Takeishi, Asuka et al. (2017) International Worm Meeting "Molecular and neuronal mechanisms underlying feeding state-dependent plasticity in thermotaxis behaviors."

Takeishi, Asuka, Sengupta, Piali

[International Worm Meeting, 2017]

Dynamic regulation of behaviors by past experience allows animals to exhibit responses that are most optimal for their reproduction and survival. Consequently, the same stimulus can elicit different behaviors in different individuals based on the individual's experience, internal state, and immediate context. The presence of food and feeding status are critical variables that modulate multiple behavioral strategies in C. elegans, including their navigation behaviors on spatial thermal gradients. While well-fed worms migrate to colder temperatures (negative thermotaxis) when they encounter temperatures higher than their cultivation temperature Tc, starvation for =30 min suppresses this behavior. Thus, feeding state-dependent regulation of thermosensory behaviors in C. elegans provides an attractive model system in which to study how internal state (starvation) is integrated with environmental cues (temperature) to alter neuronal circuit functions. Temperature-evoked responses in the AFD thermosensory neurons are largely unaffected upon starvation suggesting that the starvation signal is integrated elsewhere in the thermotaxis circuit to alter behavior. We find that the AWC and ASI sensory neurons play a role in mediating this starvation-dependent behavioral plasticity. Although ablation of ASI alone does not affect this plasticity, ablation of AWC alone, or AWC and ASI together, partially or fully abolish starvation-dependent suppression of negative thermotaxis, respectively. Interestingly, we observe that the subcellular localization of the CMK-1 CaMKI (calcium/calmodulin-dependent protein kinase I) enzyme we previously implicated in the feeding state-dependent dauer behavioral decision (Neal et al., 2015) is altered in AWC asymmetrically upon starvation. The INS-1 insulin pathway has previously been shown to contribute to starvation-dependent plasticity in thermotaxis behaviors (Kodama et al. 2006). We find that subcellular localization of CMK-1 is also altered in ins-1 mutants. Moreover, we find that basal activity of AWC is increased upon prolonged starvation, and in ins-1 and cmk-1 mutants. Taken together, we propose that feeding status is integrated into the thermotaxis circuit via regulation of AWC activity and potentially CMK-1-dependent gene expression changes to modulate thermotaxis behavior. Current experiments are aimed at examining the contribution of asymmetry in starvation-dependent changes in AWC function in mediating thermotaxis behavioral plasticity.

Takeishi*, Asuka et al. (2015) International Worm Meeting "AFD-specific receptor guanylyl cyclases can confer temperature responses onto diverse cell types."

Takeishi*, Asuka, Sengupta, Piali, Bell, Harold W., Hapiak, Vera M., Yu*, Yanxun V.

[International Worm Meeting, 2015]

C. elegans exhibits complex experience-dependent thermosensory behaviors on spatial thermal gradients. AFD has been identified as the major thermosensory neuron type, and AFD-ablated worms exhibit strong defects in thermotaxis behaviors. Measurements of temperature-evoked intracellular calcium dynamics and thermoreceptor current have shown that AFD responds to thermal variation at temperatures above a threshold temperature (T*) that is set by the animal's cultivation temperature (Tc). Thermotransduction in AFD is mediated by cGMP signaling, and requires the functions of the receptor guanylyl cyclases (rGCs), GCY-8, GCY-18 and GCY-23, the cGMP-dependent phosphodiesterase PDE-2, and the TAX-2 and TAX-4 cGMP-gated channels. However, the molecular mechanisms by which AFD senses temperature are still unknown.Previous studies have shown that many rGCs function as sensors for specific stimuli, suggesting that the AFD-expressed rGCs may themselves act as thermosensors. We found that misexpression of GCY-8, GCY-18 and GCY-23 in the non-thermosensory AWB and ASE chemosensory neurons is sufficient to confer warming-dependent changes in intracellular calcium (also see abstract by Yu, Takeishi et al). We further expressed each rGC singly or in combination in these neurons, and found that expression of GCY-23 alone confers temperature responses onto AWB and ASE in the physiological temperature range, whereas expression of GCY-18 confers responses to higher temperatures. Interestingly, in contrast to AFD, the T* of AWB and ASE misexpressing AFD-specific rGCs is not modulated by Tc, suggesting that the observed Tc -dependent plasticity in AFD thermosensory response threshold may be mediated by AFD-specific mechanisms. To ask whether misexpression in cell types lacking endogenous cGMP signaling pathways would also confer thermosensory responses, we next misexpressed the rGCs in vulval muscles. We found that vulval muscles misexpressing GCY-23 as well as TAX-2/TAX-4 also exhibit responses to temperature variation. Our results suggest that AFD-specific rGCs can confer thermosensory responses onto multiple neuronal and non-neuronal cell types, and raise the possibility that these proteins may be bona fide thermosensors in C. elegans.* - equal contributions.

