Patterning of the nervous system in I. pulchra (Acoela)

The nervous systems of animals as different as flies and mice develop deploying an astonishing amount of the same genes with conserved functions. However, their morphology ranges from diffuse nerve nets to systems comprising a brain and various nerve cords. Consequently, the anatomy of the primitive nervous system is unknown and hotly debated. In this respect investigations on the development of the nervous system in Isodiametra pulchra (Acoela) are very promising. Within the tree of life these simple worms reside between the cnidarians (anemones, corals, jellyfishes) and all the other "higher" animals (Bilateria) and very likely they possess the most ancestral brain. They also have numerous, circumferentially distributed longitudinal nerve cords contrary to vertebrates and insects, which have established the nerve cords on the dorsal and ventral side, respectively. In our project we will focus on the patterning of the nervous system along the dorsoventral (back-belly) and the mediolateral (midline-side) axis and hope to better understand the supposed anti-/neurogenic function of the BMP pathway and the establishment of the nerve cords on either side of the dorsoventral axis in the majority of the Bilateria. We will generate, sequence, and analyze embryonic EST collections and identify orthologue regulatory genes. Subsequently the spatial and temporal expression of these genes will be determined by means of in situ hybridizations, and under prevailing circumstances with double or multiplex in situ hybridizations. The functions and interactions of specific genes will be tested by knock-down-experiments (RNA interference) with subsequent characterization of the phenotypes, especially by using antibodies, mostly against the nervous system and the musculature. The microscopic size of Isodiametra pulchra and the knowledge on its morphology in combination with the possibility to knock-down gene expression should help to decipher the evolution of nervous systems in the Bilateria and to further develop I. pulchra as a model organism of the Acoela, a clade that bears the potential to answer many questions concerning animal evolution.