Head, Brian P. et al. (2013) International Worm Meeting "Whole genome expression analysis of C. elegans upon recovery from Salmonella enterica infection."

Head, Brian P., Aballay, Alejandro

[International Worm Meeting, 2013]

C. elegans are capable of mounting an immune response to a variety of pathogens. In the last decade, several major steps in the C. elegans innate immune response have been dissected including: 1) host surveillance pathways detect a pathogen and/or loss of homeostasis, 2) various intracellular signaling modules are activated in distinct cell types, and 3) immune effector molecules are produced at the site of infection (primarily the intestinal and hypodermal epithelia). Moreover, stress response pathways are activated to cope with cellular damage from both host immune effectors and pathogen-derived molecules. Much less is known about the physiology of the animal during recovery from an infection. Thus, we are utilizing the C. elegans-pathogen model to study recovery from infection by Salmonella enterica. After generating a "mild" Salmonella infection in the worm, we alleviate this infection by a combination of antibiotic treatment plus a change in food source. We demonstrate that "recovered" worms have a reduced bacterial burden and enhanced survival. To better understand the transcriptional response during recovery, we have utilized whole genome microarray technology. A variety of expected and novel gene clusters are altered during recovery. Representative genes from several clusters and other interesting candidates were confirmed by qRT-PCR. We are in the process of testing these genes for effects on recovery using standard reverse genetic techniques.

Head, Brian et al. (2015) International Worm Meeting "The role of GATA and other cell-autonomous transcription factors in mediating C. elegans recovery from acute pathogenic infection."

Head, Brian, Aballay, Alejandro

[International Worm Meeting, 2015]

The host response to acute microbial infection is complex but, at a broad level, involves sensing the pathogen, tolerating pathogen- and host-induced damage, reducing pathogen burden, and, finally, restoring homeostasis. This final phase is critical because if the host cannot restore physiological homeostasis, long-term problems can arise. In humans, these problems manifest in a multitude of disorders including recurrent pathogenic infection, inflammatory bowel diseases (IBDs), and gastritis/duodenitis.We are utilizing a C. elegans acute infection model to study recovery - the final restorative phase in the host response to acute microbial challenge. Our acute infection protocol consists of a short exposure to an intestinal pathogen - either Salmonella enterica or Pseudomonas aeruginosa - followed by antibiotic treatment and a change in food source. In previously published work, we demonstrated that "recovered" animals have a reduced bacterial burden and enhanced survival (similar to unchallenged animals). We also determined that the conserved GATA transcription factor ELT-2 acts in a cell-autonomous manner in the intestine to control the expression of genes that are important for recovery. This transcriptional output consists of genes involved in xenobiotic detoxification, redox regulation, and cellular homeostasis. We are continuining to define the network of cell-autonomous transcription factors (DAF-16, SKN-1) and non-cell autonomous signaling pathways (neuronal circuits) that shape gene expression patterns during recovery. Our recent results will be presented.

Brian Head et al. (2005) International Worm Meeting "Identification of Drp-1 Interacting Proteins"

Alexander M van der Bliek, Brian Head

[International Worm Meeting, 2005]

Mitochondrial division is essential for the development and survival of multicellular organisms. It is necessary for cell growth, homeostasis of energy production, and proper distribution of mitochondria during mitosis. Furthermore, experiments in mammalian tissue culture and C. elegans have shown that mitochondrial division plays a central role in programmed cell death, or apoptosis (Frank et al., 2001; Jagasia et al., 2005). Identification of the fundamental players Drp-1, Mdv-1, and Fis-1 has been useful in extending our basic knowledge concerning this essential process. However, it is certain that these components do not comprise an exhaustive list of mitochondrial division proteins. In the lab, we are using a combined biochemical/genetic approach in C. elegans to identify new components of the mitochondrial division apparatus. Biochemical purifications of TAP-tagged Drp-1, a GTPase that acts at mitochondrial division sites, will allow for the identification of Drp-1 binding partners. These proteins may be regulators of division or they may be novel components of the division complex. We are also conducting open-ended screens for enhancers of Drp-1 loss of function and using feeding RNAi to reveal genetic interaction with selected proteins.