Aoki, Yuki et al. (2021) International Worm Meeting "Behavioral and Ca2+ imaging analysis of odor and temperature sensory integration in C. elegans"

Aoki, Yuki, Takeishi, Asuka

[International Worm Meeting, 2021]

Most of living organisms are exposed to multiple environmental stimuli at the same time in nature. When animals sense external stimuli of heterogeneous sources, they weigh and integrate the information in their nervous system to respond appropriately. It is essential for animals to make behavior choice for survival, however, the neural and molecular mechanism of multisensory integration is still largely unknown. C. elegans exhibits behavioral responses against various stimuli such as temperature and odors. Previous studies have revealed detail neural networks and signaling pathways that are required to produce behavior in response to each stimulus. To understand how the nervous system process multiple information, we are investigating the behavior and neural response of worms that are exposed to both temperature and odor stimuli at the same time. To examine the behavior choice of worms, we evaluated the direction of worm migration on the agar plate with thermal gradient and an odor. We also set up a microscope with auto-tracking stage that enable us to observe neural responses and locomotion of free-moving worms simultaneously with stimuli of temperature and an odor. We are currently analyzing the neural activities of sensory neurons and inter neurons in order to identify the neurons and the mechanisms that drive worm behavior. These results are expected to allow us to understand the detail neural mechanism of multi-information integration in a complicated environment.

Yu*, Yanxun et al. (2015) International Worm Meeting "AFD-specific guanylate cyclases and CMK-1 mediate thermosensory signaling in AFD."

Yu*, Yanxun, Takeishi*, Asuka, Sengupta, Piali, Hapiak, Vera, Bell, Harrold

[International Worm Meeting, 2015]

Animals actively seek optimal temperatures for survival and reproduction. Unlike many organisms that exhibit a constant temperature preference, the preferred temperature of C. elegans is plastic, and set by their experience of their cultivation temperature. The AFD neurons are the primary thermosensory neurons in C. elegans, and drive thermosensory navigation behaviors on thermal gradients. Although the AFD neurons are known to respond to temperature variations of as little as 0.01 C, how worms sense temperature and set their temperature preference are still largely unknown. Thermosensation in AFD requires cGMP signaling, and molecules implicated in this pathway have been identified. These include receptor guanylyl cyclases (rGCs) expressed specifically in AFD, as well as phosphodiesterases, and cGMP-gated cation channels.To determine whether the AFD-specific rGCs GCY-8, GCY-18 and GCY-23 act as thermosensors, we misexpressed these rGCs singly or in combination in non-thermosensory neuron types, as well as in non-neuronal cells. We found that misexpression was sufficient to confer thermosensory responses onto both neuronal and non-neuronal cells (also see abstract by Takeishi & Yu et al). Each rGC appears to elicit temperature responses with different response thresholds. However, although the thermosensory response threshold in AFD adapts upon long-term exposure to a different temperature, the response threshold of rGC-misexpressing cells do not adapt similarly. Our work suggests that AFD-specific mechanisms including the function of the CMK-1 CaMKI enzyme may be important in regulating rGC gene expression and thermosensory adaptation in AFD. We are currently determining whether rGCs are sufficient to confer temperature responses upon heterologous expression, and identifying domains that may mediate thermosensation.* - equal contributions.

