Li N et al. (2018) Eur J Neurosci "Mutations in the Guanylate Cyclase gcy-28 Neuronally Dissociate Naive Attraction and Memory Retrieval."

van der Kooy D, Li N

[Eur J Neurosci, 2018]

The molecules and mechanisms that are involved in the acquisition, storage, and retrieval of memories in many organisms are unclear. To investigate these processes, we use the nematode worm Caenorhabditis elegans, which is attracted naively to the odorant benzaldehyde but learns to avoid it after paired exposure with starvation. Mutations in the receptor-like guanylate cyclase GCY-28 have previously been thought to result in a behavioral switch in the primary chemosensory neuron AWC^ON , from an attractive state to an aversive (already-learned) state. Here, we offer a different interpretation and show that GCY-28 functions in distinct neurons to modulate two independent processes: naive attraction to AWC^ON -sensed odors in the AWC^ON neuron, and associative learning of benzaldehyde and starvation in the AIA interneurons. Consequently, mutants that lack gcy-28 do not approach AWC^ON -sensed odors and cannot associate benzaldehyde with starvation. We further show that this learning deficit lies in memory retrieval, not in its acquisition or storage, and that GCY-28 is required in AIA for sensory integration only when both AWC neurons (ON and OFF) are activated by chemical stimuli. Our results reveal a novel role of GCY-28 in the retrieval of associative memories and may have wide implications for the neural machineries of learning and memory in general. This article is protected by copyright. All rights reserved.

Li N et al. (1998) FEBS Lett "Expression and characterization of human PDEdelta and its Caenorhabditis elegans ortholog CEdelta."

Baehr W, Li N

[FEBS Lett, 1998]

Cyclic GMP phosphodiesterase (PDE) is rod photoreceptor disk membrane-associated via C-terminal lipid tails. PDEdelta, a recently identified subunit, was shown to disrupt PDE/membrane interaction under physiological conditions, without affecting PDE catalytic activity. We found that a PDEdelta ortholog from the eyeless nematode Caenorhabditis elegans (termed CEdelta) solubilizes bovine PDE in vitro with an EC50 very similar to PDEdelta. Immobilized PDEdelta and CEdelta both bind, in addition to bovine PDE, an N-terminal fragment of human retinitis pigmentosa GTPase regulator, but not rhodopsin kinase and Ran binding protein 1. The results suggest that PDEdelta and CEdelta may regulate membrane binding of a variety of proteins in photoreceptors and other tissues.

Li N et al. (2013) Nucleic Acids Res "Global profiling of miRNAs and the hairpin precursors: insights into miRNA processing and novel miRNA discovery."

Li N, Friedlander MR, Gogol-Doering A, Weigt M, Hu Y, Dieterich C, You X, Chang Z, Du H, Mackowiak SD, Chen W, Chen T

[Nucleic Acids Res, 2013]

MicroRNAs (miRNAs) constitute an important class of small regulatory RNAs that are derived from distinct hairpin precursors (pre-miRNAs). In contrast to mature miRNAs, which have been characterized in numerous genome-wide studies of different organisms, research on global profiling of pre-miRNAs is limited. Here, using massive parallel sequencing, we have performed global characterization of both mouse mature and precursor miRNAs. In total, 87 369 704 and 252 003 sequencing reads derived from 887 mature and 281 precursor miRNAs were obtained, respectively. Our analysis revealed new aspects of miRNA/pre-miRNA processing and modification, including eight Ago2-cleaved pre-miRNAs, eight new instances of miRNA editing and exclusively 5' tailed mirtrons. Furthermore, based on the sequences of both mature and precursor miRNAs, we developed a miRNA discovery pipeline, miRGrep, which does not rely on the availability of genome reference sequences. In addition to 239 known mouse pre-miRNAs, miRGrep predicted 41 novel ones with high confidence. Similar as known ones, the mature miRNAs derived from most of these novel loci showed both reduced abundance following Dicer knockdown and the binding with Argonaute2. Evaluation on data sets obtained from Caenorhabditis elegans and Caenorhabditis sp.11 demonstrated that miRGrep could be widely used for miRNA discovery in metazoans, especially in those without genome reference sequences.

Li N et al. (2022) Cell Rep "A sphingolipid-mTORC1 nutrient-sensing pathway regulates animal development by an intestinal peroxisome relocation-based gut-brain crosstalk."

