Ito, Hiroko [class:all]
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10 results (0.009 seconds)
- person: Hiroko Ito
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- go term: symbiont-mediated disruption of host cell-cell adhesion
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[
International Worm Meeting,
2005] Thermotaxis (TTX), a behavioral response to temperature, is one of the sophisticated behaviors in a nematode Caenorhabditis elegans. Thermotaxis of C. elegans is observed as thermal preference, attraction or avoidance, to a certain temperature. After cultivation at a uniform temperature with sufficient food, animals migrate to the cultivation temperature and move isothermally on a thermal gradient without food. By contrast, the animals that experienced starvation at a temperature become to avoid the cultivation temperature. Thermotaxis has been analyzed by several assay systems that are divided into two types, individual TTX assay and population TTX assay. In the individual TTX assay, single animals were individually placed on a thin agar plate with a radial thermal gradient, and the track of the animal on the agar surface was photographed and analyzed. Alternatively, behavior of single animals was recorded by video tracking systems and the animal movements such as run duration time, turn frequency and run speed were analyzed. In the population TTX assay, on the other hand, hundreds of animals were placed on a linear thermal gradient, and the distribution of animals was analyzed. By these assay systems, intensive studies have been performed to elucidate the mechanisms of thermotaxis. However, the deduced models on the mechanism of thermotaxis emerged form the various studies are controversial. In order to elucidate the inconsistency between these studies, we analyzed thermotaxis by the newly developed quantitative population TTX assay. In this TTX assay, animals were placed on a thin agar plate with a linear thermal gradient and their thermotactic behaviors were analyzed by two approaches: the distribution of animals and the TTX index expressing the preference to a temperature. Wild type animals cultivated at 17C, 20C, or 23C showed clear thermal preference to their cultivation temperature in the distribution and the TTX index: they migrated up as well as down the thermal gradient to reach the preferred temperatures. Importantly, time course assay showed that thermal preference was initially suppressed at least for 10 min in the animals cultivated at 23C but not in the animals cultivated at 17C. After placed at 20C on the thermal gradient, the animals cultivated at 23C stayed at 20C for 10 minutes and then started to move up the gradient, whereas the animals cultivated at 17C immediately moved down the gradient. We suggest that these results provide one of the key explanations for the inconsistency among the previous studies.
[
East Asia Worm Meeting,
2004] C. elegans senses temperature mainly by a pair of sensory neurons (AFD) and shows a characteristic behavior towards the temperature called thermotaxis. Several mutants that are defective in thermotaxis have been isolated, and these mutants can be divided into three classes: cryophilic (cold-seeking), thermophilic (heat-seeking), and athermotactic (non-temperature responsive) phenotype. Analyses of these mutants identified several genes involved in thermotaxis. tax-4 encoding a cyclic nucleotide-gated cation channel (CNG channel) is essential for thermosensation in AFD. tax-4 is also required for olfaction by sensory neuron AWC, implicating similar components in thermosensory and olfactory signal transduction. In AFD, three guanylyl cyclase genes, gcy-8, gcy-18 and gcy-23 , play an essential role for thermosensation (see abstract by Inada et al .). Analysis of eat-16 mutant, which is defective in a regulator of G protein signaling (RGS), revealed that AWC olfactory neuron functions as a thermosensory neuron and that odr-1 guanylyl cyclase is involved in thermosensory signal transduction in AWC (Okumura et al ., submitted). To investigate genetic interaction of these four guanylyl cyclases and TAX-4 CNG channel, we constructed tax-4;gcy-23 gcy-8 gcy-18 and gcy-23 gcy-8 gcy-18;odr-1 quadruple mutants, and examined their thermotaxis phenotype. While gcy-23 gcy-8 gcy-18 mutants showed cryophilic and athermotactic phenotype, tax-4;gcy-23 gcy-8 gcy-18 mutants showed athermotactic phenotype like tax-4 mutants, suggesting that tax-4 is epistatic to gcy-8, gcy-18 and gcy-23 . gcy-23 gcy-8 gcy-18;odr-1 mutants showed athermotactic phenotype, although odr-1 single mutants showed almost normal thermotactic phenotype. This result suggests that ODR-1, which is an essential component in olfactory signal transduction, functions in thermosensory signal transduction in AWC. Our results are consistent with a molecular model in which three guanylyl cyclases (GCY-8, GCY-18 and GCY-23) and ODR-1 function upstream of TAX-4 CNG channel for thermosensation in AFD and AWC, respectively.
A process in which a symbiont alters or subverts host cell adhesion ito its extracellular matrix. The host is defined as the larger of the organisms involved in a symbiotic interaction.
