MAURES, T.*; DUAN, C. : EXPRESSION OF INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN-1 IN ZEBRAFISH

Regulation of growth factor and hormone action by soluble hormone binding proteins has emerged as a common theme for a variety of peptides including insulin-like growth factors (IGFs). Among the best studied hormone binding proteins are members of the IGF binding protein (IGFBP) gene family. Six distinct high-affinity IGFBPs have been identified and cloned. Each of these IGFBPs represents an individual gene product, and is regulated differentially. The differential tissue distribution and regulation patterns support the hypothesis that each IGFBP may have a unique function. The exact role of each IGFBP in vivo, however, is poorly understood. This lack of knowledge is particularly evident in the embryonic stage. Research in this area has heavily relied on rodent models, and attempts have been hampered by the inaccessibility of the mammalian fetus enclosed in the uterus. Our laboratory has been addressing this problem utilizing a teleost model, the zebrafish. The free-living, transparent and fast-developing zebrafish embryos and the availability of numerous genetic mutants make them a particularly suitable model system. In this paper, we report the cloning and characterization of an IGFBP in zebrafish. Sequencecomparison and phylogenetic analysis results indicated that this protein is closely related to IGFBP-1. Its sequence identity to human IGFBP-1 is 37%. RT-PCR analysis indicated that IGFBP-1 mRNA is expressed in zebrafish embryos and adult tissues and its expression is tissue-specific. Currently experiments are undergoing to determine the spatial and temporal expression of IGFBP-1 in all embryonic stages at single cell resolution. (Supported by NSF Grant IBN-9728911).