Ruan M, Chen Q, Huo Y, Zhu M, Li N, Shen H, Zhang L, Liu H, Teng F, Hua B, Zhu H, Zhuang M

[Cell Rep, 2022]

The mTOR-dependent nutrient-sensing and response machinery is the central hub for animals to regulate their cellular and developmental programs. However, equivalently pivotal nutrient and metabolite signals upstream of mTOR and developmental-regulatory signals downstream of mTOR are not clear, especially at the organism level. We previously showed glucosylceramide (GlcCer) acts as a critical nutrient and metabolite signal for overall amino acid levels to promote development by activating the intestinal mTORC1 signaling pathway. Here, through a large-scale genetic screen, we find that the intestinal peroxisome is critical for antagonizing the GlcCer-mTORC1-mediated nutrient signal. Mechanistically, GlcCer deficiency, inactive mTORC1, or prolonged starvation relocates intestinal peroxisomes closer to the apical region in a kinesin- and microtubule-dependent manner. Those apical accumulated peroxisomes further release peroxisomal-β-oxidation-derived glycolipid hormones that target chemosensory neurons and downstream nuclear hormone receptor DAF-12 to arrest the animal development. Our data illustrate a sophisticated gut-brain axis that predominantly orchestrates nutrient-sensing-dependent development in animals.

Li N et al. (2021) Front Pharmacol "Trilobatin, a Component from Lithocarpus polystachyrus Rehd., Increases Longevity in C. elegans Through Activating SKN1/SIRT3/DAF16 Signaling Pathway."

Li N, Gong QH, Shi JS, Li F, Shi YL, Li X, Gao JM, He YQ

[Front Pharmacol, 2021]

Trilobatin (TLB) is an effective component from <i>Lithocarpus polystachyrus</i> Rehd. Our previous study revealed that TLB protected against oxidative injury in neuronal cells by AMPK/Nrf2/SIRT3 signaling pathway. However, whether TLB can delay aging remains still a mystery. Therefore, the present study was designed to investigate the possible longevity-enhancing effect of TLB, and further to explore its underlying mechanism in <i>Caenorhabditis elegans</i> (<i>C. elegans</i>). The results showed that TLB exerted beneficial effects on <i>C. elegans</i>, as evidenced by survival rate, body movement assay and pharynx-pumping assay. Furthermore, TLB not only significantly decreased ROS and MDA levels, but also increased anti-oxidant enzyme activities including CAT and SOD, as well as its subtypes SOD2 andSOD3, but not affect SOD1 activity, as evidenced by heat and oxidative stress resistance assays. Whereas, the anti-oxidative effects of TLB were almost abolished in SKN1, Sir2.3, and DAF16 mutant <i>C. elegans</i>. Moreover, TLB augmented the fluorescence intensity of DAF16: GFP, SKN1:GFP, GST4:GFP mutants, indicating that TLB increased the contents of SKN1, SIRT3 and DAF16 due to fluorescence intensity of these mutants, which were indicative of these proteins. In addition, TLB markedly increased the protein expressions of SKN1, SIRT3 and DAF16 as evidenced by ELISA assay. However, its longevity-enhancing effect were abolished in DAF16, Sir2.3, SKN1, SOD2, SOD3, and GST4 mutant <i>C. elegans</i> than those of non-TLB treated controls. In conclusion, TLB effectively prolongs lifespan of <i>C. elegans</i>, through regulating redox homeostasis, which is, at least partially, mediated by SKN1/SIRT3/DAF16 signaling pathway.

Gopal E et al. (2015) J Pharmacol Exp Ther "Species-specific influence of lithium on the activity of SLC13A5 (NaCT): lithium-induced activation is specific for the transporter in primates."

Ganapathy V, Ramachandran S, Gopal E, Babu E, Prasad PD, Bhutia YD

[J Pharmacol Exp Ther, 2015]

NaCT (SLC13A5) is a Na(+)-coupled transporter for Krebs cycle intermediates and is expressed predominantly in the liver. Human NaCT is relatively specific for citrate compared with other Krebs cycle intermediates. The transport activity of human NaCT is stimulated by Li(+), whereas that of rat NaCT is inhibited by Li(+). We studied the influence of Li(+) on NaCTs cloned from eight different species. Li(+) stimulated the activity of only NaCTs from primates (human, chimpanzee, and monkey); by contrast, NaCTs from nonprimate species (mouse, rat, dog, and zebrafish) were inhibited by Li(+). Caenorhabditis elegans NaCT was not affected by Li(+). With human NaCT, the Li(+)-induced increase in transport activity was associated with the conversion of the transporter from a low-affinity/high-capacity type to a high-affinity/low-capacity type. H(+) was able to substitute for Li(+) in eliciting the stimulatory effect. The amino acid Phe500 in human NaCT was critical for Li(+)/H(+)-induced stimulation. Mutation of this amino acid to tryptophan (F500W) markedly increased the basal transport activity of human NaCT in the absence of Li(+), but the ability of Li(+) to stimulate the transporter was almost completely lost with this mutant. Substitution of Phe500 with tryptophan in human NaCT converted the transporter from a low-affinity/high-capacity type to a high-affinity/low-capacity type, an effect similar to that of Li(+) on the wild-type NaCT. These studies show that Li(+)-induced activation of NaCT is specific for the transporter in primates and that the region surrounding Phe500 in primate NaCTs is important for the Li(+) effect.

