Context-specific regulation of lysosomal lipolysis through network-level diverting of transcription factor interactions.

Plasticity in multicellular organisms involves signaling pathways converting contexts-either natural environmental challenges or laboratory perturbations-into context-specific changes in gene expression. Congruently, the interactions between the signaling molecules and transcription factors (TF) regulating these responses are also context specific. However, when a target gene responds across contexts, the upstream TF identified in one context is often inferred to regulate it across contexts. Reconciling these stable TF-target gene pair inferences with the context-specific nature of homeostatic responses is therefore needed. The induction of the Caenorhabditis elegans genes lipl-3 and lipl-4 is observed in many genetic contexts and is essential to survival during fasting. We find DAF-16/FOXO mediating lipl-4 induction in all contexts tested; hence, lipl-4 regulation seems context independent and compatible with across-context inferences. In contrast, DAF-16-mediated regulation of lipl-3 is context specific. DAF-16 reduces the induction of lipl-3 during fasting, yet it promotes it during oxidative stress. Through discrete dynamic modeling and genetic epistasis, we define that DAF-16 represses HLH-30/TFEB-the main TF activating lipl-3 during fasting. Contrastingly, DAF-16 activates the stress-responsive TF HSF-1 during oxidative stress, which promotes C. elegans survival through induction of lipl-3 Furthermore, the TF MXL-3 contributes to the dominance of HSF-1 at the expense of HLH-30 during oxidative stress but not during fasting. This study shows how context-specific diverting of functional interactions within a molecular network allows cells to specifically respond to a large number of contexts with a limited number of molecular players, a mode of transcriptional regulation we name "contextualized transcription."

A promising strategy for investigating the anti-aging effect of natural compounds: a case study of caffeoylquinic acids.

Caffeoylquinic acids, as plant-derived polyphenols, exhibit multiple biological activities such as antioxidant, anti-inflammatory, and neuroprotective activities. However, only limited information about their effect on longevity is available. In the current study, molecular docking was employed to explore the interactions between six representative caffeoylquinic acids and the insulin-like growth factor-1 receptor (IGFR), which is an important target protein for longevity. The results indicated that all six compounds were embedded well in the active pocket of IGFR, and that 3,5-diCQA exhibited the strongest affinity to IGFR. Moreover, ASP1153, GLU1080, ASP1086, and ARG1003 were the key amino acid residues during the interaction of these 6 compounds with IGFR. Furthermore, the lifespan extension effect of caffeoylquinic acids was evaluated in a Caenorhabditis elegans (C. elegans) model. The results revealed that all the caffeoylquinic acids significantly extended the lifespan of wild-type worms, of which 3,5-diCQA was the most potent compound. Meanwhile, 3,5-diCQA enhanced the healthspan by increasing the body bending and pharyngeal pumping rates and reducing the intestinal lipofuscin level. Further studies demonstrated that 3,5-diCQA induced longevity effects by downregulating the insulin/insulin-like growth factor signaling (IIS) pathway. This study suggested that the combination of molecular docking and genetic analysis of specific worm mutants could be a promising strategy to reveal the anti-aging mechanisms of small molecule natural compounds.

Temporal requirements of SKN-1/NRF as a regulator of lifespan and proteostasis in Caenorhabditis elegans.

Lowering the activity of the Insulin/IGF-1 Signaling (IIS) cascade results in elevated stress resistance, enhanced protein homeostasis (proteostasis) and extended lifespan of worms, flies and mice. In the nematode Caenorhabditis elegans (C. elegans), the longevity phenotype that stems from IIS reduction is entirely dependent upon the activities of a subset of transcription factors including the Forkhead factor DAF-16/FOXO (DAF-16), Heat Shock Factor-1 (HSF-1), SKiNhead/Nrf (SKN-1) and ParaQuat Methylviologen responsive (PQM-1). While DAF-16 determines lifespan exclusively during early adulthood and governs proteostasis in early adulthood and midlife, HSF-1 executes these functions foremost during development. Despite the central roles of SKN-1 as a regulator of lifespan and proteostasis, the temporal requirements of this transcription factor were unknown. Here we employed conditional knockdown techniques and discovered that in C. elegans, SKN-1 is primarily important for longevity and proteostasis during late larval development through early adulthood. Our findings indicate that events that occur during late larval developmental through early adulthood affect lifespan and proteostasis and suggest that subsequent to HSF-1, SKN-1 sets the conditions, partially overlapping temporally with DAF-16, that enable IIS reduction to promote longevity and proteostasis. Our findings raise the intriguing possibility that HSF-1, SKN-1 and DAF-16 function in a coordinated and sequential manner to promote healthy aging.

