Vidal-Gadea A G et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "Biogenic amines mediate transition between crawling and swimming in C. elegans"

Brauner M, Gottschalk A, Erbguth K, Kressin L, Vidal-Gadea A G, Topper S, Young L, Pierce-Shimomura J T

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

A wide variety of animals must quickly adjust their pattern of locomotion to successfully navigate through different environmental niches. Selection and execution of the appropriate locomotory pattern is therefore paramount to survival. Although C. elegans is capable of performing many adaptive behaviors, it has been controversial whether forward crawling and swimming represent distinct gait-like forms of locomotion or the modulation of a single form of locomotion [1-3]. Biogenic amines have been shown to mediate the transition between gait-like forms of locomotion across taxa as diverse as sea slugs, leeches, lampreys and humans. We previously reported that C. elegans crawls and swims with distinct kinematics and different patterns of muscle activity [2]. We now combine quantitative behavioral analysis, optogenetic tools and neuronal ablation to show that C. elegans uses biogenic amines to switch between crawling and swimming in a gait-like manner. As in other invertebrates, we find that serotonin mediates the smooth transition from crawling to swimming in C. elegans. Serotonin is further required to inhibit motor behaviors (e.g. foraging and pharyngeal pumping) during swimming that normally only accompany crawling. Mirroring the role of dopamine in other invertebrates, C. elegans uses dopamine to successfully initiate and maintain crawling when emerging from liquid. Over 600 million years of separate evolution notwithstanding, the highly conserved role played by biogenic amines such as dopamine and serotonin across taxa attests to how vital their function is to adaptive strategies for locomotion. Korta J, Clark DA, Gabel CV, Mahadevan L, Samuel AD. J. Exp. Bio. 2007 210:2383-9.Pierce-Shimomura JT, Chen BL, Mun JJ, Ho R, Sarkis R, McIntire SL. PNAS. 2008 105:20982-7.Berri S, Boyle JH, Tassieri M, Hope IA, Cohen N. HSFP J. 2009 3:186-93.

Crisp A et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "Age-related Cholinergic Neurodegeneration by Overexpression of apl-1 in C.elegans"

Pierce-Shimomura J, Crisp A

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

Alzheimer's disease (AD) is the most common cause of dementia. It is characterized by selective degeneration of cholinergic neurons involved in memory. Dying neurons are surrounded by dense plaques primarily composed of beta-amyloid peptide (Aβ). Aβ is just one cleavage product from the protein APP. Mutations in APP that affect the processing of Aβ result in early-onset AD; however, a single additional wild-type copy of APP can also lead to AD, as seen in all individuals with Down syndrome. Aβ plaques were originally thought to be the primary cause of neurodegeneration, but new research suggests the role of the APP in AD is more complex than originally appreciated. The labs of Dr. Chris Li and Dr. Chris Link have pioneered the use of C. elegans to study APP function and dysfunction. For instance, overexpression of human Aβ in C. elegans muscle leads to the formation of Aβ aggregates(1). Overexpression of multiple copies of the APP-related gene, apl-1, in C. elegans leads to gross phenotypes, including partial lethality, arrested development, and vacuolization(2). We are testing whether expression of only one additional wild-type copy of apl-1 results in AD-related phenotypes. DIC and fluorescence microscopy were used to evaluate worms for signs of neurodegeneration. We have discovered that overexpression of apl-1 in a single copy results in the age-related degeneration of a specific subset of cholinergic neurons in C. elegans. To quantify the impact of degeneration, we track the deterioration of two natural behaviors (swimming and egg-laying) that rely on these neurons. These worms displayed no obvious defects in early adulthood but began to display defects in egg-laying and swimming by the third day of adulthood ('middle age'). In addition, ablation of these specific neurons in wild-type individuals recapitulates the behavioral defects observed in egg-laying and swimming. These results suggest that the behavioral defects observed in the overexpression strain are primarily due to the selective degeneration of these neurons. The quantifiable link between these behaviors and neurodegeneration allows us to test strategies to recover the function mediated by the degenerated cholinergic neurons. We are now studying the mechanisms by which apl-1 overexpression causes death of cholinergic neurons in the worm and in the process, generate novel hypotheses about the mechanism of Alzheimer's disease. 1. Link CD. (1995) PNAS 92, 9368-9372. 2. Hornsten A. et al. (2007) PNAS 104, 1971-1976.

