Beardsley, Simon et al. (2021) International Worm Meeting "Loss of adaptor protein complexes bypasses mrp-5 deficiency and restores heme deficit in Caenorhabditis elegans"

Krause, Mike, Smith, Harold, Dutt, Sohini, Hamza, Iqbal, Beardsley, Simon, Yuan, Xiaojing

[International Worm Meeting, 2021]

Metazoans require heme as an essential cofactor and synthesize it in the mitochondria. Caenorhabditis elegans and related helminths are an exception as they are unable to synthesize heme de novo but instead acquire heme from dietary sources for their growth and development. Heme is imported from the apical surface of the intestine by HRG-1-related importers and exported by MRP-5/ABCC5 from the basolateral surface. Loss of mrp-5 causes heme deficiency in extra-intestinal tissues and embryonic lethality, which can be suppressed by dietary heme supplementation raising the possibility that heme export in the absence of mrp-5 could be mediated by alternate pathways. Here we show, by performing a forward genetic screen in an mrp-5 null mutant, that loss-of-function in vesicular transport adaptor protein complexes fully restores heme homeostasis and normal growth and development in mrp-5 mutants. We screened over 160,000 haploid genomes and identified thirty-two bypass suppressors of mrp-5(ok2067). Deep-sequencing and variant analyses revealed three suppressors, each containing mutations in different adaptor protein 3 (AP3) complex subunits. RNAi depletion of individual subunits for either AP3 or AP2 phenocopies the mrp-5 bypass suppressors. Remarkably, loss of AP3 subunits in the mrp-5 mutants reversed intestinal accumulation of fluorescent heme analog; resistance to gallium protoporphyrin IX toxicity; extra-intestinal heme deficiencies; and neuronal abnormalities including glial migration and synaptogenesis. Taken together, our results show that cargo transport by vesicular adaptor proteins play a previously unanticipated role in systemic heme homeostasis and that multiple routes govern intra- and intercellular heme trafficking in metazoans.

Matthews LR et al. (1994) Worm Breeder's Gazette "A Potential C. elegans E2F Homolog: Is it zyg-9?"

Matthews LR, Galas S

[Worm Breeder's Gazette, 1994]

A potential C. elegans E2F homolog: Is it zyg-9? Lisa Matthews and Simon Galas, CRBM, CNRS Montpellier, France

Berger S et al. (2018) Lab Chip "Correction: Long-term C. elegans immobilization enables high resolution developmental studies in vivo."

Hajnal A, Lattmann E, Hengartner M, Casadevall I Solvas X, Berger S, DeMello A, Aegerter-Wilmsen T

[Lab Chip, 2018]

Correction for 'Long-term C. elegans immobilization enables high resolution developmental studies in vivo' by Simon Berger et al., Lab Chip, 2018, 18, 1359-1368.

Davies JB (1993) Ann Trop Med Parasitol "Description of a computer model of forest onchocerciasis transmission and its application to field scenarios of vector control and chemotherapy."

Davies JB

[Ann Trop Med Parasitol, 1993]

This paper describes a computer simulation model for onchocerciasis (SIMON). Using epidemiological and entomological data from a specific hyperendemic village in the forest area of Sierra Leone, the model is used to examine the effect of vector and chemotherapeutic control strategies, both separately and in combination, as well as the risk to an uninfected population caused by immigrant, infected Simulium damnosum and humans. The model suggests that, in this village, the human population of about 420 requires an average annual input of about 200 mature fecund, female Onchocerca volvulus per year to maintain a skin-snip prevalence of just under 70%. SIMON also predicts that 99% effective vector control would lead to eradication of all adult worms in 18 years, and that abandoning control before 14 years could lead to recrudescence. Chemotherapy with ivermectin at six-month intervals reaching 90% of eligible persons (effective 66%) might take 29 years to achieve eradication because of continuing transmission, particularly in the early years, but it would probably be possible to abandon treatments after 18 years because the residual worm population would no longer be self-sustaining. Combined ivermectin and vector control, both at reduced levels, could be as effective as 99% vector control. Immigrant infected flies are likely to pose a greater threat to an uninfected human population than small numbers of infected persons. The model suggests that, at levels of infection undetectable by skin-snip, the parasite could linger in the human population for 30 or more years sustained by sporadic transmission.(ABSTRACT TRUNCATED AT 250 WORDS)

