Wallace, S.W. et al. (2017) International Worm Meeting "The roles of glial xenobiotic metabolizing enzymes (XMEs) in chemosensation."

Wallace, S.W., Shaham, S.

[International Worm Meeting, 2017]

Animals sense their environment using sense organs, consisting of sensory neurons and associated glial cells. Chemosensory signal transduction often takes place at ciliated receptive-endings of sensory neurons, where odorant molecules bind to odorant receptors. These cilia associate with sense-organ glia, and are bathed in a glia-secreted extracellular matrix. While most studies on odor perception and associated behavioral responses have focused on information processing downstream of sensory neuron activation, there is increasing evidence for modulation of sensory responses at the periphery, including regulation of odorant-receptor interactions. Xenobiotic metabolizing enzymes (XMEs) play key roles in modifying xenobiotic compounds, including drugs and toxins. XME substrates are hydrophobic compounds that are sequentially modified by phase I enzymes, including cytochrome P450 mono-oxygenases (CYPs) and carboxylesterases (CESs), to create functional groups, and phase II enzymes, including UDP-glucoronosyltransferases (UGTs) and glutathione s-transferases (GSTs), which add hydrophilic conjugates. These modifications make hydrophobic substrates more soluble, facilitating their excretion from cells through membrane transporters. In mammals XMEs are expressed in the liver, where xenobiotic detoxification takes place, and to varying degrees in other tissues. Highest extra-hepatic expression is in the olfactory epithelium. XME proteins localize to the apical region of sustentacular glial cells, in close proximity to cilia of olfactory receptor neurons. Many XMEs contain signal peptides, suggesting they may be secreted into the olfactory mucus, and enzymatic activity has been observed in nasal mucus extracts. It has therefore been proposed that XMEs modify odorant molecules to regulate local odorant levels at sites of sensory signal transduction. This idea is supported by in vitro data showing that odorant molecules are modified by reconstituted XMEs, and that modified odorants elicit altered sensory responses. However the role of XMEs in odor sensation in vivo remains unclear. We use the C. elegans amphid sensory neurons and their associated AMsh glia as a model to study glial functions in the nervous system. Through RNAseq gene expression analysis, we identified homologs of both phase I and phase II XMEs enriched in AMsh glia. We are using genetic and pharmacological manipulation of XMEs to assess whether glial XME activity regulates neuronal responses to odorants. Preliminary results suggest that XME expression in AMsh glia is regulated by experience, raising the intriguing possibility that modification of odorant molecules by glial XMEs may contribute to experience-dependent changes in behavior.

Wallace SW et al. (2017) Curr Biol "Sensory Cilia: Generating Diverse Shapes One Ig Domain at a Time."

Wallace SW, Shaham S

[Curr Biol, 2017]

How morphologically complex cilia form is not well understood. A key regulator of ciliary shape has now been identified that links the establishment of neuronal fate with the formation of cell-specific ciliary structures in Caenorhabditis elegans.

Wallace SW et al. (2016) Cell Rep "PROS-1/Prospero Is a Major Regulator of the Glia-Specific Secretome Controlling Sensory-Neuron Shape and Function in C.elegans."

Wallace SW, Shaham S, Liang Y, Singhvi A, Lu Y

[Cell Rep, 2016]

Sensory neurons are an animal's gateway to the world, and their receptive endings, the sites of sensory signal transduction, are often associated with glia. Although glia are known to promote sensory-neuron functions, the molecular bases of these interactions are poorly explored. Here, we describe a post-developmental glial role for the PROS-1/Prospero/PROX1 homeodomain protein in sensory-neuron function in C.elegans. Using glia expression profiling, we demonstrate that, unlike previously characterized cell fate roles, PROS-1 functions post-embryonically to control sense-organ glia-specific secretome expression. PROS-1 functions cell autonomously to regulate glial secretion and membrane structure, and non-cell autonomously to control the shape and function of the receptive endings of sensory neurons. Known glial genes controlling sensory-neuron function are PROS-1 targets, and we identify additional PROS-1-dependent genes required for neuron attributes. Drosophila Prospero and vertebrate PROX1 are expressed in post-mitotic sense-organ glia and astrocytes, suggesting conserved roles for this class of transcription factors.

