Robert M Steven et al. (2001) International C. elegans Meeting "THE IDENTIFICATION OF PROTEINS THAT INTERACT WITH UNC-73/TRIO IN C. ELEGANS"

Terry Kubiseski, Joseph Culotti, Tony Pawson, LiJia Zhang, Robert M Steven

[International C. elegans Meeting, 2001]

C. elegans unc-73 , also known as trio in mammals and Drosophila , was the first gene of this family to be identified with a role in axon pathfinding. The axons of many neurons fail to reach their target tissues and often travel along abnormal pathways in unc-73 mutant animals. Recently it was also discovered that trio is required for the correct formation of photoreceptor, CNS and motor axon pathways in Drosophila . Experiments in both C. elegans and Drosophila reveal that UNC-73/Trio function involves signaling through the Rac GTPase and its downstream effectors to regulate the cytoskeletal rearrangements necessary for growth cone migrations. unc-73 is a complex gene predicted to encode seven overlapping transcripts. Together the intracellular proteins encoded by these transcripts contain, from N terminus to C terminus, eight spectrin-like repeats, a tandem Dbl homology (DH) and pleckstrin homology (PH) domain combination, an SH3 domain, a second DH/PH domain combination, an immunoglobulin domain and a fibronectin type III domain. DH domains are known to have RhoGEF activity, which is the ability to activate members of the Rho family of GTPases. The first UNC-73 DH/PH domain specifically activates the Rac GTPase while the second domain is specific to Rho. Interestingly, animals with a mutation that eliminates the activity of the first DH domain are uncoordinated (Unc), presumably as a result of axon guidance defects, while a deletion of the exons encoding the second DH domain results in early larval lethality. Two approaches are being used to identify proteins that interact with UNC-73. First, a genetic screen is being set up based on the observation that overexpression of a construct encoding a truncated form of UNC-73, containing just the DH-1/PH-1 and SH3 domains, in wild-type animals results in a severe Unc phenotype, similar in character to that of the moderate to severe alleles of unc-73 . An integrated line containing this construct is fully penetrant for the Unc phenotype and will be used in a screen for nonUnc suppressors. Mutations in genes that might be expected to suppress this dominant phenotype include those that act downstream of the Rac GTPase pathway. Mutations in genes upstream of unc-73 that activate the UNC-73 DH1 domain may also suppress. Second, a yeast two hybrid screen was used to identify several proteins that potentially interact with UNC-73. One of the interacting proteins, also confirmed by pull-down experiments with bacterially expressed proteins, is an actin-binding protein. This is consistent with our hypothesis that UNC-73 is involved in the regulation of the actin cytoskeleton.

Kreeger KY (1996) The Scientist "Hot papers: Programmed cell death."

Kreeger KY

[The Scientist, 1996]

Biologist H. Robert Horvitz discusses the genetics of cell death in the nematode C. elegans.

Shuang Hu et al. (2008) C.elegans Neuronal Development Meeting "Regulation of Locomotion by UNC-73 RhoGEF-2 Isoforms"

Robert Steven, Tony Pawson, Shuang Hu

[C.elegans Neuronal Development Meeting, 2008]

unc-73 is a complex gene that functions in multiple tissue types at different stages of C. elegans development. It is required for normal fertility, pharynx and vulval muscle function and for specific cell migrations. In the nervous system unc-73 also plays a role in axon guidance and neurotransmission (Steven et al, 1998; Steven et al, 2005). unc-73 encodes at least eight protein isoforms that are differentially expressed. These isoforms are thought to function primarily through the activity of their respective RhoGEF domains, which catalyze the activation of members of either the Rac or Rho GTPase subfamilies. Here we attempt to better define the role of the UNC-73 isoforms in neurotransmission. Isoform specific rescue experiments previously revealed that the RhoGEF-2 domain-containing UNC-73C1, C2/F and E isoforms act redundantly to regulate the speed of locomotion. Transgenic animals lacking these isoforms have a lethargic movement phenotype that can be rescued by the expression of any individual isoform from this group. By using different cell-specific or inducible promoters to drive the expression of UNC-73E in transgenic unc-73 mutant animals we have begun to identify the temporal and spatial requirements of UNC-73E function. We have found that UNC-73E acts within the nervous system to physiologically regulate locomotion. It was recently reported that UNC-73E is an effector of Galphaq (Williams et al, 2007), however, it is still not clear how the UNC-73 isoforms function with Rho to regulate neurotransmission. In our hands the lethargic unc-73 mutants are not aldicarb resistant, which suggests that the UNC-73 RhoGEF-2 isoforms do not have an obvious defect in acetylcholine neurotransmitter release. This is consistent with the observation that restricted expression of UNC-73E in the cholinergic motor neurons does not rescue the unc-73lethargic movement phenotype. Epistasis analysis has revealed that activating mutations in different components of the Galphas pathway rescue the unc-73 lethargic movement phenotype caused by the loss of the UNC-73C1, C2/F and E isoforms. We are examining the possibility that these UNC-73 isoforms are required for the production or release of a neuromodulator that functions upstream of a Galphas-coupled receptor.