Neal, Scott et al. (2015) International Worm Meeting "Food-dependent regulation of developmental plasticity via CaMKI and neuroendocrine signaling."

Sengupta, Piali, Butcher, Rebecca, Neal, Scott, Takeishi, Asuka, Kim, Kyuhyung

[International Worm Meeting, 2015]

Many animals integrate information about the environment, as well as internal state, to choose between alternate developmental trajectories. Environmental conditions, including food availability, inform the choice of C. elegans larvae to enter into the reproductive cycle or the growth arrested dauer stage. This polyphenic developmental decision is mediated via regulation of insulin and TGF-beta signaling. However, the molecular and neuronal mechanisms by which food signals are assessed and integrated to regulate neuroendocrine signaling and this binary developmental decision are not well understood. Here we show that food information is integrated into the dauer pathway by the activity of the CMK-1 CaMKI enzyme in the AWC and ASI sensory neurons. AWC is hyperactive and exhibits enhanced odor responsiveness in both starved wild-type and fed cmk-1 mutants, suggesting that the state of AWC in fed cmk-1 larvae resembles that in starved wild-type animals. Food deprivation also regulates nuclear localization of CMK-1 in AWC in a dynamic manner, and we show that CMK-1 regulates the expression of insulin-like peptide (ILP) genes in AWC as a function of feeding state. CMK-1-regulated ILP signaling from AWC in turn regulates expression of the growth promoting daf-28 ILP gene in the ASJ neurons. CMK-1 also acts in parallel in ASI to regulate expression of the daf-7 TGF-beta gene. Downregulation of daf-28 and TGF-beta expression in cmk-1 mutants drives enhanced dauer formation under conditions of ample food. Together, these results identify mechanisms by which information regarding nutrient availability converges with other sensory cues in a small neuronal network to modulate neuroendocrine signaling and developmental plasticity.

Khan, M. et al. (2017) International Worm Meeting "The GCY-29 receptor guanylyl cyclase shapes thermosensory signaling in C. elegans."

Khan, M., Takeishi, A., Sengupta, P., Hapiak, V.

[International Worm Meeting, 2017]

The ability to sense and respond to external cues in the context of past experiences and current conditions is crucial for animals to survive and maintain functional homeostasis. Temperature represents a critical environmental variable that regulates nearly all physiological processes. Consequently, animals have evolved mechanisms to detect and respond to small changes in both external and internal temperature. Unlike many organisms that prefer a constant environmental temperature, the preferred temperature of C. elegans is governed by a 'memory' of its cultivation temperature (Tc). This temperature preference is plastic, and resets in an experience-dependent manner. These behaviors are mediated primarily by the AFD sensory neurons, which respond to temperature variations above a Tc-determined threshold. Thermotransduction in AFD is mediated by a subset of three receptor guanylyl cyclases (rGCs). We have recently shown that the AFD-expressed rGCs GCY-8, -18, and -23 are necessary and sufficient for thermosensation (Takeishi, Yu, et al., 2016). In addition to these rGCs, the AFD neurons also express the GCY-29 rGC. Similar to the thermosensory rGCs, GCY-29 is also localized to the AFD sensory endings. The goal of this work is to explore the role of GCY-29 in shaping AFD-mediated thermosensory signaling. Using calcium imaging and thermotaxis navigation behavioral analyses, we have found that GCY-29 contributes to the detection and tracking of temperature stimuli, as well as shaping the Tc-determined response threshold of AFD. Our findings suggest that GCY-29 may modulate the functions of the thermosensory rGCs to more precisely coordinate AFD response ranges and shape their thermosensory response profiles.