Wang, Chenyin et al. (2017) International Worm Meeting "Double transgenic Caenorhabditis elegans as a new Alzheimer's disease model: behavioral phenotyping and gene expression analysis."

Saar, Valeria, Leung, Ka Lai, Wong, Garry, Wang, Chenyin

[International Worm Meeting, 2017]

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the presence of extracellular amyloid plaques formed by accumulated Amyloid- beta peptide (A beta ) aggregates and neurofibrillary tangles, which are formed by aggregation of hypophosphorylated microtubule-associated protein TAU. We generated a new model of this disease by crossing existing A beta (CL2355) and TAU (BR5270, BR5271) pan-neuronal expressing transgenic strains of Caenorhabditis elegans. The lifespan and progeny viability of the double transgenic strain were significantly decreased compared with wild-type N2 (P<0.0001). We also observed that ectopic expression of these transgenes could interfere with neurotransmitter signaling pathways. Moreover, the double transgenic strain showed the most severe defects in chemotaxis associative learning when compared with other strains. In order to gain new insights into AD pathology mechanisms, we performed RNA-seq transcriptomic analysis. We observed 1053 genes to be regulated, of which 248 were up- and 805 were down-regulated in a comparison between the new AD model (UM0001, UM0002) and N2. Gene set enrichment analysis using David 6.7 indicated that up-regulated annotation clusters included UDP-Glucuronosyltransferase (5 genes, P<4.2E-4), PapD-like (4 genes, P<1.8E-2), aging (5 genes, P<8.1E-2) and down-regulated included nematode cuticle collagen (36 genes, P<1.5E-21), metabolic process (65 genes, P<1.9E-8). Comparing the list of regulated genes from C. elegans to the top 60 genes related to human AD confirmed an overlap of 9 genes: patched homolog 1, PTCH1 (ptc-3), the Rab GTPase activating protein, TBC1D16 (tbc-16), the WD repeat and FYVE domain-containing protein 3, WDFY3 (wdfy-3), myosin IXA, MYO9A (hum-7), ADP-ribosylation factor guanine nucleotide exchange factor 2, ARFGEF2 (agef-1), Early B-cell Factor, EBF1 (unc-3), D-amino-acid oxidase, DAO (daao-1), glutamate receptor, metabotropic 1, GRM1 (mgl-2), prolyl 4-hydroxylase subunit alpha 2, P4HA2 (dpy-18 and phy-2). Taken together, our C. elegans model provides insight on the fundamental toxic mechanisms underlying human AD and also provides some potential new therapeutic targets against TAU- and A beta -mediated proteotoxicity.

Palfreyman MT et al. (2017) Neuron "Unc13 Aligns SNAREs and Superprimes Synaptic Vesicles."

Palfreyman MT, Jorgensen EM

[Neuron, 2017]

Unc13 proteins are required for vesicle docking and priming during exocytosis. In this issue of Neuron, Lai etal. (2017) demonstrate that Unc13 ensures that the SNAREs assemble into functional subcomplexes. In a second manuscript, Michelassi etal. (2017) identify a previously unknown autoinhibited state for Unc13 mediated by the tandem C1 and C2 domains.

Shen, Linjing et al. (2019) International Worm Meeting "Role of Tar DNA binding protein-43 (TDP-43) in mediating alpha-synuclein (HASN) toxicity in a Parkinson's disease model."

Shen, Linjing, Wang, Changliang, Leung, Ka Lai, Wong, Garry, Chen, Liang

[International Worm Meeting, 2019]

Parkinson's disease (PD) is a progressive neurodegenerative disease mainly affecting the motor system. To date, the treatment for PD remains symptomatic, and the molecular mechanisms underlying its pathophysiology are still unclear. ?-Synuclein is the major component of protein aggregates in Lewy bodies and Lewy neurites of PD. Mutation or increased expression of ?-synuclein likely contributes to the development of PD. Treatment against the ?-synuclein aggregation might be an efficient therapeutic strategy . TAR DNA binding protein-43(TDP-43), mainly responsible for the pathology of amyotrophic lateral sclerosis, is also involved in PD. The synucleinopathy of PD is more serious when ?-synuclein proteinopathy and TDP-43 proteinopathy coexist, but the effects of interaction between ?-synuclein and TDP-43 in PD remain unclear. This study investigates the effect of TDP-43 on ?-synuclein. Our study found that the deletion of the gene tdp-1, TDP-43 ortholog in Caenorhabditis elegans (C. elegans), caused behavior defects to improve and human ?-synuclein (HASN) total protein and aggregation to decrease in the HASN overexpressing C. elegans PD model. These effects may be related to upgraded expression of genes belonging to the heat shock protein family, hsp-70, hsp-16.1, hsp-16.11, hsp-16.41, hsp-16.48, hsp-16.4, hsp-16.2, which were identified through both mRNA sequencing and RNA interference. These studies will further our knowledge on the interactions between TDP-43 and ?-synuclein and their roles in PD. The genes from the heat shock protein family might also be considered as promising therapeutic targets for PD and other ?-synuclein related diseases. This research was supported in part by the Research grant of Garry Wong MYRG2017-00123-FHS.

