Filina, O. et al. (2019) International Worm Meeting "Stress discrimination by body-wide, stochastic DAF-16/FoxO nuclear translocation pulses."

Olmedo, M., van Zon, J.S., Filina, O., Sanchez-Romero, M.A.

[International Worm Meeting, 2019]

The transcription factor DAF-16/FoxO is the primary output of the insulin/IGF-1 pathway in C. elegans, which induces stress-response genes upon a broad range of external stresses. How a single pathway can mount a response that is tailored to different types of stress is not understood. Upon stress, DAF-16 translocates from the cytoplasm to the nucleus to induce gene expression. So far, it is assumed that the level of nuclear DAF-16 does not change if stress conditions remain constant. Surprisingly, when we visualized DAF-16 in individual larvae under constant stress, we instead observed stochastic changes in nuclear translocation, with DAF-16 moving between the nucleus and cytoplasm in ~1hr pulses. Moreover, these pulses exhibited striking body-wide synchronization, with cells from different tissues, e.g. the intestine, hypodermis and neurons, switching within 10 minutes of one another, suggesting the presence of a long-range synchronization signal. We used automated image analysis to quantify DAF-16 pulse dynamics in the intestine, under different stresses that caused developmental arrest in L1 larvae. Whereas, for all stresses the fraction of time that DAF-16 was nuclear increased with stress magnitude, different stress types generated clearly distinguishable DAF-16 pulse dynamics: starvation resulted in pulses that resembled stochastic oscillations, while osmotic stress gave rise to random pulses whose duration increased with salt concentration. Finally, for temperature stress we still observed pulses but with a baseline that increased with temperature. Overall, this suggests that changes in the dynamics of DAF-16 nuclear translocation pulses allow cells to determine both magnitude and type of stress. An important question forming the current focus of our research is how DAF-16 pulse dynamics impacts down-stream expression of its target genes and developmental output. Finally, we also observed pulsatile dynamics of the DAF-16 homolog FoxO in mammalian cells at low nutrient levels that activate insulin signaling. Overall, this indicates that DAF-16/FoxO translocation pulses are a general feature of insulin signaling that might be crucial for its ability to differentiate between and mount the correct response to many different types of stress.

Filina, O. et al. (2017) International Worm Meeting "A ticking clock: understanding oscillatory gene expression during C. elegans development."

Filina, O., van Zon, J.

[International Worm Meeting, 2017]

Larval development of C. elegans occurs in four stages that are punctuated by molts. Each molt is accompanied by a peak in expression of a broad spectrum of genes, referred to as molting cycle genes. Expression of these genes peaks at different times but with the same period as the molts. Such periodic gene expression suggests the existence of a timing mechanism capable of precise temporal regulation. The gene lin-42 is thought to be implicated in such a mechanism as its deletion causes severe developmental defects with extended larval stage duration and asynchronous molts. The goal of the current research is to understand the mechanism of temporal control by lin-42. In particular we are interested in how lin-42 controls oscillatory expression of the molting cycle genes. To address this, we examine the dynamics of molting cycle genes in lin-42(ok2385) mutant animals. For this, we use a newly-developed fluorescence time-lapse microscopy technique, which allows us to follow gene expression at a single-animal level over the entire course of development. Initially we focused on mlt-10, a gene that encodes for one of the cuticle components, whose expression exhibits peak ~ one hour prior to ecdysis. We found that even though in lin-42(ok2385) animals time of the mlt-10 peaks was delayed, their duration was same as in wild-type. Moreover, we found that the L2 peak in mlt-10 expression was absent in 30% of animals that reached the L2/L3 molt. Interestingly, presence of peak was not correlated with initiation of subsequent ecdysis and occurred in all-or-none fashion: L2 peak was either fully absent or exhibited wild-type amplitude. We use mathematical modelling to show that these phenotypes are consistent with regulation by a mixed incoherent feed-forward loop. Currently we are extending this analysis to other molting cycle genes that peak at different phases as well as other lin-42 alleles.

Filina O et al. (2022) Proc Natl Acad Sci U S A "Temporal scaling in C. elegans larval development."

Demirbas B, van Zon JS, Haagmans R, Filina O

[Proc Natl Acad Sci U S A, 2022]

SignificanceAn enduring mystery of development is how its timing is controlled, particularly for development after birth, where timing is highly flexible and depends on environmental conditions, such as food availability and diet. We followed timing of cell- and organism-level events in individual <i>Caenorhabditis elegans</i> larvae developing from hatching to adulthood, uncovering widespread variations in event timing, both between isogenic individuals in the same environment and when changing conditions and genotypes. However, in almost all cases, we found that events occurred at the same time, when time was rescaled by the duration of development measured in each individual. This observation of "temporal scaling" poses strong constraints on models to explain timing of larval development.

