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).
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.
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.
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.
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.
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
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.
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).
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.
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.
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
- 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