We are using Genetics, Cell Biology and Developmental Biology to investigate how the correct number and pattern of interneurons forms in the vertebrate spinal cord, and how these interneurons acquire their specific characteristics and functions. The evidence so far suggests that the morphology and function of different neurons is determined, at least in part, by the specific regulatory genes that they express. Some genes are probably required for survival or specification of particular neurons, whereas other genes are required for specific aspects of neuronal morphology and function. We are therefore investigating which regulatory genes are expressed by specific interneurons and what the roles of these regulatory genes are in determining different neuronal characteristics.
We use zebrafish as a model system, as their relatively simple nervous system facilitates studies of neural circuitry and function and enables cell fate specification to be studied at the level of both single cells and populations of cells. Zebrafish are also a powerful system for combining genetic and embryological studies as their embryos are readily accessible and optically transparent, allowing us to easily follow the development of individual neurons and observe gene expression in live embryos; and mRNA over-expression methods, mutant lines and antisense oligonucleotide techniques allow us to quickly and easily examine the functions of different proteins in vivo. As most of the genes involved in spinal cord development are conserved between vertebrates, the insights that we gain about the functions of specific genes should be widely applicable.
The knowledge that we gain
from this research will ultimately be important for developing treatments
for nervous system diseases, disorders and tumors, as well as methods
for facilitating the repair of particular nerves after injury or neurodegeneration.
For example, understanding the roles of different genes in specifying
particular neurons will enable researchers to grow specific types of
neurons from stem cells for treating conditions such as Alzheimer’s
disease, Parkinson’s disease, stroke and spinal cord injuries.
In addition, understanding the genetic differences between neurons will
help us to understand why neurodegenerative diseases often only affect
specific classes of neurons.
Our long term goals are to
determine not only how different neurons are specified, but also how
specific neurons function in particular neural circuits and behaviours.
This will enable us to connect how the nervous system develops with
how it functions. Zebrafish are ideal for these studies as they are
a genetically tractable vertebrate, in which it is possible to follow
the development, and test the function, of different neurons in live
embryos. For example, we can use transgenic GFP lines to identify specific
neurons in live embryos, observe how neurons connect with each other,
test the functions of these resulting circuits, and determine how these
circuits or functions change when particular genes or neurons are lost.
We can also examine existing zebrafish mutations that potentially affect
neural development or behaviour, and conduct new mutational screens,
to identify additional, and potentially novel, genes that affect neural
development and function.
K. Wotton, F. Weierud J. L. Juarez Morales, L. E. Alvares, S. Dietrich, K. E Lewis (2010) Conservation of gene linkage in dispersed vertebrate NK homeobox clusters. Development, Genes and Evolution 219: 481 - 496. (ref).
G. Cerda, M. Hargrave and K.E. Lewis (2009) RNA profiling of FAC-sorted neurons from the developing zebrafish spinal cord" Developmental Dynamics 238: 150-162 (ref.)
(PDF of Submitted Manuscript)
M. F. Batista and K. E. Lewis (2008) Pax2/8 act redundantly to specify glycinergic and GABAergic fates of multiple spinal interneurons. Developmental Biology 323: 88–97. (ref.)
M. F. Batista, J. Jacobstein and K. E. Lewis (2008) Zebrafish V2 cells
develop into excitatory CiD and Notch signalling dependent inhibitory
VeLD interneurons. Developmental Biology 322: 263-275. (ref.)
Karl R Wotton, Frida K Weierud, Susanne Dietrich and Katharine E Lewis
(2008) Comparative genomics of Lbx loci reveals conservation of identical
Lbx ohnologs in bony vertebrates BMC Evolutionary Biology 2008,
8:171 (ref.)
G. Lupo, W.A. Harris, K.E.Lewis (2006) Mechanisms of ventral patterning
in the vertebrate nervous system: lessons from the spinal cord, the
telencephalon and the eye. Nature Reviews Neuroscience
7: 103-114 (ref.)
K. E. Lewis (2006) How do genes regulate simple behaviours? Understanding
how different neurons in the vertebrate spinal cord are genetically
specified. Philosophical Transactions of the Royal Society B: Biological
Sciences 361(1465): 45-66 (ref.)
K. E. Lewis, J. Bates & J. S. Eisen (2005). Regulation of iro3
expression in the zebrafish spinal cord. Developmental Dynamics
232:140-148. (ref.)
Wolff C, Roy S, Lewis KE, Schauerte H, Joerg-Rauch G, Kirn A, Weiler
C, Geisler R, Haffter P and Ingham PW (2004) iguana encodes a novel
zinc finger protein with coiled-coil domains essential for Hedgehog
signal transduction in the vertebrate embryo. Genes and Development
18, 1565-1576. (ref.)
Lewis KE and Eisen JS (2004) Paraxial mesoderm specifies zebrafish
primary motoneuron subtype identity. Development 131,
891-902. (ref.)
Lewis, K.E. and Eisen, J.S.
(2003) From cells to circuits: development of the zebrafish spinal cord.
Prog. Neurobiol. 69(6): 419-449. (ref.)
Lewis, K.E. and Eisen, J.S.
(2001) Hedgehog signaling is required for primary motoneuron induction
in zebrafish. Development 128(18): 3485-3495. (ref.)
Varga, Z.M., Amores, A.,
Lewis, K.E., Yan, Y. -L., Postlethwait, J.H., Eisen, J.S., and Westerfield,
. (2001) Zebrafish smoothened functions in ventral neural tube specification
and axon tract formation. Development 128(18): 3497-3509.
(ref.)
Drossopoulou, G., Lewis, K. E. , Sanz-Ezquerro, J. J., Hofmann, C.,
McMahon, A.P., and C. Tickle (2000). A new model for antero-posterior
patterning of the limb involving sequential long and short range Shh
signalling and Bmp signalling. Development 127: 1337-1348.
(ref)
Lewis, K.E., Concordet, J.P.,
and Ingham, P.W. (1999) Characterisation of a second patched gene in
the zebrafish Danio rerio and the differential response of patched genes
to hedgehog signalling. Dev. Biol. 208:14-29. (ref.)
Lewis, K.E., Currie, P.D.,
Roy, S., Schauerte, H., Haffter, P., and Ingham, P.W. (1999) Control
of muscle cell-type specification in the zebrafish embryo by hedgehog
signalling. Dev. Biol. 216(2): 469-480. (ref.)
K. E. Lewis, G. Drossopoulou,
I. R. Paton, D. R. Morrice, K. E. Robertson, D. W. Burt, P. W. Ingham
and C. Tickle (1999c). Expression of ptc and gli genes in talpid3 suggests
bifurcation in Shh Pathway. Development 126: 2297-2407.(ref.)
J. P. Concordet, Lewis, K.E.,
Moore, J.W., Goodrich, L.V., Johnson, R.L., Scott, M.P., and Ingham,
P.W. (1996) Spatial regulation of a zebrafish patched homologue reflects
the roles of sonic hedgehog and protein kinase A in neural tube and
somite patterning. Development 122(9): 2835-2846. (ref.)