Brian P Head et al. (2004) West Coast Worm Meeting "Identification of Novel Mitochondrial Division Proteins"

Alexander M van der Bliek, Brian P Head

[West Coast Worm Meeting, 2004]

Mitochondrial division is essential for the survival of eukaryotic organisms. It is necessary for cell growth, homeostasis of energy production, and proper distribution of mitochondria during mitosis. Furthermore, experiments in mammalian tissue culture have shown that mitochondrial division has a role in programmed cell death, or apoptosis (Frank, 2001). Identification of the fundamental players - Drp-1, Mdv-1, and Fis-1 - has been useful in extending our basic knowledge concerning this essential process. However, it is certain that these components do not comprise an exhaustive list of mitochondrial division proteins. In the lab, we are using a combined genetic/biochemical approach in C. elegans to identify new components of the mitochondrial division apparatus. Biochemical purifications of TAP-tagged Drp-1, a GTPase that acts at mitochondrial division sites, will allow for the identification of binding partners that also act in division. Erp-1, a protein identified by homology to components of the endocytic pit, is unlike Drp-1 because its' role in division is still hotly contested. In order to shed light on the true function of this highly conserved protein, we will purify Erp-1 using the TAP-tag system. Genetically, we will identify Drp-1 alleles and Drp-1 interacting proteins using various enhancer and lethal screens. Finally, in collaboration with other lab members, we are attempting to determine the role that phospholipids play in regulating mitochondrial division.

Hung, Wesley L. et al. (2019) International Worm Meeting "A compact circuit of interneurons coordinates two central pattern generators to control forward movement."

Sathaseevan, Anson, Meng, Jun, Zhen, Mei, Chang, Maggie M., Hung, Wesley L., Miller III, David M., Lu, Yangning, Wang, Ying, McWhirter, Rebecca, Luo, Linjiao

[International Worm Meeting, 2019]

In C. elegans, there are two central pattern generators (CPGs) that contribute to forward movement - the head CPG that controls the head swing, through currently unidentified neurons, and the body CPGs, which resides in the B-type motor neurons (Xu et al., 2017). The frequency and amplitude of the head swing and body undulation are tightly coupled to allow smooth, sinusoidal forward movement. We show here that the descending interneurons, AVG and RIF, play a critical role in two aspects of forward movement: forward speed modulation and head-body coordination. While AVG is not essential for locomotion, the loss of AVG results in animals with reduced forward speed and an increased tendency to remain in a pausing/resting state. Conversely, optogenetic activation of AVG alone rapidly increases forward velocity. This effect requires gap junction-mediated activation of RIFL/R, which subsequently activates the premotor interneurons AVBL/R to increase activity of the forward movement-driving B motor neurons. When head swinging is inhibited, body undulation is decreased. Conversely, increased head swinging frequency leads to increased body undulation frequency to potentiate higher forward velocity. This suggests communication between the head and body CPGs. Our preliminary results suggest that AVG may also be required to coordinate the head and body CPGs. Activation of AVG was sufficient to drive body bends even when head swinging was inhibited. Increased head swinging is not able change body undulation when AVG is ablated. We propose that the descending interneuron circuit (AVG-RIF-AVB) permits generation of adaptive forward movement by modulating forward speed and linking the head and body CPGs. Xu, T. et. al. PNAS May 8, 2018 115 (19) E4493-E4502

Ouellette, Marie-Helene et al. (2021) International Worm Meeting "Neurogenetics of modulatory cholinergic signaling in C. elegans interneurons"

Hendricks, Michael, Ouellette, Marie-Helene

[International Worm Meeting, 2021]

We previously identified a small circuit that integrates both sensory and motor input, involving a glutamatergic interneuron (RIA) that receives cholinergic feedback from head motor neurons (SMDs). RIA is functionally and spatially subdivided into compartments corresponding to sensory input and reciprocal motor domains. Motor input, which is mediated specifically through GAR-3 mAChRs, is received in phase with head movement during locomotion, leading to compartmentalized local calcium events and gait regulation. We found that a novel phenotype we named "head lifting" (movement of the worm's anterior section along the Z axis) appears to strongly correlate with disruption of RIA compartmentalization. Head lifting arises from bilateral (DV) activation of head muscles and occurs preferentially at particular points in the locomotion cycle. Here, we characterize this phenotype and use it to probe the genetics of compartmentalized signals in RIA.

