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Nicole A. Grieshaber et al reported the
Follicle-Stimulating Hormone-Responsive Cytoskeletal Genes in Rat Granulosa Cells: Class I ?Tubulin, Tropomyosin-4, and Kinesin Heavy Chain.
Changes in mouse granulosa cell gene expression during early luteinization. McRae RS et al. Changes in gene expression during granulosa cell luteinization have been measured using serial analysis of gene expression (SAGE). Immature normal mice were treated with pregnant mare serum gonadotropin (PMSG) or PMSG followed, 48 h later, by human chorionic gonadotropin (hCG). Granulosa cells were collected from preovulatory follicles after PMSG injection or PMSG/hCG injection and SAGE libraries generated from the isolated mRNA. The combined libraries contained 105,224 tags representing 40,248 unique transcripts. Overall, 715 transcripts showed a significant difference in abundance between the two libraries of which 216 were significantly down-regulated by hCG and 499 were significantly up-regulated. Among transcripts differentially regulated, there were clear and expected changes in genes involved in steroidogenesis as well as clusters of genes involved in modeling of the extracellular matrix, regulation of the cytoskeleton and intra and intercellular signaling. The SAGE libraries described here provide a base for functional investigation of the regulation of granulosa cell luteinization.
FSH regulates gene expression for granulosa cell differentiation and follicular development. Therefore, FSH-responsive genes are crucial, but only a few genes have been identified for the early stage of follicular development. In particular, little is known about cytoskeletal genes, which likely play essential roles in the morphological changes such as the antrum formation, a major landmark. FSH is also known to induce the differentiation of an immature, undifferentiated rat ovary granulosa (ROG) cell line. The data show that FSH induced massive yet distinct reorganization of microtubules and the actin cytoskeletons as well as morphological changes. To identify those genes responding to FSH during the differentiation, differential display was performed on ROG cells. Of the 80 FSH-responsive genes identified, there were three cytoskeleton-related genes (class I ?tubulin, tropomyosin 4, and kinesin heavy chain), which are crucial for intracellular morphogenesis, transport, and differentiation. Northern blots show that the level of these gene transcripts reached a peak at 6 h after FSH treatment and subsided at 24 h. FSH induced the similar temporal expression not only in granulosa cells isolated from immature rats, but also in vivo. For instance, in situ hybridization showed that ?tubulin mRNA was transiently expressed in the granulosa cells of large preantral and early antral follicles. Despite the same temporal expression, the regulatory mechanisms of the three genes were strikingly different. As an example, cycloheximide blocked the ?tubulin mRNA expression, whereas it increased tropomyosin-4 (TM4) mRNA. Yet, it did not impact kinesin heavy chain (Khc) mRNA. In conclusion, FSH induces the massive reorganization of the cytoskeletons and morphological changes by the selective regulation of the gene expression, protein synthesis, and rearrangement of the cytoskeletal proteins in the ROG cells and probably, specific follicles and granulosa cells.
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