Wallace SW et al. (2021) Cell Rep "Nuclear hormone receptors promote gut and glia detoxifying enzyme induction and protect C.elegans from the mold P.brevicompactum."

Hur H, Magemizoglu E, Wallace SW, Lizzappi MC, Liang Y, Shaham S

[Cell Rep, 2021]

Animals encounter microorganisms in their habitats, adapting physiology and behavior accordingly. The nematode Caenorhabditis elegans is found in microbe-rich environments; however, its responses to fungi are not extensively studied. Here, we describe interactions of C.elegans and Penicillium brevicompactum, an ecologically relevant mold. Transcriptome studies reveal that co-culture upregulates stress response genes, including xenobiotic-metabolizing enzymes (XMEs), in C.elegans intestine and AMsh glial cells. The nuclear hormone receptors (NHRs) NHR-45 and NHR-156 are induction regulators, and mutants that cannot induce XMEs in the intestine when exposed to P.brevicompactum experience mitochondrial stress and exhibit developmental defects. Different C.elegans wild isolates harbor sequence polymorphisms in nhr-156, resulting in phenotypic diversity in AMsh glia responses to microbe exposure. We propose that P.brevicompactum mitochondria-targeting mycotoxins are deactivated by intestinal detoxification, allowing tolerance to moldy environments. Our studies support the idea that C.elegans NHRs may be regulated by environmental cues.

Pedersen EM et al. (1985) Trop Med Parasitol "Quantitative studies on the transmission of Onchocerca volvulus by Simulium damnosum s.l. in the Tukuyu Valley, South West Tanzania."

Maegga BT, Pedersen EM

[Trop Med Parasitol, 1985]

A survey of the Simulium breeding and the transmission of Onchocerca volvulus was carried out in and around the Tukuyu valley, S.W. Tanzania, S. damnosum s.l. was found breeding in the midstretches of the main rivers in the valley and their bigger tributaries, and also in the boundary river to Malawi and the most northerly of the three rivers draining the Livingstone Mts. to Lake Nyasa (L. Malawi). A total of 19,500 S. damnosum s.l. females was caught and 13,200 dissected. The annual biting rate varied between 2,000 and 23,800. 7.6% of all the flies were infected with O. volvulus and 1.5% carried infective larvae in the head capsule, on average 2.7 per fly. The transmission was mainly in the dry season and the annual transmission potential varied between 0 and 1,120. The entomological data showed many similarities to those from the Mahenge Mts., Tanzania, and correlation of places with comparable transmission potentials suggests a similarity in the relationship parasite-human host between the West African rain forest and the two Tanzanian foci.

Mukhopadhyay A et al. (2006) Exp Gerontol "Worming pathways to and from DAF-16/FOXO."

Tissenbaum HA, Oh SW, Mukhopadhyay A

[Exp Gerontol, 2006]

In Caenorhabditis elegans, the insulin/IGF-1 signaling pathway controls many biological processes such as life span, fat storage, dauer diapause, reproduction and stress response . This pathway is comprised of many genes including the insulin/IGF-1 receptor (DAF-2) that signals through a conserved PI 3-kinase/AKT pathway and ultimately down-regulates DAF-16, a forkhead transcription factor (FOXO). DAF-16 also receives input from several other pathways that regulate life span such as the germline and the JNK pathway [Hsin, H., Kenyon, C., 1999. Signals from the reproductive system regulate the lifespan of C. elegans. Nature 399, 362-366; Oh, S.W., Mukhopadhyay, A., Svrzikapa, N., Jiang, F., Davis, R.J., Tissenbaum, H.A., 2005. JNK regulates lifespan in Caenorhabditis elegans by modulating nuclear translocation of forkhead transcription factor/DAF-16. Proc. Natl. Acad. Sci. USA 102, 4494-4499]. Therefore, DAF-16 integrates signals from multiple pathways and regulates its downstream target genes to control diverse processes. Here, we discuss the signals to and from DAF-16, with a focus on life span regulation.

