Mori I et al. (1987) International C. elegans Meeting "regulation of germ-line transposition and excision of Tc1."

Moerman DG, Mori I, Waterston RH

[International C. elegans Meeting, 1987]

Mori I et al. (1993) International C. elegans Meeting "Genes and cells important for thermotaxis of C. elegans."

Ohshima YM, Honda H, Mori I

[International C. elegans Meeting, 1993]

Mori H et al. (1991) International C. elegans Meeting "MOLECULAR CLONING OF C. elegans CELL CYCLE GENES."

Sternberg PW, Mori H

[International C. elegans Meeting, 1991]

We are interested in studying the regulation of cell cycle progression by signal transduction events during C. elegans postembryonic development. As the first step of this project, genes that are known to play crucial roles in cell cycle control -- cdc2 serine/threonine kinase and cdc26/string homologs --were cloned by using PCR. Using a set of degenerate oligos, a ~600 bp fragment was generated off of genomic DNA template and determined to code for a part of cdc2 homolog. This fragment was then used as a probe to: l) search for cDNA and 2) determine the physical location of the gene in the genome. Approximately 140,000 plaques from a lambdaZap cDNA library (from R. Barstead) were screened: of the five candidates thus isolated, the longest cDNA was found to contain the entire open reading frame. Partial sequence of this cDNA has revealed a high degree of sequence identity between this putative C.elegans cdc2 and other cdc2 genes. The only surprise so far has been an Ile to Val substitution in the 'PSTAIR' motif that is absolutely conserved in all cdc2 genes published to date. This gene, tentatively named ncc-l (for nematode cell cycle), was physically mapped by using the YAC grid filters to right of the cluster on III, and has subsequently been shown to reside within the region covered by cosmid T05G5. A similar approach was taken to clone the C.elegans homolog of cdc25/string. Preliminary data suggest that we have isolated partial length cDNAs that can encode a gene with significant sequence similarity to other cdc25 homologs.

Akihiro Mori et al. (2006) East Asia C. elegans Meeting "New computer algorithm for motif prediction"

Yuji KOHARA, Akihiro Mori

[East Asia C. elegans Meeting, 2006]

Multi-cellular organisms needs appropriate regulatory systems which control to activate/in-activate transcriptional process of multiple genes at proper stages and in proper cells for development. In many cases, this is regulated through the binding of proteins to a specific region of the gene. Such protein binding sites are known as cis-regulatory elements or motifs. However, despite their hypothetical importance, cell- and stage-specific regulatory motifs in multi-cellular organisms remain largely unrevealed. Moreover, the prediction of motifs by in silico methods and the verification of putative motifs by experimental methods are both challenging problems. To address these problems, we developed a new computer algorithm for extracting cell-/stage-specific regulatory motifs of C. elegans genes. Since the size and position of such motif are not known before analysis, we have to search short sequences (5 bases or so) in long target sequence area (more than 1000 bases), which cause too many pseudo positives and too long computation time. Thus, we developed an algorithm named &quotfiltering step&quot which reduces the search space (and therefore pseudo positives) dramatically, without losing the real positives. We performed multiple benchmark tests using various sets of genes that contain known motifs and artificial sequences in which some motifs are inserted. The results show that this filtering procedure effectively works to identify motifs in up to 2500 base region. We also found that our algorithm can identify combinations of short motifs very effectively. To identify novel motifs, we plan to apply the method to the gene sets that are known to be expressed stage/cell specifically by systematic in situ hybridization analysis in this laboratory.

Mori I et al. (1991) International C. elegans Meeting "Genetic and behavioral analyses of thermotaxis defective mutants."

Ohshima YM, Honda H, Mori I

[International C. elegans Meeting, 1991]

