Jamie Kass

Philip H. Kass

University of California, Davis; Davis CA, United States of America

Kass IS et al. (1979) International C. elegans Meeting "the action of avermectin B1a on Ascaris."

Walrond JP, Wang CC, Stretton AOW, Kass IS

[International C. elegans Meeting, 1979]

Picture from Kass J et al. (2001) J Neurosci "The EGL-3 proprotein convertase regulates mechanosensory responses of ...."

Figure 4. Expression of egl-3 PC2. Anti-egl-3 PC2 antibody was used to stain transgenic animals expressing KP#454, a full-length rescuing EGL-3:: GFP construct (A-C). Endogenously expressed EGL-3 was visualized by staining non transgenic wild-type animals (D) or egl-3(nu349) mutants (E). Expression of egl-3 PC2 in the command neurons was examined by staining transgenic animals containing both KP#454 and nuIs24, a GLR-1:: GFP transgene, with anti-egl-3 PC2 and anti-glr-1 GluR antibodies (B). A, Expression of EGL-3:: GFP was found in the cell bodies of many neurons in the head and in ganglia in the tail (TG). In addition, axons in the nerve ring (NR) stained brightly with the anti-egl-3PC2 antibody. B, Expression of EGL-3:: GFP in the PVC command neurons was documented by double staining with anti-egl-3 PC2 (left) and anti-glr-1 GluR (middle) antibodies. The merged image is shown on the right. This panel shows a mosaic animal in which one PVC neuron (indicated by the asterisk) expressed both GLR-1 (green) and EGL-3 (red), whereas the second PVC neuron (indicated by the arrowhead) expressed GLR-1 but not EGL-3. Similar results were obtained documenting expression of EGL-3:: GFP in AVB and AVD (data not shown). D, E, Endogenously expressed EGL-3 was stained with anti-egl-3 PC2 antibodies. In wild-type animals (D), bright staining was observed in the nerve ring (NR) and ventral cord (data not shown) axons. Cell bodies (indicated by arrows) stained very weakly. In egl-3(nu349) mutants (E), the axons of the nerve ring (NR) and ventral cord (data not shown) were poorly stained, whereas bright staining of neuronal cell bodies was observed (arrows). Scale bars, 10 um.

Kass J et al. (1996) East Coast Worm Meeting "Isolation and characterization of suppressors of glr-1."

Kaplan JM, Hart AC, Kim P, Kass J

[East Coast Worm Meeting, 1996]

How do animals distinguish between sensory stimuli? We are studying a neural circuit in which the ASH sensory neurons detect noxious chemical and mechanical stimuli and signal to the worm to move backward. Three stimuli are detected by the ASH neurons (nose touch, high osmolarity and volatile repellants) and each provokes backward locomotion. Genetic and molecular evidence suggests that different signals are produced at the ASH-interneuron synapses in response to the different stimuli. The glr-1 gene encodes a glutamate receptor required specifically for response to nose touch. GLR-1 is expressed in the command interneurons, AVA, AVD, and AVB, that receive synaptic input from ASH, suggesting that neurotransmitter release from ASH in response to nose touch is different than release in response to osmotic stimuli and volatile repellants. For example, in response to nose touch ASH may release glutamate whereas, in response to high osmolarity ASH may release both glutamate and a neuropeptide. To better understand ASH signaling, we screened for suppressors of glr-1 (n2461). glr-1 might be suppressed by mutations which cause ASH to use the other neurotransmission pathway(s); thus suppressors may give us insight into differential release of neurotransmitters. Approximately 6,500 haploid genomes have been screened and two suppressors have been isolated. One suppressor (nu349) has been mapped to chromosome V and also suppresses a deletion allele, glr-1(ky176). We are currently laser ablating ASH in the suppressed animals to determine the site of action of the suppressors. If the ablation of ASH returns the suppressed animals to the mutant phenotype then the suppressor may be acting in ASH. If the animals are still suppressed then another cell may be taking over the mechanosensory function of ASH or the interneurons may have been sensitized so that the same intensity of signal from ASH results in a greater response in the interneurons. We are also interested in determining whether the suppressors are capable of suppressing all of the defects of glr-1 including loss of responsiveness to harsh touch. We will continue to map and eventually clone the suppressors of glr-1.

Kass J et al. (1997) International C. elegans Meeting "ISOLATION AND CHARACTERIZATION OF GLR-1 SUPPRESSORS"

Kim P, Kaplan JM, Kass J

[International C. elegans Meeting, 1997]

How do animals distinguish between sensory stimuli? We are studying a neural circuit in C. elegans in which the ASH sensory neurons detect noxious chemical and mechanical stimuli and signal to the worm to move backward. Three stimuli are detected by the ASH neurons: touch to the nose, high osmolarity and volatile repellants. Genetic and molecular evidence suggests that different signals are produced at the ASH-interneuron synapses in response to the different stimuli. The glr-1 gene encodes a glutamate receptor required specifically for response to nose touch. GLR-1 is expressed in the interneurons which receive synaptic input from ASH, suggesting that neurotransmitter release from ASH in response to nose touch is different than release in response to osmotic stimuli and volatile repellants. To better understand ASH signaling, we screened for suppressors of glr-1 (n2461). glr-1 might be suppressed by mutations which cause ASH to use the other neurotransmission pathway(s) in response to nose touch; thus suppressors may give us insight into differential release of neurotransmitters. We isolated two suppressors from 6500 genomes. One suppressor, (nu349), maps to chromosome V and also suppresses a deletion allele, glr-1(ky176). nu349 has three phenotypes: it is egg-laying defective, it does not respond to gentle touch to the body and it suppresses the nose touch defect of glr-1. The second suppressor, nu348, has no additional phenotypes. I killed ASH with a laser in the suppressed animals and tested their response in the nose touch assay. Both suppressors became nose touch defective after ablation of ASH indicating that they suppress glr-1(n2461) by restoring function of the ASH-interneuron synapse. I have been mapping both suppressors with the goal of cloning and further characterizing them. Using deficiency strains and genetic markers I have narrowed down the region containing nu349 to less than 0.4 map units. I am refining the map position of nu349 by identifying polymorphisms which can serve as additional markers in the interval. I am also looking for fosmids which contain DNA from the gaps and generating new alleles of nu349 by UV mutagenesis. I am continuing to map nu348 as well.

