Program of the 2001 International Worm Meeting - Sternberg Lab ...

400
400. THE A, B, C s OF
CHEMOSENSORY NEURON
SPECIFICATION
Tali Melkman, Piali Sengupta
Department of Biology, Brandeis University,
Waltham MA 02454
Many inputs contribute to an animal’s
perception of its environment. These inputs are
transduced by different receptor cells. Each
receptor cell shares similarities with other cells
of its type in terms of the general sensory
functions, however, the specificity of different
cells of the same type varies. How are the
common features, as well as the diversity
brought about? We are using the chemosensory
system of C. elegans as a model to study these
processes. The current model proposes that all
olfactory neurons (AWA, AWB and AWC)
share a common default fate which is then
overridden by cell-fate specific transcription
factors. These transcription factors are the LIM
homeodomain genelin-11 and the nuclear
hormone receptor geneodr-7 in the AWA
neurons and the LIM homeodomain genelim-4
in the AWB neurons. When expression of any
of these transcription factors is lost, the cell
develops along the default route, losing its own
identity and function. What regulates the
expression of these factors?
In order to identify genes contributing to the
formation and specification of the AWA
neurons, we conducted a screen looking for
mutants showing abnormal expression of odr-7.
In this screen we isolated sns-10. This mutant
shows various pleiotropies suggesting that
sns-10 is involved in the formation and/or
function of a number of cells. With respect to
AWA development, in sns-10 mutants, there is a
variable loss in odr-7 expression and rarely,
ectopic expression. Behavioral studies indicate
that AWA-mediated chemosensation is
defective suggesting that its functional
specification is compromised. sns-10 encodes a
paired-like homeodomain transcription factor
with high homology to the Drosophila gene
aristaless. Interestingly, aristaless is involved in
the formation of the aristae sensory organs
(Schneitz et al. 1993). Previous studies in our
lab identified other factors that regulate odr-7
expression and hence AWA specification.
Lineage restriction of odr-7 to the AWA
400
neurons is regulated by the forkhead
transcription factor unc-130 (Sarafi-Reinach et
al. 2000), whereas the initiation of odr-7
expression involves the LIM-homeodomain
transcription factor lin-11 (Sarafi-Reinach et al.
submitted). Investigation of the interaction of
sns-10 with these genes is underway. This
analysis should elucidate the mechanisms
underlying the specification of this olfactory
neuron and possibly identify a mechanism that
is common to sensory organ specification in
different species.