A global chromatin compaction pathway that represses germline gene expression during starvation.

While much is known about how transcription is controlled at individual genes, comparatively little is known about how cells regulate gene expression on a genome-wide level. Here, we identify a molecular pathway in the C. elegans germline that controls transcription globally in response to nutritional stress. We report that when embryos hatch into L1 larvae, they sense the nutritional status of their environment, and if food is unavailable, they repress gene expression via a global chromatin compaction (GCC) pathway. GCC is triggered by the energy-sensing kinase AMPK and is mediated by a novel mechanism that involves the topoisomerase II/condensin II axis acting upstream of heterochromatin assembly. When the GCC pathway is inactivated, then transcription persists during starvation. These results define a new mode of whole-genome control of transcription.

A survey of the kinome pharmacopeia reveals multiple scaffolds and targets for the development of novel anthelmintics.

Over one billion people are currently infected with a parasitic nematode. Symptoms can include anemia, malnutrition, developmental delay, and in severe cases, death. Resistance is emerging to the anthelmintics currently used to treat nematode infection, prompting the need to develop new anthelmintics. Towards this end, we identified a set of kinases that may be targeted in a nematode-selective manner. We first screened 2040 inhibitors of vertebrate kinases for those that impair the model nematode Caenorhabditis elegans. By determining whether the terminal phenotype induced by each kinase inhibitor matched that of the predicted target mutant in C. elegans, we identified 17 druggable nematode kinase targets. Of these, we found that nematode EGFR, MEK1, and PLK1 kinases have diverged from vertebrates within their drug-binding pocket. For each of these targets, we identified small molecule scaffolds that may be further modified to develop nematode-selective inhibitors. Nematode EGFR, MEK1, and PLK1 therefore represent key targets for the development of new anthelmintic medicines.

Beneficial Effects of Cyclic Ether 2-Butoxytetrahydrofuran from Sea Cucumber Holothuria scabra against Aß Aggregate Toxicity in Transgenic Caenorhabditis elegans and Potential Chemical Interaction.

The pathological finding of amyloid-ß (Aß) aggregates is thought to be a leading cause of untreated Alzheimer's disease (AD). In this study, we isolated 2-butoxytetrahydrofuran (2-BTHF), a small cyclic ether, from Holothuria scabra and demonstrated its therapeutic potential against AD through the attenuation of Aß aggregation in a transgenic Caenorhabditis elegans model. Our results revealed that amongst the five H. scabra isolated compounds, 2-BTHF was shown to be the most effective in suppressing worm paralysis caused by Aß toxicity and in expressing strong neuroprotection in CL4176 and CL2355 strains, respectively. An immunoblot analysis showed that CL4176 and CL2006 treated with 2-BTHF showed no effect on the level of Aß monomers but significantly reduced the toxic oligomeric form and the amount of 1,4-bis(3-carboxy-hydroxy-phenylethenyl)-benzene (X-34)-positive fibril deposits. This concurrently occurred with a reduction of reactive oxygen species (ROS) in the treated CL4176 worms. Mechanistically, heat shock factor 1 (HSF-1) (at residues histidine 63 (HIS63) and glutamine 72 (GLN72)) was shown to be 2-BTHF's potential target that might contribute to an increased expression of autophagy-related genes required for the breakdown of the Aß aggregate, thus attenuating its toxicity. In conclusion, 2-BTHF from H. scabra could protect C. elegans from Aß toxicity by suppressing its aggregation via an HSF-1-regulated autophagic pathway and has been implicated as a potential drug for AD.

CLK-2/TEL2 is a conserved component of the nonsense-mediated mRNA decay pathway.

Nonsense-mediated mRNA decay (NMD) controls eukaryotic mRNA quality, inducing the degradation of faulty transcripts. Key players in the NMD pathway were originally identified, through genetics, in Caenorhabditis elegans as smg (suppressor with morphological effect on genitalia) genes. Using forward genetics and fluorescence-based NMD reporters, we reexamined the genetic landscape underlying NMD. Employing a novel strategy for mapping sterile mutations, Het-Map, we identified clk-2, a conserved gene previously implicated in DNA damage signaling, as a player in the nematode NMD. We find that CLK-2 is expressed predominantly in the germline, highlighting the importance of auxiliary factors in tissue-specific mRNA decay. Importantly, the human counterpart of CLK-2/TEL2, TELO2, has been also implicated in the NMD, suggesting a conserved role of CLK-2/TEL2 proteins in mRNA surveillance. Recently, variants of TELO2 have been linked to an intellectual disability disorder, the You-Hoover-Fong syndrome, which could be related to its function in the NMD.

