A New Model On Right Eye Migration In Metamorphosing Flounder And Relative Genes Screened

The best-known change in flatfish (Pleuronectiformes) metamorphosis from bilaterally symmetric larvae to asymmetric juveniles is the migration of their eyes: one eye migrates from one side to the other. The migrating eye differs between, and sometimes within, different species of flatfish. While the mechanism behind eye migration in flatfish has been a subject of research and speculation for several centuries, it is currently believed that deformation of the neurocranium and bone rearrangements are responsible for this phenomenon (Brewster, 1987), which fail to explain what force(s) initiates asymmetrical eye migration during development. Here we show that cell proliferation drives eye migration in metamorphosing Japanese flounder, Paralichthys olivaceus, a common flatfish species. Through a series of whole-mount in situ experiments, we detected that an asymmetrical pattern of cell proliferation initiated movement of the "strong" right eye by placing pressure on it from below, while a band of proliferating cells moved dorsally, following the right eye's eventual migration route. The left eye was stabilized by balanced proliferative forces being exerted from below and above. A model developed based on our findings helps to better explain the polymorphic nature of the asymmetrical trait in flatfish as well as providing insight into the broader natural phenomenon of asymmetry.Here we also used the in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) to describe the temporal and spatial distribution of apoptotic cells during metamorphosis of Japanese flounder from 13 to 43day post hatching (DPH). The results show the cell apoptosis play an important role in the organs rebuilding process involves transformation and functional changes, however, it is not initial power to push right eye movement.Thyroid hormone may regulate eye migration. However, the thyroid hormone receptorwas found to be universally expressed during flatfish metamorphosis, providing no evidencefor its direct involvement in eye migration. Recently, it has been revealed that the asymmetrical orientation of the internal organs is controlled by the molecular pathways. Using a reversed clonal line of Japanese flounder (rev), Hashimoto et al.(2003) found that reversal of the sidedness of the orientation of the visceral organs was not always accompanied by reversal of the direction of metamorphic eye-migration, suggesting that different mechanisms was involved downstream of the rev locus in directing these two phases of asymmetric morphogenesis in the Japanese flounder. We have adopted suppression subtractive hybridization for the identification of upregulated genes during metamorphosis involving eye migration in Japanese flounder. One of the upregulated genes was identified as the splicing factor arginine/serine rich-3 (SFRS3). Sequence analysis of SFRS3 revealed that it encodes a protein of 168 amino acids containing the typical eukaryotic RNA recognition motif (RRM) and an arginine/serine-rich region. The overall amino acid sequences of the Japanese flounder SFRS3 was highly conserved with that of other organisms. The expression of flounder SFRS3 gene increased sharply from the beginning of metamorphosis and reached a high level of expression at stage H of metamorphosis 43 days after hatching. The SFRS3 gene upregulation was mainly limited to the head region, particularly in the rapidly proliferative tissues, the lateral ethmoid and "skin thickness" on blind side, which are thought as two proliferative tissues to push the eye movement as shown in our new model. In spite of the upregulated expression of SFRS3 during metamorphosis, its role in metamorphosis involving eye migration requires further studies.we also compared the reliable of GAPDH,βactin,and 18s rRNA in relative RT- PCR as internal standard. In additional, the quality of two cDNA libraries, substracted cDNA library and full-length cDNA library, were evaluated. We also isolated the parvalbumin gene and did a initial characteristion. All this can be a solid base for the future research.