Meeting Abstract
The processes underlying left-right asymmetry are highly conserved across a wide range of species. Nodal signaling, H+/K+ ATPase-dependent ion flux and ciliary flow are required for lateral asymmetry in both protostome and deuterostome clades yet details regarding how these initial processes lateralize organ morphogenesis remain poorly characterized. We use the invertebrate chordate Ciona intestinalis to investigate asymmetric organ development. Previous research indicates that Ciona heart asymmetry is dependent on ion flux but does not require Nodal signaling. To understand the link between ion flux and lateralized organ morphogenesis, we have begun to characterize laterally asymmetric gene expression in Ciona embryos. By sequencing RNA in thin sections spanning the left-right axis, we have established a list of 19 candidate genes displaying strongly lateralized expression. We have confirmed six of these predicted expression patterns through in situ hybridization. These studies have revealed that many of the candidate genes are expressed in the trunk lateral cell lineage, a group of mesodermal cells that migrate extensively in the larval head and differentiate into blood and muscle. We have also begun to characterize the dependence of these candidate genes on ion flux using the H+/K+ ATPase inhibitor omeprazole. The further characterization of asymmetrically expressed genes should provide critical insights into the molecular mechanisms driving heart and endoderm asymmetry within Ciona and vertebrate embryos.
