentiated pyriform cells.…”