jonathan pierce-shimomura | The University of Texas at Austin (original) (raw)

Uploads

Papers by jonathan pierce-shimomura

Research paper thumbnail of Serotonergic blockade prevents age-related neurodegeneration in C. elegans model of Alzheimer's disease

Alzheimers & Dementia, 2011

Research paper thumbnail of Caenorhabditis elegans selects distinct crawling and swimming gaits via dopamine and serotonin

Proceedings of The National Academy of Sciences, 2011

Research paper thumbnail of A Central Role of the BK Potassium Channel in Behavioral Responses to Ethanol in C. elegans

Research paper thumbnail of The Fundamental Role of Pirouettes in Caenorhabditis elegans Chemotaxis

Research paper thumbnail of The fundamental role of pirouettes in C. elegans chemotaxis

Research paper thumbnail of Genetic analysis of crawling and swimming locomotory patterns in C. elegans

Proceedings of The National Academy of Sciences, 2008

Alternative patterns of neural activity drive different rhythmic locomotory patterns in both inve... more Alternative patterns of neural activity drive different rhythmic locomotory patterns in both invertebrates and mammals. The neuro-molecular mechanisms responsible for the expression of rhythmic behavioral patterns are poorly understood. Here we show that Caenorhabditis elegans switches between distinct forms of locomotion, or crawling versus swimming, when transitioning between solid and liquid environments. These forms of locomotion are distinguished by distinct kinematics and different underlying patterns of neuromuscular activity, as determined by in vivo calcium imaging. The expression of swimming versus crawling rhythms is regulated by sensory input. In a screen for mutants that are defective in transitioning between crawl and swim behavior, we identified unc-79 and unc-80, two mutants known to be defective in NCA ion channel stabilization. Genetic and behavioral analyses suggest that the NCA channels enable the transition to rapid rhythmic behaviors in C. elegans. unc-79, unc-80, and the NCA channels represent a conserved set of genes critical for behavioral pattern generation.

Research paper thumbnail of Manipulation of Behavioral Decline in Caenorhabditis elegans with the Rag GTPase raga-1

Research paper thumbnail of Conserved Role of unc-79 in Ethanol Responses in Lightweight Mutant Mice

Research paper thumbnail of Manipulation of Behavioral Decline in Caenorhabditis elegans with the Rag GTPase raga-1

Research paper thumbnail of The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Research paper thumbnail of The Dystrophin Complex Controls BK Channel Localization and Muscle Activity in Caenorhabditis elegans

Research paper thumbnail of Conserved Role of unc-79 in Ethanol Responses in Lightweight Mutant Mice

Research paper thumbnail of The Dystrophin Complex Controls BK Channel Localization and Muscle Activity in Caenorhabditis elegans

Research paper thumbnail of Analysis of the effects of turning bias on chemotaxis in C. elegans

Journal of Experimental Biology, 2005

C. elegans advances up a chemical gradient by modulating the probability of occasional large, cou... more C. elegans advances up a chemical gradient by modulating the probability of occasional large, course-correcting turns called pirouettes. However, it remains uncertain whether C. elegans also uses other behavioral strategies for chemotaxis. Previous observations of the unusual, spiral-shaped chemotaxis tracks made by the bent-head mutant unc-23 point to a different strategy in which the animal continuously makes more subtle course corrections. In the present study we have combined automated tracking of individual animals with computer modeling to test the hypothesis that the pirouette strategy is sufficient on its own to account for the spiral tracks. Tracking experiments showed that the bent-head phenotype causes a strong turning bias and disrupts pirouette execution but does not disrupt pirouette initiation. A computer simulation of disrupted pirouette behavior and turning bias reproduced the spiral tracks of unc-23 chemotaxis behavior, showing that the pirouette strategy is sufficient to account for the mutant phenotype. In addition, the simulation reproduced higher order features of the behavior such as the relationship between the handedness of the spiral and the side to which the head was bent. Our results suggest that the pirouette mechanism is sufficient to account for a diverse range of chemotaxis trajectories.

