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Isolation of differentially expressed mRNA in ovaries after estrogen withdrawal in hypophysectomized
1Department of Physiology, Göteborg University, PO Box 434, SE 405 30 Göteborg, Sweden. bodil.svanberg@fysiologi.gu.se
Abstract:
Ovarian follicular atresia occurs throughout follicular development and involves apoptosis. In addition to regulation by various hormones and growth factors, ovarian granulosa cell apoptosis was shown to be dependent on transcription and translation since the spontaneous onset of DNA degradation in incubated rat granulosa cells was inhibited by actinomycin-D or cycloheximide. Using differential display of mRNA, five transcriptionally upregulated cDNA clones were isolated in the ovary after withdrawal of the anti-apoptotic factor, estrogen. Two of these estrogen-regulated genes, designated ARG-33 and ARG-40, were further characterized using Northern blot hybridizations. ARG-40 showed increased mRNA expression during apoptosis after estrogen withdrawal in the ovary, and after androgen withdrawal in the prostate, while ARG-33 was upregulated during apoptosis only after estrogen withdrawal. This suggests that the two cDNA clones are regulated by steroids, and may be involved in apoptosis in these tissues. ARG-40 showed high homology to cytochrome b, while ARG-33 was novel.
Insights
Estrogen withdrawal triggers ovarian granulosa cell apoptosis, involving new genes like ARG-33 and ARG-40. These genes, regulated by steroids, may play a role in programmed cell death in reproductive and prostate tissues.
Area of Science:
- Reproductive biology
- Molecular endocrinology
- Cellular apoptosis
Background:
- Ovarian follicular atresia and granulosa cell apoptosis are crucial reproductive processes.
- Hormonal and growth factor regulation of apoptosis is complex.
- Granulosa cell apoptosis is dependent on active transcription and translation.
Purpose of the Study:
- To identify genes upregulated during ovarian apoptosis following estrogen withdrawal.
- To characterize the expression patterns of novel estrogen-regulated genes.
- To investigate the role of these genes in steroid-regulated apoptosis.
Main Methods:
- Differential display of mRNA to identify upregulated cDNAs.
- Northern blot hybridization to confirm gene expression.
- Bioinformatic analysis for gene homology.
Main Results:
- Five transcriptionally upregulated cDNA clones were identified after estrogen withdrawal.
- ARG-40 mRNA expression increased during apoptosis in ovaries (estrogen withdrawal) and prostates (androgen withdrawal).
- ARG-33 mRNA expression increased during apoptosis only in ovaries after estrogen withdrawal. ARG-40 showed homology to cytochrome b; ARG-33 was novel.
Conclusions:
- Steroid hormones regulate specific genes involved in apoptosis in the ovary and prostate.
- ARG-33 and ARG-40 are novel genes potentially mediating steroid-regulated programmed cell death.
- These findings contribute to understanding the molecular mechanisms of follicular atresia and tissue-specific apoptosis.