Cohen, Lianne et al. (2015) International Worm Meeting "Host Mad-Max signaling regulates intracellular pathogen growth."

Troemel, Emily, Probert, Chris, Cohen, Lianne, Botts, Michael, Wu, Fengting

[International Worm Meeting, 2015]

As intracellular pathogens grow and develop inside a host organism they may utilize host resources to facilitate their growth. Microsporidia are a phylum of fungal-related obligate intracellular pathogens that infect all animal phyla including agriculturally relevant species such as honeybees and fish, yet little is known the host factors that are required for pathogen growth. We are studying a microsporidian pathogen called Nematocida parisii that naturally infects the C. elegans intestine. Recently we defined the C. elegans transcriptional response to N. parisii infection using RNAseq (Bakowski et al PLoS Pathogens, 2014), and have now used these data to identify predicted transcription factor binding sites upstream of pathogen-regulated genes. In these analyses we found an enrichment of binding sites for the transcription factor MDL-1, which is a member of the Mad-Max family of transcription factors. Animals defective for mdl-1 are resistant to infection by N. parisii, indicating that mdl-1 somehow promotes pathogen growth. Upon analyzing the other members of the conserved Mad-Max transcription factor family, we found that there appears to be a non-canonical rewiring of the pathway in its regulation of pathogen growth. Interestingly, we found that MDL-1 protein expression is induced upon infection and possibly leading to non-canonical Mad/Max signaling in response to infection. Overall these results provide a greater understanding of how obligate intracellular pathogens can use host pathways and appropriate them for their own benefit. .

Iwanir S et al. (2019) Nat Commun "Addendum: Irrational behavior in C. elegans arises from asymmetric modulatory effects within single sensory neurons."

Itskovits E, Ruach R, Bokman E, Iwanir S, Pritz CO, Zaslaver A

[Nat Commun, 2019]

We would like to make our readers aware of the publication by Cohen et al., which reports irrational behaviour in C. elegans olfactory preference[1] . These complementary studies establish C. elegans as a model system to explore the neural mechanisms of decision making.

Lazetic, Vladimir et al. (2021) International Worm Meeting "The role of the bZIP transcription factor ZIP-1 in the Intracellular Pathogen Response of C. elegans"

Reddy, Kirthi, Troemel, Emily, Wu, Fengting, Lazetic, Vladimir, Cohen, Lianne

[International Worm Meeting, 2021]

How does the nematode Caenorhabditis elegans respond to natural pathogen infections with non-professional immune cells? To answer this question, we are studying the Intracellular Pathogen Response (IPR) - a host transcriptional response induced by infection with molecularly diverse natural pathogens - the Orsay virus and fungal-related microsporidia Nematocida parisii. In addition to intracellular pathogens, the IPR can be activated upon exposure to heat stress and following proteasome inhibition. The IPR is genetically regulated by two antagonistic paralogs of unknown function, PALS-22 and PALS-25, as well as by PNP-1, a protein involved in regulation of purine metabolism. Loss-of-function mutations in pals-22 and pnp-1 cause constitutive IPR activation with increased intracellular pathogen resistance, indicating that the IPR confers a protective response. The IPR involves transcriptional activation of about 80 genes, some of which are predicted to encode ubiquitin ligase components. One of the most highly induced IPR genes is pals-5, which serves as a robust readout for the IPR activation. Using pals-5 transcriptional and translational GFP reporters, we identified the predicted bZIP transcription factor ZIP-1 as a positive regulator of the IPR in two reverse genetic screens. We found that ZIP-1::GFP is expressed in intestinal and epidermal nuclei following IPR activation. Our qRT-PCR and smFISH studies demonstrated that ZIP-1 controls pals-5 mRNA expression early after proteasome blockade. At later time points, however, pals-5 transcription does not require ZIP-1. Interestingly, our data suggest that the majority of translated pals-5 mRNA belongs to the early, ZIP-1 dependent fraction. We also performed RNA-seq analysis, which revealed that ZIP-1 is required for mRNA expression of multiple IPR genes. Based on these results, we have identified three distinct types of IPR genes: 1) completely ZIP-1 dependent, 2) early ZIP-1 dependent and 3) ZIP-1 independent. Importantly, we found that ZIP-1 is required for the increased resistance to Orsay virus and microsporidia infections in pnp-1(-) mutants, suggesting that ZIP-1-dependent genes play an important role in innate immunity.