Notch receptor GLP-1 regulates toxicity of simulated microgravity stress by activating germline-intestine communication of insulin signaling in C. elegans.

We here investigated molecular basis of notch receptor GLP-1 in controlling simulated microgravity stress in Caenorhabditis elegans. glp-1 expression was decreased by simulated microgravity. Meanwhile, glp-1 mutation caused resistance to toxicity of simulated microgravity. GLP-1 acted in germline cells to control toxicity of simulated microgravity. In germline cells, RNAi knockdown of glp-1 increased daf-16 expression. RNAi knockdown of daf-16 suppressed resistance to toxicity of simulated microgravity in glp-1 mutant. In simulated microgravity treated worms, germline RNAi knockdown of glp-1 decreased expressions of daf-28, ins-39, and ins-8 encoding insulin peptides, and resistance to simulated microgravity toxicity could be detected in daf-28(RNAi), ins-39(RNAi), and ins-8(RNAi) worms. In simulated microgravity treated worms, RNAi knockdown of daf-28, ins-39, or ins-8 in germline cells further increased expression and nucleus localization of transcriptional factor DAF-16 in intestinal cells. Therefore, the GLP-1-activated germline-intestine communication of insulin signaling is required for control of simulated microgravity toxicity in C. elegans.

Identification of compounds that bind the centriolar protein SAS-6 and inhibit its oligomerization.

Centrioles are key eukaryotic organelles that are responsible for the formation of cilia and flagella, and for organizing the microtubule network and the mitotic spindle in animals. Centriole assembly requires oligomerization of the essential protein spindle assembly abnormal 6 (SAS-6), which forms a structural scaffold templating the organization of further organelle components. A dimerization interaction between SAS-6 N-terminal "head" domains was previously shown to be essential for protein oligomerization in vitro and for function in centriole assembly. Here, we developed a pharmacophore model allowing us to assemble a library of low-molecular-weight ligands predicted to bind the SAS-6 head domain and inhibit protein oligomerization. We demonstrate using NMR spectroscopy that a ligand from this family binds at the head domain dimerization site of algae, nematode, and human SAS-6 variants, but also that another ligand specifically recognizes human SAS-6. Atomistic molecular dynamics simulations starting from SAS-6 head domain crystallographic structures, including that of the human head domain which we now resolve, suggest that ligand specificity derives from favorable Van der Waals interactions with a hydrophobic cavity at the dimerization site.

Identification of chemical compounds as an inhibitor of mitochondrial ATP synthesis, leading to an increased stress resistance and an extended lifespan in C. elegans.

It is well known that the disruption of the mitochondrial respiratory components prolongs lifespan in many species. The mitochondrial stress response can lead to an increased survival rate through the restoration of the cellular homeostasis. Therefore, developing pharmacological interventions that induce mitochondrial stress response may be desirable to delay the onset of age-related diseases and promote a healthy life. In this study, we present chemical compounds, revealed by systematic screening of chemical libraries, which inhibit mitochondrial ATP synthesis in mammalian cells. Our study demonstrates that these compounds alter the body length and promote the oxidative stress response which leads to an increased longevity in Caenorhabditis elegans. Thus, our study identifies chemical compounds that may have potential therapeutic applications through affecting the mitochondrial function.

Caenorhabditis elegans Flamingo FMI-1 controls dendrite self-avoidance through F-actin assembly.

Self-avoidance is a conserved mechanism that prevents crossover between sister dendrites from the same neuron, ensuring proper functioning of the neuronal circuits. Several adhesion molecules are known to be important for dendrite self-avoidance, but the underlying molecular mechanisms are incompletely defined. Here, we show that FMI-1/Flamingo, an atypical cadherin, is required autonomously for self-avoidance in the multidendritic PVD neuron of Caenorhabditis elegans The fmi-1 mutant shows increased crossover between sister PVD dendrites. Our genetic analysis suggests that FMI-1 promotes transient F-actin assembly at the tips of contacting sister dendrites to facilitate their efficient retraction during self-avoidance events, probably by interacting with WSP-1/N-WASP. Mutations of vang-1, which encodes the planar cell polarity protein Vangl2 previously shown to inhibit F-actin assembly, suppress self-avoidance defects of the fmi-1 mutant. FMI-1 downregulates VANG-1 levels probably through forming protein complexes. Our study identifies molecular links between Flamingo and the F-actin cytoskeleton that facilitate efficient dendrite self-avoidance.

