Dana L. Miller et al. (2007) International Worm Meeting "Adaptation to hydrogen sulfide increases thermotolerance and lifespan."

Mark B. Roth, Dana L. Miller

[International Worm Meeting, 2007]

Hydrogen sulfide (H₂S), which is naturally produced in animal cells, has been shown to effect physiological changes that improve the capacity of mammals to survive environmental changes. We have investigated the physiological response of C. elegans to H₂S to begin to elucidate the molecular mechanisms of H₂S action. We show that nematodes exposed to H₂S are apparently healthy and do not exhibit phenotypes consistent with metabolic inhibition. However, we observed that animals exposed to H₂S had increased thermotolerance and lifespan and survived subsequent exposure to otherwise lethal concentrations of H₂S. Increased thermotolerance and lifespan is not observed in the sir-2.1(ok434) deletion mutant exposed to H₂S. However, mutants in the insulin signaling pathway (both daf-2 and daf-16), animals with mitochondrial dysfunction (isp-1 and clk-1) and a genetic model of caloric restriction (eat-2) all exhibit H₂S-induced increased thermotolerance. These data suggest that H₂S activates a pathway including SIR-2.1 that is separate from dietary restriction and insulin signaling that results in increased lifespan. Moreover, these studies suggest that SIR-2.1 activity may translate environmental change into physiological alterations that improve survival. It is interesting to consider the possibility that the mechanisms by which H₂S increases thermotolerance and lifespan in nematodes are conserved, and that studies using C. elegans may help explain beneficial effects observed in mammals exposed to H₂S.

Yukimasa Shibata et al. (2004) East Asia Worm Meeting "cdk-8-dependent transcriptional regulation is required for cell fate determination in asymmetric cell division"

Hitoshi Sawa, Yukimasa Shibata, Hisako Takeshita

[East Asia Worm Meeting, 2004]

Asymmetric cell division is a fundamental mechanism to produce cell diversity. One of the important steps of asymmetric cell division is distinct transcriptional regulation in daughter cells. Multisubunit transcriptional regulator, mediator complex, is required for asymmetric cell division of the T cell in C.elegans , Mediator complex regulates transcription as an integrator of signals between transcription factor and RNAPII. Disruption of a component of mediator complex, DPY-22/TRAP230 or LET-19/TRAP240, causes defect in asymmetric cell division of the T cell (1). By screening for abnormal T cell lineage, we isolated mutants of cdk-8 /CDK8 and cic-1 /CycC that encode other components of mediator complex. It is known that SRB10/CDK-8 and SRB11/CIC-1 forms subcomplex with SRB8/DPY-22 and SRB9/LET-19 in S.cerevisiae . To confirm the abnormal T cell lineage is caused by disruption of asymmetric cell division of the T cell, we analyzed a expression of tlp-1::gfp whose expression is observed in the posterior daughter of the T cell, not in the anterior daughter. In cdk-8 mutants, tlp-1::gfp expression is not observed in the both daughter cells, which suggests that cdk-8 is required for asymmetry between the daughter cells. In addition to the T cell lineage, dpy-22, let-19, cdk-8 and cic-1 are also required for the V5.p lineage that produces neural and hypodermal cells by an asymmetric cell division. In these mutants, V5.p produces only hypodermal cells from the both daughter cells. These results suggest that these four genes regulate asymmetric cell division through the same processes. Because CDK8 is reported as a component of transcriptional repressive mediator complex, our results suggests that transcriptional repression by mediator complex is required for distinct cell fate between daughter cells in asymmetric cell division. In addition to abnormal T and V5.p cell lineage, dpy-22 and let-19 mutants also show multivulva phenotype (1). However, that is not observed in putative null mutants of cdk-8 and cic-1 . These results suggests that DPY-22 and LET-19 have CDK-8-dependent and independent function. (1) A. Yoda, H. Kouike, H. Okano, H. Sawa (2002) West Coast Worm Meeting abstract 51

Sara Maxwell et al. (2002) European Worm Meeting "Functional analysis of the C. elegans T-box gene family"

Alison Woollard, Roger Pocock, Lizzie Clarke, Sara Maxwell

[European Worm Meeting, 2002]