Huang, Xiaobing et al. (2019) International Worm Meeting "A transgenic co-expressed Amyloid-beta and alpha-Synuclein dementia model in Caenorhabditis elegans."

Huang, Xiaobing, Leung, Ka Lai, Wang, Changliang, Chen, Liang, Shen, Linjing, Wong, Garry

[International Worm Meeting, 2019]

Purpose: Dementia with Lewy bodies (DLB) is the second most common type of progressive dementia after Alzheimer's disease dementia. Lewy bodies develop in nerve cells in brain regions where thinking, memory and movement are lost. Still, the pathology of DLB remains vague. For exploring the pathogenesis of DLB, we constructed a disease model of DLB which co-expressed Amyloid-? (A?) and ?-synuclein in pan-neurons in C. elegans. Methods: We used the locomotion, thrashing, lifespan, development and egg laying behavior assays to evaluate whether co-expressed A? and ?-synuclein would alter phenotypes in worms. Furthermore, we used confocal microscopy to analyze the neurodegeneration of worms and Thioflavin-S staining to observe the misfolded protein aggregation. Moreover, we used RNA-Seq to explore the effects of co-expressed A? and ?-synuclein in worms on transcription. Results: Our results showed that co-expressed A? and ?-synuclein severely impaired the behaviors and affected neurons in C. elegans. Worms that co-expressed A? and ?-synuclein showed uncoordinated and slower movement, shorter lifespan, less progeny and egg laying defects. Moreover, misfolded protein aggregation and damage of dopaminergic neurons were found in co-expressed A? and ?-synuclein worms, suggesting that co-expression of these 2 transgenes can cause damage to neurons beyond those observed in Alzheimer's disease or Parkinson's disease models. RNA-seq data showed that co-expression of transgenes mainly altered expression levels of genes in the TGF-beta signaling pathway, Wnt signaling pathway, ubiquitin mediated proteolysis, and protein processing pathways in endoplasmic reticulum. Conclusion: Our model might be a useful tool to discover and investigate the etiology of Dementia with Lewy bodies. Moreover, it might be an excellent model to screen drugs that can ameliorate the symptoms of dementia. Acknowledgment: This research was supported in part by the Research grant of Garry Wong MYRG2017-00123-FHS.

Solorzano E et al. (2011) BMC Evol Biol "Shifting patterns of natural variation in the nuclear genome of caenorhabditis elegans."

Bergeron RD, Sung W, Okamoto K, Thomas WK, Solorzano E, Datla P

[BMC Evol Biol, 2011]

BACKGROUND: Genome wide analysis of variation within a species can reveal the evolution of fundamental biological processes such as mutation, recombination, and natural selection. We compare genome wide sequence differences between two independent isolates of the nematode Caenorhabditis elegans (CB4856 and CB4858) and the reference genome (N2). RESULTS: The base substitution pattern when comparing N2 against CB4858 reveals a transition over transversion bias (1.32:1) that is not present in CB4856. In CB4856, there is a significant bias in the direction of base substitution. The frequency of A or T bases in N2 that are G or C bases in CB4856 outnumber the opposite frequencies for transitions as well as transversions. These differences were not observed in the N2/CB4858 comparison. Similarly, we observed a strong bias for deletions over insertions in CB4856 (1.44: 1) that is not present in CB4858. In both CB4856 and CB4858, there is a significant correlation between SNP rate and recombination rate on the autosomes but not on the X chromosome. Furthermore, we identified numerous significant hotspots of variation in the CB4856-N2 comparison.In both CB4856 and CB4858, based on a measure of the strength of selection (ka/ks), all the chromosomes are under negative selection and in CB4856, there is no difference in the strength of natural selection in either the autosomes versus X or between any of the chromosomes. By contrast, in CB4858, ka/ks values are smaller in the autosomes than in the X chromosome. In addition, in CB4858, ka/ks values differ between chromosomes. CONCLUSIONS: The clear bias of deletions over insertions in CB4856 suggests that either the CB4856 genome is becoming smaller or the N2 genome is getting larger. We hypothesize the hotspots found represent alleles that are shared between CB4856 and CB4858 but not N2. Because the ka/ks ratio in the X chromosome is higher than the autosomes on average in CB4858, purifying selection is reduced on the X chromosome.