Denham, J. et al. (2017) International Worm Meeting "An integrated neuro-mechanical model of C. elegans forward locomotion."

Ranner, T., Denham, J., Cohen, N.

[International Worm Meeting, 2017]

Behavioural responses in C. elegans can be observed through changes in locomotive patterns. It is therefore important to consider the role of the physics in computational models of the neural circuit for motor behaviours. We present a dynamical systems model of C. elegans forward locomotion in which the neural circuit is divided into a series of repeating identical units, coupled via posterior stretch receptor feedback. Each unit includes cholinergic, bistable B-type motor neurons (modelled after bistable RMD neurons, Mellem et al. 2008, Boyle et al. 2012), implicit GABAergic D-type motor neurons (Boyle et al. 2012) and nonlinear viscoelastic muscle forcing along the body (Boyle et. al. 2012). The neural model incorporates proprioceptive feedback as the mechanism for producing sustained oscillations. Integrating the neural model with a recent continuum mechanical body model (Cohen and Ranner 2017) provides this feedback and is also the method for incorporating environmental drag from the surrounding fluid, closing the neuronal-environmental loop. Biophysically realistic parameters are used to obtain sustained travelling waves in muscle activation which respond to changes in environmental viscoelasticity. To explore the pattern generation mechanism, we present results from bifurcation analysis performed in the isolated neural framework and in the fully integrated neuro-mechanical model. We show how these results are modulated by changes in the external drag and internal material properties of the passive and active body. References [1] Boyle JH, Berri S, Cohen N: Gait modulation in c. elegans: an integrated neuro-mechanical model. Frontiers in computational neuroscience 2012, 6:10. [2] Mellem JE, Brockie PJ, Madsen DM, Maricq AV: Action potentials contribute to neuronal signaling in C. elegans, Nature Neuroscience 2008, 11:865-867 [3] Cohen N, Ranner T: A new computational method for a model of C. elegans biomechanics: Insights into elasticity and locomotion performance, arXiv:1702.04988, 20

Cohen, Sarah M et al. (2021) MicroPubl Biol

Sternberg, Paul W, Le, Henry H, Cohen, Sarah M

[MicroPubl Biol, 2021]

The efficient CRISPR/Cas9 genome editing toolkit in the nematode Caenorhabditis elegans has made the creation of null mutants easier than ever. The putative lipid hydrolase lips-6 is known to function in the DAF-12/DIN-1 pathway to promote fat mobilization during periods of starvation in adult worms (Tao et al. 2016). Similarly, it was found to be strongly downregulated in response to dauer ascarosides given during the L1 to L2d decision in larval worms (Cohen et al. 2021). Here, we have created a mutant of the putative lipase lips-6 and studied its lifespan as well as its ascaroside profile.

Moll L et al. (2016) FASEB J "The inhibition of IGF-1 signaling promotes proteostasis by enhancing protein aggregation and deposition."

Reuveni H, Ben-Gedalya T, Moll L, Cohen E

[FASEB J, 2016]

The discovery that the alteration of aging by reducing the activity of the insulin/IGF-1 signaling (IIS) cascade protects nematodes and mice from neurodegeneration-linked, toxic protein aggregation (proteotoxicity) raises the prospect that IIS inhibitors bear therapeutic potential to counter neurodegenerative diseases. Recently, we reported that NT219, a highly efficient IGF-1 signaling inhibitor, protects model worms from the aggregation of amyloid peptide and polyglutamine peptides that are linked to the manifestation of Alzheimer's and Huntington's diseases, respectively. Here, we employed cultured cell systems to investigate whether NT219 promotes protein homeostasis (proteostasis) in mammalian cells and to explore its underlying mechanisms. We found that NT219 enhances the aggregation of misfolded prion protein and promotes its deposition in quality control compartments known as "aggresomes." NT219 also elevates the levels of certain molecular chaperones but, surprisingly, reduces proteasome activity and impairs autophagy. Our findings show that IGF-1 signaling inhibitors in general and NT219 in particular can promote proteostasis in mammalian cells by hyperaggregating hazardous proteins, thereby bearing the potential to postpone the onset and slow the progression of neurodegenerative illnesses in the elderly.-Moll, L., Ben-Gedalya, T., Reuveni, H., Cohen, E. The inhibition of IGF-1 signaling promotes proteostasis by enhancing protein aggregation and deposition.

