Amy Maddox et al. (2006) Development & Evolution Meeting "Cortical symmetry breaking promotes asymmetric closure of the contractile ring"

Lindsay Lewellyn, Karen Oegema, Amy Maddox, Arshad Desai

[Development & Evolution Meeting, 2006]

In many large embryos and in polarized cultured mammalian epithelial cells, cytokinesis is asymmetric within the division plane. We have investigated the molecular mechanism of asymmetric cleavage using the C. elegans early embryo. We took advantage of the reproducibility of cell division events in the C. elegans embryo to design quantitative live imaging based assays for contractile ring and furrow dynamics during cytokinesis. We found that, instead of the even ingression of a symmetric furrow encircling the cell equator, a prominent furrow forms on one side of the embryo and sweeps across the division plane toward the opposite side of the embryo. We also show that the contractile ring is structurally anisotropic, with components enriched on the faster-ingressing edge of the contractile ring. However, the anaphase spindle, the source of the signal for contractile ring assembly, is centrally positioned. We show that anillin and the septins, widely conserved structural components of the contractile ring, are required for the anisotropic distribution of structural components around the ring circumference and asymmetric furrow ingression. Anillin and the septins are not required for embryonic cytokinesis, but they become essential in sensitized backgrounds in which the ring is structurally compromised. Septins form heterooligomers that are thought to polymerize to form a plasma membrane associated filament lattice. Anillin can bind directly to F-actin, active myosin, and septin filaments, making it ideally suited to crosslink the membrane associated septin cytoskeleton with the actomyosin network in the contractile ring. We therefore speculate that, following symmetric signaling and initial deposition of contractile ring components, a stochastic symmetry-breaking event is reinforced by a plasma membrane associated scaffold containing anillin and the septins. In this way, the actomyosin network is clustered in one location around the equatorial circumference and the ring constricts asymmetrically.

Amy S Maddox et al. (2005) International Worm Meeting "Distinct roles for two C. elegans anillins in the gonad and the early embryo"

Amy S Maddox, Karen Oegema, Bianca Habermann, Arshad Desai

[International Worm Meeting, 2005]

Anillins are conserved proteins important for stabilizing and remodeling the actin cytoskeleton. Anillins have been implicated in cytokinesis in several systems and in cellularization of the syncytial Drosophila embryo. Here we examine the functions of three C. elegans proteins with homology to anillin (ANI-1, 2 and 3). We show that ANI-1 and ANI-2 contribute to embryonic viability by performing distinct functions in the early embryo and gonad, respectively. In contrast, ANI-3 appears to be dispensable for embryonic development. ANI-1 is essential for cortical contractile ruffling and pseudocleavage during pronuclear migration, but not for the establishment of polarity. ANI-1 is also required for the highly asymmetric cytokinetic events that extrude the two polar bodies during oocyte meiosis, but is dispensable for cytokinesis following mitotic chromosome segregation. During both meiosis and mitosis, ANI-1 targets the septins, but not myosin II, to the contractile ring and does not require either for its own targeting. In contrast to ANI-1, ANI-2 functions during oogenesis to maintain the structure of the rachis, the central core of cytoplasm that connects the developing oocytes in the syncytial gonad. In ANI-2 depleted worms, oocytes disconnect prematurely from the defective rachis, generating embryos of varying sizes. Our results highlight specialization of divergent anillin family proteins in the C. elegans life cycle and reveal conserved roles for this protein family in organizing syncytial structures and cortical contractility.

Paul Maddox et al. (2007) International Worm Meeting "Functional genomics identifies a Myb domain-containing protein family required for assembly of CENP-A chromatin."

Francie Hyndman, Joost Monen, Paul Maddox, Arshad Desai, Karen Oegema

[International Worm Meeting, 2007]

Nucleosomes containing the centromere-specific histone H3 variant centromere protein A (CENP-A) create the chromatin foundation for kinetochore assembly. To understand the mechanisms that selectively target CENP-A to centromeres, we took a functional genomics approach in the nematode Caenorhabditis elegans, in which failure to load CENP-A results in a signature kinetochore-null (KNL) phenotype. We identified a single protein, KNL-2, that is specifically required for CENP-A incorporation into chromatin. KNL-2 and CENP-A localize to centromeres throughout the cell cycle in an interdependent manner and coordinately direct chromosome condensation, kinetochore assembly, and chromosome segregation. The isolation of KNL-2-associated chromatin coenriched CENP-A, indicating their close proximity on DNA. KNL-2 defines a new conserved family of Myb DNA-binding domain-containing proteins. The human homologue of KNL-2 is also specifically required for CENP-A loading and kinetochore assembly but is only transiently present at centromeres after mitotic exit. These results implicate a new protein class in the assembly of centromeric chromatin and suggest that holocentric and monocentric chromosomes share a common mechanism for CENP-A loading.

Wender, Nora et al. (2011) International Worm Meeting "Analysis of cellular toxicity mechanisms of alpha-synuclein in C. elegans."

