Internal Seminar: Masai Unit and Mitarai Unit

Join us for June's first Internal Seminar Series on June 12, from 17:00 to 18:00 in B250. This month's first seminar features the Developmental Neurobiology Unit (Ichiro Masai) and the Marine Biophysics Unit (Satoshi Mitarai).

Developmental Neurobiology Unit (Ichiro Masai)

Speaker : Sachihiro Suzuki

Title : Pattern formation of the cone photoreceptor mosaic in the zebrafish retina

Abstract : Perception of color relies on multiple types of cone photoreceptors, each of which shows sensitivity to a distinct spectrum of light. It is prerequisite for proper functioning of color vision not only to generate appropriate numbers of individual cone types but also to arrange them spatially in a species-specific manner. Zebrafish have four cone types: red, green, blue and UV-light sensitive cones. Zebrafish four cone types form a strikingly precise lattice pattern, namely cone mosaic. In this lattice pattern, the position of each cone type and the ratios of cone types are strictly determined. Pairs of red and green cones associate tightly to form double cones and are organized into radiating rows. The double cone rows and Blue-/UV-cone rows that are consisted of alternating blue- and UV-cones appear in turn. Although theoretical approaches were taken to understand cone mosaic formation mechanisms previously, molecular and cellular mechanisms underlying formation of the precise lattice pattern are poorly understood. To address this, we asked whether double cones are essential for formation of the regular lattice pattern. We perturbed red cone genesis by disrupting the thyroid hormone receptor beta 2 (thrb2) gene using the CRISPR/cas9 system. Injection of the cas9 mRNA and thrb2 gRNA into one-cell stage eggs produced chimeric fish with retinal areas lacking red cones. In the areas without red cones, the remaining cone types still form a regular lattice pattern and also the ratios among them were not affected. Therefore double cone formation is dispensable for formation of the regular lattice pattern.

Marine Biophysics Unit (Satoshi Mitarai)

Speaker : Mary Grossmann

Title : Temporal dynamics of pelagic dinoflagellates.

Abstract : Dinoflagellates are a diverse group of marine unicellular eukaryotes. They play a key role in marine ecosystems by creating a link between the bacterial food web and metazoan higher trophic levels. Some recent studies have also hypothesized pelagic dinoflagellates might be used as biological indicators of global warming. We tested this hypothesis by collecting monthly plankton samples at Bise, in northern Okinawa. We studied the temporal variations in abundance and species composition of pelagic dinoflagellates, and how these could be correlated with environmental parameters.