Russell J C et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "Development of a Novel Hygrotaxis Assay for C. elegans"

Russell J C, Pierce-Shimomura J

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

Moisture is essential for life -- critically influencing physiology, behavior and evolution. As such, many animals have adapted different behavioral mechanisms to migrate toward their preferred level of moisture. This ability to detect moisture is called hygrosensation and the ability to migrate to a favored moisture level is called hygrotaxis. These behaviors are often critical to keep an animal within its niche and regulate essential processes like growth and reproduction. It is therefore surprising that although the basic neuromolecular mechanisms for the detection of light, sound, tastants, odorants, and even temperature have been identified, the molecular basis for how a nervous system senses moisture remains mostly unknown. In order to uncover the molecular basis for hygrosensation we have developed a novel behavioral hygrotaxis assay for C. elegans. With this assay we have shown that C. elegans has the ability to move directly to a preferred level in a moisture gradient, whereas it moves randomly when there is no moisture gradient. By assaying extant mutants, we have found that molecular pathways that are essential for taste, olfaction, thermosensation and hyperosmotic repulsion are not required for hygrotaxis. We are currently characterizing the neural network for hygrosensation and hygrotaxis by combining behavioral assays of additional mutant and transgenic worms, a forward genetic screen for hygrotaxis (htx) mutants, and functional imaging of identified neurons. Study of the molecular basis for hygrosensation in C. elegans may provide insight into this sensory modality in other organisms.

Griffith A M et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "C. elegans Model of Down Syndrome"

Griffith A M, Pierce-Shimomura J

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

Down syndrome (DS) is the most common genetic cause of mental retardation, occurring at a rate of 1 in 733 live births in the United States. Individuals with DS often suffer from additional neurological and neuromuscular symptoms including congenital heart defects, hypotonia (poor muscle tone), defects in learning and memory, as well as early-onset Alzheimer's disease. While DS is known to result from an extra copy of chromosome 21, it is unknown which specific genes cause the associated phenotypes. The human 21st chromosome encodes 226 known protein-coding genes. Only a small portion of these genes have been studied for potential roles in DS. We have found that, excluding keratin genes, over 85% of the 21st chromosome genes have equivalents in the C. elegans genome suggesting that the worm can be an extremely useful model for DS. We now aim to identify the subset of these genes which may cause neural and/or muscle dysfunction in DS. To this end, we are first focused on identifying the in vivo role of these genes using RNAi. In our initial screen, we found that approximately half of the RNAi treatments caused worms to exhibit abnormal neuromuscular phenotypes. By examining the locomotion, pharyngeal pumping, and neural anatomy of RNAi-treated worms we can further describe how these genes elicit phenotypes related to DS. Furthermore, by generating strains of worms which overexpress genes of interest, we will be able to observe the effects of DS-equivalent doses of the genes and test putative treatments for DS-related phenotypes. Knowledge of the genes which contribute to the phenotypes of DS will help us understand the causes of this condition and aid in the development of novel treatments to improve the quality of life of people with DS.

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.

Topper S et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "A Role for Dopamine in Switching Locomotory Patterns in C. elegans"

Young L, Pierce-Shimomura J, Erbguth K, Brauner M, Vidal-Gadea A, Kressin L, Gottschalk A, Topper S

