Spichal, Maya et al. (2021) International Worm Meeting "Understanding the spatial organization of the somatic RNAi response"

Mello, Craig, Spichal, Maya, Yang, Yuchen

[International Worm Meeting, 2021]

RNA interference (RNAi) was first discovered in C. elegans and is a well conserved mechanism that regulates gene expression and fights pathogens like viruses. Gene expression is tightly controlled in the nuclear space and the genome has been shown to spatially segregate into active "euchromatin" and silenced "heterochromatin". Heterochromatin is often localized at the nuclear periphery, while euchromatin is more likely to be found in the nuclear space. Our preliminary results indicate that the RNAi silencing response is able to initiate a reorganization of the nuclear space of the germline. Upon silencing initiation, RNAi silenced mRNA and DNA localize to one germ granule at the nuclear periphery, which can be visualized by smRNA and DNA FISH. Mutants deficient for RNAi fail to concentrate the silenced DNA and/or mRNA at the granule, suggesting that the reorganization has functional implications. We are currently analyzing whether the somatic RNAi silencing response leads to a similar restructuring of the nuclear space. Somatic cells possess somatic granules that can be visualized by GFP tagged to the DEAD box RNA helicase, RDE-12, which also localizes to germ granules. DEAD box RNA helicases trigger the unwinding of RNA molecules, which is required for many RNA processing steps. In an effort to uncover functional properties of somatic granules, we mutated different RDE-12 DEAD box helicase motifs by CRISPR. Mutations in these motifs lead to RNAi dysfunction and RDE-12 mislocalization in germ granules. One mutation in the DEAD box domain, which likely prohibits RNA substrate release, provokes an aggregation of RDE-12 specifically in somatic granules. Our results suggest that RDE-12 plays distinct roles in RNAi processing in the germline and somatic tissue.

Maya A et al. (1997) Cell Biol Int "Necrosis of lung epithelial cells by filarial parasitic protein via an early induction of c-H-ras and TNF alpha expression."

Jayaraman K, Balakrishnan A, Maya A

[Cell Biol Int, 1997]

The direct interaction of filarial proteins with lung epithelial cells was examined to determine the possible mechanism of inducing cell death, an event that is observed in patients with tropical pulmonary eosinophilia. Exposure of lung epithelial cells to filarial parasitic proteins, Brugia malayi (BmA), Setaria digitata (Sd), and recombinant filarial protein (pGT 7) in vitro for more than 2 days, causes the appearance of DNA fragments both in the cytoplasm and culture supernatants, while no fragmentation was observed in the untreated controls. The release of DNA fragments both in the cytoplasm and the culture supernatants simultaneously, indicates that cell death is induced by a necrotic event rather than apoptosis. Fluorescent-labelled studies also indicate the fragmentation of DNA increasing in a time-dependent manner. Normal cellular function is controlled through several oncogenes. The modulation of specific proto-oncogenes like myc, ras and TNF alpha during exposure to filarial parasitic proteins reveal elevated levels of expression of ras and TNF alpha as early as 2 hours, implicating their involvement prior to DNA fragmentation leading to pathogenesis.

Davidovich-Cohen, Maya (2010) C. elegans: Development and Gene Expression, EMBL, Heidelberg, Germany "Analyzing the role of specific residues in barrier-to-autointegration factor (BAF) in C.elegans"

Davidovich-Cohen, Maya

[C. elegans: Development and Gene Expression, EMBL, Heidelberg, Germany, 2010]

