A Yuan et al. (1999) International C. elegans Meeting "nSLO2, A Novel Cl- Activated K+ Channel"

M Dourado, L Salkoff, A Yuan, ZW Wang, A Butler

[International C. elegans Meeting, 1999]

SLO1 channels are high conductance K + channels activated by voltage and Ca 2+ . These channels serve as a link between membrane excitability and changes in intracellular Ca 2+ . We unexpectedly found a new SLO-like channel in C. elegans called nSLO2. Nslo2 (nematode slo-2 ) was subsequently cloned from a C. elegans embryonic cDNA library, and was expressed in Xenopus oocytes. Surprisingly, nSLO2 requires intracellular Cl - as well as Ca 2+ for activation. This unique property has never been described for any other ion channel. Perhaps nSLO2 is an intracellular Cl - sensor; changes in [Cl - ] i may directly influence membrane electrical behavior by modulating the activity of nSLO2. Changes in [Cl - ] i have been observed in different cells, for example the [Cl - ] i decreases as mammalian neurons mature. As the first step in elucidating the physiological role of nSLO2, we determined its tissue specific expression pattern in C. elegans . The slo-2 genomic sequence and its native promotor were fused to GFP. Nematodes transformed with this promotor:GFP fusion revealed an expression pattern in muscles and in some neurons. Interestingly, this expression pattern overlaps with that of nSLO1 (see related poster by Wang et al.), suggesting that the two subunits may form functional heteromeric channels in vivo . Preliminary results show that nSLO1 and nSLO2 are capable of forming functional heteromers when co-expressed in Xenopus oocytes.

Yuan JY et al. (1989) International C. elegans Meeting "molecular analysis of ced-3 and ced-4."

Yuan JY, Horvitz HR

[International C. elegans Meeting, 1989]

Yuan Jiang et al. (2006) Development & Evolution Meeting "CEH-20 regulates the expression of mls-2 in the postembryonic mesoderm"

Yuan Jiang, Jun Liu

[Development & Evolution Meeting, 2006]

mls-2 encodes a HMX homeodomain protein that plays critical roles in the C. elegans postembryonic mesodermal lineage, the M lineage. mls-2 is expressed in the M lineage as well as a few other cell types, such as several pairs of head neurons including ASK and AIM. To uncover mechanisms involved in regulating the expression of mls-2, we generated a series of promoter deletions and identified an M lineage enhancer (position -2221 to -2076) that is required for mls-2 expression in the M lineage. We further identified several essential elements within this M enhancer. Among these elements are two putative Exd/Abd-B binding sites that are conserved in C. briggsae. We have found that mls-2 expression in the M lineage is dependent on the C.elegans Exd/Pbx homolog CEH-20. We are currently testing whether CEH-20 directly binds to the mls-2 promoter and whether CEH-20 regulates mls-2 expression through acting together with the Abd-B class Hox proteins, EGL-5/PHP-3/NOB-1, and the Hth/Meis homolog, UNC-62.

Yuan JY et al. (1987) International C. elegans Meeting "genetic and molecular studies of ced-3 and ced-4."

Yuan JY, Horvitz HR

[International C. elegans Meeting, 1987]

ZHOU, Yuan et al. (2011) International Worm Meeting "Identification of the sex pheromone receptors in AWA neuron."

ZHOU, Yuan, CHOW, King-Lau

[International Worm Meeting, 2011]

Chemosensation is an important process used by animals to perceive changes in the environment and to coordinate appropriate responses. The chemosensory system detects a diverse range of chemical cues, including sex pheromone, via different chemosensory receptors. We have previously shown that C. remanei females produce a sex pheromone with long-range attractiveness for both C. remanei and C. elegans males. Our data also implicate the involvement of G protein-coupled receptors (GPCRs) acting in AWA neurons in this perception process. In order to identify the receptors acting within AWA, an in vivo cell-specific pull-down experiment was conducted, followed by a microarray analysis. Over 150 GPCR-transcripts were identified from the AWA-specific transcriptome, the validity of their involvement demands further experimental verification. Some mutants with defective candidate GPCRs have been tested with the standard pheromone-attractant assays. As a result, 21 candidate GPCRs were eliminated from functioning in the sex pheromone perception process, while a male-specific candidate was shown to be involved. Tagged with a gfp reporter, this gene showed expression in cilia of the ASIs of both sexes and in male AWAs. Preliminary experiments were conducted to evaluate AWA-specific expression of this gene for function rescue in the null mutant, while AWA-specific knock-down of this same gene will be tested in transgenic animals. In addition, the relationship between its function and its cellular targets will be ascertained by ASI-expression rescue and the results will be presented. In parallel, transcriptional reporter expression study was conducted to validate the other candidates. Nine GPCRs were confirmed to express in AWA from the top 50 candidates. Behavioral tests will be conducted using the corresponding mutants or knock-down animals in order to explore their functions in AWA-mediated chemosensation. In addition, this subset of AWA-specific genes opens the door for the definition of the potential AWA-specific cis-element, which might help uncover the regulatory architecture of AWA cell fate specification. (This study is supported by Research Grants Council, Hong Kong.).

