Chen, Yutao et al. (2011) International Worm Meeting "Insulin-like Signaling in Nutritional Control of L1 Development in C. elegans ."

Baugh, Ryan, Kurhanewicz, Nicole, Chen, Yutao

[International Worm Meeting, 2011]

In the wild animals must coordinate development with fluctuating nutrient availability. Insulin-like signaling is conserved among metazoan, and it functions to buffer the physiological effects of nutrient fluctuation. In C. elegans, newly hatched L1 larvae remain developmentally arrested until feeding. This phenomenon, called L1 arrest or L1 diapause, provides an opportunity to study regulatory mechanisms mediating nutritional control of growth and development. Insulin-like signaling is a key regulator of L1 arrest (Baugh and Sternberg, 2006; Kao et al, 2007). In spite of great interest in the insulin-like pathway given its function in dauer formation, aging and L1 arrest, the function of specific insulin-like peptide ligands is generally not characterized. The C. elegans genome encodes 40 insulin-like peptides. Although redundancy of these genes is likely, some of them have been shown to have specific phenotypes (Lin et al. 2001, Li et al., 2003, Murphy et al., 2007, Patel et al. 2008, Michaelson et al. 2010,). In addition, over-expression analysis suggests that insulin-like peptides function as either agonists or antagonists of the insulin-like receptor DAF-2, promoting development or arrest, respectively (Pierce et al., 2001). With an mRNA expression analysis platform called nCounter by Nanostring, we comprehensively characterized expression dynamics for all 40 insulin-like genes in response to feeding and starvation. From these expression data we identified several insulin-like genes up-regulated by feeding and several up-regulated by starvation, and we hypothesize that they function as agonists and antagonists, respectively. Destabilized YFP reporter gene analysis confirms nutritional control of transcription, reveals the intestine as the primary site of regulation, and suggests that the putative agonists and antagonists are expressed in different subsets of neurons in L1 worms. We are currently using genetic analysis to study the function of putative agonists during recovery from L1 arrest. By combining expression and phenotypic analysis, we aim to determine the timing and site of action for the insulin-like peptides governing L1 development, dissecting the organismal regulatory network they comprise.

Chen, Yutao et al. (2013) International Worm Meeting "Nutritional Control of Insulin-Like Peptide Expression during L1 Arrest and Recovery."

Chen, Yutao, Baugh, Ryan

[International Worm Meeting, 2013]

Animals must coordinate development with fluctuating nutrient availability. Nutrient availability governs post-embryonic development in C. elegans: larvae that hatch in the absence of food do not initiate post-embryonic development but enter "L1 arrest" (or "L1 diapause") and can survive starvation for weeks. Insulin-like signaling is a key regulator of L1 arrest and recovery. However, the C.elegans genome encodes 40 putative insulin-like peptides (ILPs), and there is evidence that they can function to promote development ("agonists") or arrest ("antagonists"). We used the nCounter platform to measure high-resolution mRNA expression dynamics for all 40 ILPs in response to feeding and fasting in recently hatched L1 larvae. Expression of 23 of the ILPs is significantly affected by nutrient availability. We classified several ILPs as candidate agonists or antagonists based on up-regulation in response to feeding or fasting, respectively. 10 candidate agonists (daf-28, ins-3, ins-4, ins-5, ins-6, ins-7, ins-9, ins-26, ins-33 and ins-35) were selected for further analysis. Phenotypic analysis of single or several multiple deletion mutants has not revealed detectable effects on L1 growth or development. Destabilized YFP reporter gene analysis shows that ten putative agonists are expressed in the intestine and various neurons. 6 out of 10 are expressed in the chemosensory neuron ASI and interneuron PVT. ASI is known to regulate dauer formation and lifespan but PVT has not been shown to be directly involved in feeding or stress response. Quantitative image analysis confirms nutritional control of transcription and reveals the intestine as the primary site of transcriptional regulation. Up-regulation in response to feeding in ASI is also evident in 3 candidates. We are currently testing if intestinal expression is regulated autonomously by ingestion of food or non-autonomously by neuronal signals. In summary, our expression analysis reveals the dynamics and sites of ILP expression in response to nutrient availability, providing insight into how post-embryonic development is governed by insulin-like signaling.

Po MD et al. (2012) Neuron "Releasing the inner inhibition for axon regeneration."

Po MD, Calarco JA, Zhen M

[Neuron, 2012]

The adult mammalian central nervous system exhibits restricted regenerative potential. Chen etal. (2011) and El Bejjani and Hammarlund (2012) used Caenorhabditis elegans to uncover intrinsic factors that inhibit regeneration of axotomized mature neurons, opening avenues for potential therapeutics.

Kaplan, Rebecca et al. (2015) International Worm Meeting "dbl-1/TGF-beta and daf-12/NHR signaling mediate cell-nonautonomous effects of daf-16/FOXO on starvation-induced developmental arrest."