[
International Worm Meeting,
2013] Temperature is a ubiquitous stimulus that affects numerous biological phenomena such as homeostasis, metabolism, behavior and aging. Although TRP ion channels play pivotal roles to detect a wide range of temperatures, molecular machinery of TRP independent thermosensation is largely unknown. C. elegans senses the environmental temperature by two pairs of sensory neurons, AFD and AWC to exhibit thermotaxis. Signal transduction pathway for temperature in AFD and AWC is similar to that in visual and olfactory system in mammals (Mori et al., 2007; Kuhara et al., 2008). A recent study in Drosophila larva showed that Rhodopsin GPCR known as a light sensor plays critical role for thermosensation (Shen et al., 2011). Thus, it is plausible to hypothesize that GPCRs evolutionarily play an important role for sensing the environmental temperature. Previous reports showed that srtx-1 encodes the GPCR specifically expressed in AFD and AWC (Colosimo et al., 2004; Biron et al., 2008). To reveal the role of SRTX-1, we isolated srtx-1 null mutants and examined thermotaxis (Hedgecock and Russell, 1975). We found that srtx-1 null mutants exhibited abnormal thermotaxis. The ability to migrate higher or lower regions on a thermal gradient is severely lost in srtx-1 mutants, whereas wild type animals migrated up or down the gradient to reach the past cultivation temperature. The abnormal thermotaxis was rescued by expressing srtx-1cDNA only in AFD and Ca2+ imaging showed that AFD response to temperature is decreased in srtx-1 mutants. In contrast, the overexpression of srtx-1cDNA in AFD caused wild type animals to disperse on thermal gradient, which is the opposite phenotype to the narrowed migration phenotype of srtx-1 null mutants. We suggest that SRTX-1 ensures AFD to sense a wide range of environmental temperature.
[
Lab Chip,
2013] Caenorhabditis (C.) elegans is a model animal used in genetics, neuroscience, and developmental biology. Researchers often immobilize squirming worms to obtain high-quality images for analysis. However, current methods usually require physical contact or anesthetics. This can cause injuries to worm bodies or neuron disturbances. This study presents an alternative technique, called addressable light-induced heat knockdown (ALINK), to effectively immobilize worms by using light-induced sublethal heat. A microchip composed of an indium-tin-oxide (ITO) glass plate and an ITO glass plate coated with a photoconductive layer (a-Si:H) was produced. Worms to be immobilized were immersed in a liquid medium and sandwiched between the two plates. When the worms were irradiated with a focused laser beam in the presence of electric fields (referred to as an optoelectric treatment), the optoelectric effect heated the liquid medium. The neural functions of the worms shut down temporarily when a critical temperature (>31 C) was reached. Their neural functions resumed after the heat source was removed. A temperature above 37 C killed all worms. Using short-wavelength light reduced the worms' recovery time. An equivalent circuit was modeled to predict the operating modes, and an optoelectric treatment with a high-concentration medium enhanced rapid heating. A safe operating range (20 Vpp (peak-to-peak voltage), 100 kHz to 10 MHz, 31 to 37 C) to induce heat knockdown (KD) was also investigated. The results show that the heat KD was well controlled, autonomous, and reversible. This technique can be used for worm immobilization.
[
International Worm Meeting,
2013] kri-1 is necessary for promoting DNA damaged-induced apoptosis in the germline by a cell non-autonomous mechanism that acts in parallel to the p53-like gene cep-1 (Ito et al., 2010). kri-1 is the homologue of human KRIT1, which when mutated leads to the neurovascular disease in humans Cerebral Cavernous Malformations. The C.elegans ERK homologue, MPK-1, is phosphorylated and activated in the germline upon irradiation, and this activation is necessary for apoptosis. To determine if kri-1 is involved in MAPK regulation I ablated gla-3, an inhibitor of MPK-1, by RNAi, and found that apoptosis was restored. To determine if kri-1 is required to modulate the MAPK pathway, I immunostained germlines for activated MPK-1 and found reduced levels in kri-1(0) worms compared to wild type. Since KRI-1 is expressed in the soma, this suggests that kri-1 is somehow able to activate MAPK signalling in the germline. Currently, I am exploring various transport mechanisms, such as the vitellogenesis pathway, to determine how KRI-1 signals from the soma to germline. In order to identify downstream targets of kri-1 in the apoptosis signaling pathway, I plan to use an unbiased mutagenesis suppressor screen.