Research paper thumbnail of A Neural Network Model of Chemotaxis Predicts Functions of Synaptic Connections in the Nematode Caenorhabditis elegans

Journal of Computational Neuroscience, 2004

Research paper thumbnail of The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Nature, 2001

The ability to discriminate between different chemical stimuli is crucial for food detection, spa... more The ability to discriminate between different chemical stimuli is crucial for food detection, spatial orientation and other adaptive behaviours in animals. In the nematode Caenorhabditis elegans, spatial orientation in gradients of soluble chemoattractants (chemotaxis) is controlled mainly by a single pair of chemosensory neurons. These two neurons, ASEL and ASER, are left-right homologues in terms of the disposition of their somata and processes, morphology of specialized sensory endings, synaptic partners and expression profile of many genes. However, recent gene-expression studies have revealed unexpected asymmetries between ASEL and ASER. ASEL expresses the putative receptor guanylyl cyclase genes gcy-6 and gcy-7, whereas ASER expresses gcy-5 (ref. 4). In addition, only ASEL expresses the homeobox gene lim-6, an orthologue of the human LMX1 subfamily of homeobox genes. Here we show, using laser ablation of neurons and whole-cell patch-clamp electrophysiology, that the asymmetries between ASEL and ASER extend to the functional level. ASEL is primarily sensitive to sodium, whereas ASER is primarily sensitive to chloride and potassium. Furthermore, we find that lim-6 is required for this functional asymmetry and for the ability to distinguish sodium from chloride. Thus, a homeobox gene increases the representational capacity of the nervous system by establishing asymmetric functions in a bilaterally symmetrical neuron pair.

Research paper thumbnail of erratum: The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Research paper thumbnail of erratum: The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Research paper thumbnail of Clustered Neural Dynamics Identify Motifs for Chemotaxis in Caenorhabditis elegans

Although anatomical connectivity of the nematode Caenorhabditis elegans has been almost completel... more Although anatomical connectivity of the nematode Caenorhabditis elegans has been almost completely described, determination of the neurophysiological basis of behavior is just beginning. Here, we performed a stochastic search to determine neural network parameters sufficient for a model worm to exhibit chemotaxis, a form of spatial orientation behavior in which turning probability is modulated by the rate of change of chemical concentration. To better comprehend network solutions, we developed a novel method (neural dynamic clustering) to identify neural dynamic motifs. We identified two types of motifs, one of which had been previously identified, and validated the behavior generated by the motifs against experimental chemotaxis.

Research paper thumbnail of Serotonergic blockade prevents age-related neurodegeneration in C. elegans model of Alzheimer's disease

Alzheimers & Dementia, 2011

Research paper thumbnail of Caenorhabditis elegans selects distinct crawling and swimming gaits via dopamine and serotonin

Proceedings of The National Academy of Sciences, 2011

Research paper thumbnail of A Central Role of the BK Potassium Channel in Behavioral Responses to Ethanol in C. elegans

Research paper thumbnail of The Fundamental Role of Pirouettes in Caenorhabditis elegans Chemotaxis

Research paper thumbnail of The fundamental role of pirouettes in C. elegans chemotaxis

Research paper thumbnail of Genetic analysis of crawling and swimming locomotory patterns in C. elegans

Proceedings of The National Academy of Sciences, 2008

Alternative patterns of neural activity drive different rhythmic locomotory patterns in both inve... more Alternative patterns of neural activity drive different rhythmic locomotory patterns in both invertebrates and mammals. The neuro-molecular mechanisms responsible for the expression of rhythmic behavioral patterns are poorly understood. Here we show that Caenorhabditis elegans switches between distinct forms of locomotion, or crawling versus swimming, when transitioning between solid and liquid environments. These forms of locomotion are distinguished by distinct kinematics and different underlying patterns of neuromuscular activity, as determined by in vivo calcium imaging. The expression of swimming versus crawling rhythms is regulated by sensory input. In a screen for mutants that are defective in transitioning between crawl and swim behavior, we identified unc-79 and unc-80, two mutants known to be defective in NCA ion channel stabilization. Genetic and behavioral analyses suggest that the NCA channels enable the transition to rapid rhythmic behaviors in C. elegans. unc-79, unc-80, and the NCA channels represent a conserved set of genes critical for behavioral pattern generation.