Ju J et al. (2023) Nucleic Acids Res "Structure of the Caenorhabditis elegans m6A methyltransferase METT10 that regulates SAM homeostasis."

Tomita K, Ju J, Kuroyanagi H, Aoyama T, Yashiro Y, Yamashita S

[Nucleic Acids Res, 2023]

In Caenorhabditis elegans, the N6-methyladenosine (m6A) modification by METT10, at the 3'-splice sites in S-adenosyl-l-methionine (SAM) synthetase (sams) precursor mRNA (pre-mRNA), inhibits sams pre-mRNA splicing, promotes alternative splicing coupled with nonsense-mediated decay of the pre-mRNAs, and thereby maintains the cellular SAM level. Here, we present structural and functional analyses of C. elegans METT10. The structure of the N-terminal methyltransferase domain of METT10 is homologous to that of human METTL16, which installs the m6A modification in the 3'-UTR hairpins of methionine adenosyltransferase (MAT2A) pre-mRNA and regulates the MAT2A pre-mRNA splicing/stability and SAM homeostasis. Our biochemical analysis suggested that C. elegans METT10 recognizes the specific structural features of RNA surrounding the 3'-splice sites of sams pre-mRNAs, and shares a similar substrate RNA recognition mechanism with human METTL16. C. elegans METT10 also possesses a previously unrecognized functional C-terminal RNA-binding domain, kinase associated 1 (KA-1), which corresponds to the vertebrate-conserved region (VCR) of human METTL16. As in human METTL16, the KA-1 domain of C. elegans METT10 facilitates the m6A modification of the 3'-splice sites of sams pre-mRNAs. These results suggest the well-conserved mechanisms for the m6A modification of substrate RNAs between Homo sapiens and C. elegans, despite their different regulation mechanisms for SAM homeostasis.

Benjamin Leung et al. (2001) International C. elegans Meeting "Characterization of Intestinal Morphogenesis Defects in zu450"

Benjamin Leung, James R Priess

[International C. elegans Meeting, 2001]

The C. elegans intestine is a bilaterally symmetric tube of 20 polarized epithelial cells. Cell polarity in the intestine involves a reorganization of the microtubule cytoskeleton, followed by migration of the intestinal nuclei apically, and other organelles basally. Small apical membrane separations coalesce into a continuous compartment to form the lumen of the intestine. Cell ablation experiments suggest that morphogenesis of the intestine requires interactions between intestinal cells and interactions between intestinal and non-intestinal cells surrounding the intestine 1,2 . We have been conducting screens for embryonically-expressed genes required for intestinal morphogenesis, and are currently characterizing one mutant, zu450 , in more detail. The intestines of zu450 homozygotes appear slightly disorganized, and have abnormally wide intestinal lumens. Analysis of zu450 intestines using two indicators of epithelial polarity, the adherens junction marker MH27 and the lumenal marker MH33, reveal defects in the attachment of the intestine to the pharynx and rectum as well as discontinuities in the intestinal lumens. Preliminary analysis of the mutation zu450 suggests that it may play a role in multiple epithelia; zu450 homozygotes have elongation and enclosure defects in addition to intestinal morphogenesis defects. 1 Leung, B., G. J. Hermann, and J. R. Priess (1999). Developmental Biology 216 : 114-134. 2 Hermann, G. J., B. Leung, and J. R. Priess (2000). Development 127 : 3429-3440.

Hilbi H et al. (2011) Environ Microbiol Rep "Legionella spp. outdoors: colonization, communication and persistence."

