Ms. Emi Yamaguchi's fascination with marine biology began at an early age, with dreams of becoming a marine biologist and working with dolphins. It wasn't until her time as an undergraduate at the University of Southern California that she realized there was so much more to marine biology. While spending a semester at the Wrigley Marine Science Center on Santa Catalina Island, she was exposed to the enormous diversity of marine invertebrate animals and decided she wanted to seriously pursue science for her degree.
Back on the main campus, Ms. Yamaguchi worked on a project comparing the larval physiology of temperate versus polar echinoderms, which was how she "fell in love with marine invertebrate larvae" and decided to study developmental biology and begin her graduate degree at the University of Hawaiʻi.
As a Master's student in the Seaver Lab, Ms. Yamaguchi's research is focused on eye evolution, and specifically on eye development in the marine polychaete worm, Capitella teleta.
"All animals must be able to receive, process, and respond to information that they sense from the surrounding environment. In many animals the nervous system provides these functions and influences behaviors critical for their survival. To develop a functional nervous system requires many carefully regulated steps, which involve large numbers and networks of genes and cells," explains Ms. Yamaguchi. "Eyes are unique to animals and come in a variety of forms, such as the pigment-cup eye in a polychaete worm, mirror eyes in the scallop, and lens-bearing eyes of the squid. One of the fundamental questions of animal biology is how the diversity of such complex structures evolved."
A powerful approach for understanding the evolution of complex structures is by comparative developmental biology. By studying across many taxa how molecular and genetic mechanisms of development have been modified, one can begin to understand how the diversity of sensory organs may have evolved.
Most of the work that has been done on eye development has focused on model organisms from two large clades, the Deuterostomia, which includes vertebrates, and the Ecdysozoa, which includes the fruit fly Drosophila.
In contrast, eye development in the other protostome clade, Lophotrochozoa, has not been as well characterized, even though it includes the most morphological diversity and a great diversity of eye types like those mentioned above.
"The lophotrochozoans are a good group in which to take a comparative approach, because they share a stereotypic cleavage program, called spiral cleavage," noted Ms. Yamaguchi. "In animals that have spiral cleavage, early cell divisions in the embryo follow a strict pattern in which each cell is identifiable. In fact, in many cases, the ontological origins of body structures are similar even among species with diverse body plans and sensory structures."
Currently, few if any studies have examined the potential of embryonic cells in lophotrochozoans, including polychaete annelids. Ms. Yamaguchi's research project takes advantage of the availability of a detailed cell fate map for the polychaete Capitella teleta. From the cell fate map, it is known that, similar to other spiralians, the larval eyes in Capitella are generated by the lineages of the 1a and 1c cells.
"Using single-cell laser ablation, I experimentally deleted 1a, which is known to generate the left larval eye as well as portions of the brain and prototrochal ciliary band, or 1c, which generates the right larval eye and right dorsal brain. Preliminary results suggest that the cell fates of the larval as well as adult eyes are specified very early in the embryo, and other cells in the embryo are not able to regulate for loss of the eye."
Ms. Yamaguchi is currently working on double ablations of the two eye-generating cells, and the results of her laser ablation experiments will be used to investigate the molecular mechanisms controlling eye and nervous system development in Capitella.
"We all know that the gene pax6 is a key regulatory gene in eye and nervous system development in model systems such as the fruit fly and the mouse, " says Ms. Yamaguchi, "so an obvious place to start is to look at the expression and function of pax6 during nervous system development in Capitella."
"I have already characterized the spatiotemporal expression pattern of pax6 in Capitella during embryonic and larval development", she adds. "Currently, I am working with Dr. Neva Meyer to use microinjection techniques to examine the function of pax6 in this polychaete by morpholino-oligonucleotide gene knockdown."
By studying when, where, and how this important gene functions in Capitella, Ms. Yamaguchi aims to fill a gap in our understanding of the ancestral roles for this gene in nervous system development and its evolution across the Bilateria.