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

Humans have the ability to switch smoothly between a wide variety of movement patterns including distinct locomotory gaits. This ability is severely disrupted in certain neurological diseases such as Parkinson's disease which is caused by degeneration of dopamine neurons. We have found that C. elegans displays alternate forms of locomotion; crawling when on firm substrates and swimming when in liquid [1]. Moreover, we examined worm locomotion in different viscosities and found that C. elegans swims at low viscosities, crawls at high viscosities, and continually switches between bouts of crawl- and swim-like motions at intermediate viscosities. This suggests that the worm switches between two distinct forms of locomotion. To investigate a potential role for dopamine in this switching, we examined how activation of dopamine neurons with channelrhodopsin2 (ChR2) affected locomotion.ChR2 is a light-activated cation channel which depolarizes neurons after stimulation with blue light. Activation of dopamine neurons was sufficient to induce a switch from swimming to crawl-like behavior. Application of exogenous dopamine to swimming worms also induced bouts of crawl-like behavior suggesting that dopamine alone acts as a chemical switch sufficient to initiate crawling. Exogenous application of serotonin, which is known to encourage swimming behavior in other species [2], significantly reduced the probability of switching to crawl-like behavior during dopaminergic activation. Lastly, we also have found that ablation of dopamine neurons specifically perturbs the worm's ability to switch from swimming to crawling. Dopamine has been previously implicated in reducing the rate of crawling in the basal-slowing response [3]. Consistent with this, we found that activation of dopamine neurons in animals crawling on unseeded plates induced a transition to a slower form of crawling. This suggests that dopamine can induce context-dependent changes in locomotory patterns. The fact that dopamine is both necessary and sufficient for the swim to crawl transition suggests that C. elegans can be used to model the abnormal motor switching in human Parkinson's disease. Further investigations should shed light on the fundamental neural mechanisms that underlie the switching between distinct patterns of neural activity.1. Pierce-Shimomura JT, Chen BL, Mun JJ, Ho R, Sarkis R, McIntire SL. PNAS. 20082. Friesen WO, Kristan WB.Current Opinion in Neurobiology. 20073. Sawin ER, Ranganathan R, Horvitz HR. Neuron. 2000

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.

Yamazoe A et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "The Worms Responds to the Gradient Direction of the Repulsive Odor 2-nonanone"

Kimura K, Yamazoe A

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

To understand the neural mechanisms underlying behavioral responses to a chemical signal, we are studying the avoidance behavior of C. elegans to the repulsive odor 2-nonanone as a model. We have found that the avoidance behavior of the animals to 2-nonanone is enhanced rather than reduced after pre-exposure to the odor: The preexposed animals migrate farther away from the odor source than do the control animals, and this plasticity is acquired as a type of non-associative learning (see abstract by Kimura and Fujita). Here, we present evidence to support that the animal''s 2-nonanone avoidance appear to depend on the bearing angle—the angle between the direction of their locomotion and of a putative spatial gradient of 2-nonanone. A bearing angle of 0° indicates that the movement is directly down the gradient, and a bearing angle of 180° indicates that the movement is directly up the gradient. For a quantitative behavioral analysis, the animals' movements during the 2-nonanone avoidance were divided into periods of straight movements (runs) and of frequent turnings (pirouettes), as previously reported in salt chemotaxis (Pierce-Shimomura et al., J. Neurosci., 1999). When an animal's bearing was within ~60° during movement down the gradient, pirouette initiation rates were low and constant. By contrast, when an animal's bearing was greater than ~60°, pirouette initiation rate increased. Interestingly, only when an animal's bearing during a run was within ~60°, the pre-exposed animals exhibited much lower pirouette initiation rates and longer run durations than did the control animals; this difference may reflect the memory of pre-exposure to cause the enhancement of 2-nonanone avoidance. Consistent with this sensitive response to bearing, the animals appeared to exhibit a more accurate course correction after pirouetting during 2-nonanone avoidance than during the salt chemotaxis. We are currently attempting to measure the actual changes in the concentration of 2-nonanone during the assay by using a sensitive gas chromatography and planning to confirm our model by a computer simulation. We thank Drs. J. Pierce-Shimomura, M. Fujiwara, and N. Masuda for providing their suggestions on our project.

Akiko Yamazoe et al. (2010) East Asia Worm Meeting "The worms respond to the gradient direction of the repulsive odor 2-nonanone"

Kotaro Kimura, Akiko Yamazoe

[East Asia Worm Meeting, 2010]