Hegermann, Jan, Eimer, Stefan, Wender, Nora

[International Worm Meeting, 2011]

Aggregation of a-synuclein (aS) in Lewy bodies is one of the pathological hallmarks of Parkinson's disease (PD). Mutations in aS as well as increased aS expression levels have been associated with PD. As the PD mutants of aS are more prone to forming fibrillar aggregates, these fibrils were initially considered to be causing toxicity. However, in different model systems no clear correlation between toxicity and fibril formation was found. This indicates that small oligomeric precursors rather than fibrils might be the toxic species. In order to investigate which form of aS is causing toxicity, we were making use of a designed variant of aS that stops at the stage of soluble oligomers. This variant is called TP aS (triple proline aS) as it was derived from wt aS by introduction of three proline residues. In vitro NMR studies as well as in vivo analysis of the aggregation of aS variants tagged with YFP in C. elegans muscle cells confirmed that the occurrence of aS fibrils was strongly reduced in TP aS. Next we were assessing toxicity of TP aS in comparison to wt aS as well as PD mutants of aS by investigation of neurite degeneration and impairment of dopamine-associated behavior upon expression of different aS variants in C. elegans dopaminergic neurons. We found that TP is the most toxic aS variant, exhibiting the most severe effects on dopaminergic neuron morphology and function. This suggests that indeed the small oligomers rather than aS fibrils are causing toxicity. So far, the cellular function of aS and the mechanisms causing toxicity remain unclear. It is known that aS binds to intracellular membranes including the mitochondrial membrane. Furthermore, mitochondrial impairment upon expression of wt and mutant aS was reported. Recently it has been reported that several PD-associated genes play a role in mitochondrial dynamics and that loss of function or overexpression leads to morphological changes in the mitochondrial network. Therefore we aimed in understanding how expression of different variants of aS affects mitochondrial dynamics. Thus we were analyzing mitochondrial morphology and distribution by Electron Microscopy as well as Spinning Disk Microscopy. We found that expression of aS in C. elegans muscles and neurons leads to mitochondrial fragmentation and severe changes in mitochondrial morphology. Remarkably, similar changes could be observed in aged worms not expressing aS. It is therefore tempting to suggest that increased expression levels of aS accelerate mitochondrial aging.

Fotopoulos, Nellie et al. (2011) International Worm Meeting "Roles for anillin (ani-1) in regulating cell shape changes during C. elegans embryogenesis."

Chen, Yun, Piekny, Alisa, Makil, Neetha, Fotopoulos, Nellie

[International Worm Meeting, 2011]

Changes in cell shape involve reorganization and contraction of the actin-myosin cytoskeleton. During C. elegans embryogenesis, both cytokinesis and elongation use Rho-mediated shape changes. Elongation is where lateral epidermal cells (seam cells) change shape from cube-like to cylindrical, which is transmitted to the ventral and dorsal epidermal cells, transforming the ovoid embryo into the long, thin worm. In the seam cells, actin filaments become highly organized and are shortened by myosin contraction via the Rho kinase LET-502. Myosin phosphatase (MEL-11) inactivates myosin in the dorsal and ventral cells and is sequestered to cell boundaries in the seam cells, which limits its interaction with myosin. LET-502 is likely regulated by RHO-1, but the lack of rho-1 alleles precluded studying its role in elongation. Using a deletion allele generated by the Knockout Consortium, we found that rho-1 is required for elongation and other morphogenetic events, including ventral enclosure. Cytokinesis is the final stage of cell division and requires the Rho-mediated formation and ingression of an actin-myosin ring. The same genes regulate both elongation and cytokinesis, suggesting they use analogous shape change mechanisms. In other eukaryotes, anillin is required for cytokinesis by coordinating actin and myosin filaments. It can also bind to RhoA, scaffolding the upstream regulator to actin and myosin. ani-1 (anillin in C. elegans) is required for polar body extrusion during meiosis and asymmetric furrow ingression during cytokinesis. Since elongation and cytokinesis may use similar shape change mechanisms, we hypothesize ani-1 functions in elongation. Using ani-1 RNAi, we observed phenotypes consistent with elongation defects. We also performed zygotic-specific ani-1 RNAi (by rescuing maternal RNAi) and observed elongation defects, suggesting this phenotype does not arise from earlier defects in meiosis or cytokinesis. We found genetic interactions between ani-1 and genes that function in elongation using zygotic alleles for rho-1 and mlc-4. Furthermore, using GFP:ANI-1 (gift from A. S. Maddox), we observed non-cytokinetic localization patterns for ANI-1 during embryogenesis. These findings may be the first evidence to support developmental-specific functions for anillin outside cytokinesis in any organism.

Cain, S. et al. (2019) International Worm Meeting "Genome Browsing at WormBase."

Harris, T., Wright, A., Stein, L., Cain, S., Gao, S., Grove, C., Nuin, P.

[International Worm Meeting, 2019]

Here we present recent updates to the genome browser at WormBase, JBrowse. Since it's introduction three years ago, JBrowse's presence in WormBase has grown, as has its functionality. JBrowse updates include the addition of new datasets, display improvements and increased functionality. Dataset changes include the addition of common and rare predicted introns from RNAseq data as well as the ability to add modERN and other public datasets. Visualization changes include improvements to how modENCODE tracks are displayed as well as the addition of new and improved glyphs throughout the app.