Tsung-Yuan Hsu et al. (2007) International Worm Meeting "The role of INA-1 integrin in the engulfment of apoptotic cells."

Tsung-Yuan Hsu, Yi-Chun Wu

[International Worm Meeting, 2007]

During the development of C. elegans hermaphrodites, 131 out of 1090 somatic cells undergo programmed cell death. After cells die by programmed cell death, their cell corpses are swiftly recognized and removed by engulfing cells. The engulfment process is controlled by two partially redundant pathways. One pathway involves the receptor PSR-1 that signals through the trimeric complex CED-2/CrkII, CED-5/Dock180 and CED-12/Elmo-1 to activate CED-10/Rac for actin reorganization as an engulfing cell extends pseudopodia around an apoptotic cell. Our genetic and molecular studies show that ina-1, which encodes an integrin alpha subunit, also acts in this signaling pathway during cell-corpse engulfment. Mutants defective in ina-1exhibited increased numbers of cell corpses in early embryos. The 4-D microscopic recording of cell-corpse duration demonstrates that ina-1 mutants are defective in cell-corpse engulfment. To test if ina-1 acts in the genetic pathway mediated by ced-2,ced-5 and ced-12, we counted and compared cell corpses of single and double mutants. Cell corpses of ina-1; ced-2, ina-1; ced-5 and ina-1;ced-12 double mutants were indistinguishable from those of ced-2, ced-5, and ced-12 single mutants, respectively. In addition, overexpression of ced-2,ced-5 or ced-12 rescued the engulfment defect of the ina-1 mutants. These results suggest that ina-1 may act upstream of ced-2,ced-5 and ced-12 during the engulfment process of programmed cell death. We are currently investigating if ina-1 acts in dying or engulfing cells to promote cell-corpse engulfment.

Li, Yuan et al. (2015) International Worm Meeting "qx193 affects lysosome integrity and dynamics in C. elegans."

Sun, Yanan, Wang, Xiaochen, Zou, Wei, Chen, Baohui, Li, Yuan

[International Worm Meeting, 2015]

Lysosomes are specialized membrane bound organelles that degrade macromolecular cargoes derived from endocytosis, phagocytosis or autophagy. The resulting catabolites are exported by membrane transporters on lysosomes for re-utilization in cellular metabolism. Over 50 human disorders have been identified due to dysfunctions of lysosomes, indicating important roles of lysosomes in cell homeostasis and animal development.In C. elegans, lysosomes appear as both small puncta and thin tubules, displaying highly dynamic patterns during development, in aging process and under different culture conditions. qx193 is a recessive mutation that causes abnormally enlarged globular lysosomes and lack of the tubular ones. We found that lysosomes, which are quite dynamic in wild type, become static in qx193 worms and are defective in degrading cargoes derived from both autophagy and phagocytosis. Our further cell biological and genetic analyses revealed that qx193 causes accumulation of damaged lysosomes, which can be cleared by autophagy. Moreover, qx193 mutants display a delayed larval development and significantly shortened life span, suggesting important roles of lysosomes in animal development and aging process. We have cloned the gene affected in qx193 and are further characterizing its roles in maintaining lysosome integrity and function. This study will help us to understand how lysosomes are regulated and contribute to cell homeostasis and animal development.

ZHOU, Yuan et al. (2009) International Worm Meeting "Identification of molecules in specific neurons required for pheromone perception."

Chow, King L., ZHOU, Yuan, LI, Ching K.