To understand the neural mechanisms underlying behavioral responses to a chemical signal, we are studying the avoidance behavior of C. elegans to the repulsive odor 2-nonanone as a model. We have found that the avoidance behavior of the animals to 2-nonanone is enhanced rather than reduced after pre-exposure to the odor: The preexposed animals migrate farther away from the odor source than do the control animals, and this plasticity is acquired as a type of non-associative learning (see abstract by Fujita and Kimura). Here, we present evidence to support that the animal's 2-nonanone avoidance appear to depend on the bearing angle - the angle between the direction of their locomotion and of a putative spatial gradient of 2-nonanone. A bearing angle of 0 deg indicates that the movement is directly down the gradient, and a bearing angle of 180 deg indicates that the movement is directly up the gradient. For a quantitative behavioral analysis, the animals' movements during the 2-nonanone avoidance were divided into periods of straight movements (runs) and of frequent turnings (pirouettes), as previously reported in salt chemotaxis (Pierce-Shimomura et al., J. Neurosci., 1999). When an animal's bearing was within ~60 deg during movement down the gradient, pirouette initiation rates were low and constant. By contrast, when an animal's bearing was greater than ~60 deg, pirouette initiation rate increased. Interestingly, only when an animal's bearing during a run was within ~60 deg, the preexposed animals exhibited much lower pirouette initiation rates and longer run durations than did the control animals; this difference may reflect the memory of pre-exposure to cause the enhancement of 2-nonanone avoidance. Consistent with this sensitive response to bearing, the animals appeared to exhibit a more accurate course correction after pirouetting during 2-nonanone avoidance than during the salt chemotaxis. We are currently attempting to measure the actual changes in the concentration of 2-nonanone during the assay by using a sensitive gas chromatography and planning to confirm our model by a computer simulation. We thank Drs. J. Pierce-Shimomura, M. Fujiwara, and N. Masuda for providing their suggestions on our project.

Mitchell PH et al. (2008) European Worm Meeting "Modelling alcohol dependence in Caenorhabditis elegans"

James C, Mitchell PH, Mould RN, Hopper NA, Glautier SP, Dillon J, Oconnor VM, Holden-Dye LM,, Adrianakis I

[European Worm Meeting, 2008]

Ethanol is one of the most widely used and socially acceptable drugs in the. world. However its chronic use can lead to serious problems due to the. development of dependence. Ethanol has been shown have wide-ranging but. selective effects on many different neurotransmitter circuits including;. glutamatergic, GABAergic, serotonergic, dopaminergic and opioid peptidergic. systems. The basis for alcohol tolerance and withdrawal involves. counteradaptive neurochemical changes within these systems to adapt to the. prolonged presence of ethanol in the brain. Here we are using C. elegans to. enable an analysis at all levels of organization from gene, molecule, and. neurone through to neuronal circuit and behaviour. We want to use C.. elegans to investigate the development of neuroadaptation to ethanol. In. order to achieve this we have first provided evidence that ethanol rapidly. equilibriates across the cuticle of C. elegans (Mitchell et al. 2007) thus. enabling experiments in which the concentration-dependent effects of. ethanol on behaviour can be defined. In line with previous studies (Davies. et al. 2003) we have established that external concentrations of ethanol. >100mM are required to overtly affect the visually observable measures of. behaviour. This is equivalent to concentrations that are supra-intoxicating. in mammals. In order to determine whether ethanol elicits any effects on. C. elegans at concentrations equivalent to those that are intoxicating in. mammals we have performed more discreet analyses of behaviours. Pharyngeal. recordings have revealed that concentrations as low as 10mM ethanol have. significant effects on the activity of neural networks, thus providing an. opportunity to investigate the molecular determinants of acute ethanol. effects. We are also in the process of refining the analysis of locomotory. behaviour with the aim of determining whether ethanol elicits effects at. low mM concentrations. As part of this effort we have developed a paradigm. in which we can demonstrate withdrawal from ethanol, and relief from. withdrawal due to low concentrations of acute ethanol. We have used this to. study the onset and recovery rates of this neuroadaptation and the. concentration dependence of this effect in order to understand the. mechanisms involved. This has been extended to investigate if genes already. implicated in acute effects of ethanol in C. elegans are involved in. controlling the withdrawal and tolerance behaviours. These studies are. aimed at better defining how well C. elegans can model aspects of. alcoholism.. Funded by the BBSRC, UK.. References. Davies, A. G., Pierce-Shimomura, J. T., Kim, H., VanHoven, M. K., Thiele,. T. R., Bonci, A., Bargmann, C. I., & McIntire, S. L. 2003, "A central role. of the BK potassium channel in behavioral responses to ethanol in C.. elegans", Cell, vol. 115, no. 6, pp. 655-666.. Mitchell, P. H., Bull, K., Glautier, S., Hopper, N. A., Holden-Dye, L., &. O''connor, V. 2007, "The concentration-dependent effects of ethanol on. Caenorhabditis elegans behaviour", Pharmacogenomics.J., vol. 7, no. 6, pp.. 411-417.