Chun-Yi Huang et al. (2007) International Worm Meeting "eif-3.K is a pro-apoptotic gene in C. elegans."

Jia-Yun Chen, Yi-Chun Wu, Chun-Yi Huang

[International Worm Meeting, 2007]

Programmed cell death (or apoptosis) is an important feature of C. elegans development. Previous studies have identified pro-apoptotic genes egl-1, ced-3 and ced-4 and anti-apoptotic genes ced-9 and icd-1 that control programmed cell death.. We have identified and characterized a novel pro-apoptotic gene eif-3.K. Loss-of-function by mutation or RNAi inactivation in eif-3.K resulted in a decrease of cell corpses, whereas heatshock-induced over-expression of eif-3.K weakly but significantly increased cell corpses. Interestingly, the eif-3.K mutation partially suppressed ectopic cell deaths caused by over-expression of egl-1 or ced-4. This result suggests that eif-3.K may act downstream of or in parallel to egl-1 and ced-4 in the programmed cell death pathway. Using a cell-specific promoter to express eif-3.k in touch neurons, we showed that eif-3.K likely promoted cell death in a cell-autonomous manner. To further explore EIF-3.K function, we generated antibodies against bacterially expressed EIF-3.K protein. We found that EIF-3.K was ubiquitously expressed during embryogenesis and localized to the cytoplasm. As human eif-3.K can functionally substitute C. elegans eif-3.K in an eif-3.K mutant, the function of eif-3.K in apoptosis is likely conserved in evolution.

Chun-Yi Huang et al. (2006) East Asia C. elegans Meeting "eif-3.K is a pro-apoptotic gene in C. elegans"

Teng-Wei Huang, Chun-Yi Huang

[East Asia C. elegans Meeting, 2006]

Programmed cell death or apoptosis is an important feature during C. elegans development. The pro-apoptotic genes egl-1, ced-4 and ced-3 are required for the execution of cell death. We have identified and characterized a novel pro-apoptotic gene eif-3.K. A loss-of-function mutation or inactivation by RNA interference in eif-3.K resulted in a reduction of cell corpse number during embryogenesis, whereas heatshock-induced over-expression of eif-3.K weakly but significantly promoted programmed cell death. In addition, eif-3.K mutation partially suppressed ectopic cell deaths caused by over-expression of egl-1 and ced-4. This result suggests that eif-3.K may act downstream of or in parallel to egl-1 and ced-4 in the genetic pathway during programmed cell death. Using a cell-specific promoter we showed that eif-3.K likely promoted cell death in a cell-autonomous manner. We generated antibodies against bacterially expressed EIF-3.K protein. The immunostaining result showed that EIF-3.K was ubiquitously expressed during embryogenesis and localized to the cytoplasm. To better understand the cell-death defect of eif-3.K mutants, we are currently performing a 4D microscopic analysis of the cell death process in wild-type and eif-3.K mutants.

Chalasani S H et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "Neuropeptide feedback modifies odor induced responses in Caenorhabditis elegans olfactory neurons"

Bargmann C I, Kato S, Chalasani S H, Albrecht D R

[Neuronal Development, Synaptic Function and Behavior, Madison, WI, 2010]

Neural circuits transform sensory signals to generate behaviors on timescales from seconds to hours. In some C.elegans behaviors, sensory inputs lead to long lasting and complex behavioral outputs. Animals that have been removed from food spend about 15 minutes exploring a local area by interrupting long forward movements with reversals and turns (Wakabayashi et al., 2004, Gray et al 2005). AWC sensory neurons regulate this behavior by releasing two neurotransmitters, glutamate (promoting turns) and NLP-1 (inhibiting turns). AWC sensory neuron released glutamate activates AIB and inhibits AIY and AIA interneurons (Chalasani et al 2007). In contrast to glutamate, AWC neuron released NLP-1 acts on AIA interneurons to suppress reversals, indicating that turn frequencies are regulated by at least two opposing systems. AWC calcium responses are modulated in these neurotransmitter mutants suggesting that multiple pathways can influence AWC dependent behavior and neuronal activity. ReferencesChalasani, S. H., et. al. Dissecting a neural circuit for olfactory behaviour in Caenorhabditis elegans. Nature 450, 63-70 (2007).Gray, J.M., et. al. A circuit for navigation in Caenorhabditis elegans. Proc. Natl. Acad. Sci. 102, 3184-3191 (2005).Wakabayashi, T., et. al. Neurons regulating the duration of forward locomotion in Caenorhabditis elegans. Neurosci. Res. 50, 103-111 (2004).