T-box genes are a group of developmentally important transcription factors united by a common DNA binding domain. T-box genes are present in all metazoan species so far analysed but are absent from yeast. There are 20 T-box genes in C. elegans, more than twice the number found in Drosophila. Many of the C. elegans T-box genes are highly diverged from those found in other species while others have clear orthologues present throughout the metazoan kingdom. One highly conserved T-box gene is mab-9, a member of the tbx20 sub-family1. This was the first C. elegans T-box gene to be identified by mutation and is required for cell fate specification during hindgut and male tail development, and aspects of nervous system function. One other conserved T-box gene has recently been reported to be important for a particular muscle cell fate specification2. We have inactivated the remaining C. elegans T-box genes by RNAi and have found obvious phenotypes only in very few cases. These phenotypes include embryonic lethality, L1 lethality, and a Dpy phenotype with weakly penetrant male tail defects, and will be described in detail. The remaining T-box genes give no obvious phenotype by RNAi. Phylogenetic analysis reveals that several pairs of T-box genes are very similar to eachother and are therefore likely to be the result of recent duplications. This might suggest functional redundancy. Double RNAi experiments have revealed this to be the case with at least two of the T-box gene pairs (see also poster by Pocock et al). Study of the expression patterns of the whole T-box family may suggest other potential redundancy relationships which can be explored by RNAi. Comparison of the C. elegans T-box genes with the set of T-box genes now defined for C. briggsae is being used as a tool for defining potentially important regulatory regions present in orthologous genes.

Chen, W.-L. et al. (2019) International Worm Meeting "Dopamine-Mediated Gravitaxis in Caenorhabditis elegans."

Bau, H. H., Raizen, D., Chen, W.-L., Chuang, H.-S., Ko, H.-T.

[International Worm Meeting, 2019]

Molecular and circuit-based mechanisms that allow animals to sense and respond to gravity are still not clear. We found that well-nourished as well as starved wild-type N2 and AB1 adults suspended in aqueous solutions orient with the direction of the gravity vector and swim with their nose facing downwards. Paralyzed worms settle with a random orientation, indicating that nonuniform mass distribution is unlikely to cause gravitaxis behavior. In an aqueous solution that is slightly denser than the worms, worms still rotate to swim in the downwards direction, indicating that gravitaxis is not explained by hydrodynamic effects. Che-2 and osm-6 mutants, which have disrupted sensory cilia, show defective gravitaxis, suggesting that sensing gravity is mediated by sensory neurons. Cat-2 mutants, which have reduced dopamine, are gravitaxis defective, but show restored gravitaxis when dopamine is repleted pharmacologically. The mec-4 gene is not required for gravitaxis, suggesting that other mechanically responsive ion channels mediate the response to gravity. We establish C. elegans as a genetic system to study the sensation and response to gravity and conclude that gravity sensing requires ciliated neurons and dopamine.

Abergel, Z. et al. (2017) International Worm Meeting "Adaptation of the nematode C. elegans to hypoxia and reoxygenation stress reveals an unexpected function of the neuroglobin GLB-5 in innate immunity."

Zuckerman, B., Zelmanovich, V., Abergel, Z., Abergel, R., Gross, E., Smith, Y., Romero, L., Livshits, L.

[International Worm Meeting, 2017]

Deprivation of oxygen (hypoxia) followed by reoxygenation (H/R stress) is a major component in several pathological conditions such as vascular inflammation, myocardial ischemia, and stroke. However how animals adapt and recover from H/R stress remains an open question. Previous studies showed that the neuroglobin GLB-5(Haw) is essential for the fast recovery of the nematode Caenorhabditis elegans (C. elegans) from H/R stress. Here, we characterize the changes in neuronal gene expression during the adaptation of worms to hypoxia and recovery from H/R stress. Our analysis shows that innate immunity genes are differentially expressed during both adaptation to hypoxia and recovery from reoxygenation stress. Moreover, we reveal that the prolyl hydroxylase EGL-9, a known regulator of both adaptation to hypoxia and the innate immune response, inhibits the fast recovery from H/R stress through its activity in the O2-sensing neurons AQR, PQR, and URX. Finally, we show that GLB-5(Haw) acts in AQR, PQR, and URX to increase the tolerance of worms to bacterial pathogenesis. Together, our studies suggest that innate immunity and recovery from H/R stress are regulated by overlapping signaling pathways.

