About Us

alcium has been described as a universal second messenger, carrying signaling information across cells, tissues and organs; communicating between the external and internal environments; modulating cellular processes through binding with a diverse range of Ca2+-sensitive regulatory proteins; and interacting with genes via Ca2+-sensitive transcription factors.  All of these may help to orchestrate normal development and function.  We are primarily interested in understanding the Ca2+ signaling pathways in embryonic pattern formation, from fertilization through to hatching in the developing zebrafish (Danio rerio).  Zebrafish embryos are large (~600 µm in diameter) and transparent, and are thus ideal for imaging.  They also develop extremely quickly; from fertilization, an embryo takes just 72 hours to develop into a swimming larva, with all the major body organs in place.  We can directly visualize the Ca2+ signals in zebrafish embryos by injecting them at the single cell stage with aequorin; a photoprotein derived from the luminescent jellyfish Aequoria aequoria that reacts with Ca2+ ions and emits blue light at ~460 nm.  Through the use of ultra-sensitive, custom-designed photon-imaging microscopes (PIMs; Science Wares, Inc.), a series of aequorin-generated Ca2+ signals can be imaged continuously through the first 24 hours of development, beginning at fertilization (Lee et al., 1999), during ooplasmic segregation (Leung et al., 1998), through cytokinesis in the early cleavage period (Webb et al., 1997; Lee et al., 2003; 2005), to epiboly in the gastrula period (Gilland et al., 1999; Webb and Miller, 2003) and into the early segmentation period (Webb and Miller, 2000). 
While our research mainly focuses on the development of zebrafish embryos, we also investigate the calcium signaling events that occur during pattern formation in the embryos both of other fish species, for example during cytokinesis in Rosy Barb (Barbus conchonius) and Medaka (Oryzias latipes) embryos, and also of amphibians, for example, during neural induction in Xenopus laevis embryos (Leclerc et al., 2000, 2003).  The latter project is in collaboration with Marc Moreau and Catherine Leclerc at UMR 5547, Université Paul Sabatier, Toulouse, France.
In addition to characterizing the Ca2+ signaling events that occur at the different stages of development, we also modulate these signals in order to investigate their significance and function, and to determine the source and mechanism of Ca2+ transient generation in both zebrafish (Lee et al., 2003; 2005) and Xenopus (Leclerc et al., 2000, 2003) embryos. In addition ,we are interested in exploring the Ca2+-sensitive target elements that interact with both intracellular and intercellular Ca2+ signals.  These include cytoskeletal components (Lee et al., 2004; Cheng et al., 2004), components of the exocytic pathway (Li et al., 2005), and localized developmental gene expression via Ca2+-sensitive transcription factors (Leclerc et al., 2003).
We are also in the process of generating and raising stably transformed zebrafish that express apo-aequorin (the protein part of the calcium-sensitive bioluminescent complex, aequorin) in specific tissues and organs.  We are currently using an α-actin-apo-aequorin construct to produce transgenic lines of fish that express the apo-aequorin gene specifically in the skeletal muscle. To help us with this project, we are making use of our recent success in targeting apo-aequorin to the cytoplasmic space and the ER in H4IIE liver cells (Chan et al., 2004), which was part of a collaborative project with Greg Barritt, Flinders University, Adelaide, Australia. Our aim is to generate a non-mammalian vertebrate model that is tailor-made for the study of Ca2+ signaling at the cellular, tissue and whole animal level.  The generation of such fish will provide a powerful approach for gaining insight into the roles played by Ca2+ under both natural and pathological conditions within a whole living vertebrate.