Mark J Alkema et al. (2003) International Worm Meeting "Tyramine Modulates Foraging Behavior and Head Movements."

Mark J Alkema, Bob Horvitz, Melissa Hunter-Ensor, Niels Ringstad

[International Worm Meeting, 2003]

Tyramine and octopamine are biogenic amines implicated in several invertebrate behaviors. Tyramine biosynthesis requires the decarboxylation of tyrosine. Octopamine is synthesized by subsequent -hydroxylation of tyramine. We obtained mutant strains carrying deletions in a putative C. elegans amino acid decarboxylase gene (tdc-1) (gifts from M. Dong and M. Koelle) and a tyramine--hydroxylase gene (tbh-1). Using HPLC analysis and radioenzymology we showed that both the tdc-1 and tbh-1 deletion mutants lack octopamine, indicating that tdc-1 and tbh-1 are required for octopamine biosynthesis. Furthermore, we showed that TDC-1 can decarboxylate tyrosine in vitro. TDC-1 and TBH-1 expression overlap in the RIC interneurons and the gonadal sheath cells. TDC-1, but not TBH-1, is expressed in the RIM motor neurons and four UV cells. The co-expression of TDC-1 and TBH-1 suggest that the RIC interneurons and gonadal sheath cells are octopaminergic, whereas the RIM motor neurons and UV cells are tyraminergic. C. elegans foraging behavior consists of forward locomotion interrupted by brief reversals. tdc-1 mutants, unlike tbh-1 mutants, have a marked increase in spontaneous reversals, suggesting that tdc-1 plays a role in the regulation of backward and forward locomotion. Foraging is usually accompanied by oscillatory head movements. In wild-type animals these head movements are suppressed when backward locomotion is induced by anterior touch. tdc-1 but not tbh-1 mutants fail to suppress head movements during backward locomotion. We characterized the neural circuit underlying the modulation of foraging behavior and head movements by laser ablation studies. Ablations of the RIMs but not the RICs increased spontaneous reversals. In addition, animals in which the RIMs are ablated fail to suppress head movements upon anterior touch. The RIMs synapse onto the head muscles and the RMD and SMD motor neurons. The RIMs also synapse onto the AVB forward command neurons and are connected by gap junctions to the AVA backward command neurons. Our ablation experiments indicate that the RIMs link suppression of head movements to a backing response mediated by anterior touch. We hypothesize that tyramine controls foraging and head movements by acting as an inhibitory neurotransmitter on the head muscles and interneurons that coordinate backward and forward locomotion. To identify new factors that function in tyraminergic signaling we screened for mutants that fail to suppress head movements upon anterior touch. We have identified over 50 mutants, which we are characterizing and assigning to complementation groups.

Emerson F et al. (2020) Elife "A memory of longevity."

Lee SS, Li CL, Emerson F

[Elife, 2020]

Worms with increased levels of the epigenetic mark H3K9me2 have a longer lifespan that can be passed down to future generations.

Pirri, Jennifer K et al. (2013) International Worm Meeting "Synaptic engineering: an ionic switch of behavior."

Alkema, Mark J, Rayes, Diego, Pirri, Jennifer K

[International Worm Meeting, 2013]

The unraveling of the human brain connectivity map is considered by many as an essential step in the understanding how the brain controls behavior and how brain malfunction underlies behavioral disorders. Although the behavioral output of neural networks depends on a delicate balance between excitatory and inhibitory synaptic connections, the neural connectivity map does not carry information about the sign of synaptic connections.. Is it possible to reverse the behavioral output of a neural circuit by changing the sign of a synapse? Does the sign of a synapse provide constraints to the development, the specification, and behavioral output of a connectome? Here, we address these questions using the neuronal circuit that mediates the C. elegans escape response. In the escape response a single pair of tyraminergic neurons coordinate the suppression of head movements with backward locomotion through the activation of an inhibitory postsynaptic receptor, the tryamine-gated chloride channel LGC-55. LGC-55 is a member of the Cys-loop ligand gated ion channel (LGIC) family, whose ion selectivity is determined by the M2 domain. Amino acid substitution of the M2 domain LGC-55 allowed us to change the selectivity from Cl- to Na+ and K+. We generated transgenic animals that express the excitatory LGC-55 cation channel under control of its endogenous promoter in an LGC-55 anion mutant background. A fluorescently tagged LGC-55 cation channel localizes opposite to tyramine release sites indistinguishable from the wild-type LGC-55 anion channel. Exogenous tyramine induces neck muscle relaxation and backward locomotion in the wild-type LGC-55 anion animals, but induces neck muscle contraction and forward locomotion in transgenic animals that express the LGC-55 cation. Similarly, touch or optogentically induced release of endogenous tyramine triggers opposite behavioral responses in animals that express the LGC-55 cation vs LGC-55 anion channel. Our data show that changing the nature of a synapse within a neural circuit can reverse its behavioral output and indicate that the C. elegans connectome is established independent of the nature of synaptic activity or behavioral output.