Lars Nilsson et al. (2006) European Worm Meeting "C. elegans NUM-1 Modulates Endocytosis by Targeting the TAT-1 Phospholipid Flippase"

Simon Tuck, Lars Nilsson

[European Worm Meeting, 2006]

Lars Nilsson and Simon Tuck. We have previously reported that C. elegans NUM-1 modulates both endocytosis and the activity of LIN-12, a receptor that mediates a number of cell fate specification events in the worm. In order to understand better how NUM-1 functions, we carried out a yeast 2-hybrid screen for interacting proteins. One clone we isolated encodes TAT-1, a transmembrane P-type ATPase. Work in S. cerevisiae has shown that these proteins function as so-called inward phospholipid flippases to concentrate specific phospholipids to the cytosolic leaflet of biological membranes. They are known to be associated with endosomes and to be required for correct vesicle trafficking. We have found that TAT-1 is expressed in tissues in which NUM-1 functions. Mapping of the regions required for binding revealed that the PTB domain of NUM-1 associates with an NXXF motif at the C-terminus of TAT-1. RNAi experiments show that tat-1 affects membrane trafficking in C. elegans. Our results suggest that NUM-1 functions in the worm by modulating TAT-1 activity.

JJ Yochem (1999) International C. elegans Meeting "Mutations that confer aspects of the molting defects seen with lrp-1 mutations or sterol starvation"

JJ Yochem

[International C. elegans Meeting, 1999]

Mutations that produce larvae that are completely stuck in old cuticle, that have rings of unshed cuticle that constrict regions of the body, or that have attached to the tail a train of old cuticle will be described. Such larvae can be detected with a dissecting microscope, permitting a semi-clonal screen. The search for such mutations was begun because a failure to complete molting is an aspect of the phenotype conferred by loss-of-function mutations in lrp-1 , the product of which resembles mammalian gp330/megalin, a large member of the LDL receptor family of proteins [Yochem et al., Development 126, 597 (1999)]. It is hoped that new mutations will reveal genes whose products are required for the same process as LRP-1. The mutations also have the potential for increasing our understanding of molting, a process that has not been much studied genetically in nematodes. To date, mutations have defined eight candidate genes. Of particular note are mlt-3(sv8) and mlt-7(sv16) , both of which closely resemble the lrp-1 mutant phenotype. Thanks to Simon Tuck, Min Han, and Bob Herman.

Morten K. Larsen et al. (2006) European Worm Meeting "MAA-1, A Novel Acyl-CoA Binding Protein Involved in Endosomal Vesicle Transport in C. elegans"

Simon Tuck, Morten K. Larsen, Jens K. Knudsen, Nils J. Faergeman

[European Worm Meeting, 2006]

Morten K. Larsen1, Simon Tuck1, Nils J. Faergeman2 and Jens K. Knudsen2. The formation of transport vesicles during membrane trafficking requires an intricate interplay between many proteins including those coating the vesicles, adaptor proteins that recruit components of the coat, and small GTPases involved in initiation of vesicle formation. In addition to the protein factors, membrane bilayer lipids are increasingly being recognised as molecules participating actively during vesicle formation. For example, formation of transport carriers is promoted by the hydrolysis of acyl-CoA lipid esters in vitro. The mechanisms by which these lipid esters are directed to the appropriate membranes during vesicle biogenesis is not yet understood. Here we present the first study of MAA-1, a novel member of the acyl-CoA-binding protein family. We show that in C. elegans, MAA-1 is membrane associated and localizes to intracellular membrane organelles in several polarised tissues in C. elegans. MAA-1 binds fatty acyl-CoA in vitro and the ability to form high affinity ligand-protein complexes is necessary for function. Lack of maa-1 reduces the rate of endosomal recycling and enhances phenotypes caused by rme-1, an EH domain protein involved in endosomal recycling. Our results are consistent with a role for acyl-CoA and MAA-1 during endosomal recycling in vivo.

Hom, Sabrina et al. (2009) International Worm Meeting "Identifying genes required for the miR-1 and MEF-2 induced retrograde synaptic signal."