Hisako Takeshita et al. (2005) International Worm Meeting "Direction of cell polarity is determined by Wnt in C.elegans"

Hisako Takeshita, Hitoshi Sawa, Kota Mizumoto

[International Worm Meeting, 2005]

Asymmetric cell division is a fundamental process that produces cellular diversity during development. In C. elegans, asymmetric divisions of many cells are regulated by Wnt signaling. In particular, asymmetry of the T cell division is regulated by LIN-44/Wnt and the LIN-17/Frizzled receptor. LIN-44/Wnt is expressed in hypodermal cells at the tip of the tail, posterior to the T cell. In lin-44 mutants, the polarity of the T cell division is frequently reversed, while in lin-17 mutants, the division is symmetric. It has been proposed that LIN-44 activates the LIN-17 receptor on the posterior side of the T cell to polarize it. To determine whether LIN-44/Wnt acts as an asymmetric cue that polarizes the T cell, we ectopically expressed LIN-44 in cells anterior to the T cell using the egl-5 promoter (egl-5::LIN-44) to find that polarity reversal phenotype of lin-44 was strongly enhanced. Moreover lin-17 was required for egl-5::LIN-44 to reverse the T-cell polarity. These results suggest that LIN-44 polarize the T cell through the LIN-17 receptor. To further confirm that LIN-44 directly acts on LIN-17 in the T cell, we analyzed the localization of LIN-17::GFP fusion proteins expressed by the seam cell specific promoter (SCM::LIN-17::GFP). This construct rescued defects of lin-17 mutants in the T cell division, indicating that lin-17 functions cell-autonomously in the T cell. We found that LIN-17 localization was localized in the posterior cortex of the T cell in wild type. In lin-44 mutants, the LIN-17 localization was uniform on the cortex. Furthermore, egl-5::LIN-44 reversed the LIN-17 localization to the anterior cortex. These results strongly indicate that LIN-44 directly acts on LIN-17 in the T cell to orient the polarity.

Hryshkevich, Uladzislau et al. (2011) International Worm Meeting "Core promoter T-blocks correlate with gene expression levels in C. elegans."

Yanai, Itai, Hryshkevich, Uladzislau, Hashimshony, Tamar

[International Worm Meeting, 2011]

Core promoters mediate transcription initiation by the integration of diverse regulatory signals encoded in the proximal promoter and enhancers. It has been suggested that genes under simple regulation may have low-complexity permissive promoters. For these genes, the core promoter may serve as the principal regulatory element; however the mechanism by which this occurs is unclear. We report here a periodic poly-thymine motif, we term T-blocks, enriched in occurrences within core promoter forward strands in C. elegans. An increasing number of Tblocks on either strand is associated with increasing nucleosome eviction. Strikingly, only forward strand T-blocks are correlated with expression levels, whereby genes with ³6 T-blocks have five fold higher expression levels than genes with 3 T-blocks. We further demonstrate that differences in T-block numbers between strains predictably affect expression levels of orthologs. Highly expressed genes and genes in operons tend to have a large number of T-blocks, as well as the previously characterized SL1 motif involved in trans-splicing. The presence of T-blocks thus correlates with low nucleosome occupancy and the precision of a trans-splicing motif, suggesting its role at both the DNA and RNA levels. Collectively our results suggest that core promoters may tune gene expression levels through the occurrences of T-blocks, independently of the spatio-temporal regulation mediated by the proximal promoter.

TM Morse et al. (1999) International C. elegans Meeting "Time-series analysis of pirouettes in C. elegans chemotaxis."

TM Morse, JT Pierce, SR Lockery, ML Moravec, TC Ferree, SE Owens, AB Bates

[International C. elegans Meeting, 1999]

