Li C et al. (1989) International C. elegans Meeting "positioning of the vulval muscles."

Chalfie M, Li C

[International C. elegans Meeting, 1989]

Li C et al. (1987) International C. elegans Meeting "external cues necessary for vulval innervation."

Chalfie M, Li C

[International C. elegans Meeting, 1987]

Li C et al. (2000) East Coast Worm Meeting "Function of the family of FMRFamide-related neuropeptides in C. elegans"

Li C, Kim KY

[East Coast Worm Meeting, 2000]

FMRFamide-related peptides (FaRPs) are short peptide neurotransmitters that have been found throughout the animal kingdom. FaRPs have been shown to have many general functions, including cardioregulation, muscle control, pain modulation and learning. Our lab uses Caenorhabditis elegans as a model system to study FaRPs. In C. elegans, at least 50% of the neurons express FaRPs, which are encoded by at least 22 genes (flp-1 through flp-22). To determine the cell-specific expression of the flp genes in C. elegans, transgenic animals carrying a gfp (green fluorescent protein) reporter construct under the control of each flp promoter are being generated. To date, the cell-specific expression patterns of 13 flp genes have been determined. Each flp gene is expressed in distinct, but sometimes overlapping, sets of cells. The cell-specific expression patterns of the remaining flp genes are being determined. To determine the function of the flp genes in C. elegans, several flp deletion mutants, including flp-3, flp-4, flp-6, flp-8, flp-10, and flp-12, were isolated by screening libraries of chemically-mutagenized C. elegans. Both flp-3 and flp-8 deletion mutants have no obvious behavioral phenotypes thus far, suggesting that these genes have overlapping functions with other flp genes. flp-4, flp-6, flp-10, and flp-12 deletion mutants are being characterized. To identify genes that may regulate expression of the flp genes, we are using transgenic animals expressing a gfp reporter construct under the control of a flp-1 or flp-12 promoter in genetic screens. These strains were mutagenized, and mutants showing altered expression of these markers were isolated. Several mutants which show no, faint, or strong GFP expression have been isolated. These mutants, called mof (modifier of flp expression), are being mapped, characterized, and cloned.

Li, C. et al. (2017) International Worm Meeting "The UNC-7 innexin coordinates vulval muscle contraction and egg release."

Li, C., Collins, K.

[International Worm Meeting, 2017]

Gap junctions are intercellular connections needed for cellular communication and exchange. We have been investigating how gap junctions drive coordinated activity between cells in developing and mature neural circuits using the egg-laying behavior circuit as a model system. Gap junctions are thought to facilitate the coordinated activity of neurons and the muscle cells they innvervate. Gap junctions are of particular interest because they are thought to be targets of neuromodulators like serotonin whose dysfunction is implicated in human depression. We hypothesize that gap-junction proteins regulate egg-laying circuit activity and behavior. Previous work has shown that unc-7 and unc-9 mutants habe uncoordinated (unc) locomotion and are resistant to serotonin-induced egg laying. I found that unc-7 or unc-9 mutants have hyperactive egg-laying behavior. The locomotion and egg-laying behavior phenotypes resemble mutants with defective acetylcholine signaling from the presynaptic VC motor neurons that innervate the vulval muscles. To test this hypothesis, I have begun using Ca2+ imaging to quantify changes in cell activity in behaving animals. Wild-type animals show coordinated vulval muscle activity with strong egg-laying Ca2+ transients that allow release of eggs from the uterus within ~1 second. In contrast, unc-7 mutants show uncoordinated vulval muscles, with eggs often getting stuck in the contracting vulva. Eggs are finally released after ~30 seconds of sustained, tetanic muscle contraction. unc-9 mutants do not show as dramatic of an egg-laying or vulval muscle Ca2+ defect. To show where unc-7 and unc-9 function. I will re-express UNC-7 or UNC-9 in the VC neurons and look for a restoration of normal circuit activity and behavior. I hope to also perform dominant-negative experiments to see if inactivation of UNC-7 in specific cells of the egg-laying circuits recapitulates the null mutant phenotype. This work will begin to address how gap junction proteins like UNC-7 promote the proper development and function of neural circuits to execute a coordinated behavior.