Aspock G et al. (1997) International C. elegans Meeting "HOMEOBOX GENES IN HEAD DEVELOPMENT"

Aspock G, Cassata G, Browning M, Burglin TR

[International C. elegans Meeting, 1997]

We found that ceh-2 is an orthologue of the head/brain development genes empty spiracles and Emx in Drosophila and vertebrates, respectively (80% identity in the homeodomain). Antibodies, GFP and lacZ constructs show expression in the anterior of the pharynx, in e2, m2 and several neurons (I3, M4, NSML/R, M3L/R). In addition, we see expression in the vulva. This dual expression in the head and the body is reminiscent of ems, which plays a role in the head, as well as in the posterior spiracles. To approximate the loss-of-function phenotype, antisense RNA injection experiments are currently being performed. The restricted expression of ceh-2 in the anterior of the pharnyx poses an intriguing evolutionary question. Did the anterior of the pharynx evolve originally from head structures? Thus, to investigate head and brain development further, we have generated GFP constructs for an orthodenticle orthologue, another homeobox gene which has been shown to play an important role in head development in flies. Expression is seen in sensory neurons in the head, which is consistent with expression patterns of the vertebrate Otx genes. Further, we are in the process of constructing and examining GFP constructs for sine oculis, Bar, NEC and ro homeobox gene orthologues. Another gene, which might play a role in head develpoment is ceh-21, which has a cut domain. However, it is not an orthologue of Drosophila cut. Rather, together with 4 other C. elegans genes and the new rat HNF-6 factor, it forms a novel family, CENF. We are now examinating GFP constructs. Antisense injection of ceh-21 showed embryos and larvae with abnormal head structures. Thus we want to examine the role of CENF genes in head development.

Ransom D et al. (1995) International C. elegans Meeting "DISRUPTIVE MYOSIN HEADS"

De Stasio E, Ransom D, Sharp S, Alberico C

[International C. elegans Meeting, 1995]

smg-dependent dominant alleles of unc-54 are hypothesized to produce truncations of myosin head domains responsible for disrupted muscle organization. Our goal is to test this hypothesis. We used PCR-directed mutagenesis to create successive stop codons at specific sites in the myosin head domain. Sites chosen include the head/rod junction, the carboyx-terminal end of a highly conserved domain at amino acid 519, and amino acid 417 which mimics a non-dominant unc-54 null allele (negative control). PCR products were cloned into a low copy vector which lacks rod-encoding sequences.

Clark C M et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "Optogenetic analysis of a C. elegans escape response"

Clark C M, Alkema M J, Maguire S M

[Neuronal Development, Synaptic Function and Behavior, Madison, WI, 2010]

In response to gentle anterior touch, C. elegans moves backward and ceases exploratory head oscillations. Reinitiation of forward locomotion is accompanied by a steep ventral bend (omega turn). In a model for the neural circuit of the escape response, the touch sensory neurons (ALM/AVM) activate the backward locomotion command neurons (AVA), and inhibit the forward locomotion command neurons (AVB); activation of the AVA then activates the tyraminergic motor neurons (RIM). Tyramine release from the RIM modulates the cessation of head oscillations and inhibition of forward locomotion. We expressed the light-activated cation channel, Channelrhodopsin-2, in the ALM/AVM, AVA, and RIM, and quantified reversal behavior and exploratory head oscillations. Photo-activation of either the ALM/AVM, AVA, or RIM neurons resulted in the efficient suppression of head oscillations. However, only activation of the mechanosensory neurons yielded long reversals. We found that tyramine deficient, tdc-1, animals and tyramine-gated chloride channel, lgc-55, mutants expressing ChR2 in the mechanosensory or RIM neurons exhibited shorter reversals and failed to suppress head oscillations in response to blue light. Our findings indicate that tyramine release from the RIM neurons is sufficient for the suppression of head oscillations. Furthermore, our findings suggest that the inhibition of the forward command program is required to induce long reversals.

S Aslam et al. (1999) International C. elegans Meeting "Identification of fork head transcription factors expressed during C. elegans embryogenesis."

P Bauer, A Mounsey, S Aslam, IA Hope, C Royall

[International C. elegans Meeting, 1999]

The pes-1 gene was identified in a promoter trapping screen for C. elegans genes expressed in specific cell lineages during early embryogenesis. The predicted PES-1 proteins have homology to the fork head family of transcription factors which includes members from vertebrates, Drosophila and yeast. Most amino acid identity is in a 60 amino acid domain which has been shown to have DNA-binding activity. This suggests that the fork head gene family encodes transcription factors involved in the developmental control of other genes. We have sought to identify fork head transcription factors which could function to control events in early C. elegans embryogenesis by identifying those expressed at this stage of development. The C. elegans genome sequencing project has provided the entire complement of fork head genes in the genome. Eleven novel fork head genes have been revealed in addition to the four previously identified. Reporter gene constructs have been made for ten of these eleven genes, five of which show embryonic expression or an embryonic component in their expression pattern. These embryonic expression patterns are now being characterized in terms of the cell lineage. We plan to examine the function of the embryonically expressed fork head genes using RNA interference.