Parker JA et al. (1997) International C. elegans Meeting "A C. elegans huntingtin interacting protein?"

Parker JA, Rose AM

[International C. elegans Meeting, 1997]

One of the areas of research in our lab concerns the identification and placement of lethal mutations along LGIII. The recent identification of a gene within this area has led to a collaborative effort between ourselves and the Michael Hayden lab, here at UBC. Within LGIII there is a gene that shares considerable sequence identity with human hip-1 (huntingtin interacting protein 1), and SLA-2 in yeast. Hip-1 has been found to interact with the Huntingtons disease gene product, huntingtin. (M. Kalchman, M. Hayden, personal communication). Hip-1s ability to interact with huntingtin is modulated by the size of the expanded polyglutamine repeat in the first exon of huntingtin. The repeat is greatly expanded in individuals with Huntingtons disease, and the strength of the hip-1/huntingtin interaction decreases with an increase in repeat size. Thus, the specific neuronal deterioration observed in Huntingtons disease may be attributable to the role of hip-1. Previous work has localised huntingtin to the plasma membrane.(Gutekunst,1995) This observation is supported by the observation that hip-1 shares identity with talin. Talin is a member of a group of proteins postulated to serve as structural links between the plasma membrane and the cytoskeleton. SLA-2 is a synthetic lethal mutation of yeast, and has been found to be membrane and cytoskeletal associated protein as well. Although, the yeast system is an excellent one for the study of the cellular function of this gene, C. elegans could provide insights into its potential developmental and tissue specificity. We have been characterising the 5 prime end of the gene in order to study its expression pattern. In addition, we are surveying our library of existing mutants for possible candidates, as well as conducting new mutagenesis screens.

Parker JA et al. (1998) West Coast Worm Meeting "Towards Characterisation of ZK370.3, a C. elegans Homologue of Human Huntingtin Interacting Protein 1"

Parker JA, Rose AM

[West Coast Worm Meeting, 1998]

Duhaime, S. et al. (2019) International Worm Meeting "Characterization of novel C. elegans models of amyotrophic lateral sclerosis."

Bretonneau, C., Parker, JA., Duhaime, S.

[International Worm Meeting, 2019]

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive and selective loss of motor neurons. ALS is incurable and there are no effective treatments available for people living with the disease. About 90% of the cases are sporadic and 10% are familial, and patients usually die two to five years after symptom onset. Many gene defects are associated with ALS, including mutations in the gene encoding the DNA/RNA-binding protein TAR DNA Binding Protein 43 (TDP-43). Therefore, the development of novel genetic ALS models will provide insight on pathological molecular mechanisms. Here, we have developed a transgenic C. elegans model expressing human mutant TDP-43(Q331K) in motor neurons. A TDP-43(Q331K) mouse model has been previously reported but the elaboration of a C. elegans model will allow us to investigate important facets of the disease in a simple nervous system. We have also generated physiologically accurate models based on mutations in tdp-1, the C. elegans orthologue of TARDBP. Our objective is to characterize these models and determine if they can recapitulate key aspects of the disease such as motor deficits and age-dependent neurodegeneration. Furthermore, we will compare these models to previous transgenic TDP-43 models generated by our laboratory to compare phenotypic differences. These new TDP-43 and TDP-1 models could be useful tools to study ALS and elucidate new pathogenic mechanisms of the disease. An update of our findings will be presented.

Cendrine Tourette et al. (2007) International Worm Meeting "Classification of oligonucleotide microarray data for mutant polyglutamine toxicity in cell-sorted neurons using gene networks C.elegans."

Cendrine Tourette, Christian Neri, Alex, J Parker, Anne Louise

[International Worm Meeting, 2007]

The limitations of cellular and rodent models preclude the detailed analysis of molecular and genetic factors involved in polyglutamine neuronal toxicity in vivo. Invertebrates provide convenient and robust experimental systems to study the regulators of polyglutamine neuronal toxicity in whole organisms and at the genomic level. We have previously described C.elegans models of the early phases of mutant polyglutamine (polyQ) cytotoxicity in neurons, namely the dysfunction of touch receptor neurons before cell death produced by the expression of N-ter huntingtin fused to a fluorescent protein under the control of the mec-3 promoter (Parker et al., PNAS 2001). We have illustrated the value of these animals to defining disease targets and active compounds for neuroprotection in Huntingtons disease (Parker et al., Nature Genet 2005). We analyzed the effects of mutant polyQ pathogenicity using FACS-purified neurons and oligonucleotide microarrays from Agilent. Data classification using C. elegans gene networks and the comparison of our data to microarray data from other models of mutant huntingtin neurotoxicity will be presented.