In silico and In vivo Evaluation of Oxidative Stress Inhibitors Against Parkinson's Disease using the C. elegans Model.

BACKGROUND: Parkinson's disease ranks second, after Alzheimer's as the major neurodegenerative disorder, for which no cure or disease-modifying therapies exist. Ample evidence indicate that PD manifests as a result of impaired anti-oxidative machinery leading to neuronal death wherein Cullin-3 has ascended as a potential therapeutic target for diseases involving damaged anti-oxidative machinery. OBJECTIVE: The design of target specific inhibitors for the Cullin-3 protein might be a promising strategy to increase the Nrf2 levels and to decrease the possibility of "off-target" toxic properties. METHODS: In the present study, an integrated computational and wet lab approach was adopted to identify small molecule inhibitors for Cullin-3. The rational drug designing process comprised homology modeling and derivation of the pharmacophore for Cullin-3, virtual screening of Zinc natural compound database, molecular docking and Molecular dynamics based screening of ligand molecules. In vivo validations of an identified lead compound were conducted in the PD model of C. elegans. RESULTS AND DISCUSSION: Our strategy yielded a potential inhibitor; (Glide score = -12.31), which was evaluated for its neuroprotective efficacy in the PD model of C. elegans. The inhibitor was able to efficiently defend against neuronal death in PD model of C. elegans and the neuroprotective effects were attributed to its anti-oxidant activities, supported by the increase in superoxide dismutase, catalase and the diminution of acetylcholinesterase and reactive oxygen species levels. In addition, the Cullin-3 inhibitor significantly restored the behavioral deficits in the transgenic C. elegans. CONCLUSION: Taken together, these findings highlight the potential utility of Cullin-3 inhibition to block the persistent neuronal death in PD. Further studies focusing on Cullin-3 and its mechanism of action would be interesting.

Opposing effects of an F-box protein and the HSP90 chaperone network on microtubule stability and neurite growth in Caenorhabditis elegans.

Molecular chaperones often work collaboratively with the ubiquitylation-proteasome system (UPS) to facilitate the degradation of misfolded proteins, which typically safeguards cellular differentiation and protects cells from stress. In this study, however, we report that the Hsp70/Hsp90 chaperone machinery and an F-box protein, MEC-15, have opposing effects on neuronal differentiation, and that the chaperones negatively regulate neuronal morphogenesis and functions. Using the touch receptor neurons (TRNs) of Caenorhabditis elegans, we find that mec-15(-) mutants display defects in microtubule formation, neurite growth, synaptic development and neuronal functions, and that these defects can be rescued by the loss of Hsp70/Hsp90 chaperones and co-chaperones. MEC-15 probably functions in a Skp-, Cullin- and F-box- containing complex to degrade DLK-1, which is an Hsp90 client protein stabilized by the chaperones. The abundance of DLK-1, and likely other Hsp90 substrates, is fine-tuned by the antagonism between MEC-15 and the chaperones; this antagonism regulates TRN development, as well as synaptic functions of GABAergic motor neurons. Therefore, a balance between the UPS and the chaperones tightly controls neuronal differentiation.

Polarized epidermal growth factor secretion ensures robust vulval cell fate specification in Caenorhabditis elegans.

The anchor cell (AC) in C. elegans secretes an epidermal growth factor (EGF) homolog that induces adjacent vulval precursor cells (VPCs) to differentiate. The EGF receptor in the nearest VPC sequesters the limiting EGF amounts released by the AC to prevent EGF from spreading to distal VPCs. Here, we show that not only EGFR localization in the VPCs but also EGF polarity in the AC is necessary for robust fate specification. The AC secretes EGF in a directional manner towards the nearest VPC. Loss of AC polarity causes signal spreading and, when combined with MAPK pathway hyperactivation, the ectopic induction of distal VPCs. In a screen for genes preventing distal VPC induction, we identified sra-9 and nlp-26 as genes specifically required for polarized EGF secretion. sra-9(lf) and nlp-26(lf) mutants exhibit errors in vulval fate specification, reduced precision in VPC to AC alignment and increased variability in MAPK activation. sra-9 encodes a seven-pass transmembrane receptor acting in the AC and nlp-26 a neuropeptide-like protein expressed in the VPCs. SRA-9 and NLP-26 may transduce a feedback signal to channel EGF secretion towards the nearest VPC.