The establishment of thermotaxis in C. elegans possibly requires proper expression of genes involved in thermoreception, maintenance and assessment of thermal information, and general tactic behavior. Since our previous report (WBG 11 No. 2: 92, 1990), we have continued our analysis of thermotaxis-defective (ttx ) mutants to identify genes important for different steps in the pathway. Of EMS-induced ttx mutations isolated from N2 and daf-6(el377) backgrounds (about 104 genomes screened each), 5 athermotactic mutations identified 2 genes, ( kslO, kslS, ks31 ) I, and (ksll, ks28 ) III. Both ksll and ks28 also abolish normal chemotaxis to NaCl, but show normal osmotic avoidance against a high concentration of NaCl. Likewise, ksl O and kslS are CHE( -) OSM(+), but ks31 is CHE(+) OSM(+). AFD is a likely thermosensory neuron in the amphid (Perkins et. al., 1986, Dev. Biol. 117: 456) and has a single synaptic connection to AIY (White et. al., 1986, The Mind of a Worm). ASE is a single major chemosensory neuron for normal chemotaxis tO a variety of attractants (Bargmann and Horvitz, 1989, CSH meeting abstract) and has the most prominent synaptic connection to AIY (White et. al., 1986). An interesting hypothesis is that the gene defined by kslO, kslS, and ks31 is required in AIY for convergence of thermo- and chemo- signals. Dusenbery et. al. (Genetics 80: 297, 1975) isolated several tax mutants, which disrupt both chemo- and thermotaxis. We are currently testing if any of tax genes corresponds to our atactic genes. ks4 III, which is CHE(+) OSM(+), was first isolated as a straight cryophilic mutation in daf-6 background. Interestingly, the elimination of daf-6 from the background somehow reduced the cryophilic nature of ks4. This suggests that certain che mutations act as enhancers of certain ttx mutations, again reflecting close relationship between chemo- and thermosensory transductions. ksS, CHE(+) OSM(+), is another cryophilic mutation isolated from daf-6 mutagenesis. ksS remains as straight cryophilic in daf-6-free background. ks4 and ksS complement ttx-l (p767), which was mapped to V. We thank Ed Hedgecock for strains, information, and suggestion.

Mori I et al. (1995) International C. elegans Meeting "A SIMPLE NEURONAL CIRCUIT MEDIATING AN ESSENTIAL PROCESS OF THERMOTAXIS IN C. ELEGANS"

Mori I, Ohshima YM

[International C. elegans Meeting, 1995]

C. elegans can sense a range of temperatures in the environment and migrate to the cultivation temperature on a thermal gradient. We have identified neurons critical for this thermotactic response by killing individual cells in live animals. The results indicate that an amphid sensory neuron AFD is a major thermosensory neuron. Further, some of the genetically defined cryophilic and thermophilic mutant phenotypes were mimicked, when amphid interneurons AIY and AIZ, respectively, were killed, suggesting that AIY is responsible for thermophilic movement and AIZ for cryophilic movement. The observation that the phenotypes of AFD+AIZ-killed animals were more abnormal than and significantly different from those of AFD-killed animals implicates another thermosensory neuron which independently activates AIZ. Killing RIA interneurons, which could receive chemical inputs from both AIY and AIZ, resulted in partially defective responses. Altogether, these results led us to propose a neuronal model in that counterbalancing the activities of the two interneurons AIY and AIZ, depending on the cultivation temperature, may be essential for thermotaxis. The counterbalancing regulation could be achieved in two ways; AIY could inhibit AIZ directly via chemical synapses or indirectly through downstream neurons such as RIA.

Mori I et al. (1997) International C. elegans Meeting "GENETIC STUDIES ON THERMOTAXIS: PROGRESS IN CLONING TTX GENES AND ISOLATION OF MUTANTS DEFECTIVE IN TEMPERATURE AVOIDANCE"

Mori I, Shirakawa M, Yamashita Y, Ohshima YM, Ishii K

[International C. elegans Meeting, 1997]

C. elegans possesses a biological system to sense, process and store thermal cues, and this sensory system can be behaviorally observed as thermotaxis. We have been undertaking cellular and genetic analyses of thermotaxis in order to address how the C. elegans nervous system functions to detect and process temperatures, and what sorts of signal transduction pathways are involved in thermotaxis. The counterbalanced regulation of two interneurons AIY and AIZ has been implicated to be essential for thermotaxis. ttx-1, ttx-2 and ttx-3 mutants all show cryophilic phenotypes, although their detailed properties differ. Unlike athermotactic or thermophilic mutants, cryophilic mutants show severe defects only in thermotaxis, suggesting that these ttx genes are specifically involved in thermosensory transduction cascades. We have demonstrated in collaboration with O. Hobert and G. Ruvkun that ttx-3 gene encoding a LIM homeodomain protein is expressed only in AIY and the unbalanced crosstalk between AIY and AIZ is indeed responsible for the phenotype of ttx-3 mutants (see Abstract by Hobert et al.). To elucidate further the molecular basis underlying cryophilic phenotype, we are attempting to clone ttx-1 V and ttx-2 III genes. Thermotaxis is strongly modulated by starvation: the animals migrate away from temperatures at which they were starved only for 2-4 hours. This negative thermotaxis might imply that the animals can somehow associate exposed temperature and food signal. We are currently setting up a genetic screen to isolate mutants defective in avoiding starvation temperature. Some mutants to be isolated could be defective in temperature and food association.