Alex Parker et al. (2006) Neuronal Development, Synaptic Function, and Behavior Meeting "Studying the modifier genes of neuronal cell response to mutant huntingtin expression in C. elegans"

Christian Neri, Alex Parker, Maryline Mage, Emmanuel Lambert, Sabine Cloax, Cendrine Tourette, Salima Abderrahmane, Beate Gertsbrein

[Neuronal Development, Synaptic Function, and Behavior Meeting, 2006]

Huntington"s disease (HD) is a neurodegenerative disease caused by polyglutamine expansion in huntingtin. Although HD is inherited, its age of onset shows great variability, suggesting neuronal dysfunction and death in HD is influenced by modifier genes. To study how the neuronal cell may respond to mutant htt, we have developed C. elegans transgenics that overexpress mutant N-terminal htt fused to fluorescent proteins in touch receptor neurons. This model shows neuronal dysfunction without cell death, an effect accompanied by aggregate formation and dystrophy of neuronal processes (Parker et al., PNAS 2001). To study the pathways underlying these transgenic phenotypes, we use a combination of C. elegans mutants, RNAi screens, microarray analysis, and physiological analysis. This effort has led us to identify sirtuin activation as a neuroprotective mechanism against the effects of mutant htt expression, an effect mediated by daf-16/FOXO, (Parker et al., Nature Genetics 2005). Our findings indicated that modulators of organismal longevity like sir2 and FOXO may modify early-stage pathogenesis of neurodegenerative diseases, defining a new strategy with therapeutic potential. We will present an update on the progress made with our models in better understanding how mutant htt may be toxic to the neuronal cell and how neuroprotection may be achieved.

Vazquez-manrique, Rafael et al. (2011) International Worm Meeting "AMPK activation is protective in models of neuron dysfunction and death in Huntington's disease."

Deglon, Nicole, Neri, Christian, Offner, Nicolas, Vazquez-manrique, Rafael, Cambon, Karine, Orfila, Anne-marie, Darbois, Aurelie

[International Worm Meeting, 2011]

Huntington's disease (HD) is a neurodegenerative disease caused by polyglutamine (polyQ) expansion in the huntingtin protein (Htt). Expression of the first exon of Htt containing an expanded polyQ produces neuronal dysfunction and axonal dystrophy in mechanosensory neurons in C. elegans (Parker et al., 2001). Genetic pathway analysis using this nematode model has emphasized a role for the longevity-promoting factor daf-16/FoxO in the protection of neurons from expanded polyQ toxicity (Parker et al., 2005). Here, we investigated the role of AMP-activated protein kinase (AMPK), a well-known energy sensor involved in lifespan and health span extension, on neuronal dysfunction in expanded-polyQ nematodes and vulnerability to cell death in mutant Htt striatal cells (HdhQ111 knock-in mice). In C. elegans, activating this enzyme (aak-2/AMPK) with metformin reduces the neuronal dysfunction caused by expanded polyQ expression. In contrast, aak-2 mutants show enhanced neuronal impairment. In striatal cells from HdhQ111 knock-in mice, reducing AMPK levels by siRNA treatment enhances the susceptibility to cell death of mutant htt cells, and metformin treatment has the opposite effect. Additionally, overexpressing AMPK reduced striatal neurodegeneration in a rat lentiviral-based fragment model of HD pathogenesis. Collectively, our results suggest that AMPK activation has therapeutic potential to protect from neuron dysfunction and degeneration in HD.

Kumar N et al. (1993) International C. elegans Meeting "Isolation of learning specific mutants in C. elegans."

Wen JYM, Morrison GE, van der Kooy D, Parker JA, Kumar N

[International C. elegans Meeting, 1993]

Nichols, Courtney Rose et al. (2013) International Worm Meeting "A role for the insulin signaling pathway in development of neuronal aging markers in a polyglutamine protein aggregation C. elegans model."

Parker, J. Alex, Nichols, Courtney Rose, Driscoll, Monica, Neri, Christian, Vayndorf, Elena, Taylor, Barbara

[International Worm Meeting, 2013]

Neurodegenerative diseases, such as Huntington's, Alzheimer's, and Parkinson's disease, result in the progressive loss of neuronal structure and function with age. Many neurodegenerative disorders are caused by genetic mutations and characterized by toxic aggregation of proteins within neurons. We explored the mechanism of accelerated neuronal aging in a polyglutamine (polyQ) protein aggregation model through genetic manipulation. Caenorhabditis elegans expressing the first 57 amino acids of human huntingtin protein with a toxic polyglutamine chain (polyQ128) fluorescently labeled with CFP in YFP-labeled mechanosensory neurons (Parker et al, 2001) were used to monitor neuronal aging phenotypes. We found an age-associated increase in aberrant neuronal morphology, protein aggregation, and functional impairment of the mechanosensory neurons expressing toxic 128 polyQ. We also tested the hypothesis that the insulin signaling pathway is involved in morphological and functional health of aging mechanosensory neurons using neuron-specific RNA interference (RNAi). Furthermore, we measured levels of endogenous oxidative stress and lifespan of aging animals that contain toxic polyQ128 repeats following RNAi manipulation of the insulin signaling pathway. Overall, we found that DAF-16/FOXO is neuroprotective in this accelerated aging model, which corroborates previous findings on the role of DAF-16/FOXO in polyQ128 young adults (Parker et al. 2005). To further characterize overall muscle and neuronal health, we measured action potentials of pharyngeal muscle contractions and neurons that innervate the pharynx using microfluidic electropharyngeography (EPG). In total, our observations support that insulin signaling via DAF-16/FOXO is a mechanism through which accelerated aging and neurodegeneration occurs in this model.