Franz M et al. (1987) Parasitol Res "Electron-microscopic observations on the female worms of six Onchocerca species from cattle and red deer."

Copeman DB, Franz M, Schulz-Key H

[Parasitol Res, 1987]

The midbody regions of female worms of six Onchocerca species (O. flexuosa, O. tarsicola, O. lienalis, O. gutturosa, O. armillata, O. gibsoni) were studied by transmission electron microscopy. The cuticular layering was rather similar in all species with the ridges built up by the cortical layers and the inner cuticular striations by the median or basal layers. Differences in the epicuticular morphology were considerable. O. flexuosa and O. lienalis had a thin epicuticle without protuberances, the epicuticle of O. armillata carried small knobs, and O. tarsicola, O. gutturosa, and O. gibsoni had a thick trilaminar epicuticle with long protuberances. Extreme hypertrophy of hypodermis and reductions of somatic musculature were observed in O. flexuosa and O. gibsoni. Less extended thickenings of the hypodermis were observed in the other species. No degenerative alterations were found in the muscle cells of O. gutturosa and O. lienalis. The intestinal lumen of most of the species was in a central position, but in O. tarsicola and O. gibsoni the lumen was reduced to small clefts between the intestinal cells. In these species, numerous electron-dense, concentric granules were observed in the cytoplasm of the intestinal cells. The proportions of the various organs differed considerably from species to species, e.g., the uteri contained the embryos filed one behind the other in O. tarsicola, whereas 50 or more embryos were found beside one another in cross-sections of the uterus of O. gibsoni. The comparative study showed that O. gibsoni and O. volvulus have many derived morphological characteristics in common and that in the other species more primitive stages of development of these morphological marks can be observed.

Zhang S et al. (2021) Environ Pollut "Responses of Caenorhabditis elegans to various surface modifications of alumina nanoparticles"

Zhang Z, Xu Y, Mao X, Chu Q, Zhang S, Zhang M

[Environ Pollut, 2021]

The surface modifications of nanoparticles (NPs), are well-recognized parameters that affect the toxicity, while there has no study on toxicity of Al(2)O(3) NPs with different surface modification. Therefore, for the first time, this study pays attention to evaluating the toxicity and potential mechanism of pristine Al(2)O(3) NPs (p-Al(2)O(3)), hydrophilic (w-Al(2)O(3)) and lipophilic (o-Al(2)O(3)) modifications of Al(2)O(3) NPs both in vitro and in vivo. Applied concentrations of 10, 20, 40, 80,100 and 200 &#956;g/mL for 24 h exposure on Caenorhabditis elegans (C. elegans), while 100 &#956;g/mL of Al(2)O(3) NPs significantly decreased the survival rate. Using multiple toxicological endpoints, we found that o-Al(2)O(3) NPs (100 &#956;g/mL) could induce more severe toxicity than p-Al(2)O(3) and w-Al(2)O(3) NPs. After uptake by C. elegans, o-Al(2)O(3) NPs increased the intestinal permeability, easily swallow and further destroy the intestinal membrane cells. Besides, cytotoxicity evaluation revealed that o-Al(2)O(3) NPs (100 &#956;g/mL) are more toxic than p-Al(2)O(3) and w-Al(2)O(3). Once inside the cell, o-Al(2)O(3) NPs could attack mitochondria and induce the over-production of reactive oxygen species (ROS), which destroy the intracellular redox balance and lead to apoptosis. Furthermore, the transcriptome sequencing and RT-qPCR data also demonstrated that the toxicity of o-Al(2)O(3) NPs is highly related to the damage of cell membrane and the imbalance of intracellular redox. Generally, our study has offered a comprehensive sight to the adverse effects of different surface modifications of Al(2)O(3) NPs on environmental organisms and the possible underlying mechanisms.

Bain O et al. Ann Parasitol Hum Comp "[Redescription of Onchocerca gibsoni C. et J., 1910 (author's transl)]."

Bain O, Beveridge I

[Ann Parasitol Hum Comp]

O. gibsoni is redescribed; the hypoderma and the musculature of the female body are studied on transversal sections and compared to several other species of Onchocerca. These structures and the general morphology show the autonomy of a small line of asiatic and african Onchocerca of Bovines (O. gibsoni, O. dukei, O. ochengi and, probably, the other nodular Onchocerca of Bovinae), to which the human parasite, O. volvulus, belongs. The presence of O. gibsoni in Africa is doubtful.

Wang P et al. (2012) Proc Natl Acad Sci U S A "O-GlcNAc cycling mutants modulate proteotoxicity in Caenorhabditis elegans models of human neurodegenerative diseases."