Thomas JH et al. (1994) Worm Breeder's Gazette "lin-36, a Class B Synthetic Multivulva Gene, Encodes a Novel Protein"

Thomas JH, Horvitz HR

[Worm Breeder's Gazette, 1994]

lin-36, a Class B Synthetic Multivulva Gene, Encodes a Novel Protein Jeffrey H. Thomas and H. Robert Horvitz, HHMI, Dept. Biology, MIT, Cambridge, MA 02139, USA

Goff SP (1999) Cancer Research "Genetic control of programmed cell death in the nematode Caenorhabditis elegans - Introduction."

Goff SP

[Cancer Research, 1999]

It is an honor and a great pleasure to introduce Dr. Robert Horvitz to you as the 1998 recipient of the Alfred Sloan Prize of the General Motors Cancer Research Foundation. Let me begin by telling you a little bit about Bob's

Alexandra Byrne et al. (2008) C.elegans Neuronal Development Meeting "UNC-73 Functions Autonomously in an UNC-40 Pathway to Regulate Muscle Arm Extension"

Guillermo Selman, Alexandra Byrne, Peter Roy, Kevin Chan

[C.elegans Neuronal Development Meeting, 2008]

The body muscles of C. elegans extend plasma membrane, called muscle arms, to the nearest nerve cord. There, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Previous work demonstrated that muscle arms are attracted to motor axons, irrespective of their position, suggesting that motor axons secrete a chemotropic cue that guides muscle arm extension. To identify genes required for muscle arm extension, we screened for mutants with fewer muscle arms. One of the resulting mutants, tr117, extends fewer than 50% of the normal number of muscle arms. Genetic mapping, complementation tests and sequencing revealed that tr117 is allelic to unc-73/Trio, which encodes many isoforms of a guanine nucleotide exchange factor. Specifically, tr117 encodes a missense polymorphism in the RhoGEF-1 domain of unc-73. Expression of a YFP-tagged UNC-73B isoform (a kind gift from Robert Steven) in the body wall muscles rescues the muscle arm defect of unc-73(e936) mutants, demonstrating that UNC-73 functions cell autonomously to regulate muscle arm extension. We found that functional UNC-73::YFP is enriched at the leading edge of muscle arm termini, consistent with a role in regulating muscle arm extension. Concurrent work in our lab demonstrated that the UNC-40/DCC transmembrane receptor likely directs muscle arm extension to the nerve cord (see Chan et al. abstract): UNC-40 functions autonomously to regulate muscle arm extension and is also enriched at the muscle arm termini. As part of a systematic search for genes required to localize UNC-40::YFP to the muscle arm termini, we discovered that UNC-40::YFP localization to the termini is dramatically deficient in an unc-73(e936) background. The disrupted sub-cellular localization of UNC-40 is unlikely a secondary consequence of the fewer muscle arms of e936 because other Madd mutants with similarly disrupted muscle arm extension, including madd-2 (a tripartite motif superfamily member), unc-60B (ADF/Cofilin), and unc-95 (a paxillin homolog) exhibit normal localization of UNC-40::YFP. These results suggest that the role of UNC-73 in muscle arm extension is (at least) to properly localize UNC-40 to the leading edge of extending membrane, consistent with recently proposed models of UNC-73 function in the nervous system.

Chen X et al. (2015) Mol Neurodegener "Erratum to: Ethosuximide ameliorates neurodegenerative disease phenotypes by modulating DAF-16/FOXO target gene expression."