Kass J et al. (1995) International C. elegans Meeting "A NEW SCREEN FOR OSMOTIC AVOIDANCE MUTANTS."

Kass J, Kaplan JM

[International C. elegans Meeting, 1995]

We are interested in the molecular basis of mechanosensory transduction and sensory modality coding. The detection of regions of high osmolarity is primarily mediated through the ASH neurons. These neurons are also required for response to volatile repellents and touch to the nose. All three stimuli provoke an avoidance response characterized by backward locomotion for several body lengths. In order to identify genes required specifically for osmotic avoidance we are conducting an EMS screen for mutants which are defective for osmotic avoidance but retain normal ASH morphology and respond appropriately to nose touch and volatile repellents. We hope to identify genes encoding the components of an osmoreceptor as well as those required in the circuit for differentiating between sensory stimuli transduced by the ASH polymodal neurons. Thus far 11,221 haploid genomes have been screened, resulting in the isolation of 14 mutant strains with the above characteristics. The mutant strains also respond normally in chemotaxis assays and are able to form dauers. We are currently mapping the mutant strains and will continue to screen for additional mutants.

Kass J et al. (2001) J Neurosci "The EGL-3 proprotein convertase regulates mechanosensory responses of Caenorhabditis elegans."

Kass J, Jacob TC, Kaplan JM, Kim P

[J Neurosci, 2001]

Neuroactive peptides are packaged as proproteins into dense core vesicles or secretory granules, where they are cleaved at dibasic residues by copackaged proprotein convertases. We show here that the Caenorhabditis elegans egl-3 gene encodes a protein that is 57% identical to mouse proprotein convertase type 2 (PC2), and we provide evidence that this convertase regulates mechanosensory responses. Nose touch sensitivity (mediated by ASH sensory neurons) is defective in mutants lacking GLR-1 glutamate receptors (GluRs); however, mutations eliminating the egl-3 PC2 restored nose touch sensitivity to glr-1 GluR mutants. By contrast, body touch sensitivity (mediated by the touch cells) is greatly diminished in egl-3 PC2 mutants. Taken together, these results suggest that egl-3 PC2-processed peptides normally regulate the responsiveness of C. elegans to mechanical stimuli.

J Kass et al. (1999) International C. elegans Meeting "The EGL-3 prohormone convertase modulates ASH-interneuron synapses"

JM Kaplan, J Kass, P Kim

[International C. elegans Meeting, 1999]

How do animals distinguish between sensory stimuli? We are studying a neural circuit in C. elegans in which the ASH sensory neuron, detect noxious chemical and mechanical stimuli and signal to the worm to move backward. Three stimuli are detected by the ASH neurons: nose touch, high osmolarity and volatile repellants. Genetic and molecular evidence suggests that different signals are produced at the ASH-interneuron synapses in response to the different stimuli. GLR-1 glutamate receptors are expressed in interneurons, are clustered at ASH-interneuron synapses, but are required specifically ASH-mediated touch sensitivity. We isolated egl-3(nu349) as a suppressor of glr-1(n2461) touch insensitivity, Alleles of egl-3 cause three phenotypes: they are egg-laying defective, insensitive to gentle touch to the body, and they suppresses the nose touch defect of glr-1 . The egl-3 mutation restores function of the ASH-interneuron synapses because glr-1(n2461); egl-3(nu349) double mutants became nose touch defective after ablation of ASH. The egl-3 mutants were also defective for habituation of the nose touch response. We have cloned egl-3 , and found that it encodes a homolog of Prohormone Convertase 2, a neuroendocrine-specific protease (C51E3.7). Two egl-3 alleles correspond to mutations in predicted exons of C51E3.7: n150ts contains two missense mutations, in the catalytic domain and the homoB domain; nu349 contains a missense mutation in the homoB domain. The homoB domain has been shown to be required for maturation and secretion of the protease (Taylor et al., 1998). Both alleles are recessive. These results suggest that a neuropeptide (processed by EGL-3) inhibits ASH-interneuron signaling, and is involved in habituation to repeated sensory stimuli.

Kass IS et al. (1980) Proc Natl Acad Sci U S A "Avermectin B1a, a paralyzing anthelmintic that affects interneurons and inhibitory motoneurons in Ascaris."

Kass IS, Stretton AOW, Walrond JP, Wang CC

[Proc Natl Acad Sci U S A, 1980]

Avermectin B1a (AVM) is an antiparasitic agent that paralyzes nematodes without causing hypercontraction or flaccid paralysis. Using selective stimulation techniques, we have shown that AVM blocks transmission between interneuron(s) and excitatory motorneurons in the ventral nerve cord of Ascaris. It also inhibits transmissin between inhibitory motoneurons and muscle but has little effect on excitatory neuromuscular transmission. Picrotoxin can reverse the AVM- induced block of interneuron-excitatory motoneuron transmission but has no effect on the inhibitory motoneuronal synapse in either the presence or absence of AVM. Our results provide an explanation of how AVM may cause paralysis of nematodes.