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Functional genomics and sexual differentiation in amphibians
Christian Bögi1, Gregor Levy, Ilka Lutz
1Department of Inland Fisheries, Leibniz-Institute of Freshwater Ecology, Müggelseedamm 310, 12587, Berlin, Germany.
Summary
Sexual differentiation in Xenopus laevis involves maternal steroids and endogenous production during development. Estradiol (E2) and estrogen receptors (ER) are crucial, with higher levels in females and roles in gene expression and sex determination.
Area of Science:
- Developmental Biology
- Endocrinology
- Amphibian Research
Background:
- Sexual differentiation mechanisms in amphibians are not fully understood.
- Maternal and endogenous sex steroid dynamics are critical during larval development.
Purpose of the Study:
- Investigate the time course of sexual steroids and their receptors during Xenopus laevis larval development.
- Determine the roles of estradiol (E2) and androgens in sexual differentiation.
Main Methods:
- Quantified sexual steroid levels and receptor mRNA expression (androgen receptor [AR], estrogen receptor [ER]) via semiquantitative RT-PCR.
- Administered exogenous steroids (E2, methyltestosterone, dihydrotestosterone, testosterone) and anti-steroids (cyproterone acetate, tamoxifen) to assess effects on sexual differentiation.
Main Results:
- Maternal androgens and E2 accumulate in tadpoles, decreasing post-hatching and rising at metamorphosis.
- AR and ER mRNA levels peak post-hatching and remain elevated.
- Females exhibit higher E2 and ER mRNA levels than males.
- Exogenous E2 upregulates both ER and AR mRNA.
- Steroid treatments induce feminization (E2, cyproterone acetate), neutralization (tamoxifen), or masculinization (methyltestosterone, dihydrotestosterone).
Conclusions:
- Estrogen signaling plays a significant role in amphibian sexual differentiation.
- A new hypothesis for functional genomics in amphibian sexual differentiation is proposed based on steroid and receptor dynamics.