Effects of TCDD on spermatogenesis related factor-2 (SRF-2): gene expression in Xenopus.

2,3,7,8-Tetra-chlorodibenzo-p-dioxin (TCDD) is one of the most toxic dioxins belonging to the wide family of Endocrine Disruptors (EDs), environmental chemicals that adversely interfere with endocrine processes and upset normal function of some target systems. It has been hypothesized that EDs enter cellular cytosol, bind to the Aryl Hydrocarbon Receptor (AhR) and form a heterodimer with the AhR nuclear translocator; this complex binds xenobiotic responsive elements that drive activation of the so-called "Ah gene battery". Spermatogenesis Related Factor-2 (SRF-2) is one of the most recently cloned genes involved in germ cell division and differentiation, whose expression seems to be affected by treatment with TCDD. With the aim to try to clarify the underlying mechanism of TCDD and to investigate if SRF-2 gene represents a good biomarker for ED exposure, we used Xenopus laevis as an animal model, considered to be almost insensitive toward TCDD effects. In this study we reported the partial cloning of SRF-2 cDNA in X. laevis; we then evaluated the SRF-2 expression in embryos exposed to TCDD 0.62 microM by real-time PCR. We also analyzed SRF-2 expression in several adult control tissues and in testis after perilymphatic injection of a single dose of 10 microg/kg body weight. Although SRF-2 expression does not seem to be affected by the treatment, exposed embryos died within 15 days. In the light of these results, we can conclude that SRF-2 is not a good candidate in signalling EDs exposure and that the molecular mechanism for TCDD toxicity in Xenopus likely involves the AhR signalling cascade, as in other vertebrate species.