Ikuko Sugiura, Masahiro Ito, Keiko Hirono, Yuji KOHARA, Michiko Serizawa, Tokie Oba, Takami Suzuki, Yohei Minakuchi, Kyoko Nakata, Masumi Obara, Mina Iwata, Tadasu SHIN-I, Yumiko Ueta
[
International C. elegans Meeting,
2001] We have been performing whole mount in situ hybridization using the cDNAs that have been classified in our EST project (See Thierry-Mieg et al.) as gene probes. Although there was a big delay in the project last year because we needed almost half a year to fix problems due to which our standard protocol suddenly didn't work, now we get the project back on the track and have finished some 7,600 genes. We have given minimal annotation to the in situ results; 10 stages for embryogenesis, 4 stages for larval-adult stage, on average 10 patterns (cell(s), tissue, region) per stage, 3 levels of relative intensity of signals per each pattern. Using the information, clustering analysis and extraction of consensus sequences in the upstream regulatory regions are in progress (see Ito et al.). Subsets of genes whose expression patterns are identical are being subjected to various analysis including RNAi, immunostaining and bioinformatic analysis (motif search, for example). This is a unique and powerful approach and, for example, we identified the function of proteasome in oocyte maturation and fertilization (see Hirono et al.). All the relevant data are integrated in NEXTDB and we are preparing to make them open by the worm meeting (See the demo by Shin-i et al.). In this report, we will show the content and the results of studies based on the database. Furthermore, we are planning "Annotation Relay" in which experts in various fields are invited to this lab by turns (a week or two per round and several people per round depending on the number of microscope) and look at the in situ slides on the microscope with the expert eyes to give more precise and deeper annotations to the in situ data than those we gave.
[
International Worm Meeting,
2015] kri-1 promotes radiation-induced apoptosis in the C. elegans germline by a cell non-autonomous mechanism that functions independently of the p53-like gene cep-1 (Ito et al., 2010). KRI-1 is the homologue of human KRIT1, which when mutated leads to the neurovascular disease in humans Cerebral Cavernous Malformations (CCM). To understand how kri-1 promotes germline apoptosis, I am taking a candidate approach with known apoptosis genes, as well as an unbiased mutagenesis suppressor screen. The C. elegans ERK homologue, MPK-1, is phosphorylated and activated in the germline upon irradiation, and this activation is necessary for promoting both cep-1-dependent and cep-1-independent apoptosis (Rutkowski et al., 2011, Eberhard et al. 2013). To determine if kri-1 regulates the Ras/MAPK pathway, I immunostained germlines for activated p-MPK-1 and observed reduced levels in kri-1(0) worms compared to wild type controls. To determine if kri-1 is regulating apoptosis through Ras/MAPK signalling, I ablated GLA-3, an inhibitor of MPK-1 by RNAi and found that apoptosis was restored. Furthermore, apoptosis is restored in kri-1;lip-1 double mutant worms. LIP-1 is a germline phosphatase that negatively regulates MPK-1. Since KRI-1 is expressed in the soma, this suggests that kri-1 is somehow able to non-autonomously activate Ras/MAPK signalling in the germline. In order to identify additional downstream targets of kri-1 and to determine how kri-1 is sending signals from the soma to the germline, I performed an EMS mutagenesis suppressor screen. To isolate candidates from many mutagenized ­kri-1 worms, I first selected for mutations that restore other easy to screen kri-1 phenotypes. From the candidates that made it past this first round of selection, I have sent fourteen candidates, with restored sensitivity to radiation-induced germline apoptosis, for whole genome sequencing. I am now investigating various genes mutated in my suppressor strains to determine the causal mutations that restore apoptosis. .
[
International Worm Meeting,
2003] The male tail of C. elegans is a specialised structure consisting of a cuticular fan in which are embedded 18 symmetrically placed mechanosensory sensilla called rays, which each have distinct characteristics due to their morphology, position and neurotransmitter usage. The mab-2 mutation causes loss of both the V and T cell derived rays1. We have found this mutation to be allelic with a rnt-1 knockout and to be rescued by the cosmid B0414 which contains rnt-1. We will further analyse the ray phenotype by lineage analysis using suitable markers. In addition, mutations appear to be temperature sensitive for sterility and an intestinal mitotic defect. It is interesting that a rnt-1::gfp reporter construct has been shown previously to be expressed in the intestine as well as seam cells2 so lending support to the hypothesis that both the ray loss and intestinal phenotypes may be caused by mutation of rnt-1.Initial attempts at cloning mab-2 involved screening genes mapping to the same region by feeding RNAi (Chromosome I feeding library was a gift from J. Ahringer). As a result of the screen two genes which phenocopied mab-2 mutants were identified. In light of our subsequent identification of mab-2, it is interesting to find that 3 genes giving a virtually identical ray loss phenotype are located within a 0.21 cM region of LGI.The two novel Mab genes are situated in a putative operon and so are presumably co-regulated. Do worm operons represent functional cassettes of genes as in bacteria? The common RNAi phenotypes of these two co-regulated genes imply interesting co-functionality. Further support for their co-functionality is provided by the fact that homologues of these two genes plus another in the operon are involved in rRNA processing in yeast. In addition, orthologues of one of these Mab genes and another gene in the operon are thought to modulate the Notch signalling pathway in mammals. We are in the process of investigating the possibility that these functions are conserved in C. elegans.References: 1) Hodgkin, J. Genetics (1983) 103: 43-64; 2) Nam S, Jin YH, Li QL, Lee KY, Jeong GB, Ito Y, Lee J, Bae SC. Mol Cell Biol. (2002) 22(2):547-54.