Dr. Néva Meyer started her research career in cancer biology while an undergraduate at Purdue University, but as a graduate student at the University of Washington, rotations through different research labs led her towards an interest in nervous system development. Her doctoral research focused the role of the Gli3 gene in dorsovental fate specification of neurons in the chick spinal cord. As a post-doctoral research fellow in Dr. Seaver's lab at Kewalo Marine Lab, she has become interested in the broader question of how centralized nervous systems (CNS) evolved.
Multiple groups of animals throughout the Bilateria possess centralized nervous systems – vertebrates have an anterior brain and dorsal nerve cord, whereas annelids (segmented worms) and arthropods (insects and crustaceans) have an anterior brain and a ventral nerve cord.
"However", Dr. Meyer points out, "animals with centralized nervous systems are phylogenetically separated from each other by animals with nerve nets, or non-centralized nervous systems, which raises the question of how and when centralized nervous systems evolved".
Most of the modern molecular descriptions of neurogenesis come from only two of the three major bilateral clades, the deuterostomes (e.g., vertebrates) and the ecdysozoans (e.g., arthropods). There remains a huge gap in knowledge of central nervous system development in the third bilateral clade, the lophotrochozoans (e.g., annelids).
"By studying CNS development in annelids, I hope to make significant contributions to our understanding of the basic mechanisms of neurogenesis in annelids and to our understanding of the evolution of centralized nervous systems."
A key step during CNS development in arthropods and vertebrates is specifying the fate of the neural precursor cells (NPCs), or the cells that generate the brain and nerve cord. The cellular mechanisms that are involved in internalizing the neural precursor cells from the outer ectodermal layer are different between vertebrates and arthropods, yet they both use the same genes (the proneural bHLH transcription factors achaete-scute and neurogenin) and signaling pathways (Notch/Delta) to specify the NPCs. Using several approaches, Dr. Meyer has characterized some cellular and molecular aspects of early brain development in the segmented worm, Capitella teleta.
"My results suggest that the cellular mechanisms of Capitella brain neurogenesis are similar to those found in the development of the arthropod CNS. However, some of my preliminary functional analyses of a proneural homolog in Capitella (CapI-ash1) suggest a function that is more similar to proneural gene function during vertebrate neurogenesis."
What this might mean in terms of the evolution of CNS development is a question on which Dr. Meyer continues to work. You can read more about her research here.
In addition to her novel work on annelid neurogenesis, Dr. Meyer has completed a project mapping the early blastomere fate in Capitella using intracellular lineage analysis. With this technique, a fluorescent dye is injected into a single blastomere at the early cleavage stages of the embryo, and the fate of this blastomere - the cells and tissues to which it gives rise - can be determined through its fluorescently labeled progeny. These types of lineage analyses are possible because Capitella, similar to many lophotrochozoans, develops by spiral cleavage, which is a highly stereotypic cleavage program that produces a wide range of body plans and structures and allows homologous cells to be recognized across different groups of animals.
"This provides a powerful tool for understanding the development and evolution of structures", explains Dr. Meyer, "as well as the ability to inject reagents such as nucleic acids into blastomeres with a known fate."
This fate map of Capitella teleta development by Dr. Meyer represents the very first complete lineage analysis of a polychaete annelid using intracellular labeling techniques. An abstract of this research is available on-line.
Dr. Meyer received her Ph.D. from the University of Washington and is currently a post-doctoral research fellow in Dr. Elaine Seaver's Lab.