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.

Tabuse Y (1996) Worm Breeder's Gazette "Lithium arrests embryonic development of C. elegans"

Tabuse Y

[Worm Breeder's Gazette, 1996]

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 bea most effective treatment of manic-depressive illness. Although several models have been proposed to explain Li action, the molecular mechansm remains unclear. The most widely accepted model is the inositol depletion hypothesis, in which Li is thought to affect inositol phosphate turnover by inhibiting inositol monophosphatase, thus resulting in the depletion of endogenous inositol. 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 C and observed the laid embryos. 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, which propagated on Li-containing medium. So far, I obtained one mutant. The mutation was tentatively assigned to chromosome V. Preliminary genetic analysis showed that the mutation showed maternal effect. 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. I am now trying to isolate other mutants and also to identify early defects of embryogenesis caused by lithium treatment. I would like to thank J. Miwa for encouragement and discussions.

Inokuchi A et al. (2015) J Appl Toxicol "Effects of lithium on growth, maturation, reproduction and gene expression in the nematode Caenorhabditis elegans."

Matsusaki H, Yamamoto R, Takumi S, Morita F, Inokuchi A, Arizono K, Tominaga N, Ishibashi H

[J Appl Toxicol, 2015]

Lithium (Li) has been widely used to treat bipolar disorder, and industrial use of Li has been increasing; thus, environmental pollution and ecological impacts of Li have become a concern. This study was conducted to clarify the potential biological effects of LiCl and Li(2)CO(3) on a nematode, Caenorhabditis elegans as a model system for evaluating soil contaminated with Li. Exposure of C. elegans to LiCl and Li(2)CO(3) decreased growth/maturation and reproduction. The lowest observed effect concentrations for growth, maturation and reproduction were 1250, 313 and 10 000m, respectively, for LiCl and 750, 750 and 3000m, respectively, for Li(2)CO(3). We also investigated the physiological function of LiCl and LiCO(3) in C. elegans using DNA microarray analysis as an eco-toxicogenomic approach. Among approximately 300 unique genes, including metabolic genes, the exposure to 78m LiCl downregulated the expression of 36 cytochrome P450, 16 ABC transporter, 10 glutathione S-transferase, 16 lipid metabolism and two vitellogenin genes. On the other hand, exposure to 375m Li(2)CO(3) downregulated the expression of 11 cytochrome P450, 13 ABC transporter, 13 lipid metabolism and one vitellogenin genes. No gene was upregulated by LiCl or Li(2)CO(3). These results suggest that LiCl and Li(2)CO(3) potentially affect the biological and physiological function in C. elegans associated with alteration of the gene expression such as metabolic genes. Our data also provide experimental support for the utility of toxicogenomics by integrating gene expression profiling into a toxicological study of an environmentally important organism such as C. elegans.

McColl G et al. (2008) J Biol Chem "Pharmacogenetic analysis of lithium-induced delayed aging in Caenorhabditis elegans."

Melov S, McColl G, Lithgow GJ, Vantipalli MC, Killilea DW, Hubbard AE

[J Biol Chem, 2008]

Lithium (Li+) has been used to treat mood affect disorders, including bipolar, for decades (1;2). This drug is neuroprotective and has several identified molecular targets. However, it has a narrow therapeutic range and the underlying mechanism(s) of its therapeutic action is not understood. Here we describe a pharmacogenetic study of Li+ in the nematode Caenorhabditis elegans. Exposure to Li+ at clinically relevant concentrations throughout adulthood increases survival during normal aging (up to 46% median increase). Longevity is extended via a novel mechanism with altered expression of genes encoding nucleosome-associated functions. Li+ treatment results in reduced expression of the worm ortholog of LSD-1 (T08D10.2), a histone demethylase; knockdown by RNA interference (RNAi) of T08D10.2 is sufficient to extend longevity (~25% median increase), suggesting Li+ regulates survival by modulating histone methylation and chromatin structure.