Baugh, Ryan, Jordan, James, Chen, Yutao, Kaplan, Rebecca

[International Worm Meeting, 2015]

C. elegans responds to the absence of food upon hatching by entering a state of developmental arrest in the first larval stage. This "L1 arrest" is associated with increased stress resistance, allowing the larvae to better survive starvation. Loss of the transcription factor daf-16/FOXO, an effector of insulin/IGF signaling, results in arrest-defective and starvation-sensitive phenotypes. We show that daf-16/FOXO regulates L1 arrest cell-nonautonomously, suggesting that insulin/IGF signaling regulates at least one additional signaling pathway. We also show that dbl-1/TGF-beta and daf-12/NHR steroid hormone signaling pathways are required for the arrest-defective phenotype. Furthermore, loss of dbl-1/TGF-beta and daf-12/NHR pathway components delayed L1-stage development in fed larvae. Though the dbl-1/TGF-beta and daf-12/NHR pathways are epistatic to daf-16/FOXO for the arrest-defective phenotype, disruption of these pathways does not suppress the starvation sensitivity of the daf-16/FOXO mutant. This observation uncouples starvation survival from developmental arrest, showing that daf-16/FOXO mutants do not die rapidly during starvation as a result of inappropriate development and indicating that different DAF-16/FOXO targets function as effectors of developmental regulation and starvation resistance. Overall, this study shows that daf-16/FOXO promotes developmental arrest by repressing pathways that promote development.

Silverstein NJ et al. (2017) Immunity "Interleukin-17: Why the Worms Squirm."

Huh JR, Silverstein NJ

[Immunity, 2017]

IL-17 is a cytokine known primarily for its role in inflammation. In a recent issue of Nature, Chen etal. (2017) demonstrate that IL-17 plays a neuromodulatory role in Caenorhabditis elegans by acting directly on neurons to amplify neuronal responses to stimuli and produce changes in animal behavior.

Artan M et al. (2016) Dev Cell "Heat FLiPs a Hormonal Switch for Longevity."

Lee SV, An SW, Artan M

[Dev Cell, 2016]

Temperature-sensing neurons in C.elegans reduce the life-shortening effects of high temperatures via steroid signaling. In this issue of Developmental Cell, Chen etal. (2016) elucidate the underlying mechanisms by which the transcription factor CREB induces the neuropeptide FLP-6 in the temperature-sensing neurons to counteract the life-shortening effects of high temperature.

Akin O et al. (2014) Cell "The shape of things to come."

Akin O, Zipursky SL

[Cell, 2014]

Surface receptors can link binding of ligands to changes in the actin-based cell cytoskeleton. Chia etal. and Chen etal. provide evidence for direct binding between the cytoplasmic tails ofreceptorsand the WAVE complex, a regulator of the actin nucleator Arp2/3 complex, which mighthelp to explain how environmental signals are translated into changes in morphology andmotility.

Chen X et al. (2015) Mol Neurodegener "Erratum to: Ethosuximide ameliorates neurodegenerative disease phenotypes by modulating DAF-16/FOXO target gene expression."

McCue HV, Chen X, Morgan A, Kashyap SS, Barclay JW, Kraemer BC, Burgoyne RD, Wong SQ

[Mol Neurodegener, 2015]

The original version of this article [1] unfortunately contained a mistake. The author list contained a spelling error for the author Hannah V. McCue. The original article has been corrected for this error. The corrected author list is given below:Xi Chen, Hannah V. McCue, Shi Quan Wong, Sudhanva S. Kashyap, Brian C. Kraemer, Jeff W. Barclay, Robert D. Burgoyne and Alan Morgan

Palikaras K et al. (2016) Bio Protoc "Measuring Oxygen Consumption Rate in Caenorhabditis elegans."

Palikaras K, Tavernarakis N

[Bio Protoc, 2016]

The rate of oxygen consumption is a vital marker indicating cellular function during lifetime under normal or metabolically challenged conditions. It is used broadly to study mitochondrial function (Artal-Sanz and Tavernarakis, 2009; Palikaras et al., 2015; Ryu et al., 2016) or investigate factors mediating the switch from oxidative phosphorylation to aerobic glycolysis (Chen et al., 2015; Vander Heiden et al., 2009). In this protocol, we describe a method for the determination of oxygen consumption rates in the nematode Caenorhabditis elegans.

Chen CH et al. (2021) STAR Protoc "Live-cell imaging of PVD dendritic growth cone in post-embryonic C.elegans."

Chen CH, Pan CL

[STAR Protoc, 2021]

Live-cell imaging analysis provides tremendous information for the study of cellular events such as growth cone migration in neuronal development. Here, we describe a protocol for live-cell imaging of migrating PVD dendritic growth cones in the nematode <i>C.elegans</i> by spinning-disk confocal microscopy. Fluorescently labeled growth cones and cytoskeletal proteins could be continuously observed for 4-6h in mid-stage larvae. This protocol is suitable for revealing the dynamic molecular and cellular events in dendrite and axon development of <i>C.elegans</i>. For complete details on the use and execution of this protocol, please refer to Chen etal. (2019).