Mutations in the nuclear envelope proteins lamins A/C and emerin cause Emery Dreifuss muscular dystrophy (EDMD). The mammalian barrier to autointegration factor (BAF) is present in protein complexes with lamin A and emerin. However, the role of BAF in EDMD is unknown. Previous studies of human BAF identified many residues in which mutations abolished, reduced or enhanced binding to specific partners. Most of these residues conserved in BAF-1 C. elegans, which is 52% identical to human BAF. In C. elegans early embryos BAF-1 is required for chromatin organization, capture segregated chromosomes within the nascent nuclear envelope and to assemble lamin and emerin proteins in reforming nuclei. In turn, BAF-1 requires lamin and emerin proteins to localize at the nuclear periphery. Animals homozygous for a deletion of the entire baf-1 ORF, in which the maternal su pply of BAF-1 is sufficient to complete embryogenesis and larval stages, revealed that BAF-1 is required for nuclear organization and several different tissue-specific pathways including maturation and survival of the germline, the second and third phases of distal tip cell migration, vulva formation and prevention of premature fusion of cells, suggesting specialized roles for BAF-1 in gene expression. BAF-1 also inhibits premature fusion of seam cells by binding to the promoters of EFF-1 and AFF-1 fusogens. Interestingly, BAF-1 is also required to maintain the integrity of specific muscles in the mid-body and tail regions of the adult animal. The requirement of BAF-1 interactions with emerin, lamin and DNA for these functions is currently being investigated by analysis of BAF-1 that has mutation at specific residues in vitro. We are also testing these mutants for physiological rescue of baf-1 null phenotypes. These results probably have direct implications on the mechanism of human muscular dystrophies caused by mutations in either A-type lamins or the protein emerin

Magana, Maya et al. (2011) International Worm Meeting "High Saturated Fat Diet Disrupts Mitochondrial Function via Reactive Oxygen Species Pathways in C. elegans."

Bryner, Stephanie, Magana, Maya, Carnell, Lucinda, Thomas, Carin

[International Worm Meeting, 2011]

We have investigated the role of high-fat diets on mitochondrial function in a well-established model for studying metabolism, C. elegans. We were interested in examining the link between diet and oxidative stress and its implication for type 2 diabetes. Therefore, we initiated studies comparing effects of high saturated (18:0) and unsaturated (18:1D9) fatty acid diets in wild-type nematodes and a mutant animal with a deletion in the nicotinamide nucleotide transhydrogenase gene, nnt-1. NNT is a mitochondrial inner membrane protein that is important in reactive oxygen species (ROS) scavenger pathways. In addition, NNT gene polymorphisms have been associated with glucose intolerance and decreased insulin secretion in mouse models. Both wild-type and nnt-1 mutant animals fed saturated fat diets induced high levels of mitochondrial superoxide production as measured using the fluorescent dye, MitoSOX. We also have evidence that superoxide is being converted into hydrogen peroxide and activating oxidative stress pathways. Transgenic animals that contain a glutathione transferase transcriptional fusion (gst-4::gfp), showed increased fluorescent intensity indicating induction of transcription when fed a saturated high fat diet. GST-4 is involved in Phase II oxidative stress response. In wild-type worms measurements of oxygen consumption and mitochondrial membrane potential (DYm) were decreased and normal, respectively, compared to control worms fed a normal diet. However, the nnt-1 mutant animals displayed increased oxygen consumption and lowered DYm, indicating the uncoupling of mitochondrial membranes and oxidative phosphorylation. These results suggest that NNT plays a pivotal role in maintaining mitochondrial respiratory function under conditions of high saturated fat diet-induced ROS generation. Animals fed unsaturated fatty acid diets showed no increase in superoxide production, decreased oxygen consumption and a tendency toward increased DYm in both wild-type and nnt-1 mutant animals, suggesting that oleic acid may play a protective role in mitochondrial function.

Quartey MO et al. (2021) Sci Rep "The A(1-38) peptide is a negative regulator of the A(1-42) peptide implicated in Alzheimer disease progression."

Pennington PR, Heistad RM, Nyarko JNK, Barnes JR, Bolanos MAC, Parsons MP, Knudsen KJ, De Carvalho CE, Leary SC, Mousseau DD, Buttigieg J, Maley JM, Quartey MO

[Sci Rep, 2021]

The pool of -Amyloid (A) length variants detected in preclinical and clinical Alzheimer disease (AD) samples suggests a diversity of roles for A peptides. We examined how a naturally occurring variant, e.g. A(1-38), interacts with the AD-related variant, A(1-42), and the predominant physiological variant, A(1-40). Atomic force microscopy, Thioflavin T fluorescence, circular dichroism, dynamic light scattering, and surface plasmon resonance reveal that A(1-38) interacts differently with A(1-40) and A(1-42) and, in general, A(1-38) interferes with the conversion of A(1-42) to a -sheet-rich aggregate. Functionally, A(1-38) reverses the negative impact of A(1-42) on long-term potentiation in acute hippocampal slices and on membrane conductance in primary neurons, and mitigates an A(1-42) phenotype in Caenorhabditis elegans. A(1-38) also reverses any loss of MTT conversion induced by A(1-40) and A(1-42) in HT-22 hippocampal neurons and APOE 4-positive human fibroblasts, although the combination of A(1-38) and A(1-42) inhibits MTT conversion in APOE 4-negative fibroblasts. A greater ratio of soluble A(1-42)/A(1-38) [and A(1-42)/A(1-40)] in autopsied brain extracts correlates with an earlier age-at-death in males (but not females) with a diagnosis of AD. These results suggest that A(1-38) is capable of physically counteracting, potentially in a sex-dependent manner, the neuropathological effects of the AD-relevant A(1-42).