Wu Y et al. (2017) Curr Top Dev Biol "Regulation of Cell Polarity by PAR-1/MARK Kinase."

Wu Y, Griffin EE

[Curr Top Dev Biol, 2017]

PAR-1/MARK kinases are conserved serine/threonine kinases that are essential regulators of cell polarity. PAR-1/MARK kinases localize and function in opposition to the anterior PAR proteins to control the asymmetric distribution of factors in a wide variety polarized cells. In this review, we discuss the mechanisms that control the localization and activity of PAR-1/MARK kinases, including their antagonistic interactions with the anterior PAR proteins. We focus on the role PAR-1 plays in the asymmetric division of the Caenorhabditis elegans zygote, in the establishment of the anterior/posterior axis in the Drosophila oocyte and in the control of microtubule dynamics in mammalian neurons. In addition to conserved aspects of PAR-1 biology, we highlight the unique ways in which PAR-1 acts in these distinct cell types to orchestrate their polarization. Finally, we review the connections between disruptions in PAR-1/MARK function and Alzheimer's disease and cancer.

Benecke M et al. (1994) Worm Breeder's Gazette "DNA Fingerprinting in C. elegans - An Approach."

Epplen JT, Schierenberg E, Benecke M

[Worm Breeder's Gazette, 1994]

DNA fingerprinting in C. elegans - an approach Mark Beneckea, Jorg T. Epplenb and Einhard Schierenberga a Zoologisches Institut der Univeritat, 50923 Koln, Germany b Ruhr-Universitat, Ab1. fur Molekulare Humangenetik, 44780 Bochum, Germany

McGhee JD (1987) Biochemistry "Purification and characterization of a carboxylesterase from the intestine of the nematode Caenorhabditis elegans."

McGhee JD

[Biochemistry, 1987]

The major intestinal esterase from the nematode Caenorhabditis elegans has been purified to essential homogeneity. Starting from whole worms, the overall purification is 9000-fold with a 10% recovery of activity. The esterase is a single polypeptide chain of Mr 60,000 and is stoichiometrically inhibited by organophosphates. Substrate preferences and inhibition patterns classify the enzyme as a carboxylesterase (EC 3.1.1.1), but the physiological function is unknown. The sequence of 13 amino acid residues at the esterase N- terminus has been determined. This partial sequence shows a surprisingly high degree of similarity to the N-terminal sequence of two carboxylesterases recently isolated from Drosophila mojavensis [Pen, J., van Beeumen, J., & Beintema, J. J. (1986) Biochem. J. 238, 691-699].

Butkevich E et al. (2016) Sci Rep "Phosphorylation of FEZ1 by Microtubule Affinity Regulating Kinases regulates its function in presynaptic protein trafficking."

Grosche J, Erck C, Urlaub H, Nikolov M, Klopfenstein DR, Butkevich E, Chua JJ, Hartig W, Schmidt CF

[Sci Rep, 2016]

Adapters bind motor proteins to cargoes and therefore play essential roles in Kinesin-1 mediated intracellular transport. The regulatory mechanisms governing adapter functions and the spectrum of cargoes recognized by individual adapters remain poorly defined. Here, we show that cargoes transported by the Kinesin-1 adapter FEZ1 are enriched for presynaptic components and identify that specific phosphorylation of FEZ1 at its serine 58 regulatory site is mediated by microtubule affinity-regulating kinases (MARK/PAR-1). Loss of MARK/PAR-1 impairs axonal transport, with adapter and cargo abnormally co-aggregating in neuronal cell bodies and axons. Presynaptic specializations are markedly reduced and distorted in FEZ1 and MARK/PAR-1 mutants. Strikingly, abnormal co-aggregates of unphosphorylated FEZ1, Kinesin-1 and its putative cargoes are present in brains of transgenic mice modelling aspects of Alzheimer's disease, a neurodegenerative disorder exhibiting impaired axonal transport and altered MARK activity. Our findings suggest that perturbed FEZ1-mediated synaptic delivery of proteins arising from abnormal signalling potentially contributes to the process of neurodegeneration.