[International Worm Meeting, 2009]

Chemosensation is important function for animals to perceive ongoing changes in the environment and coordinate appropriate responses. The chemosensory system detects different chemical cues, including sex pheromone, using one of the hundreds of chemosensory receptors (CRs). We have previously shown that C. remanei females can produce a sex pheromone with long range attractiveness towards both C. remanei and C. elegans males. The attractive response of males towards the chemical involves the neural circuit composed of the two ciliated neurons, CEM, AWA, and the interneuron, AIZ. Our data also implicate the presence of G protein-coupled receptors involved in this perception process acting in AWA. In order to identify these receptors and related molecules acting in AWA, we have initiated the experiments to identify AWA-enriched mRNA through cell-specific pull down experiment. At the same time, we are characterizing the AWA-specific odr-7 promoter and odr-10 promoter by a serial deletion study to define the AWA-specific cis-element. We hope that the consensus definition can help identify the GPCRs that are uniquely expressed in AWA neurons and allow functional testing to be conducted. Similarly, very little information about CEM neuronal function has been reported. Since they are also required in pheromone perception, we take a similar approach described above for AWA characterization and will identify key components acting uniquely in CEM. The details about systematic deletion of CEM-specific promoters and preliminary results of identifying key regulator acting in CEM will be reported. Collectively, we hope to define the molecular identities of these two cell types and understand how these two cell types function to coordinate the pheromone perception process. (This study is supported by Research Grants Council, Hong Kong.).

Tsung-Yuan Hsu et al. (2004) East Asia Worm Meeting "Screen for genes involved in the engulfment of cell corpses"

Bin-Kuan Chou, Wei-Chun Wang, Tsung-Yuan Hsu, Yi-Chun Wu

[East Asia Worm Meeting, 2004]

Programmed cell death, which removes unwanted and harmful cells, are important for the development and homeostasis of multicellular organisms. Cell corpses generated by programmed cell death are eliminated by the engulfment process. At least eight genes that function in cell-corpse engulfment have been identified in C. elegans . They likely defined two partially redundant pathways during the engulfment process. One pathway consists of ced-1 , ced-6 and ced-7 and the other psr-1 , ced-2 , ced-5 , ced-10 and ced-12 . Studies by transcriptional overexpression showed that psr-1 genetically acts upstream of ced-2 , ced-5 , ced-10 and ced-12 to promote cell-corpse engulfment. In Interestingly, psr-1 (null) mutants exhibited less persistent cell corpses than do ced-2 , ced-5 , ced-10 and ced-12 strong or null mutants. This observation suggests that other genes may act together with psr-1 to promote cell-corpse engulfment. In order to identify these genes, we performed an RNAi-based screen for mutants with more cell corpses using Nomarski microscopy. In a pilot screen, mutants (RNAi) with more cell corpses were identified. We will present results in the meeting.

Yuan, Y. et al. (2011) International Worm Meeting "Proteomic profiling dietary restriction pathways with 13C-labeled Caenorhabditis elegans."

Kramp, K., Saha, S., Ewing, R., Xu, H., Ching, T., Hsu, A., Miyagi, M., Feng, Z., Yuan, Y., Kadiyala, C.

[International Worm Meeting, 2011]

Dietary restriction (DR) modifies the metabolism of animals and humans, extends lifespan and improves age-related health of various animals. The underlying mechanism of these physiological outputs of DR and their interplay remains to be clarified. Here, we developed a quantitative proteomic method called stable isotope labeling by amino acids in C. elegans (SILACE) by labeling worms with isotope labeled amino acids. Using SILACE, we reliably quantified the abundance of 1805 proteins. The average and median levels of these 1805 proteins of dietary restricted worms were lower than that of control worms when comparing both the same number and the same weight of worms, indicating that DR systematically decreases protein synthesis. In this background, we were able to identify 237 proteins with quantities significantly up- or down- regulated by DR. We found that DR specifically modified the expression of key genes involved in the catabolism/synthesis of carbohydrates, fatty acids, amino acids and other small molecules, as well as mitochondrial/ribosome functions and stress responses. Many transcriptional factors, translational factors and signaling molecules that are associated with or play a key role in the pathology of human metabolic, cancer and other diseases were also identified as significantly altered in abundance by DR. Most of these proteins have a previously unknown relationship with both DR and lifespan. Lifespan and qPCR assays confirmed some of these findings. In summary, DR has a profound effect on metabolisms of this organism and elicits consequent signaling and physiological responses. We also concluded that SILACE provides sensitive, reliable and scalable proteomic analysis.