Asundi, A. et al. (2017) International Worm Meeting "The Role of Small RNA Pathway Machinery in Mitosis and Cell Cycle."

Suzuki, A., Rohrberg, J., Asundi, A., Goga, A., L'Etoile, N.

[International Worm Meeting, 2017]

Small RNAs have recently emerged as interesting potential candidates for regulating various cell processes from differentiation to non-autonomous cell communication. We hypothesize that small RNAs may also have a role in regulating mitosis and the cell cycle, particularly in rapidly dividing cell populations. We have approached this question using both an in vivo model (C. elegans reproductive tract) and an in vitro model (oncogenic mammalian epithelial breast cells) to examine cell proliferation in the absence of two conserved proteins in the small RNA pathway: the double stranded RNA import channel, SIDT-1/SID-1 and the nuclear RNAi protein NRDE-2. The adult C. elegans germ line contains the only population of mitotically dividing stem cells in the organism and is a tractable system by which to study the influence of small RNA machinery on proliferating germ cell (PGC) population and reproduction. Various canonical cell signaling pathways including, TGF-b (Dalfo et al. 2012), IGF-1/insulin (Michaelson et al. 2010) and GLP-1/Notch (Kimble et al. 1997) are known to regulate the number of PGCs. To test whether small RNA signals may also play a role in maintaining PGC number, our lab examined PGC number and brood size in sid-1 and nrde-2 null mutants. We found that PGC number is significantly reduced in nrde-2 null mutants as compared to wild type worms. In addition, the brood size of these worms is significantly decreased as compared to wild type. We also find that although sid-1 null mutants have a significantly reduced number of PGCs, the number of sid-1 mutant progeny is comparable to that of wild type. We hypothesized that since sid-1 and nrde-2 are conserved between C. elegans and mammals, these proteins might also function in regulating mitosis in mammalian cells. We used siRNA to knockdown NRDE-2 or SIDT-1 in MCF10A breast epithelial cells that have been transformed to overexpress the oncogene Aurora B Kinase (AUBK). We have shown that in NRDE-2 siRNA treated AUBK overexpressing MCF10A cells, the number of metabolically active cells significantly decreases as compared to control siRNA treated cells. Similarly, treating AUBK overexpressing cells with SIDT-1 siRNA significantly decreases metabolic cell activity. However, untransformed MCF10A cells treated with NRDE-2 siRNA or SIDT-1 do not show a significant decrease in viable cell number when compared to control siRNA treated untransformed MCF10A cells. Taken together, these data suggest that the small RNA pathway may be required maintain mitotic integrity, particularly in rapidly dividing cell populations, such as the C. elegans stem cell niche and cancerous cell populations.

Asundi, Aarati et al. (2015) International Worm Meeting "Olfactory Sensory Neuron Regulation of the Germline in Response to Environment."

L'Etoile, Noelle, Suzuki, Atsushi, Goga, Andrei, Asundi, Aarati

[International Worm Meeting, 2015]

The balance between proliferation and differentiation of stem cell populations must be responsive to changing molecular and physiological conditions. However, the mechanism behind this plasticity is not well understood. The C. elegans nematode is a tractable organism to study the influence of food sensation on physiology. Recent studies suggest that the number of proliferating germ cells (PGCs), the only stem cell population in the adult C. elegans body, respond to the environment by communicating with sensory neurons. Sensory neurons are able to relay information about food abundance to the PGCs. Specifically, TGF-b signaling from the ASI gustatory neuron promotes increased PGCs when food is abundant and reduced PGCs when food is scarce [Dalfo et al. 2012]. The olfactory sensory neurons (OSNs), AWA and AWC, are also food-sensing neurons [Chalasani et al. 2007] and thus, may also regulate the PGCs. Indirect evidence suggests that the OSNs along with ASI reduce lifespan, perhaps via the germline [Alcedo et al. 2004 and Hsin et al. 1999]. Studies also suggest that the neurons secrete signals to affect behavioral responses to odor [Chalasani et al. 2010]. We propose that the OSNs may affect the physiology of the C. elegans nematode, as assessed by the PGCs and brood size, via secreted molecules. PGC counts and brood sizes from animals with genetically dysfunctional AWA or AWC neurons are discussed in this poster.A mobile RNA intermediate is an attractive candidate to mediate the communication between the OSNs and the germline. Published data from the L'Etoile lab shows that 22G RNAs synthesized in the AWC show increased levels worm-wide upon odor exposure [Juang et al. 2013] and unpublished data indicate that this increase is dependent on the presence of SID-1 dsRNA channels. We discuss the effect of dysfunctional SID-1 channels on the PGC pool and brood size.Finally, the nuclear RNAi pathway, involving NRDE-1, 2 and 4, is able to regulate gene expression in the germline nuclei [Burton et al. 2011]. Preliminary studies have shown that siRNA knockdown of the human homolog of NRDE-2 decreases the viability of mammalian cells transformed with the oncogene Aurora B kinase, which functions in chromosomal segregation during both mitosis and meiosis. We therefore examined the effect of mutant nrde-2 on the C. elegans PGC pool and brood size. Our results lead us to believe that nrde-2 has a conserved function in maintaining proper cellular proliferation.

Juang BT et al. (2014) Hum Mol Genet "Expression of an expanded CGG-repeat RNA in a single pair of primary sensory neurons impairs olfactory adaptation in Caenorhabditis elegans."

Collins K, Ludwig AL, Morales C, Asundi A, Hagerman PJ, Benedetti KL, Juang BT, Gu C, L'etoile N, Wittman T

[Hum Mol Genet, 2014]

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a severe neurodegenerative disorder that affects carriers of premutation CGG-repeat expansion alleles of the fragile X mental retardation 1 (FMR1) gene; current evidence supports a causal role of the expanded CGG repeat within the FMR1 mRNA in the pathogenesis of FXTAS. Though the mRNA has been observed to induce cellular toxicity in FXTAS, the mechanisms are unclear. One common neurophysiological characteristic of FXTAS patients is their inability to properly attenuate their response to an auditory stimulus upon receipt of a small pre-stimulus. Therefore, to gain genetic and cell biological insight into FXTAS, we examined the effect of expanded CGG repeats on the plasticity of the olfactory response of the genetically tractable nematode, Caenorhabditis elegans (C. elegans). While C. elegans is innately attracted to odors, this response can be downregulated if the odor is paired with starvation. We found that expressing expanded CGG repeats in olfactory neurons interfered with this plasticity without affecting either the innate odor-seeking response or the olfactory neuronal morphology. Interrogation of three RNA regulatory pathways indicated that the expanded CGG repeats act via the C. elegans microRNA (miRNA)-specific Argonaute ALG-2 to diminish olfactory plasticity. This observation suggests that the miRNA-Argonaute pathway may play a pathogenic role in subverting neuronal function in FXTAS.

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.

Schaeffer JM et al. (1990) J Antibiot (Tokyo) "Cochlioquinone A, a nematocidal agent which competes for specific [3H]ivermectin binding sites."

Williamson JM, Schaeffer JM, Bergstrom AR, Liesch JM, Goetz MA, Frazier EG

[J Antibiot (Tokyo), 1990]

Cochlioquinone A, isolated from the fungus Helminthosporium sativum, was found to have nematocidal activity. Cochlioquinone A is a competitive inhibitor of specific [3H]ivermectin binding suggesting that cochlioquinone A and ivermectin interact with the same membrane receptor.