Research paper thumbnail of Manipulation of Behavioral Decline in Caenorhabditis elegans with the Rag GTPase raga-1

Research paper thumbnail of Conserved Role of unc-79 in Ethanol Responses in Lightweight Mutant Mice

Research paper thumbnail of Manipulation of Behavioral Decline in Caenorhabditis elegans with the Rag GTPase raga-1

Research paper thumbnail of The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Research paper thumbnail of The Dystrophin Complex Controls BK Channel Localization and Muscle Activity in Caenorhabditis elegans

Research paper thumbnail of Conserved Role of unc-79 in Ethanol Responses in Lightweight Mutant Mice

Research paper thumbnail of The Dystrophin Complex Controls BK Channel Localization and Muscle Activity in Caenorhabditis elegans

Research paper thumbnail of Analysis of the effects of turning bias on chemotaxis in C. elegans

Journal of Experimental Biology, 2005

C. elegans advances up a chemical gradient by modulating the probability of occasional large, cou... more C. elegans advances up a chemical gradient by modulating the probability of occasional large, course-correcting turns called pirouettes. However, it remains uncertain whether C. elegans also uses other behavioral strategies for chemotaxis. Previous observations of the unusual, spiral-shaped chemotaxis tracks made by the bent-head mutant unc-23 point to a different strategy in which the animal continuously makes more subtle course corrections. In the present study we have combined automated tracking of individual animals with computer modeling to test the hypothesis that the pirouette strategy is sufficient on its own to account for the spiral tracks. Tracking experiments showed that the bent-head phenotype causes a strong turning bias and disrupts pirouette execution but does not disrupt pirouette initiation. A computer simulation of disrupted pirouette behavior and turning bias reproduced the spiral tracks of unc-23 chemotaxis behavior, showing that the pirouette strategy is sufficient to account for the mutant phenotype. In addition, the simulation reproduced higher order features of the behavior such as the relationship between the handedness of the spiral and the side to which the head was bent. Our results suggest that the pirouette mechanism is sufficient to account for a diverse range of chemotaxis trajectories.

Research paper thumbnail of A Neural Network Model of Chemotaxis Predicts Functions of Synaptic Connections in the Nematode Caenorhabditis elegans

Journal of Computational Neuroscience, 2004

Research paper thumbnail of The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Nature, 2001

The ability to discriminate between different chemical stimuli is crucial for food detection, spa... more The ability to discriminate between different chemical stimuli is crucial for food detection, spatial orientation and other adaptive behaviours in animals. In the nematode Caenorhabditis elegans, spatial orientation in gradients of soluble chemoattractants (chemotaxis) is controlled mainly by a single pair of chemosensory neurons. These two neurons, ASEL and ASER, are left-right homologues in terms of the disposition of their somata and processes, morphology of specialized sensory endings, synaptic partners and expression profile of many genes. However, recent gene-expression studies have revealed unexpected asymmetries between ASEL and ASER. ASEL expresses the putative receptor guanylyl cyclase genes gcy-6 and gcy-7, whereas ASER expresses gcy-5 (ref. 4). In addition, only ASEL expresses the homeobox gene lim-6, an orthologue of the human LMX1 subfamily of homeobox genes. Here we show, using laser ablation of neurons and whole-cell patch-clamp electrophysiology, that the asymmetries between ASEL and ASER extend to the functional level. ASEL is primarily sensitive to sodium, whereas ASER is primarily sensitive to chloride and potassium. Furthermore, we find that lim-6 is required for this functional asymmetry and for the ability to distinguish sodium from chloride. Thus, a homeobox gene increases the representational capacity of the nervous system by establishing asymmetric functions in a bilaterally symmetrical neuron pair.

Research paper thumbnail of erratum: The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Research paper thumbnail of erratum: The homeobox gene lim-6 is required for distinct chemosensory representations in C. elegans

Research paper thumbnail of Clustered Neural Dynamics Identify Motifs for Chemotaxis in Caenorhabditis elegans

Although anatomical connectivity of the nematode Caenorhabditis elegans has been almost completel... more Although anatomical connectivity of the nematode Caenorhabditis elegans has been almost completely described, determination of the neurophysiological basis of behavior is just beginning. Here, we performed a stochastic search to determine neural network parameters sufficient for a model worm to exhibit chemotaxis, a form of spatial orientation behavior in which turning probability is modulated by the rate of change of chemical concentration. To better comprehend network solutions, we developed a novel method (neural dynamic clustering) to identify neural dynamic motifs. We identified two types of motifs, one of which had been previously identified, and validated the behavior generated by the motifs against experimental chemotaxis.