Love DC, Wang P, Hanover JA, Krause MW, Lazarus BD, Forsythe ME

[Proc Natl Acad Sci U S A, 2012]

O-GlcNAcylation is an abundant posttranslational modification in the brain implicated in human neurodegenerative diseases. We have exploited viable null alleles of the enzymes of O-GlcNAc cycling to examine the role of O-GlcNAcylation in well-characterized Caenorhabditis elegans models of neurodegenerative proteotoxicity. O-GlcNAc cycling dramatically modulated the severity of the phenotype in transgenic models of tauopathy, amyloid -peptide, and polyglutamine expansion. Intriguingly, loss of function of O-GlcNAc transferase alleviated, whereas loss of O-GlcNAcase enhanced, the phenotype of multiple neurodegenerative disease models. The O-GlcNAc cycling mutants act in part by altering DAF-16-dependent transcription and modulating the protein degradation machinery. These findings suggest that O-GlcNAc levels may directly influence neurodegenerative disease progression, thus making the enzymes of O-GlcNAc cycling attractive targets for neurodegenerative disease therapies.

Cheung BHH et al. (2005) Curr Biol "Experience-dependent modulation of C. elegans behavior by ambient oxygen."

Cohen M, Rogers C, Cheung BHH, De Bono M, Albayram O

[Curr Biol, 2005]

Background: Ambient oxygen (O(2)) influences the behavior of organisms from bacteria to man. In C. elegans, an atypical O(2) binding soluble guanylate cyclase (sGC), GCY-35, regulates O(2) responses. However, how acute and chronic changes in O(2) modify behavior is poorly understood. Results: Aggregating C. elegans strains can respond to a reduction in ambient O(2) by a rapid, reversible, and graded inhibition of roaming behavior. This aerokinetic response is mediated by GCY-35 and GCY-36 sGCs, which appear to become activated as O(2) levels drop and to depolarize the AQR, PQR, and URX neurons. Coexpression of GCY-35 and GCY-36 is sufficient to transform olfactory neurons into O(2) sensors. Natural variation at the npr-1 neuropeptide receptor alters both food-sensing and O(2)-sensing circuits to reconfigure the salient features of the C. elegans environment. When cultivated in 1% O(2) for a few hours, C. elegans reset their preferred ambient O(2), seeking instead of avoiding 0%-5% O(2). This plasticity involves reprogramming the AQR, PQR, and URX neurons. Conclusions: To navigate O(2) gradients, C. elegans can modulate turning rates and speed of movement. Aerotaxis can be reprogrammed by experience or engineered artificially. We propose a model in which prolonged activation of the AQR, PQR, and URX neurons by low O(2) switches on previously inactive O(2) sensors. This enables aerotaxis to low O(2) environments and may encode a "memory" of previous cultivation in low O(2).

Wells L et al. (2001) Science "Glycosylation of nucleocytoplasmic proteins: signal transduction and O-GlcNAc."

Hart GW, Wells L, Vosseller K

[Science, 2001]

The dynamic glycosylation of serine or threonine residues on nuclear and cytosolic proteins by O-linked beta-N-acetylglucosamine (O-GlcNAc) is abundant in all multicellular eukaryotes. On several proteins, O-GlcNAc and O-phosphate alternatively occupy the same or adjacent sites, leading to the hypothesis that one function of this saccharide is to transiently block phosphorylation. The diversity of proteins modified by O-GlcNAc implies its importance in many basic cellular and disease processes. Here we systematically examine the current data implicating O-GlcNAc as a regulatory modification important to signal transduction cascades.

Wang, Peng et al. (2011) International Worm Meeting "Caenorhabditis elegans O-GlcNAc cycling mutants alter the proteotoxicity of models of human neurodegenerative disorders."

Forsythe, Michele, Wang, Peng, Lazarus, Brooke, Hanover, John, Love, Dona, Krause, Michael

[International Worm Meeting, 2011]

O-linked N-acetylglucosamine (O-GlcNAc) addition is an important post-translational modification that occurs on hundreds of proteins, including nuclear pore proteins, transcription factors, proteasome components and neuronal proteins. O-GlcNAc can be added onto and removed from serine or threonine residue by two evolutionally conserved enzymes: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. O-GlcNAcylation is abundant in the brain and it has been linked to human neurodegenerative disease. We have exploited viable null alleles of the enzymes of O-GlcNAc cycling to examine the role of O-GlcNAcylation in well-characterized C. elegans models of neurodegenerative proteotoxicity. O-GlcNAc cycling dramatically modulated the severity of the proteotoxic phenotype in transgenic models of tauopathy, b-amyloid peptide and polyglutamine expansion. Intriguingly, loss-of-function of OGT alleviated, while loss of OGA enhanced these proteotoxicity phenotype. Consistent with these observations, the O-GlcNAc cycling mutants exhibit altered stress responses and changes in the protein degradation machinery. These findings suggest that modulators of O-GlcNAc cycling may prove useful for anti-neurodegenerative disease therapies.