Schwarz EM et al. (1996) East Coast Worm Meeting "Cellular and molecular analysis of thermosensation"

Chalfie M, Schwarz EM

[East Coast Worm Meeting, 1996]

While senses like sight, hearing, and mechanosensation are becoming well understood, thermosensation remains obscure. Work by Hedgecock (1) and Mori (2) has shown that C. elegans is a promising model system for metazoan thermosensation, but neither the cells nor the genes required for thermosensation in C. elegans are fully known. Previous work in this laboratory (3) has shown that at least three new deg mutations cause cells in the head to degenerate while partially crippling thermosensation; none of these are allelic to previously described ttx mutations . We have therefore begun to determine which cells are defective in these deg mutations. We have also begun genetic mapping experiments aimed at positional cloning of the wild-type deg loci. References: 1. Hedgecock, E.M. and Russell, R.L. (1975). Proc. Natl. Acad. Sci. U.S.A. 72, 4061-4065. 2. Mori, I. and Ohshima, Y. (1995). Nature 376, 344-348. 3. Treinin, M. and Chalfie, M. (1993). International C. elegans meeting abstracts, p. 446.

Lasse, S. et al. (2013) International Worm Meeting "Thermoreceptor neurons regulate the temperature-dependence of motor programs."

Wang, V. Y., Lasse, S., Goodman, M. B.

[International Worm Meeting, 2013]

In small ectotherms like C. elegans, temperature can influence behavioral performance directly or indirectly through signaling from specialized thermoreceptor neurons. Such temperature-dependence is also found in endotherms like mammals and birds. For instance, cooling decreases rhythmic movements associated with essential tremor and can also reduce pain and itch in humans. Essentially nothing is known in either ectotherms or endotherms about the potential role for thermoreceptor neurons in regulating the temperature-dependence of behavioral performance. We are working to fill this gap in understanding, focusing on two simple C. elegans behaviors: egg laying and locomotion. In wild-type N2 worms both behaviors display a similar dependence on temperature: rates increase with temperature and reach a maximum at 22-25 deg C then sharply decline above 26 deg C (egg laying) or 30 deg C (locomotion). If thermoreceptor neurons contribute to the temperature dependence of behavioral performance, then the rate-temperature (R-T) relationship should differ between wild-type worms and mutants with defects in thermosensation. Consistent with this idea, tax-4 mutants which lack the ability to respond to thermal gradients (Mori and Ohshima 1995) laid fewer eggs and crawled more slowly at 25-30 deg C. However, R-T curves had similar shapes in wild type and tax-4 worms. This suggests that egg laying and locomotion motor programs are intrinsically dependent on temperature, but input from the thermoreceptor neurons is required for wild type performance. This relationship may represent an evolutionary optimization of behavioral performance over a physiological range of temperatures. The neural circuits that regulate egg laying and locomotion do not overlap, indicating this as a general strategy that worms use to modulate behavioral performance. Mori I, Ohshima Y (1995) Neural regulation of thermotaxis in Caenorhabditis elegans. Nature 376:344 -348.

Paola Jurado et al. (2009) European Worm Neurobiology Meeting "Insights into the molecular mechanisms of Caenorhabditis elegans memory"

Paola Jurado, Ikue Mori

[European Worm Neurobiology Meeting, 2009]

Caenorhabditis elegans responds to a variety of environmental signals (volatile and water soluble chemicals, temperature, etc). The animals memorize these cues and are able to associate them with other existent conditions. Thermotaxis is a well characterized behavior in which C. elegans associates its cultivation temperature with food (Escherichia coli). This association drives the worms to seek their memorized temperature even in the absence of bacteria (1,2). This presents an ideal situation to investigate the molecular and cellular bases of sensory integration leading to complex processes such as memory and learning. We are trying to thoroughly investigate how the assimilation of thermo-sensory cues leads to memory, and how this thermal memory is modified over time. We have performed a screen to look for mutants with an abnormal memory or an altered decission making balance over thermal conditioning. We searched for animals conditioned to find E. coli at a certain temperature that take longer to leave it, in the absence of food, than wild type animals. These animals display a longer lasting memory or a slower decission making when thermal memory is confronted with hunger or the absence of food. One of the mutants isolated from this screening has been mapped to chromosome I and is currently under characterization. 1. I. Mori and Y. Ohshima (1995). "Neural regulation of thermotaxis in C. elegans." Nature 376(6538): 344-8. 2. I. Mori, H. Sasakura and A. Kuhara (2008). "Worm thermotaxis: a model system for analyzing thermosensation and neural plasticity." Curr Opin Neubiol. 2007 Dec 17(6):712-9.