Maguire, Sean et al. (2011) International Worm Meeting "Behavioral adaptation of soil nematodes facilitates escape from predacious fungi."

Clark, Christopher M., Maguire, Sean, Alkema, Mark J., Pirri, Jennifer K.

[International Worm Meeting, 2011]

Animal nervous systems need to respond to challenges in their natural environment. This is epitomized by predator-prey interactions where survival depends on the animal's ability to escape. However, we have few insights into how natural selection has shaped the molecular and neural mechanisms of behavior. We investigated predator-prey interactions between C. elegans and predacious fungi that catch and devour nematodes using constricting rings as trapping devices. Gentle touch to the anterior half of the body of C. elegans induces an escape response in which the animal reverses and suppresses exploratory head movements. We found that the constricting rings of Drechslerella doedycoides catch early larval stages with a diameter similar to the trap opening. There is a delay between the ring entry and ring closure, which allows the animal to withdraw from the trap before getting caught. Tyramine-signaling mutants that fail to suppress head movements in response to touch are caught more efficiently than the wild type in constricting fungal rings. Competition experiments show that the suppression of head movements in response to touch is an ecologically relevant behavior that allows the C. elegans to smoothly retract from a fungal noose and evade capture. Behavioral analysis of other soil nematodes suggests that selective pressures imposed by predacious fungi have shaped the evolution of escape behavior of free-living soil nematodes.

Florman, Jeremy T. et al. (2021) International Worm Meeting "Chemical in vivo activation of C. elegans neurons using a histamine-gated cation channel"

Francis, Michael M., Florman, Jeremy T., Araya Budnik, Antonia, Alkema, Mark J.

[International Worm Meeting, 2021]

The ability to non-invasively activate and inactivate neurons in intact behaving animals provides powerful methods to study the functions of neural circuits. Recently, transgenic expression of a Drosophila melanogaster histamine-gated chloride channel (HisCl1) in C. elegans has enabled hyperpolarization of specific neurons in response to histamine (Pokala et al., 2014). The small molecule histamine is used as a transmitter in many species however C. elegans lack endogenous histamine signaling. We will present data to show that modification of the pore domain of this histamine-gated channel renders it selective to cations rather than anions. We find that cell specific expression of this modified channel, which we named HisCat1, enables histamine induced activation of neurons and can elicit specific behaviors. Pan-neuronal expression of HisCat1 induced uncoordinated seizure like behavior, whereas expression in cholinergic neurons caused hypercontraction and inhibited locomotion in animals exposed to histamine. When we expressed HisCat1 in serotonergic neurons, histamine exposure induced persistent pharyngeal pumping in the absence of food, consistent with the serotonin release. Finally, we demonstrate that HisCat1 can be used to depolarize non-neuronal tissues as expression in body-wall muscle induces calcium influx in response to histamine. Chemical activation using the HisCat1 channel provides a useful complement to existing optogenetic tools. Neuronal activation using HisCat1 appears to be stable over long durations, allowing prolonged activation that is more difficult to achieve with existing optogenetic methods. Furthermore, the HisCat1 channel can be combined with Channelrhodopsin and optical sensors such as GCaMP, so light and histamine can be used to activate and monitor several neurons independently in the same experiment. Therefore, HisCat1 is an effective means to non-invasively activate neurons in C. elegans and increases the existing toolkit of light induced sensors and ion channels. Pokala, N., Liu, Q., Gordus, A., Bargmann, C.I., 2014. Inducible and titratable silencing of Caenorhabditis elegans neurons in vivo with histamine-gated chloride channels. Proc. Natl. Acad. Sci. U. S. A. 111, 2770-5.

Skourti-Stathaki K et al. (2013) Mol Cell "Histone 3 s10 phosphorylation: "caught in the R loop!"."

Skourti-Stathaki K, Proudfoot NJ

[Mol Cell, 2013]

In this issue of Molecular Cell, Castellano-Pozo etal. (2013) describe a connection between R loop structures and histone 3 S10 phosphorylation (H3S10P), a mark of chromatin compaction. Their results constitute asignificant advance in our understanding of the role of R loops in genomic instability.