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Current Projects

For some years this laboratory has been involved in two main programs of research, both devoted to aspects of the ontogeny and evolution of the nervous system, using the accessible nervous systems offered by certain invertebrate species. Each program exploits the characteristics of its particular nervous system. The two are: the visual system of the fly; and the larval nervous system of the ascidian, or sea-squirt. Both offer morphological and eutelic determinacy (they have fixed numbers of cells that occupy fixed locations relative to each other, and can thus be repeatedly recognised in different animals).

  1. To address the problem of how nerve cells establish, maintain and modify their synaptic connections, we have examined the determinate synaptic circuits of the first neuropile, or lamina, of the optic lobe behind the fly's compound eye. Various studies indicate considerable plasticity amongst these synapses. We have a longstanding collaboration with the laboratory of Elzbieta Pyza, a visiting scientist from the Jagiellonian University in Kraków, Poland, who has examined circadian fluctuations in the number of synaptic contacts, and in the size of the lamina cells that form these, as well as in the action of neuromodulators in bringing these changes about. Ruth Fabian-Fine a Killam Postdoctoral Fellow, is examining the expression of gene products thought to be involved in synaptic plasticity and synaptogenesis. A Research Associate, Jürgen Rybak, has examined the spacing of new photoreceptor synaptic sites that form after a light pulse, using computer 3-D reconstructions of EM series, to examine the possible influence of interactions between a new site and existing sites. Supported by the National Eye Institute of NIH.
  2. Monika Balys a new postdoctoral fellow, is using cell and tissue culture approaches that bring the essential aspects of neural development and synaptogenesis in this system in vitro. Supported by the National Eye Institute of NIH.
  3. Janusz Borycz, a NATO Postdoctoral Fellow, has developed an HPLC method to determine histamine, a neurotransmitter of photoreceptors in the fly, and has examined the metabolism of histamine via carcinine. Various mutants of histamine metabolism, in particular the null mutant for the synthetic enzyme histidine decarboxylase, and two mutants tan and ebony of the metabolic pathway, reveal these pathways in Drosophila. Supported by the CIHR.
  4. To examine the functional anatomy of the photoreceptor terminal, and help establish it as a model of synaptic function in a genetically manipulable organism, Ruth Fabian-Fine and Agnes Kwasniowska are examining the molecular architecture of the photoreceptor synapse, or tetrad. Using confocal imaging methods, a visiting EMBL postdoctoral fellow Robin Hiesinger is using computer deconvolution methods on eyes immunolabelled with characterised antibodies to synaptic and other epitopes to characterise the distribution of subcellular organelles.
  5. Using these projects as background knowledge, we are increasingly concentrating on the instrumental use of Drosophila mutants to induce functional perturbations in the fly's photoreceptor terminals. Our collaborations with a number of other fly laboratories have recently intensified. We are examining, in particular, the action of various mutants of presumed synaptic protein genes, derived from screens currently underway in other laboratories. For example, we have studied the mutant milton in collaboration with the lab of Dr. Tom Schwarz, which unexpectedly encodes a kinesin binding protein required to target mitochondria to the terminal. We also collaborate with two separate laboratories in Toronto, Drs. Harold Atwood and Gabrielle Boulianne, in comparisons between fly neuromuscular and photoreceptor synaptic terminals. A growing number of other mutants of synaptic genes are being studied in collaboration with the laboratory of Dr. Hugo Bellen. These studies are made possible through a major eye screen underway in the Bellen lab, using mutants isolated by a visiting postdoctoral fellow Robin Hiesinger. In this laboratory, they are enabled through ultrastructural studies by three technicians: Rita Kostyleva, Agnes Kwasniowska and Zhiyuan Lu. Supported by a Genomics Grant from NSERC.
  6. In collaboration with Elzbieta Pyza's lab in the Department of Cytology of the Institute of Zoology, at the Jagiellonian University, in Kraków, Poland, we are examining circadian changes in Drosophila , using various mutants that perturb the circadian clock or its output pathways, and in the housefly Musca we have examined the actions of various neuromodulator candidates from microinjections made by Harjit Seyan. Supported by the CIHR (MRC).
  7. In collaboration with a visiting scientist, Kouji Yasuyama, from Kawasaki Medical School, in Okayama, Japan, we have undertaken studies on a small extraocular photoreceptor system called eyelet, and a graduate student Tara Edwards has demonstrated its origin from the larval organ of sight, Bolwig's organ. Also with Kouji Yasuyama and in collaboration with a recent sabbatical visitor, Dr. Friedrich-Wilhelm Schürmann, from the Zoological Institute of Göttingen University, we have examined the transmitter identities and synaptic connections of the glomeruli in the calyx neuropile of the Drosophila mushroom body. Supported by NSERC.
  8. We have also examined the neuroembryogenesis of the ascidian larva, and the normal structure of its simple nervous system. The latter is remarkable both as the evolutionary herald of the chordate dorsal nerve cord, and because it has only about 300 cells, some of which at least are uniquely identifiable. A recent graduate student Sarah Stanley has plotted the number and distribution of all cells in the nervous system, and has derived the pattern of their synaptic connections in the visceral ganglion from serial EM. A second recent M.Sc. student Alison Cole has used confocal methods to continue our analysis of the lineage of these cells. We hope that a complete developmental analysis will begin to lay the foundation at single-cell level needed to promote this embryo as a prototype of vertebrate neurulation. This work is being continued by Janice Imai. Supported by NSERC.
  9. We have also initiated a project to create 3-D reconstructions of the larval brains of Drosophila and Ciona. In parallel with the related FlyBrain project, a former Research Associate, Xue Jun Sun, and a computer consultant, Jane Anne Horne, have created three-dimensional cell maps of the tiny brain of Drosophila, as a basis for importing data on gene expression. This project was initiated in a collaboration with laboratories in Ontario: H.L. Atwood (University of Toronto), A. Hilliker (Guelph University) and M. Sokolowski (York University). Using similar methodologies, Sarah Stanley and Alison Cole have generated computer 3-D reconstructions of the larval brain of Ciona, with a similar view to creating the database from which gene expression and developmental interactions can be catalogued and analysed. Our methods include the reconstruction of: image stacks derived from confocal microscopy using a Sun Ultra 60 workstation running Amira software; and serial electron micrographs using ICAR. Supported by NSERC.