McCue HV, Chen X, Morgan A, Kashyap SS, Barclay JW, Kraemer BC, Burgoyne RD, Wong SQ

[Mol Neurodegener, 2015]

The original version of this article [1] unfortunately contained a mistake. The author list contained a spelling error for the author Hannah V. McCue. The original article has been corrected for this error. The corrected author list is given below:Xi Chen, Hannah V. McCue, Shi Quan Wong, Sudhanva S. Kashyap, Brian C. Kraemer, Jeff W. Barclay, Robert D. Burgoyne and Alan Morgan

Rachel Wragg et al. (2008) C.elegans Neuronal Development Meeting "Octopamine inhibits aversive responses to 30 and 100% octanol through two different G-protein coupled receptors"

Sarah Miller, Richard Komuniecki, Robert Steven, Lindsay Hughes, Rachel Wragg

[C.elegans Neuronal Development Meeting, 2008]

Nematodes lack an autonomic nervous system and epinephrine/norepinephine and instead appear to use tyramine (TA) and octopamine (OA) to modulate many key behaviors. In Caenorhabditis elegans distinct TA/OA neurons, receptors and behaviors have been identified. Previously, we demonstrated that OA abolishes 5-HT dependent increases in responses to dilute (30%) octanol through the G-protein coupled receptor, F14D12.6 (Wragg et al., 2007). The ASH sensory neurons are necessary and sufficient for detection of 30% octanol, and based on neuron-specific rescue, F14D12.6 appears to function in the ASHs to inhibit 5-HT mediated aversive responsiveness to dilute octanol. In contrast, the ADL and AWB sensory neurons in addition to the ASHs are all involved in the detection of 100% octanol (Chao et al., 2004). In the present study, we have demonstrated that OA inhibits aversive responses to 100% octanol in the presence or absence of food or 5-HT and this inhibition requires a different, previously uncharacterized, G-protein coupled receptor, Y54G2A.35, but not F14D12.6. OA inhibition in y54g2a.35(tm2104) null mutants can be restored by the expression of a full length y54g2a.35 transgene that includes 5 kb upstream of the predicted ATG. We have confirmed the WORMBASE prediction of the y54g2a.35 cDNA by RT-PCR. Interestingly, this cDNA predicts a receptor with an extremely short N-terminus that is most identical to mammalian alpha2A adrenergic receptors. Y54G2A.35 clusters with invertebrate OA receptors that couple to Galphaq. We are currently characterizing the pharmacology and coupling of Y54G2A.35 after heterologous expression in mammalian cells and Xenopus oocytes. Since two different OA receptors, F14D12.6 and Y54G2A.35 appear essential for OA inhibition of aversive responses to 30 and 100% octanol, respectively, future studies will focus on the identification of the specific neurons and signaling molecules involved in these two different pathways of OA inhibition. This work supported by NIH grant AI45147 to RWK.

Casey DL (1999) Human Genome News "International team delivers C. elegans sequence."

Casey DL

[Human Genome News, 1999]

For the first time, scientists have the nearly complete genetic instructions for an animal that, like humans, has a nervous system, digests food, and reproduces sexually. The 97-million-base genome of the tiny roundworm Caenorhabditis elegans was deciphered by an international team led by Robert Waterston and John Sulston. The work was reported in a special issue of the journal Science (December 11, 1998) that featured six articles describing the history and significance of the accomplishment and some early sequence-analysis results.

Brownlee DJA et al. (1996) Parasitol Today "Nematode neuropeptides: Localization, isolation and functions."

Holden-Dye L, Brownlee DJA, Walker RJ, Fairweather I

[Parasitol Today, 1996]

Historically, peptidergic substances (in the form of neurosecretions) were linked to moulting in nematodes. More recently, there has been a renewal of interest in nematode neurobiology, initially triggered by studies demonstrating the localization of peptide immunoreactivities to the nervous system. Here, David Brownlee, Ian Fairweather, Lindy Holden-Dye and Robert Walker will review progress on the isolation of nematode neuropeptides and efforts to unravel their physiological actions and inactivation mechanisms. Future avenues for research are suggested and the potential exploitation of peptidergic pathways in future therapeutic strategies