Danielle Thierry-Mieg et al. (2003) Worm Breeder's Gazette "www.wormgenes.org , a new gene centered database"

Vahan Simonyan, Michel Potdevin, Mark Sienkiewicz, Yuji KOHARA, Jean Thierry-Mieg, Danielle Thierry-Mieg, Tadasu SHIN-I

[Worm Breeder's Gazette, 2003]

Wormgenes is a new resource for C.elegans offering a detailed summary about each gene and a powerful query system.

Tangrodchanapong T et al. (2020) Front Pharmacol "Frondoside A Attenuates Amyloid- Proteotoxicity in Transgenic Caenorhabditis elegans by Suppressing Its Formation."

Tangrodchanapong T, Sobhon P, Meemon K

[Front Pharmacol, 2020]

Oligomeric assembly of Amyloid- (A) is the main toxic species that contribute to early cognitive impairment in Alzheimer's patients. Therefore, drugs that reduce the formation of A oligomers could halt the disease progression. In this study, by using transgenic <i>Caenorhabditis elegans</i> model of Alzheimer's disease, we investigated the effects of frondoside A, a well-known sea cucumber <i>Cucumaria frondosa</i> saponin with anti-cancer activity, on A aggregation and proteotoxicity. The results showed that frondoside A at a low concentration of 1 M significantly delayed the worm paralysis caused by A aggregation as compared with control group. In addition, the number of A plaque deposits in transgenic worm tissues was significantly decreased. Frondoside A was more effective in these activities than ginsenoside-Rg3, a comparable ginseng saponin. Immunoblot analysis revealed that the level of small oligomers as well as various high molecular weights of A species in the transgenic <i>C. elegans</i> were significantly reduced upon treatment with frondoside A, whereas the level of A monomers was not altered. This suggested that frondoside A may primarily reduce the level of small oligomeric forms, the most toxic species of A. Frondoside A also protected the worms from oxidative stress and rescued chemotaxis dysfunction in a transgenic strain whose neurons express A. Taken together, these data suggested that low dose of frondoside A could protect against A-induced toxicity by primarily suppressing the formation of A oligomers. Thus, the molecular mechanism of how frondoside A exerts its anti-A aggregation should be studied and elucidated in the future.

Hodgkin JA (1998) International Journal of Developmental Biology "Seven types of pleiotropy."

Hodgkin JA

[International Journal of Developmental Biology, 1998]

Pleiotropy , a situation in which a single gene influences multiple phenotypic tra its, can arise in a variety of ways. This paper discusses possible underlying mechanisms and proposes a classification of the various phenomena involved.

Tuck S (2011) Curr Biol "Extracellular vesicles: budding regulated by a phosphatidylethanolamine translocase."

Tuck S

[Curr Biol, 2011]

Recent work on a Caenorhabditis elegans transmembrane ATPase reveals a central role for the aminophospholipid phosphatidylethanolamine in the production of a class of extracellular vesicles.

Viney ME et al. (2004) Naturwissenschaften "Is dauer pheromone of Caenorhabditis elegans really a pheromone?"

Viney ME, Franks NR

[Naturwissenschaften, 2004]

Animals respond to signals and cues in their environment. The difference between a signal (e.g. a pheromone) and a cue (e.g. a waste product) is that the information content of a signal is subject to natural selection, whereas that of a cue is not. The model free-living nematode Caenorhabditis elegans forms an alternative developmental morph (the dauer larva) in response to a so-called 'dauer pheromone', produced by all worms. We suggest that the production of 'dauer pheromone' has no fitness advantage for an individual worm and therefore we propose that 'dauer pheromone' is not a signal, but a cue. Thus, it should not be called a pheromone.