Dostal V et al. (2010) J Vis Exp "Assaying -amyloid toxicity using a transgenic C. elegans model."

Dostal V, Link CD

[J Vis Exp, 2010]

Accumulation of the -amyloid peptide (A) is generally believed to be central to the induction of Alzheimer's disease, but the relevant mechanism(s) of toxicity are still unclear. A is also deposited intramuscularly in Inclusion Body Myositis, a severe human myopathy. The intensely studied nematode worm Caenorhabditis elegans can be transgenically engineered to express human A. Depending on the tissue or timing of A expression, transgenic worms can have readily measurable phenotypes that serve as a read-out of A toxicity. For example, transgenic worms with pan-neuronal A expression have defects is associative learning (Dosanjh et al. 2009), while transgenic worms with constitutive muscle-specific expression show a progressive, age-dependent paralysis phenotype (Link, 1995; Cohen et al. 2006). One particularly useful C. elegans model employs a temperature-sensitive mutation in the mRNA surveillance system to engineer temperature-inducible muscle expression of an A transgene, resulting in a reproducible paralysis phenotype upon temperature upshift (Link et al. 2003). Treatments that counter A toxicity in this model [e.g., expression of a protective transgene (Hassan et al. 2009) or exposure to Ginkgo biloba extracts (Wu et al. 2006)] reproducibly alter the rate of paralysis induced by temperature upshift of these transgenic worms. Here we describe our protocol for measuring the rate of paralysis in this transgenic C. elegans model, with particular attention to experimental variables that can influence this measurement.

Stefano Berri et al. (2008) European Worm Meeting "The role of the body in determining C. elegans locomotion waveforms: experiment and theory."

Ian A Hope, Stefano Berri, Netta Cohen, Jordan H Boyle

[European Worm Meeting, 2008]

C. elegans locomotion is typically studied on agar, where forward crawling. is well described by a characteristic waveform. Models of the neural and. neuromuscular control of locomotion have been restricted to modeling such. crawling behavior. Specifically, Niebur and Erdos (1991) suggest that the. sinusoidal track, or groove, left by a worm on an agar surface is. functionally significant.. The importance of the groove in determining the shape of the body may. resolve an important difference between the two existing classes of models. of forward locomotion. In the model of Niebur and Erdos (1991), the worm. relies on a central pattern generator (CPG) in the head to determine the. frequency of undulations and effectively create a groove for the rest of. the body to follow through. The body shape is therefore determined by the. path of the head. In contrast, the Bryden and Cohen model (2004, 2008) does. not include the constraints of a groove, and so the shape of the body is. determined by the muscle activation pattern all along the worm. To. determine to what extent the entire body is used by the worm to determine. its waveform during crawling behavior, we set out to investigate whether. the worm can determine its own waveform in the absence of a groove.. We compared the locomotion on agar with that of worms on a smooth, solid. (nitrocellulose) surface, which precludes the possible formation of a. groove.. Results indicate the following:. (i) The worm is capable of generating and propagating a waveform very. similar to that of forward crawling on agar.. (ii) Nonetheless, no forward motion results on the solid surface.. (iii) Using locomotion data analysis, we are able to estimate the. properties of the groove on agar and to confirm the absence of similar. forces on a solid surface.. (iv) Using a model adapted from Niebur and Erdos (1991) (Boyle, Bryden and. Cohen 2007), we successfully replicate the results in an environment. mimicking a groove. However, for insufficiently strong grooves (in. particular matching the strength of the groove to our observations of. behavior on agar) the mechanism breaks down, as the muscle activation. pattern alone is not sufficient to fully determine the body shape.. (v) Simulations of model worms with imposed waveforms and undulation. frequencies on a solid surface successfully explain the observed. experimental results.. Our work suggests that the crawling waveform of the worm does not require a. groove, and therefore that the body shape cannot be purely determined by. the motion of the head and the properties of the environment. In. particular, a minimal muscle activation pattern that generates thrust. within a groove is not sufficient to explain the behavior of the worm on a. solid surface. The worm must recruit muscles along the body to determine. the shape of the body in time.. Our conclusions may have important implications for further modeling of. neural control of locomotion in general and for predictions about the. distribution of postulated stretch receptors along ventral cord. motoneurons, in particular.