Tauffenberger A et al. (2010) Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI "Glucose rescues age-dependent proteotoxicity in C.elegans"

Vaccaro A, Parker A, Tauffenberger A

[Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI, 2010]

As the population shifts to an older demographic, it has become important to find new therapeutic ways to combat neurological disease. To model neurodegeneration we use a C. elegans model for Huntington's Disease (HD). HD is a late-onset fatal neurodegenerative disease caused by an expanded CAG trinucleotide repeat that codes for glutamine (Q), and is characterized by the intracellular accumulation of mutant proteins. Our transgenic C. elegans strains expressing normal (19Q) and expanded mutant (128Q) polyQ in mechanosensory neurons show a progressive and polyQ size dependent loss-of-mechanosensation and increased-aggregation phenotypes in vivo1. The difference between mutant (128Q) and controls (19Q) is easily distinguished and the effects of genetic and pharmacological modifiers can be rapidly derived from small populations of animals2. Disrupted metabolism is one of a number of mechanisms that may contribute to neurodegeneration. Indeed, conditions that reprogram metabolism like dietary restriction are active areas of investigation in efforts to identify new therapeutic targets. We have observed that opposite to the effects on organismal lifespan, excess glucose suppresses toxicity in worm models of proteotoxicity. Furthermore, many of the genes essential for glucose-mediated suppression of proteotoxicity are in common with genes required for dietary restriction. These data demonstrate that glucose enrichment and dietary restriction utilize many of the same genetic pathways with opposite metabolic endpoints both of which are beneficial in models of neurodegeneration. A summary of our recent data will be presented. 1.Parker, J.A. et al. Expanded polyglutamines in Caenorhabditis elegans cause axonal abnormalities and severe dysfunction of PLM mechanosensory neurons without cell death. Proc Natl Acad Sci U S A 98, 13318-23 (2001). 2.Parker, J.A. et al. Resveratrol rescues mutant polyglutamine cytotoxicity in nematode and mammalian neurons. Nat Genet 37, 349-50 (2005).

Aggad, D. et al. (2015) International Worm Meeting "Drug screening in C. elegans leads to a clinical trial for amyotrophic lateral sclerosis."

Maios, C., Drapeau, P., Korngut, L., Aggad, D., Armstrong, G., Patten, K., Robitaille, R., Parker, JA.

[International Worm Meeting, 2015]

Amyotrophic lateral sclerosis (ALS) is a fatal, incurable neurodegenerative disease characterized by a progressive loss of motor neurons in the brain and spinal cord. A better understanding of disease pathogenesis is crucial for disease diagnosis and intervention strategies. To this end, there has been a revolution in identifying the genetic causes of both sporadic and familial ALS. ALS is caused by mutations in a growing number of genes, one of which being TARDBP, which codes for TDP-43 and is a major component of neuronal inclusions. Since TDP-43 is evolutionarily conserved we turned to the model organisms C. elegans and zebrafish to learn more about their biological functions and screen for potential therapeutic modifiers. We generated C. elegans and zebrafish models expressing wild-type or mutant human TDP-43 that reflect aspects of ALS. To explore the potential of our models in identifying chemical suppressors of mutant TDP-43 neuronal toxicity, we screened a set of chemical libraries for FDA-approved compounds with potential neuroprotective properties. Chemical libraries were screened using motility and stress response assays with mutant TARDBP worms and hits were validated in zebrafish using motility assays. The expression of mutant TDP-43 in worm motor neurons produced robust, adult onset motility defects and in both models this was caused by motor neuron deficits. We isolated a number of chemical suppressors of mutant TARDBP toxicity. Under normal conditions TDP-43 regulates specific aspects of the cellular stress response. The transgenic models allowed us to isolate chemical suppressors of motor defects. In particular, several neuroleptics protected against development of motor phenotypes by maintaining neuromuscular transmission. One compound, pimozide, is also protective in a mouse model of ALS, and is currently being tested in a clinical trial (Health Canada PIMOZIDE_ALS-001). Together these data provide clues to help unravel the mechanism for TDP-43 toxicity that should also provide leads for early drug discovery.Supported by the US Dept. Defense CDMRP-USAMRMC/ALSRP, Canadian Institutes of Health Research, ALS Canada and the Muscular Dystrophy Association.