Validation of a GC-MS method for screening of chemically-induced modulation of steroid hormones in Ciona intestinalis

The ascidian, C. intestinalis is one of the most common modern urochordates that represent one of the closest invertebrate relatives of vertebrates. For many years, ascidians have been proposed as good experimental model organisms, due to the typical mosa ic development where embryogenic cell fate is well established and a simple body plan, that represent a good model for studies on differentiation and cell-cell interaction of the central nerve system, muscles, and sensory organs. Many endocrine organs and hormonereceptor systems are conserved among vertebrates, but the identification of corresponding systems in protostomes have proved difficult. Thus, this species provides a unique opportunity to gaining insight into the hormonal signaling pathways of cho rdates and their relatedness to vertebrate hormones. In addition, identification and availability of these hormones in chordates will also provide more insights on signal transduction pathways prior to the large-scale genome duplication processes that are universally believed to have occurred twice during an evolutionary process and are integral aspects of early stages of vertebrate evolution. In addition to their evolutionary positioning, the ascidians are simple experimental models to investigate the mo lecular mechanisms underlying the effects of environmental pollutants on the endocrine systems. Therefore, Ciona hormones and their relatedness to vertebrate hormones provide a unique opportunity to determine which of the vertebrate endocrine pathways tha t may have been present in ancient chordates. Thus, hormonal modulation by an endocrine disrupting chemical (EDC) such as TBT, will form a solid basis for a realistic extrapolation of endocrine disrupting effects across taxonomic groups and phyla.