Michael Han et al. (2007) International Worm Meeting "WormBase: Comparative Genomics."

Michael Han, Sheldon McKay, Todd Harris

[International Worm Meeting, 2007]

WormBase is the reference database for multiple Caenorhabditae species and provides comprehensive information on comparative Nematode genomics. The comparative genomics data in Wormbase has been extended by including more species, additional methods for comparison and by more regular updates. Data on the new Caenorhabditis briggsae assembly and the draft Caenorhabditis remanei genome has been included as well as the first draft of the Caenorhabditis sp 2801. Additional and updated ortholog predictions like EnsEMBL - Compara, TreeFam and InParanoid, supplemental experimental evidence and tighter integration with EnsEMBL provides a wider range of species for intergenome comparisons as well as a more comprehensive view of currently available data. Pairwise genome alignments from WABA as well as multiple genome alignments using MLAGAN / PECAN can be accessed through the new syntheny viewer in addition to being downloadable as flatfiles from the WormBase FTP-servers.

Queiros, Libania et al. (2021) International Worm Meeting "Evidence for the inclusion of Caenorhabditis elegans in Environmental Risk Assessment routines"

Aschner, Michael, Pacheco, Mario, Queiros, Libania, Pereira, Patricia, L. Pereira, Joana, J. M. Goncalves, Fernando

[International Worm Meeting, 2021]

Caenorhabditis elegans has long been used as a choice for a laboratory model organism, and it has been linked to several discoveries that have led to Nobel Prizes. Although C. elegans' journey as an invaluable model in developmental biology and neurobiology is long, dating to the 1960s, its application in other research fields such as environmental toxicology is more recent. As a well-known experimental organism bearing high sensitivity to different environmental contaminants, and representing important functional levels in soil and aquatic ecosystems, C. elegans has high potential to be extensively integrated within Environmental Risk Assessment (ERA) routines. The major advantages supporting the inclusion of C. elegans in lower tiers of ERA, where a first screening of potential hazardous scenarios to the biota of both environmental compartments is performed, as well as the large array of endpoints that can be tested in this context, are herein presented. In addition, its sensitivity to contaminants such as metals and pesticides, as well as specific strengths and limitations, are compared to other laboratorial model organisms commonly used in ERA, such as Daphnia magna (crustacean) and Eisenia fetida (earthworm). The inclusion of C. elegans in ERA routines is encouraged, since it may provide ecologically relevant insights on the effects of contaminants, thus improving the establishment of appropriate environmental protection benchmarks.

Johnson CJ et al. (1997) International C. elegans Meeting "CHARACTERIZATION OF A STRESS-RESPONSIVE REPORTER TRANSGENE"

Cypser JR, Johnson TE, Link CD, Johnson CJ

[International C. elegans Meeting, 1997]

We have characterized a set of integrated reporter transgenes that are inducible by a variety of physiological stresses. These transgenes are based on a construct employing an hsp-16-2 promoter element and GFP. In addition to a robust response to heat shock, these transgenes express GFP in response to induced reactive oxygen species (ROS) stress, as well as "endogenous" stresses. Specifically, these lines have been observed to express GFP in respone to incubation in juglone (a redox cycling quinone that generates intracellular superoxide), as well as hydrogen peroxide. Experiments examining transgene response to hyperbaric oxygen are currently underway. Expression of these reporter transgenes has also been observed in aging animals (not heat shocked), as well as in transgenic animals co-expressing beta amyloid peptide. As these transgenic lines allow visualization of stress response in living animals, they may be valuable in genetic screens designed to identify mutations that modulate the stress response.

Vivian Hsiu-chuan Liao et al. (2005) International Worm Meeting "gcs-1 confers resistance to arsenic-induced oxidative stress in Caenorhabditis elegans"

Vivian Hsiu-chuan Liao, Chan-Wei Yu

[International Worm Meeting, 2005]

47;-Glutamylcysteine synthetase (47;-GCS) catalyzes the first, rate-limiting step in the biosynthesis of glutathione (GSH). To evaluate the protective role of cellular GSH against arsenic-induced oxidative stress in Caenorhabditis elegans (C. elegans), we examined the effect of the C. elegans ortholog of GCS(h), gcs-1, in response to inorganic arsenic exposure. We have evaluated the responses of wild-type and gcs-1 mutant nematodes to both inorganic arsenite (As(III)) and arsenate (As(V)) ions and found that gcs-1 mutant nematodes are more sensitive to arsenic toxicity than that of wild-type animals. The amount of metal ion required to kill half of the population of worms falls in the order of wild-type / As(V) > gcs-1 / As(V) > wild-type / As(III) > gcs-1 / As(III). gcs-1 mutant nematodes also showed an earlier response to the exposure of As(III) and As(V) than that of wild-type animals. Addition of GSH significantly raised the survival rate of gcs-1mutant worms compared to As(III)-treated worms alone. These results indicate that GCS-1 is essential for the synthesis of intracellular GSH in C. elegans and consequently that the intracellular GSH status plays a critical role in protection of C. elegans from arsenic-induced oxidative stress.