Chemotaxis in C. elegans involves a series of abrupt turns (pirouettes) triggered by movement down a gradient of chemical attractant * . Analysis of the time series of concentration change experienced by a worm, together with its pirouette record, suggests a three-stage chemotaxis mechanism in which chemical concentration (C(t)) is differentiated (dC(t)/dt), smoothed (q(t)), and converted into pirouette probability by a nonlinear function (P(q[t])). To test the plausibility of this mechanism, we constructed a computer model in which the smoothing filter and the nonlinearity were estimated from the time series of dC(t)/dt and the pirouette records of real worms. Pirouettes were modeled by sampling randomly, via a Poisson process with probability P(q[t]), from the distribution of direction changes associated with pirouettes in real worms. The average chemotaxis index (time-average of normalized C(t)) of model worms (0.47 +/- 0.05 SD, n = 2000) closely matched the average chemotaxis index of real worms (0.45 +/- 0.04 SD, n = 45), indicating that the three-stage mechanism is quantitatively sufficient to account for C. elegans chemotaxis. To determine the form of the smoothing filter and nonlinearity directly, we have devised a new behavioral assay that subjects unrestrained worms to negative-going impulses in dC/dt as they swim across a sharp border between high and low concentrations of attractant. Preliminary results show that immediately after a border crossing, large impulses make P(t)~= 1, while small impulses make 0 t) >< C. elegans . * Pierce, J.T., and Lockery, S.R., J. Neurosci. (Submitted)

McPhee, Christina K. et al. (2011) International Worm Meeting "Role of PHA-4/FoxA binding in cell fate specification during organogenesis."

Mango, Susan E., McPhee, Christina K.

[International Worm Meeting, 2011]

Embryonic cells are born pluripotent, but their cell fate choices become restricted during development, and they differentiate. What mechanisms mediate the transition from plasticity to differentiation in the developing embryo? The C. elegans embryo is an excellent model to study the transition from plasticity to differentiation in vivo because the stages of plasticity versus commitment are well defined temporally. FoxA transcription factors control gut development in all animals studied to date (1). C. elegans pha-4/FoxA is critical to specify foregut/pharynx fate during early embryogenesis and to drive gut differentiation and morphogenesis at later stages (2). PHA-4 accomplishes these tasks in a changing nuclear environment, in which chromatin in early embryos is in a more open, permissive state compared to older embryos (3, 4). We are currently testing models of cell fate commitment and plasticity by probing PHA-4/FoxA association with its target genes during development, and assessing cell fate specification. We are examining the interaction of C. elegans PHA-4/FoxA with its target genes beginning at the onset of gastrulation, when developmental plasticity is lost. 1.K. H. Kaestner, Curr Opin Genet Dev 20, 527 (Oct, 2010). 2.S. E. Mango, Annu Rev Cell Dev Biol 25, 597 (2009). 3.T. Yuzyuk, T. H. Fakhouri, J. Kiefer, S. E. Mango, Dev Cell 16, 699 (May, 2009). 4.H. Niwa, Genes Dev 21, 2671 (Nov 1, 2007).

Rasika Kalamegham et al. (2004) East Coast Worm Meeting "EGL-26 belongs to the NlpC/P60 superfamily of putative enzymes and is closely related to a mammalian acyl transferase"

Wendy Hanna-Rose, Rasika Kalamegham

[East Coast Worm Meeting, 2004]

egl-26 was identified in a genetic screen to uncover mutants with vulval morphology defects. In egl-26 mutants the morphology of a single vulval toroid (vulF) is abnormal and a proper connection to the uterus is not made leading to the egg-laying defect. EGL-26 is a member of the NlpC/P60 superfamily of enzymes, which is characterized by a Histidine containing domain and a Cysteine containing domain (H-box and NC domain, respectively). EGL-26 along with other eukaryotic proteins belongs to a distinct subclass of NlpC/P60-related putative enzymes. The mammalian proteins lecithin: retinol acyltransferase or LRAT and H-ras revertant 107 or H-Rev107 are the most closely related to EGL-26. Both LRAT and H-Rev107 contain putative transmembrane domains in addition to the H-box and NC domains. Although EGL-26 contains no putative transmembrane domains, it is localized at the apical membrane of cells where it is expressed. Proper localization of LRAT within the retinal pigment epithelium is essential for its function. Significantly, an S-F substitution at amino acid 275 of EGL-26 found in the egl-26 (n481) allele causes mislocalization of an EGL-26::GFP fusion leading to general cytoplasmic expression as opposed to normal apical membrane localization. The corresponding Serine residue is conserved in both LRAT and H-Rev107. We are attempting to analyze the relationship between the mammalian proteins and EGL-26 by attempting a rescue of egl-26 mutants by expression of either LRAT or H-Rev107 or both. We plan to test the importance of membrane localization by restoring membrane localization to EGL-26n481 via addition of alternative membrane localization signals.