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

904
ttx-6(nj8) mutants always move toward lower
temperatures, independently of cultivation
temperature. The ttx-6 mutant animals thus
manifest cryophilic behavior. ttx-6 mutants
displayed mild defects in the osmotic avoidance
response, but showed normal chemotaxis toward
the water-soluble attractant NaCl and volatile
odorants. These results suggest that ttx-6(nj8)
mutation, which was found to be a reduction of
function allele, affects thermotactic behavior
specifically. We mapped ttx-6(nj8) to the
unc-29, lin-11 interval on the chromosome I.
We are attempting to rescue the ttx-6(nj8)
mutant phenotype with DNA fragments.
1. Okochi et al., 1999, International C. elegans
Meeting
905. Systematic gene knockout to
identify genes required for
thermotaxis in C. elegans
Hitoshi Inada 1 , Mikihiro Kosaki 1 ,
Ikue Mori 1,2
905
1 Laboratory of Molecular Neurobiology,
Division of Biological Science, Graduate
School of Science, Nagoya University, Nagoya
464-8602 Japan
2 PRESTO, JST, Japan
C. elegans can sense and memorize temperature,
and change its temperature response, depending
on the past experience. For example, after
cultivation with sufficient food at 20 degree, C.
elegans migrates to its cultivation temperature
(i.e. 20 degree) and then moves isothermally on
a thermal gradient without food. This behavior
is called thermotaxis, and several mutants
defective in thermotaxis have been isolated. Of
these, tax-4 and tax-2 show athermotactic
phenotype, and both tax-4 and tax-2 gene were
found to encode two different subunits of cyclic
nucleotide-gated cation channel (CNG channel),
which functions in several sensory neurons
including AFD thermosensory neurons. The
TAX-4/TAX-2 CNG channel shows higher
affinity to cGMP than cAMP, suggesting that
cGMP acts as a second messenger in
thermosensory signal transduction. Thermotaxis
must also require execution of some form of
associative learning between temperature and
food. Recently, our laboratory has been isolating
mutants designated aho (abnormal hunger
orientation), which are likely to be defective in
mechanism of associative learning between
temperature and food (see abstract by Mohri et
al).
The completion of C. elegans genome project
makes us possible to systematically analyze the
function and development of the nervous system
by reverse genetic approach. Among 19,000
genes that exist in the C. elegans genome, about
1,700 genes are thought to function in the
nervous system. In order to dissect the
molecular mechanism of thermotaxis, we have
started to construct TMP/UV-induced deletion
mutants for the genes that likely function in
neurons required for thermotaxis. Since (1)
cGMP could be a second messenger in
thermosensation and (2) associative learning in
thermotaxis can be established only in a few