Chalasani, Sreekanth H. et al. (2009) International Worm Meeting "AWC sensory neurons release two neurotransmitters to regulate exploratory behavior upon removal from food."

Albrecht, Dirk, Bargmann, Cornelia I., Chalasani, Sreekanth H., Kato, Saul

[International Worm Meeting, 2009]

Animals increase their pirouette frequency in response to removal from food stimulus for a period of 15 min. The AWC and ASK sensory neurons and the AIB interneurons stimulate pirouettes immediately after removal from food, while the AIY and AIA interneurons inhibit pirouettes (Wakabayashi et al 2004, Gray et al 2005). We have found that AWC sensory neurons become active in response to removal of stimulus, releasing two neurotransmitters (glutamate and a neuropeptide NLP-1). The released glutamate acts to activate AIB and inhibit AIY interneurons, promoting reversals (Chalasani et al 2007). In contrast to glutamate, AWC-released NLP-1 acts on AIA interneurons to suppress reversals, suggesting that reversal frequencies are regulated by at least two opposing signaling systems. AWC calcium responses are modulated in these neurotransmitter mutants, suggesting that feedback pathways affect AWC neuronal activity. References: Chalasani, S. H., Chronis, N., Tsunozaki, M., Gray, J. M., Ramot, D., Goodman, M. B., and Bargmann, C. I. (2007). Dissecting a circuit for olfactory behaviour in Caenorhabditis elegans. Nature 450, 63-70. Gray, J.M., Hill, J.J., and Bargmann, C.I. (2005). A circuit for navigation in Caenorhabditis elegans. Proc. Natl. Acad. Sci. 102, 3184-3191. Wakabayashi, T., Kitagawa, I., and Shingai, R. (2004). Neurons regulating the duration of forward locomotion in Caenorhabditis elegans. Neurosci. Res. 50, 103-111.

Sreekanth Chalasani et al. (2007) International Worm Meeting "Functional analysis of a neural circuit controlling turning behavior in Caenorhabditis elegans."

Cornelia Bargmann, Jesse Gray, Makoto Tsunozaki, Sreekanth Chalasani, Nikolas Chronis

[International Worm Meeting, 2007]

C. elegans increase its frequency of reversals and turns (jointly termed pirouettes, Pierce-Shimomura et al 1999) after removal of a food stimulus. The AWC and ASK sensory neurons and the AIB interneurons stimulate pirouettes immediately after removal from food, while the AIY and AIA interneurons inhibit pirouettes (Wakabayashi et al 2004, Gray et al 2005). We have found that the sensory neuron AWC releases two neurotransmitters (glutamate and a neuropeptide, NLP-1) when the worm is removed from food. The released glutamate acts to activate AIB and inhibit AIY, promoting reversals. Strains with different reversal frequencies can be generated by manipulating the level of glutamate receptors on interneurons AIB and AIY. Decreasing receptor expression leads to fewer reversals, and increasing receptor expression results in more reversals than in wild-type. The AWC released neuropeptide NLP-1 serves to reduce reversals, suggesting that reversal frequencies are regulated by at least two opposing signaling systems. Consistent with behavioral responses, AWC and AIB respond (by increasing calcium concentration) to removal of stimulus. We plan to extend the imaging studies to other neurons in the circuit. These results provide a plausible molecular explanation that links neurotransmitters, their receptors, and neuronal circuitry to generate behavior. References: Gray, J.M., Hill, J.J., and Bargmann, C.I. (2005). A circuit for navigation in Caenorhabditis elegans. Proc. Natl. Acad. Sci. 102, 3184-3191. Pierce-Shimomura, J.T., Morse, T.M., and Lockery, S.R. (1999). The fundamental role of pirouettes in Caenorhabditis elegans chemotaxis. J. Neurosci 19, 9557-9569. Wakabayashi, T., Kitagawa, I., and Shingai, R. (2004). Neurons regulating the duration of forward locomotion in Caenorhabditis elegans. Neurosci. Res. 50, 103-111.

Johnson, Christina K. et al. (2019) International Worm Meeting "Requirement of glial Na+/K+-ATPase in touch sensation highlights ionic and metabolic link between glia and touch neurons in C. elegans."