Kaplan, Joshua, Thompson-Peer, Katherine, Hom, Sabrina, Choi, Seungwon, Hu, Zhitao

[International Worm Meeting, 2009]

A fundamental question pertaining to the regulation of synaptic activity concerns how pre- and post-synaptic sites coordinate function. While retrograde signaling has been well-documented in the regulation of synaptic activity, little is known about the molecular mechanisms underlying this phenomenon. We have recently demonstrated that the muscle-specific microRNA miR-1 regulates aspects of both pre- and post-synaptic activity at the NMJ, a process that is thought to involve the generation of a retrograde signal resulting in diminished excitatory presynaptic release (Simon et al., 2008). This signal is dependant on the transcription factor MEF-2, indicating that transcriptional regulation is a key component in the retrograde pathway. We have carried out a microarray analysis of mir-1 mutants that reveals a list of about 100 candidate genes that are up- or down-regulated in the mir-1 background. To distinguish those genes potentially involved in the activation of the MEF-2 dependant retrograde signal, we are currently carrying out a small-scale RNAi screen to identify suppressors of the mir-1 induced signal. In identifying and characterizing components of the retrograde signaling pathway, we hope to clarify the roles of miR-1 and MEF-2 in regulating synaptic activity.

Gautam Kao et al. (2006) European Worm Meeting "The ATPase ASNA-1 Positively Regulates Insulin Secretion in C. elegans and Mammals and Promotes Growth Non-autonomously"

Simon Tuck, Maria Still, Peter Naredia, Cecilia Nordensson, Gautam Kao, Agneta Rannlund

[European Worm Meeting, 2006]

Gautam Kao1, Cecilia Nordensson2, Maria Still2, Agneta Rnnlund1, Peter Naredi2 & Simon Tuck1. C. elegans embryos that hatch in the absence of food arrest growth during the first larval stage (L1). While much has been learned about the later diapause, called dauer that worms enter on encountering adverse conditions little is known presently about the mechanisms governing L1 arrest. We have identified and characterized a gene, asna-1, which when mutated, causes a complete but reversible arrest at the L1 stage even in the presence of food. We find that asna-1 encodes an ATPase that functions non-autonomously to regulate larval growth. asna-1 is expressed in a restricted set of sensory neurons and in the intestine; cells that produce insulin. asna-1 mutants have reduced insulin signaling while overexpression of asna-1 mimics the effects of overexpressing insulin. The human homologue ASNA1, which rescues the C. elegans mutant phenotype, is expressed at high levels in human pancreatic ?eta cells but not in other pancreatic endocrine or exocrine cell types. Increase or decrease of ASNA1 function in mouse insulinoma cells causes an increase or decrease in insulin secretion respectively. Similarly, reducing asna-1 gene function in C. elegans causes a decrease in levels of secreted insulin. We propose that ASNA1 is a novel evolutionarily conserved modulator of insulin signaling.

A Barrios et al. (2004) European Worm Meeting "IDENTIFYING MOLECULAR AND CELLULAR COMPONENTS INVOLVED IN THE DETECTION OF THE MATE FINDING CUE"

S Nurrish, A Barrios

[European Worm Meeting, 2004]

A pheromone is a chemical substance secreted by an animal that serves as a cue for other individuals of the same species to elicit one or more behaviours. Pheromone comunication regulates social interactions important for the survival of the individual and the species. For the C.elegans male, mating with an hermaphrodite is essential for the transmission of his genetic pool. Recently, evidence of the existance of an hermaphrodite specific chemical cue detected by the C.elegans male has been published (Simon and Sternberg 2002). In a chemotaxis assay where a population of C.elegans males are given the choice between a spot conditioned with C.elegans hermaphrodites and a control spot, we observe that males accumulate at the condition spot. This does not occur when males are given the choice between a control spot and and a spot conditioned with C.briggsae hermaphrodites suggesting that what we observe is the male response to a pheromone. With the aim of identifying some of the molecular and cellular components involved in the detection of the mate pheromone, we have performed a mutant and RNAi screen of several candidate genes. Mutations that disrupt the male response to the hermaphrodite cue include a GPCR, a G potein alpha subunit and a transmembrane guanylyl cyclase all expressed in one amphid neuron. We are further investigating the role of this neuron in the male detection of the mate pheromone.