Kwok S-M et al. (2000) East Coast Worm Meeting "Molecular Genetics of Li+ Sensitivity in C. elegans"

Hsieh E, Kwok S-M, Sirotin N, Royal MA, Kao G, Royal DC, Driscoll MA, Bowerman BA

[East Coast Worm Meeting, 2000]

Lithium has multiple developmental effects. Xenopus embryos injected with 10 mM lithium are dorsalized because lithium inhibits glycogen synthase kinase (GSK). This inhibition blocks phosphorylation of beta-catenin, which prevents B-catenin from activating target genes in the nucleus. Mouse oocytes treated with lithium have cytokinesis defects and are induced to undergo a second meiotic cleavage. In Dictyostelium, lithium alters gene expression and development by affecting proliooligopeptase and therefore altering the breakdown of IP5 to IP4 . Little is known about the effects of lithium in C. elegans (Y. Tabuse 1997 Int. Worm Meeting 1997 abstract # 586). Here, we report that lithium has a dosage dependent effect on C. elegans embryos. Depending on the concentration of lithium, ranging from 20mM to 10mM, animals exhibit cytokinesis defects, spindle orientation defects, and morphogenic effects that lead to eggs that are unable to hatch. We demonstrate that lithium has an effect on larval development in a dosage-dependent manner. Animals laid on plates containing 10-20mM lithium have delays in the timing of developmental events proportional to the concentration of lithium. They then go on to become progressively paralyzed. To learn more about the biology of Li+ sensitivity, we screened for Li+ sensitive mutants. We isolated one mutant in a screen of 22,000 haploid genomes that is resistant to both the larval and embryonic effect caused by 16mM lithium. We also isolated three mutants that are resistant to late embryonic lethal effects caused by 10mM lithium. To understand the importance of phosphatidylinositol metabolites and the potential role they play in lithium sensitivity we are using in vivo RNAi to disrupt gene function at different times in development. We targeted C. elegans homologues of the genes rdgB (Drosophila phosphatidyl inositol transfer protein), OCR (Human 4,5-phosphatase), and skittles (Drosophila 5-kinase) for dsRNAi disruption to examine if the null phenotype of these genes mimic any aspects of worms reared on lithium.

Tabuse Y (1997) International C. elegans Meeting "LITHIUM CAUSES DEVELOPMENTAL DISORDER IN C. ELEGANS"

Tabuse Y

[International C. elegans Meeting, 1997]

Lithium (Li) has long been known to have teratogenic effects on the development of many organisms, including sea urchin, Xenopus and Dictyostelium. In Li-treated Xenopus embryos, ventral blastmeres are respecified to develop into dorsal structures, leading to dorsalized embryos lacking ventral mesodermal tissues. In Dictyostelium, Li alters the fate of prespore cells to become prestalk cells instead. Besides teratogenic effects, Li is also known to be a most effective treatment of manic-depressive illness.!@Although several models have been proposed to explain Li action, the molecular mechanism has remained unclear. Recently, GSK (glycogen synthase kinase)-3b was proposed to be a target of Li, suggesting that Li affects the wnt signaling pathway. To understand the mechanism of Li action, I first examined the effect of Li on C. elegans embryogenesis. I inoculated N2 animals at the late L4 stage onto NG plates containing 20 mM LiCl, incubated them at 20 oC. The number of eggs produced by treated animals was reduced to about half of the untreated control. Although cell division seemed to proceed, no embryos hatched on Li plates. Treated-embryos developed to produce gut granules, but did not execute normal morphogenesis at later embryonic stages. To identify genes involved in the action of Li, I have begun to screen for Li-resistant mutants that propagated on Li-containing medium. Several mutants were isolated, and one of them was mapped on the left side of unc-42 on chromosome V. On Li plates, the hatching rate of mutant eggs cross-fertilized by wild-type males was essentially the same as that for self-fertilized mutant eggs. On the contrary, no wild-type eggs cross-fertilized by mutant males hatched on Li-containing plates. So, this mutation appeared to be maternal. Further genetic analyses of the mutants and the observation on the cellular phenotype of Li-treated embryos are underway.

D Royal et al. (2001) International C. elegans Meeting "Towards the Cloning of Gene That Can Mutate to Confer Lithium Resistance In C. elegans"

J White, M Driscoll, E Hsieh, N Sirotin, M A Royal, D Royal, S Kwok, K O'Connell, B Bowerman

[International C. elegans Meeting, 2001]

Little is known about how ions permeate the C. elegans gut and cuticle. How various ions influence development and behavior is also not understood. One ion with considerable impact in human biology is Li + , which modulates bipolar disorder by an unknown mechanism. In particular, the targets of lithium that cause side effects remain to be identified. We are using C. elegans to genetically identify targets of lithium and to elaborate on mechanisms of transport, which may have an impact on human health. Li + has dosage-dependent effects on C. elegans embryos. When L4 animals mature on NGM plates with Li + added to the final concentrations of 10mM-20mM, they produce embryos that are unable to hatch. We demonstrated that this failure to hatch is due to defects in cytokinesis that result in multi-nucleated embryos and symmetrically partitioned cells. Li + also has a dosage-dependent effect on larval development. When adult hermaphrodites are permitted to lay embryos on 10mM-20mM Li + NGM plates, the resulting offspring experience a developmental delay proportional to the concentration of Li + . The offspring become progressively paralyzed as they reach adulthood. We demonstrated earlier that there is a delay in the entry into the S phase of the cell cycle larval stages. To learn more about the biology of Li + sensitivity, we screened for Li + resistant mutants. We developed three screens that took advantage of the embryonic arrest and the larval delay caused by Li + . We isolated one mutant bz71 , in a screen of 44,000 haploid genomes, that is resistant to both the larval and embryonic blocks of 16mM Li + . bz71 is dominant. Using classical mapping techniques, we positioned it on LGIII between unc-32 and dpy-18 . We are currently using SNP strategy to obtain a higher resolution map and we hope to report on the identification and cloning of this locus.