Optimized criteria for locomotion-based healthspan evaluation in C. elegans using the WorMotel system.

Getting a grip on how we may age healthily is a central interest of biogerontological research. To this end, a number of academic teams developed platforms for life- and healthspan assessment in Caenorhabditis elegans. These are very appealing for medium- to high throughput screens, but a broader implementation is lacking due to many systems relying on custom scripts for data analysis that others struggle to adopt. Hence, user-friendly recommendations would help to translate raw data into interpretable results. The aim of this communication is to streamline the analysis of data obtained by the WorMotel, an economically and practically appealing screening platform, in order to facilitate the use of this system by interested researchers. We here detail recommendations for the stepwise conversion of raw image data into activity values and explain criteria for assessment of health in C. elegans based on locomotion. Our analysis protocol can easily be adopted by researchers, and all needed scripts and a tutorial are available in S1 and S2 Files.

trans-Fatty acids facilitate DNA damage-induced apoptosis through the mitochondrial JNK-Sab-ROS positive feedback loop.

trans-Fatty acids (TFAs) are unsaturated fatty acids that contain one or more carbon-carbon double bonds in trans configuration. Epidemiological evidence has linked TFA consumption with various disorders, including cardiovascular diseases. However, the underlying pathological mechanisms are largely unknown. Here, we show a novel toxic mechanism of TFAs triggered by DNA damage. We found that elaidic acid (EA) and linoelaidic acid, major TFAs produced during industrial food manufacturing (so-called as industrial TFAs), but not their corresponding cis isomers, facilitated apoptosis induced by doxorubicin. Consistently, EA enhanced UV-induced embryonic lethality in C. elegans worms. The pro-apoptotic action of EA was blocked by knocking down Sab, a c-Jun N-terminal kinase (JNK)-interacting protein localizing at mitochondrial outer membrane, which mediates mutual amplification of mitochondrial reactive oxygen species (ROS) generation and JNK activation. EA enhanced doxorubicin-induced mitochondrial ROS generation and JNK activation, both of which were suppressed by Sab knockdown and pharmacological inhibition of either mitochondrial ROS generation, JNK, or Src-homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1) as a Sab-associated protein. These results demonstrate that in response to DNA damage, TFAs drive the mitochondrial JNK-Sab-ROS positive feedback loop and ultimately apoptosis, which may provide insight into the common pathogenetic mechanisms of diverse TFA-related disorders.

Novel pharmacological modulation of dystonic phenotypes caused by a gain-of-function mutation in the Na+ leak-current channel.

The Na leak-current channel (NALCN) regulates the resting membrane potential in excitable cells, thus determining the likelihood of depolarization in response to incoming signals. Gain-of-function (gf) mutations in this channel are associated with severe dystonic movement disorders in man. Currently, there are no known pharmacological antagonists or selective modulators of this important channel. A gain-of-function mutation in NALCN of C. elegans [known as unc-77(e625)] causes uncoordinated, hyperactive locomotion. We hypothesized that this hyperactive phenotype can be rescued with pharmacological modulators. Here, we summarize the results of targeted drug screening aimed at identification of drugs that corrected locomotion deficits in unc-77(e625) animals. To assay hyperactive locomotion, animals were acutely removed from food and characteristic foraging movements were quantified. Drug screening revealed that 2-aminoethoxydiphenyl borate (2-ABP), nifedipine, nimodipine, flunarizine and ethoxzolamide significantly decreased abnormal movements in unc-77(e625) animals. 2-APB also corrected egg release and coiling deficits in this strain. In addition, serotonin and dopamine both reduced hyperactive locomotion, consistent with regulatory interactions between these systems and the NALCN. 2-APB induced movement phenotypes in wild-type animals that faithfully mimicked those observed in NALCN knockout strains, which suggested that this drug may directly block the channel. Moreover, 2-APB and flunarizine showed significant structural similarities suggestive of overlap in their mode of action. Together, these studies have revealed new insights into regulation of NALCN function and led to the discovery of a potential pharmacological antagonist of the NALCN.

