Meeting Abstract

P1.53  Tuesday, Jan. 4  Evolutionary conserved regulation of Hox genes by RA pathway, hints from Platynereis dumerilii HANDBERG-THORSAGER, M.*; TOMER, R.; ARENDT, D.; EMBL, Heidelberg, Germany mette.handberg-thorsager@embl.de

The Hox gene family comprises a group of transcription factors that has been shown to play a fundamental role in the formation of the animal body plan. With the description of a variety of new roles of the Hox genes in important developmental processes e.g. in the formation of organs and in the motoneuron identity, it is unclear which of these roles is ancestral. To shed light on this, we study Hox gene function in the marine model system Platynereis dumerilii (Annelida). It is a slow-evolving organism making it ideal for evolutionary comparative studies. From larval stages onwards, it possesses homonomous segments, which allows us to determine the Hox function in an organism with no morphological differences between segments along the body axis (homonomous segmentation as opposed to heteronomous segmentation with tagmata in other protostomes and vertebrates). A previous study has shown that a subset of the Platynereis Hox genes are expressed along the anteriorposterior axis (Kulokova et al ., 2007). Furthermore, we investigate the regulation of Hox genes in the annelid. I am especially interested in the retinoic-acid (RA) pathway, an upstream regulator of Hox genes described in deuterostomes. New phylogenetic analysis has demonstrated that lophotrochozoans including annelids and molluscs also possess genes involved in RA signalling ( Aldh1a, Cyp26 and rar ) (Albalat and Cañestro (2008)). Yet the functionality of the signalling pathway in lophotrochozoans has not yet been investigated. Expression of the genes in Platynereis shows an overlap with the anterior Hox genes. We will use Platynereis to study evolutionary conservation of this pathway and its possible ancestral regulation of the Hox genes.