Harrison CF, Hoffmann C, Hilbi H

[Environ Microbiol Rep, 2011]

Bacteria of the genus Legionella persist in a wide range of environmental habitats, including biofilms, protozoa and nematodes. Legionellaceae are 'accidental' human pathogens that upon inhalation cause a severe pneumonia termed 'Legionnaires' disease'. The interactions of L. pneumophila with eukaryotic hosts are governed by the Icm/Dot type IV secretion system (T4SS) and more than 150 'effector proteins', which subvert signal transduction pathways and promote the formation of the replication-permissive 'Legionella-containing vacuole'. The Icm/Dot T4SS is essential to infect free-living protozoa, such as the amoeba Dictyostelium discoideum, as well as the nematode Caenorhabditis elegans, or mammalian macrophages. To adapt to different niches, L. pneumophila not only responds to exogenous cues, but also to endogenous signals, such as the -hydroxyketone compound LAI-1 (Legionella autoinducer-1). The long-term adaptation of Legionella spp. is based on extensive horizontal DNA transfer. In fact, Legionella spp. have acquired canonical 'genomic islands' of prokaryotic origin, but also a number of eukaryotic genes. Since many aspects of Legionella virulence against environmental predators and immune phagocytes are similar, an understanding of Legionella ecology provides valuable insights into the pathogenesis of legionellaceae for humans.

Tsai-Fang Huang et al. (2006) East Asia C. elegans Meeting "dpy-24 prevents DTC from precocious dorsal turn by transcriptional repression of unc-5"

Tsai-Fang Huang, Yi-Chun Wu

[East Asia C. elegans Meeting, 2006]

Distal Tip Cells (DTCs) are located at the tip of gonadal arms in hermaphrodites and guide gonadal arm extensions during larval development. During migration, DTCs first move to the end of the body along the ventral side (phase I), then make a dorsal turn (phase II) and finally migrate back to the mid-body along the dorsal side (phase III). In a genetic screen for mutants defective in DTC migration, we isolated tp3. A time-course analysis showed that DTC underwent a precocious dorsal turn in tp3 mutants. Previous studies showed that unc-5, a receptor of UNC-6/netrin ligand, was required for the dorsal migration of DTCs (Leung-Hagesteijn et al., 1992). In addition, precocious expression of unc-5 in DTCs by the emb-9 promoter was sufficient to cause DTC premature dorsal turn (Su et al. ,2000). We found that the mutations unc-5(e53) and unc-5(e152) significantly reduced DTC precocious dorsal turn in tp3 mutants, indicating that the premature dorsal migration of DTCs in tp3 mutants required unc-5. Using the transgene P<SUB>unc-5</SUB>::gfp, we found that unc-5 was expressed earlier in the DTCs of tp3 than those of wild type in a time-course analysis. Therefore, the precocious dorsal turn in tp3 was likely caused by premature expression of unc-5. Genetic analysis of tp3 revealed that it was an allele of dpy-24. We cloned dpy-24 and found that it encodes a protein with a PR domain and five zinc fingers. DPY-24 is homologous to human PRDI-BF1 and mouse Blimp-1, which have been shown to function as transcription repressors during B lymphocyte maturation. We raised antibodies against DPY-24. DPY-24 was expressed in DTCs only before but not after their dorsal turns. We propose that DPY-24 transcriptionally represses unc-5 to prevent DTCs from premature dorsal turn during phase I migration and that disappearance of DPY-24 releases the repression and allows DTCs to migrate dorsally during phase II migration. References: Leung-Hagesteijn et al. (1992) Cell 71, 289-99; Su et al. (2000) Development 127, 585-94.

Rose JK et al. (2022) Front Behav Neurosci "Neuroligin Plays a Role in Ethanol-Induced Disruption of Memory and Corresponding Modulation of Glutamate Receptor Expression."

Liang J, Lin CHS, Rose JK, Parvand M, Butterfield M, Rankin CH

[Front Behav Neurosci, 2022]

Exposure to alcohol causes deficits in long-term memory formation across species. Using a long-term habituation memory assay in Caenorhabditis elegans, the effects of ethanol on long-term memory (> 24 h) for habituation were investigated. An impairment in long-term memory was observed when animals were trained in the presence of ethanol. Cues of internal state or training context during testing did not restore memory. Ethanol exposure during training also interfered with the downregulation of AMPA/KA-type glutamate receptor subunit (GLR-1) punctal expression previously associated with long-term memory for habituation in C. elegans. Interestingly, ethanol exposure alone had the opposite effect, increasing GLR-1::GFP punctal expression. Worms with a mutation in the C. elegans ortholog of vertebrate neuroligins (nlg-1) were resistant to the effects of ethanol on memory, as they displayed both GLR-1::GFP downregulation and long-term memory for habituation after training in the presence of ethanol. These findings provide insights into the molecular mechanisms through which alcohol consumption impacts memory.