Johnson, Christina K., Bianchi, Laura, Wang, Ying, Fernandez Abascal, Jesus

[International Worm Meeting, 2019]

Isolated microenvironments, such as the tripartite synapse, where the concentration of ions is regulated independently from the surrounding tissues, exist throughout the nervous system, including in mechanoreceptors. Modulation of the ionic composition of these microenvironments has been suggested to be achieved by glia and other accessory cells. However, the molecular mechanisms of ionic regulation and effects on neuronal output and animal behavior are poorly understood. Using the model organism C. elegans, our lab published that Na+ channels of the DEG/ENaC family expressed in glia control neuronal Ca2+ transients and animal behavior in response to sensory stimuli. DEG/ENaC Na+ channels are known to establish a favorable driving force for K+ excretion, which occurs via inward rectifier K+ channels, in epithelial tissues across species. We hypothesized that a similar mechanism exists in the nervous system. Using molecular, genetic, in vivo imaging, and behavioral approaches, we showed that expression in glia of inward rectifier K+ channels and cationic channels rescues the sensory deficits caused by knock-out of glial DEG/ENaCs without disrupting neuronal morphology, supporting our hypothesis. Based on this model, Na+/K+-ATPases are also needed to maintain ionic concentrations following influx of Na+ and excretion of K+. We show here that, in addition to glial Na+ and K+ channels, two specific glial Na+/K+-ATPases, EAT-6 and CATP-1, are needed for touch sensation and that their requirement can be bypassed by a high glucose diet. The effect of glucose is dependent on ATP binding capability of the pump, translation, transcription, and the activity of CATP-2, a third Na+/K+-ATPase ?-subunit. Taken together, our results support metabolic and ionic cooperation between glia and neurons in C. elegans mechanosensors, a mechanism that is essential to regulating neuronal output and may be conserved across species.

Sreekanth H Chalasani et al. (2005) International Worm Meeting "Molecular analysis of a neural circuit for navigation in Caenorhabditis elegans."

Sreekanth H Chalasani, Nikolas Chronis, Jesse M Gray, Cornelia I Bargmann

[International Worm Meeting, 2005]

Navigation in C.elegans is achieved by sustained forward movement that is interrupted with reversals and turns (jointly termed pirouettes, Pierce-Shimomura et al 1999). We are interested in the neural circuit that controls the frequency of reversals and turns during exploratory behavior. After worms are taken off bacterial food, they exhibit an initial local search with a high frequency of pirouettes. The AWC and ASK sensory neurons and the AIB interneurons stimulate pirouettes immediately after removal from food, while the AIY interneurons inhibit pirouettes. (Tsalik and Hobert 2003, Wakabayashi et al 2004, Gray et al 2005). How is activity transmitted through this neuronal circuit? The neurotransmitters glutamate and dopamine regulate turning frequency (Hills et al 2004). We found that the vesicular glutamate transporter EAT-4 is essential for the generation of pirouettes after removal from food. Using cell-specific rescue of eat-4 mutants, we show that both AWC and ASK sensory neurons can release glutamate to stimulate pirouettes. The released glutamate appears to be sensed by a glutamate-gated chloride channel (GLC-3) that inhibits the AIY interneurons, and the glutamate-gated cation channel GLR-1, which stimulates the AIB interneurons. These results provide a plausible molecular explanation that links neurotransmitters, their receptors, and neuronal circuitry to generate behavior. We are currently attempting to image neuronal activity in these neurons using genetically encoded calcium sensors. References: Gray, J.M., Hill, J.J., and Bargmann, C.I. (2005). A circuit for navigation in Caenorhabditis elegans. Proc. Natl. Acad. Sci. 102, 3184-3191. Hills, T., Brockie, P.J., and Maricq, A.V. (2004). Dopamine and glutamate control area-restricted search behavior in Caenorhabditis elegans. J. Neurosci 24, 1217-1225. Pierce-Shimomura, T., Morse, T.M., and Lockery, S.R. (1999). The fundamental role of pirouettes in Caenorhabditis elegans chemotaxis. J. Neurosci 19, 9557-9569. Wakabayashi, T., Kitagawa, I., and Shingai, R. (2004). Neurons regulating the duration of forward locomotion in Caenorhabditis elegans. Neurosci. Res. 50, 103-111.

Maelle Jospin et al. (2001) International C. elegans Meeting "Basic electrophysiological properties of body wall muscle from the Nematode C elegans."

Maelle Jospin, Laurent Segalat, Bruno Allard

[International C. elegans Meeting, 2001]

Electrophysiological properties of striated muscle cells were investigated with the patch clamp technique in the Nematode C elegans . Worms were immobilised with cyanoacrylate glue and longitudinally incised using a tungsten rod sharpened by electrolysis. Recording pipettes were sealed on GFP-expressing body wall muscle cells. In the whole cell configuration, under current clamp conditions, in the presence of Ascaris medium in the bath and K-rich solution in the pipette, no action potential could be induced in response to current injection. Under voltage clamp control and in the same ionic conditions, depolarizations above -30 mV from a holding potential of -70 mV gave rise to outward K currents. Outward K currents resulted from two components, one fast inactivating component blocked by 4-aminopyridine, one delayed sustained component blocked by tetraethylammonium. In the presence of both blockers, an inward Ca current was revealed and inhibited by cadmium. Single channel recording using the inside-out configuration revealed the existence of a Ca-activated Cl channel and a Ca-activated K channel. Single channel experiments are currently performed to characterise voltage-gated conductances at the unitary level.

