E- and N-cadherin expression and distribution during luteinization in the rat ovary.

Cadherins, a family of Ca(2+)-dependent cell adhesion molecules, play an important role in ovarian tissue remodelling processes. The aim of this study was to examine the expression pattern of E- and N-cadherin in rat preovulatory follicles, luteinizing follicles and corpora lutea. Immature female rats were treated with equine chorionic gonadotrophin (eCG) to promote preovulatory follicle development. At 48 h after eCG treatment, the rats were injected with an ovulatory dose of hCG. Ovaries were analysed by western blot analysis and immunofluorescence for E- and N-cadherin expression at 48 h after eCG injection, and at 24 and 72 h after hCG injection. Ovaries of cyclic adult rats were examined to assess whether the changes in the expression pattern of cadherin were in agreement with those of the gonadotrophin-treated rats. Finally, expression of E-cadherin in luteinizing granulosa cells in vitro was assessed by RT-PCR and western blot analysis. Immunofluorescence results indicate that E-cadherin is expressed in the theca-interstial cells surrounding preovulatory follicles. N-cadherin expression is prominent in the membrana granulosa of these follicles. The initiation of luteinization with hCG leads to a decreased expression of N-cadherin in the membrana granulosa, whereas expression of E-cadherin starts within the luteinizing follicle. Both cadherins are prominently expressed in the fully formed corpus luteum at 72 h after hCG treatment. Immunofluorescence results revealed that the patterns of E- and N-cadherin expression in the gonadotrophin-treated rats were similar to those of the cyclic adult rats. Western blot analysis reflected similar changes for N-cadherin in the ovaries of both the cyclic adults and gonadotrophin-treated rats; however, they were different in E-cadherin expression. The expression of E-cadherin mRNA and protein was induced in vitro in luteinized granulosa cells. These results support the hypothesis that modulation of cadherin expression is an integral component of remodelling processes, including corpus luteum formation, in the ovary. The results also indicate that expression of E- and N-cadherin in granulosa-lutein cells appear to be under hormonal control.

Developmental expression and distribution of N- and E-cadherin in the rat ovary.

The calcium-dependent cell adhesion molecules, cadherins, regulate intercellular junction formation, cell sorting, and the establishment of cell polarity. Their important role in tissue remodeling suggests an involvement in ovarian cellular rearrangements throughout postnatal development. The ovary has a complex topology, and the ovarian follicle undergoes significant cellular rearrangements during its development. Cadherins have been detected previously in whole ovaries and in ovarian cells and cell lines with some immunolocalization in fetal and adult ovaries. This study examines the expression and localization of N- and E-cadherin throughout prepubertal ovarian and follicular development in the rat. We analyzed ovarian cadherin expression in rats from Day 19-20 of gestation to 25 days postpartum, during which follicle formation and folliculogenesis are the dominant ovarian events. Reverse transcriptase polymerase chain reaction detected N- and E-cadherin mRNA expression in the ovaries at all the ages examined. Semiquantification of Western blots of whole ovary extracts confirmed the presence of ovarian N- and E-cadherin protein at all ages with both showing peak expression at 7 days of age. Immunostaining revealed N- and E-cadherin expression in follicular and extrafollicular cell types, but only E-cadherin showed follicle-stage-dependent expression. The changes in cadherin expression, concurrent with ovarian growth and folliculogenesis, suggest a function for cadherins in the morphological and functional development of the prepubertal rat ovary.

Interphase cells of the centric diatom, Thalassiosira fluviatilis, lack detyrosinated, nontyrosinatable and acetylated tubulin.

Within eukaryotic cells tubulin generally exists in protein families composed of closely related isoforms generated either by differential gene transcription or by posttranscriptional and posttranslational mechanisms. In this study, immunological approaches were used to examine the contribution of posttranslational modifications to tubulin heterogeneity in a centric diatom, Thalassiosira fluviatilis, and to show the spatial distribution of microtubules in these cells during their interphase. After blotting to nitrocellulose, tubulin in cell-free homogenates of T. fluviatilis was recognized by several general tubulin antibodies including one to the tyrosinated isoform, but not by antibodies to detyrosinated, nontyrosinatable nor acetylated tubulins. Immunofluorescent staining of methanol-fixed cells revealed a net-like reticulum of microtubules originating at or near the cell nucleus. For all antibodies, except one (TU-01), results obtained by immunofluorescent experiments corrobated the analysis of blotted tubulins. Furthermore, microtubules exhibited differential staining patterns corresponding to the intensity of antibody reactivity on blots. Antibody to detyrosinated tubulin, as well as TU-01, yielded a spotty pattern of fluorescence on chloroplasts. Microtubules in T. fluviatilis support normal cell function in the absence of detectable amounts of three common posttranslationally modified tubulins, perhaps due to the rigid silica frustule which maintains shape and to the absence of flagella in interphase cells.