Baran, Renee A. et al. (2009) International Worm Meeting "zyg-8 Function in C. elegans Motor Neuron Development."

Baran, Renee A., Shirazi, Farah, Tang, Garland

[International Worm Meeting, 2009]

Mutations in alpha-tubulin, doublecortin, and LIS1 block neuron migration and cause lissencephaly in humans. Doublecortin/DCX and doublecortin-like proteins bind microtubules and function to promote microtubule assembly and stability while LIS1 mediates interactions with the dynein motor complex. Doublecortin proteins have also been shown to localize to neurite endings and influence axon outgrowth and dendrite arborization (Friocourt et al., 2003; Deuel et al., 2006; Cohen et al., 2008). zyg-8, the sole C. elegans member of the doublecortin family, encodes a doublecortin-like protein required for positioning the mitotic spindle during embryonic divisions (Gonzcy et al., 2001). We utilized conditional zyg-8 mutants to study the role of zyg-8 in later stages of neuronal development. zyg-8(b235ts) mutants were shifted to the nonpermissive temperature as late embryos or early L1 larvae prior to synapse formation, and the GABAergic motor neurons of mutant adults were analysed for expression of the synaptic vesicle marker SNB-1::GFP, active zone marker UNC-10::RFP, and an axon-restricted microtubule plus-end binding protein. zyg-8 mutants exhibited defects in synapse morphology similar to gain-of-function tba-1 mutants (R. Baran & Y. Jin). SNB-1::GFP puncta were irregular in size and spacing and GFP was mislocalized in the commissures. Synapses were sometimes missing from the most distal regions of axons along the dorsal nerve cord, a phenotype also observed in tba-1(ju89) mutants. These results suggest that zyg-8 may play a significant role in larval and adult motor neurons in maintaining axon and synapse integrity.

Sanders, Tom et al. (2015) International Worm Meeting "Nonlinear sensory integration in C. elegans: a computational model."

Cohen, Netta, Ghosh, D.D., Sanders, Tom, Nitabach, M.N.

[International Worm Meeting, 2015]

Animal survival depends on a combination of often conflicting demands such as foraging and evading of dangers. To navigate effectively in such unknown and changing conditions, animals must continuously integrate over a variety of sensory cues, and adapt their decision making strategy in a context dependent manner. Here, we examine the neural control of a sensory integration task in the nematode C. elegans. The task involves an ASH-triggered aversive response to high osmolarity fructose and an AWA-triggered attractive response to diacetyl [1]. In the assay, worms are placed in the center of a ring of fructose; two drops of diacetyl are located outside the ring. We present a computational model, consisting of point worms, situated in a virtual arena that closely mimics this experimental assay, and endowed with a sensory motor pathway of two sensory neurons, a neural integration pathway and two motor programs (pirouettes and steering). A monoamine (PDF-2 and tyramine) modulation circuit involving RIM and ASH is overlaid on the synaptic circuit, in line with molecular data [1]. Model parameters were constrained by behavioral data for wild type and mutant animals for a range of stimulus concentrations. Based on our simulation results, we reject a null hypothesis of a linear sensory integration mechanism in RIM and present results that are consistent with the data for a sensory "coincidence detector" like process in RIM.[1] Ghosh, D.D., Sanders, T., Hong, S., Chase, D.L., Cohen, N., Koelle, M.R., and Nitabach, M.N. "Neuroendocrine reinforcement of a dynamic multisensory decision." International C. elegans meeting.