Figure 2. Expression pattern and cell-autonomous function of TTX-7 in RIA neurons. (A) The
ttx-7::EGFP fusion gene. (B) Expression of
ttx-7::EGFP. Anterior is to the left, dorsal is up. (Top panel) Strong fluorescence was observed in head and tail neurons (arrow) and coelomocytes (arrowhead). Bar, 100 μm. (Bottom left panel) In the head, a limited number of neurons express
ttx-7::EGFP. Bar, 5 μm. (Bottom right panel) Expression in RIA neurons was observed in another focal plane. Bar, 5 μm. Other identified neurons are listed in the figure. (C) The proposed thermotaxis neural circuit (Mori and Ohshima 1995). AFD is a major thermosensory neuron, and X is a putative minor thermosensory neuron. AFD and AIY neurons promote thermophilic behavior (indicated as 'T'), and AIZ neurons promote cryophilic behavior (indicated as 'C'). RIA neurons are proposed to integrate these signals. In this circuit, AFD and RIA express
ttx-7 and are colored green. (D) Cell-specific rescue of the thermotaxis defect in
ttx-7 mutants by
ttx-7a cDNA expression. Bars show the percentage of animals that moved to the cultivation temperature (20C).
osm-6p induces expression in many sensory neurons. Compared with naive
ttx-7 mutants, only transgenic strains with RIAp::
ttx-7a showed improved thermotaxis (Dunnett's multiple comparison test; n = 3 or more assays). (E) Genetic epistasis of
ttx-7 and
tax-6 mutants in thermotaxis. Note that the bars indicate the percentage of thermophilic animals. The
ttx-7 mutation suppressed the thermophilic behavior of
tax-6 mutants, but the double mutants were still more thermophilic than
ttx-7 mutants (Dunnett's multiple comparison test; n = 4 or more assays). (F) Cell-specific rescue of the SNB-1 localization defect in
ttx-7 mutants. Localization indexes were calculated as shown in Figure 3B and Materials and Methods. The localization was rescued not with AIYp::
ttx-7a but with RIAp::
ttx-7a (Steel's multiple comparison test; n = 10 animals).