Gillian M Stanfield et al. (2001) International C. elegans Meeting "Screening for sperm competition mutants"

Gillian M Stanfield, Anne M Villeneuve

[International C. elegans Meeting, 2001]

C. elegans hermaphrodites produce a supply of self sperm, which are normally used with extremely high efficiency (>99%). However, if a hermaphrodite mates with a male, its self sperm must compete with any transferred male sperm to fertilize oocytes. In this situation, sperm provided by the male are used preferentially(1). Male sperm precedence requires sperm motility(2) and involves displacement of self sperm from the hermaphrodite spermatheca. However, successive mating experiments have shown that sperm from different males do not exhibit any precedence relationship, indicating that sperm usage is not dictated by a "last in" mechanism of placement within the spermatheca and that there is a bona fide difference between hermaphrodite sperm and male sperm(1,3). Male sperm precedence is nearly complete: after mating, very few if any self progeny are produced until a mated hermaphrodite runs out of transferred male sperm. The strength of this effect provides a robust assay for alterations in the normal pattern of sperm usage. To identify factors that confer male sperm advantage, we are screening for mutants that do not show the normal precedence of male sperm. Specifically, we are assaying males from mutagenized him-5 lines for lack of precedence in crosses to spe-8; dpy-4 hermaphrodites. spe-8 hermaphrodites are defective in sperm activation, but spe-8 self sperm can be trans - activated upon mating to a male; dpy-4 provides a readily-scored marker for self vs. cross progeny. We expect that sperm precedence-defective males should produce sperm that are capable of fertilizing oocytes but do not suppress the production of hermaphrodite self progeny. Matings to such males should result in a mixture of self and cross progeny, and the relative numbers of self and cross progeny produced should be dependent on the numbers of each sperm type present within the hermaphrodite spermatheca. Sperm precedence mutants should be distinct from the previously described spe and fer mutants, which show defects in various aspects of spermatogenesis and/or fertilization(4). 1. Ward, S. and J.S. Carrel, Dev Biol 73 : 304-321, 1979. 2. Singson, A., K.L. Hill and S.W. L’Hernault, Genetics 152 : 201-208, 1999. 3. LaMunyon, C.W. and S. Ward, Experientia 51 :817-823, 1995. 4. L’Hernault, S.W., Spermatogenesis (p.271-294) in C. elegans II , 1997.

WB Derry et al. (1999) International C. elegans Meeting "Analysis of the C. elegans homolog of the FHIT tumor suppressor gene"

WB Derry, S van Kreeveld, JH Rothman

[International C. elegans Meeting, 1999]

Alterations in the FHIT gene occur frequently in the development of several human cancers (1). The Fhit protein is a diadenosine P 1 , P 3 -triphosphate hydrolase and is a member of the histidine triad superfamily of nucleotide binding proteins (2). The cellular mechanism of Fhit activity and the relationship between Fhit signaling and tumorigenesis are presently unknown. The C. elegans and Drosophila FHIT genes encode a fusion protein in which the Fhit domain is fused with a novel domain showing homology to bacterial and plant nitrilases, and are referred to as NitFhit (3). We are interested in understanding the role of NitFhit in development and programmed cell death. RNAi of C. elegans NitFhit causes an embryonic arrest phenotype, suggesting an essential role for this gene in development. We are currently analyzing the loss-of-function phenotype and the effect of ectopic NitFhit expression on viability and programmed cell death in the worm. (1) Huebner, K., Garrison, P.N., Barnes, L.D. & Croce, C.M. (1998). Ann. Rev. Genet ., 32 : 7-31. (2) Barnes, L.D., Garrison, P.N., Siprashvili, Z., Guranowski, A, Robinson, A.K., Ingram, S.W., Croce, C.M., Ohta, M. & Huebner, K. (1996). Biochemistry , 35 : 11529-11535. (3) Pekarsky, Y., Campiglio, M., Siprashvili, Z, Druck, T., Sedkov, Y, Tillib, S., Draganescu, A., Wermuth, P., Rothman, J.H., Huebner, K., Buchberg, A.M., Mazo, A., Brenner, C. & Croce, C.M. (1998). Proc. Natl. Acad. Sci. USA , 95 : 8744-8749.