Modeling succinate dehydrogenase loss disorders in C. elegans through effects on hypoxia-inducible factor.

Mitochondrial disorders arise from defects in nuclear genes encoding enzymes of oxidative metabolism. Mutations of metabolic enzymes in somatic tissues can cause cancers due to oncometabolite accumulation. Paraganglioma and pheochromocytoma are examples, whose etiology and therapy are complicated by the absence of representative cell lines or animal models. These tumors can be driven by loss of the tricarboxylic acid cycle enzyme succinate dehydrogenase. We exploit the relationship between succinate accumulation, hypoxic signaling, egg-laying behavior, and morphology in C. elegans to create genetic and pharmacological models of succinate dehydrogenase loss disorders. With optimization, these models may enable future high-throughput screening efforts.

Peripheral cathepsin L inhibition induces fat loss in C. elegans and mice through promoting central serotonin synthesis.

BACKGROUND: Cathepsin L and some other cathepsins have been implicated in the development of obesity in humans and mice. The functional inactivation of the proteases reduces fat accumulation during mammalian adipocyte differentiation. However, beyond degrading extracellular matrix protein fibronectin, the molecular mechanisms by which cathepsins control fat accumulation remain unclear. We now provide evidence from Caenorhabditis elegans and mouse models to suggest a conserved regulatory circuit in which peripheral cathepsin L inhibition lowers fat accumulation through promoting central serotonin synthesis. RESULTS: We established a C. elegans model of fat accumulation using dietary supplementation with glucose and palmitic acid. We found that nutrient supplementation elevated fat storage in C. elegans, and along with worm fat accumulation, an increase in the expression of cpl-1 was detected using real-time PCR and western blot. The functional inactivation of cpl-1 reduced fat storage in C. elegans through activating serotonin signaling. Further, knockdown of cpl-1 in the intestine and hypodermis promoted serotonin synthesis in worm ADF neurons and induced body fat loss in C. elegans via central serotonin signaling. We found a similar regulatory circuit in high-fat diet-fed mice. Cathepsin L knockout promoted fat loss and central serotonin synthesis. Intraperitoneal injection of the cathepsin L inhibitor CLIK195 similarly reduced body weight gain and white adipose tissue (WAT) adipogenesis, while elevating brain serotonin level and WAT lipolysis and fatty acid ß-oxidation. These effects of inhibiting cathepsin L were abolished by intracranial injection of p-chlorophenylalanine, inhibitor of a rate-limiting enzyme for serotonin synthesis. CONCLUSION: This study reveals a previously undescribed molecular mechanism by which peripheral CPL-1/cathepsin L inhibition induces fat loss in C. elegans and mice through promoting central serotonin signaling.

A Screen of the Conserved Kinome for Negative Regulators of LIN-12 Negative Regulatory Region ("NRR")-Missense Activity in Caenorhabditis elegans.

Genetic analysis of LIN-12/Notch signaling in C. elegans has provided many insights into human biology. Activating missense mutations in the Negative Regulatory Region (NRR) of the ectodomain of LIN-12/Notch were first described in C. elegans, and similar mutations in human Notch were later found to cause T-cell acute lymphoblastic leukemia (T-ALL). The ubiquitin ligase sel-10/Fbw7 is the prototype of a conserved negative regulator of lin-12/Notch that was first defined by loss-of-function mutations that enhance lin-12 NRR-missense activity in C. elegans, and then demonstrated to regulate Notch activity in mammalian cells and to be a bona fide tumor suppressor in T-ALL. Here, we report the results of an RNAi screen of 248 C. elegans protein kinase-encoding genes with human orthologs for enhancement of a weakly activating NRR-missense mutation of lin-12 in the Vulval Precursor Cells. We identified, and validated, thirteen kinase genes whose loss led to increase lin-12 activity; eleven of these genes have never been implicated previously in regulating Notch activity in any system. Depleting the activity of five kinase genes (cdk-8, wnk-1, kin-3, hpo-11, and mig-15) also significantly enhanced the activity of a transgene in which heterologous sequences drive expression of the untethered intracellular domain of LIN-12, suggesting that they increase the activity or stability of the signal-transducing form of LIN-12/Notch. Precedents set by other regulators of lin-12/Notch defined through genetic interactions in C. elegans suggest that this new set of genes may include negative regulators that are functionally relevant to mammalian development and cancer.