Jie Li et al. (2001) International C. elegans Meeting "The role of unc-86 in the development of serotonergic neurons"

Ji Ying Sze, Jie Li

[International C. elegans Meeting, 2001]

Li Sun et al. (1999) International C. elegans Meeting "Towards Cloning of daf-5"

Garth Patterson, Li Sun

[International C. elegans Meeting, 1999]

A TGF-ß-like signaling pathway is involved in the developmental determination of dauer/L3 fate in C. elegans. Dauer-formation defective mutations in daf-3 and daf-5 are epistatic to dauer-formation constitutive mutations in daf-7 (encoding TGF-ß ligand), daf-1 and daf-4 (encoding the likely receptors for DAF-7), and daf-8 and daf-14 (encoding Smad proteins). This epistasis relationship suggests that daf-3 and daf-5 are either negatively regulated by the TGF-ß pathway or acting in parallel. DAF-3 is a Smad transcription factor; daf-5 is not yet cloned. DAF-5 may function in a parallel subpathway, or act as a transcription cofactor or a modifier of DAF-3. We are pursuing cloning of daf-5 to allow us to better understand the developmental program of larvae in C. elegans. daf-5 is located on Chromosome II, close to unc-52 , with very few useful mapping markers around. We are trying to get fine mapping with DNA polymorphisms according to the method described by Anneliese M. Schaefer et al. ( Worm Breeder's Gazette 15(4): 17), injecting cosmids for transformation rescue, and analyzing candidate genes in the region.

Cody J Locke et al. (2007) International Worm Meeting "RhoGTPase Depletion Enhances Seizure-Like Activity Associated with LIS-1 in C. elegans."

Kim A Caldwell, S Kyle Lee, Guy A Caldwell, Bwarenaba B Kautu, Cody J Locke, Kalen P Berry

[International Worm Meeting, 2007]

Lissencephaly is a rare neurological disorder characterized by intractable epileptic seizures and a lack of convolutions in the brain. The symptoms of lissencephaly are chiefly thought to result from microtubule-based neuronal migration defects, associated with loss-of-function mutations in either LIS1 or DCX, regulators of the dynein motor complex. Yet, our previous results provide some evidence that convulsive behavior in lissencephaly patients may also have a functional basis that is dependent upon dynein-mediated vesicle transport. We showed by lactose-induced RNAi feeding with a Punc-25::snb-1::gfp strain that lis-1, as well as other C. elegans homologues of human genes thought to function in concert with LIS1 in neuronal migration, including cdka-1, cdk-5, nud-1, and nud-2, are important for the proper localization of GABA-containing synaptic vesicles in D-type motoneurons. Moreover, we found that worms depleted of these LIS-1 pathway members by RNAi feeding exhibited hypersensitivity to pentylenetetrazole (PTZ), a chemical antagonist of GABAergic reception, and to aldicarb, an inhibitor of acetylcholinesterase. Hypersensitivity to these neural stimulants is also mimicked by loss-of-function alleles of lis-1, dhc-1, and GABA function genes, such as unc-25 and unc-47, likely pointing to an accumulation of chronic levels of excitatory neurotransmission at C. elegans neuromuscular junctions. Here we report that mutants carrying loss of function alleles of the RhoGTPases, cdc-42 and rac-1, also exhibit hypersensitivity to PTZ and aldicarb. RNAi feeding against LIS-1 pathway members in the sensitized rac-1(n3246) background revealed significant genetic interactions. Likewise, we also uncovered hypersensitivity to PTZ and aldicarb with a strong allele of mig-15, which encodes an Nck-interacting kinase that functions along with rac-1 in C. elegans axon guidance. RNAi feeding against LIS-1 pathway members in the mig-15(rh148) background correspondingly led to enhancement of sensitivity to PTZ and aldicarb. These data suggest that the LIS-1/dynein motor complex may function in a common pathway with specific regulators of the actin cytoskeleton to maintain neuronal synchrony. Accordingly, promotion of actin polymerization through the maintenance of intracellular RhoGTPase levels by LIS1 has been shown in human neurons, while Dictyostelium homologues of LIS1 and RAC1 physically interact in vitro. In all, this work provides us with a greater understanding of the molecular nature of the seizure-like activity exhibited in our model and further implicates dysregulation of the cytoskeletal network in epilepsy. .