Kim, Grace S et al. (2009) International Worm Meeting "unc-3 is necessary for axon pioneering and guidance in C. elegans."

Hall, David H., White, John G., Xu, Meng, Kim, Grace S

[International Worm Meeting, 2009]

Genetic and phenotypic studies of unc-3 mutants have shown that unc-3 is required for proper organization of ventral cord processes (1,2). The defasciculation and wiring defects seen in unc-3 mutants have been attributed to disruption of pathfinding in the pioneer neurons during embryonic development. We have used Elegance, a 3D reconstruction software program developed at AECOM (3), to analyze the deformed morphology of the unc-3 (e151) ventral cord to unprecedented detail at the EM level. Both the e151/e151 and e151/Df animals display severe axon guidance errors that affect some pioneers (AVKs) and some motor neurons more strongly than the command interneurons. These results support the essential role of the unc-3 gene in axon pioneering and guidance. We present the pattern of severe axon guidance errors in terms of the mispositioning of specific axons, their deviance from their normal neighborhoods, and their synaptic wiring defects. This study, along with molecular genetic studies identifying the unc-3 gene product as a CeO/E transcription factor, should guide future studies of specific axon guidance cues at the molecular level and provide further insight into the role of the mammalian O/E family members. This study used annotated unc-3 TEM datasets received from John White (MRC/LMB and U. Wisconsin) that are now part of the MRC archive in the Hall lab. This work was supported by NIH RR12596 (to DHH) and an AECOM summer research fellowship (to GSK). 1.Wightman, B., Baran R. and Garriga, G. (1997) Development 124: 2571-2580. 2.Prasad, B.C. et al. (1998) Development 125: 1561-1568. 3.Emmons, S.W. et al. (2009) at this meeting.

Gilbert, Sophie P. R. et al. (2013) International Worm Meeting "Defining the role of the Caenorhabditis elegans homeobox protein, PAL-1, in the development of the stem-like seam cells."

Brabin, Charles, Appleford, Peter J., Woollard, Alison, Gilbert, Sophie P. R.

[International Worm Meeting, 2013]

pal-1, the C. elegans homologue of Drosophila caudal, has previously been shown to have an important role in establishing posterior patterning during embryogenesis 1. Here we investigate a novel role for pal-1 during seam cell development. pal-1 was identified in a small scale candidate RNAi screen to detect genes acting redundantly with rnt-1, a gene already known to be essential for maintaining correct seam cell divisions. Synthetic lethality of pal-1 with rnt-1 was observed, indicating that the two gene products may physically interact during embryogenesis. Although pal-1 null animals are embryonic lethal, worms homozygous for a pal-1 mutant allele e2091 survive embryogenesis but on hatching display an uneven distribution of seam cells along their length, together with other seam defects. Analysis of this strain has previously identified two point mutations in the last intron of pal-1 2; we have found that a wild-type copy of this intron is capable of driving specific seam GFP expression, whereas an intron bearing the two mutations fails to express correctly, suggesting a separate seam-specific role for pal-1. We have demonstrated that the last intron of pal-1 contains an enhancer element (perturbed in e2091) required to correctly specify pal-1 expression in the seam and enable correct seam cell development and orientation. To identify transcription factors that bind to this tissue-specific intronic enhancer we are carrying out a yeast one-hybrid screen using both the wild-type and e2091 mutant version of the pal-1 intron. We will also report our phenotypic analysis of pal-1(e2091) with respect to the cell biology of the seam cells. 1. Edgar, L.G., et al., Dev Biol, 2001. 229(1): p. 71-88. 2. Zhang, H. and S.W. Emmons, Genes Dev, 2000. 14(17): p. 2161-72.