The Observation of Craniofacial Cartilages and a Single Floor Plate Cell using a Gal4-Enchancer Trap Line

â—‹Sohei Nakayama1,2, Chihiro Kamihagi1, Takanori Ikenaga1, Koichi Kawakami3and Kohei Hatta1

1) Graduate School of Life Science, University of Hyogo,
2)Research Fellow of the Japan Society for the Promotion of Science,
3)National Institute of Genetics, Department of zebrafish

Zebrafish are good models for studying vertebrate development because of transparency during embryogenesis, rapid development, and availability of powerful genetic tools. In the genetic tools for zebrafish, Gal4 enhancer trap screening has been performed intensely, and has allowed us to achieve great success with understanding zebrafish development. Here, we analysed Gal4 expression pattern of one enhancer trap line, SAGFF(LF)134A, in detail and found this line is useful to study the development and morphology of some tissues including craniofacial cartilages and floor plate. At first we focused on craniofacial cartilages. Strong GFP signals were detected in not only chondrocytes but also perichondrial cells in the cartilages. Perichondrial cells, enveloping chondrocytes to form single-layered structure, have not been studied well. We attempted to trace their lineages using a local gene activation technique (IR-LEGO system), and its results suggested that it was likely that perichondrial cells were derived from the mesenchyme in pharyngeal arches as well as chondrocytes. Secondly, we found that floor plate cells changed their shapes dynamically. In order to observe their changes of morphology in detail, we generated SAGFF(LF)134A/UAS:KikGR double transgenic fish and photoconverted a single floor plate cells by UV irradiation. The time laps imaging revealed that the floor plate cell changed from a cuboidal or trapezoidal shape to a cyathiform shape during 48 hours.