K Omata et al. (1999) International C. elegans Meeting "Habituation of C. elegans for the touch sensitivity"

K Kawamura, F Yonezawa, K Omata

[International C. elegans Meeting, 1999]

In order to study the habituation of C. elegans for the touch sensitivity, we carry out computer simulations, in which the neural circuit is formed by making use of the data table constructed recently by Oshio et al [1]. The i -th neuron is connected with the neighboring j -th neuron through the coupling strength K ij , which is varied dynamically by the Hebb rule. Note that K ij is not necessarily equal to K ji because there are one-way connections between the neurons by chemical synapses. As a reference state, we first deal with the neural circuit consisting only of the neurons ALM, AVM, PLM, PVM, AVA, AVB, PVC, AVD, A and B, that are related to the forward and backward movement directly. We give periodic stimuli to the sensory neurons PLM, PVM, and monitor the response of the motor neuron A. We find that the frequency of the response decreases with time, which indicates that the habituation to the touch sensitivity actually takes place. As one deviation from the reference state, we kill the inter-neuron AVD, and perform the same analysis described in the above. There is a tendency that the decay of the response curve becomes faster, and the habituation is enhanced. As the other deviations, there are several possibilities of killing the inter-neurons AVA, AVB, PVC and/or AVD. We discuss the enhancement of the habituation in relation with the recent experimental results by Hosono. [1.] K. Oshio, S. Morita, Y. Osana and K. Oka; C. elegans synaptic connectivity data'', Technical Report, CCEP, Keio Future No.1 (1998)

Jamie White et al. (2006) Neuronal Development, Synaptic Function, and Behavior Meeting "Neurons necessary for sex-specific social behaviors"

Thomas Nicholas, Eliott Davidson, Jamie White, Erik Jorgensen

[Neuronal Development, Synaptic Function, and Behavior Meeting, 2006]

C. elegans nematodes sense and respond to other individuals in their environment via signals released by hermaphrodites. The response is sex-specific: males are attracted to the signals and hermaphrodites avoid them. This is interesting because the male and hermaphrodite nervous systems have highly similar anatomy, and the stimulus detected by each is the same--hermaphrodite-derived signals--but the response is opposite. This could arise from (1) sex-specific neurons, (2) sex-specific connectivity of anatomically similar neurons, (3) sex-specific physiology of similar neurons, or (4) a combination of these mechanisms. We are therefore interested in which neurons are necessary and sufficient for male-attraction and hermaphrodite avoidance behaviors. To determine this, we are using a combination of mutant analysis, neuron-specific rescue, and laser ablation. Avoidance requires tax-4 and osm-3. These genes overlap in the ASE, ASG, ASI, ASJ, and ASK pairs. Avoidance behavior is normal in unc-130 (required for the ASG fate) and in che-1 (required for proper ASE fate) mutants, indicating that ASI/J/K are most likely necessary for avoidance behavior. Avoidance can be rescued in a tax-4(p678) background by tax-4(+) expression from an odr-4 promoter, which includes expression in ASG and ASI/J/K but not ASE, indicating that ASI/J/K are sufficient for avoidance. ASI/J/K will be laser-ablated in the rescued strain to show which are necessary. Attraction behavior requires osm-9. Attraction behavior can be partially rescued in an osm-9(ky10) background by osm-9(+) expression in either male-specific neurons (pkd-2 promoter), or by expression in the AWB, AWC, and ASI/J/K pairs (odr-1 or daf-11 promoters). This indicates these two sets of neurons are each partially sufficient for attraction behavior. Of the second set, attraction is normal in ceh-36 mutants (required for AWC fate), indicating the AWB and/or ASI/J/K pairs are sufficient for partial rescue. We predict full rescue will be obtained by a combination of expression from the pkd-2 and odr-1/daf-11 promoters. Laser ablation will be carried out in the fully rescued strain to show which neurons of the sufficient set are necessary. It appears, then, that the different sexes may use the same neurons--one or more of the ASI/J/K pair--to generate sex-specific behaviors, but males need at least some input from sex-specific neurons.