Methods to Test Endocrine Disruption in Drosophila melanogaster.

In recent years there has been growing evidence that all organisms and the environment are exposed to hormone-like chemicals, known as endocrine disruptor chemicals (EDCs). These chemicals may alter the normal balance of endocrine systems and lead to adverse effects, as well as an increasing number of hormonal disorders in the human population or disturbed growth and reduced reproduction in the wildlife species. For some EDCs, there are documented health effects and restrictions on their use. However, for most of them, there is still no scientific evidence in this sense. In order to verify potential endocrine effects of a chemical in the full organism, we need to test it in appropriate model systems, as well as in the fruit fly, Drosophila melanogaster. Here we report detailed in vivo protocols to study endocrine disruption in Drosophila, addressing EDC effects on the fecundity/fertility, developmental timing, and lifespan of the fly. In the last few years, we used these Drosophila life traits to investigate the effects of exposure to 17-α-ethinylestradiol (EE2), bisphenol A (BPA), and bisphenol AF (BPA F). Altogether, these assays covered all Drosophila life stages and made it possible to evaluate endocrine disruption in all hormone-mediated processes. Fecundity/fertility and developmental timing assays were useful to measure the EDC impact on the fly reproductive performance and on developmental stages, respectively. Finally, the lifespan assay involved chronic EDC exposures to adults and measured their survivorship. However, these life traits can also be influenced by several experimental factors that had to be carefully controlled. So, in this work, we suggest a series of procedures we have optimized for the right outcome of these assays. These methods allow scientists to establish endocrine disruption for any EDC or for a mixture of different EDCs in Drosophila, although to identify the endocrine mechanism responsible for the effect, further essays could be needed.

Cloning and functional characterization of the intersex homologous gene in the pest lepidopteron Maruca vitrata.

The intersex (ix) gene works in concert with doublesex (dsx) at the bottom of the sex-determination hierarchy to control somatic sexual differentiation in Drosophila melanogaster females. Here we report the isolation and characterization of the Drosophila intersex (ix) homologue in the pest lepidopteron Maruca vitrata (Mvix). The Mvix gene exhibits major complexity with respect to the Drosophila homolog. It is expressed in males and females and its pre-mRNA is subject to differential splicing events which affect both the protein coding and the non-coding regions. Moreover, Northern blot experiments revealed the presence of a female-specific transcript in pupae RNA, which appears to be the first described sex specific transcript of ix homologs characterized to date. The expression of Mvix cDNA in D.melanogaster transgenic flies indicates that the MvIX product, which shares a relatively high degree of homology with the D.melanogaster IX protein, is able to partially rescues the Drosophila mutant phenotype.