Paul W. Sternberg

Receptor tyrosine kinases (RTKs) are key therapeutic targets in cancer, diabetes, and other diseases. With only one transmembrane α-helix—compared with seven in G-protein-coupled receptors—RTKs are thought to be activated by ligand-induced dimerization. Complicating this view, however, one of the best-studied RTKs, the insulin receptor (IR), forms allosterically regulated covalent dimers. Moreover, noncovalent “preformed” dimers have frequently been reported for the sequence-related epidermal growth factor receptor (EGFR), one of the first RTKs for which ligand-induced dimerization was described. Here, we describe a detailed structural view of a preformed EGFR dimer. Using cryo-EM, we describe how the Caenorhabditis elegans EGFR (LET-23) dimerizes without ligand. We show that preformed dimer formation modulates ligand sensitivity in vivo, but is not required for signaling itself. We also elucidate substantial ligand-induced conformational changes in LET-23 required for signaling. Our structures reveal unexpected similarities between regulation of LET-23 and the IR, suggesting that LET-23 may represent an evolutionary “missing link” between the IR and EGFR families. In the absence of ligand, intermolecular interactions within preformed receptor dimers hold the extracellular juxtamembrane regions far apart to separate the intracellular kinase domains so that they remain inactive. Ligand binding disrupts these interactions to remove the restraints on the kinase domains, which then can associate to become activated. Our analysis further suggests a unified model for the allosteric activation of preformed RTK dimers that has important implications for understanding cell-surface EGFR.

Recent studies demonstrated that the predacious fungi Arthrobotrys oligospora emits a mixture of volatile chemical cues that function to attract nematode prey. The strong attraction elicited by one of the mixture components, methyl 3-methyl-2-butenoate (MMB), was highly female- and hermaphrodite-specific within several Caenorhabditis species, including C. remanei and C. elegans , suggesting that MMB might function as a mimic of an endogenous, male-produced, volatile sex pheromone (VSP) within these species. Here, we report evidence that MMB is produced by C. remanei males at levels that are attractive to C. remanei females and C. elegans hermaphrodites. Notably, MMB production was not detected for C. elegans males; a finding which correlates with behavioral assays for which worm-conditioned media (WCM) prepared from C. remanei , but not from C. elegans adult males is strongly attractive to both C. remanei females and C. elegans hermaphrodites. Our findings establish MMB as the first chemically identified VSP in nematodes and show that A. oligospora exploits a dual strategy of chemical deception—mimicry and eavesdropping—to enhance prey capture.

C. elegans detects food, mates, and danger through a large repertoire of chemosensory receptors. The volatile odorant 2-nonanone is a well-established aversive stimulus that reliably elicits avoidance chemotaxis. However, the receptor(s) responsible for its detection have not been identified. Here, we leveraged CeNGEN single-cell expression profiles to identify candidate receptors required for sensing 2-nonanone. We narrowed the list of candidate chemoreceptor genes by selecting genes expressed in the aversive amphid neurons AWB and ASH while excluding genes expressed in other amphid sensory neurons. We tested available mutants from the C. elegans Genetics Center (CGC) and identified srh-30 as a candidate required for normal 2-nonanone avoidance. Two independent srh-30 null alleles generated using CRISPR-Cas9 confirmed that loss of srh-30 causes a partial defect in 2-nonanone sensing. srh-30 promoter-driven fluorescent reporter, mKate, localized to the distal tips of AWB sensory cilia, consistent with a direct sensory role. Finally, ectopic expression of srh-30 in the attractive AWA neuron shifted the behavioral response to 2-nonanone toward neutrality, supporting srh-30 as a sensory receptor. Together, these results identify srh-30 as a sensory receptor mediating 2-nonanone-evoked avoidance and demonstrate a transcriptome-guided strategy for mapping odor receptors.

Some organisms exhibit a remarkable ability to adapt their life history strategies within a single lifespan in response to dynamic biotic and abiotic cues, such as Caenorhabditis elegans larval facultative diapause. However, the molecular basis of how conspecific and prey cues are processed to conditionally alter the time to reproductive maturation remains largely unexplored. Here we discover that the longest transcript of the forkhead transcription factor FKH-7/FOXP is expressed and acts in C. elegans pheromone and bacteria-sensing neurons to promote larval development into growth-arrested diapause under resource-scarce conditions. We further demonstrate that human FOXP1 can functionally substitute for FKH-7 in these chemosensory neurons and that incorporating a hypomorphic missense mutation associated with a human neurodevelopmental disorder characterized by social interaction deficits reduces frequency of the adaptive response in nematode populations. In the fkh-7/FOXP1 missense variant, single-cell transcriptomics of chemosensory neurons identifies the set of candidate genes for deeper characterization of variant-specific molecular pathology at single neuron resolution in the context of an adaptive developmental decision.

Spatial transcriptomics has advanced our understanding of tissue organization by mapping gene expression in its native context yet applying these techniques to whole organisms remains a significant challenge. Caenorhabditis elegans is well-suited to whole organism-level analysis because its compact size, transparency, reproducible anatomy, and genetic tractability make it possible to link molecular and cellular changes to circuit function and behavior within the same animal. However, current transcriptomic approaches in C. elegans are often limited by spatial resolution or multiplexing capacity, making it challenging to profile multiple gene expression patterns across intact worms while preserving spatial context. Here, we present a single-molecule fluorescence in situ hybridization workflow that enables multiplex imaging with single-cell resolution across the entire worm. This approach allows sequential imaging of one gene per fluorescent channel using two channels across 20 hybridization rounds, enabling the profiling of up to 40 genes while preserving spatial context. We further provide a curated marker-gene panel for reproducible neuron identification, which, together with probabilistic assignment of transcripts to segmented nuclei, enables quantitative measurements of gene expression levels. We used this method to identify up to 86 neuronal classes and reveal sex- and neuron-specific expression patterns at single-cell resolution. Together, these results establish a scalable framework for the spatial analysis of gene expression and cell identity in intact C. elegans .

Chemotaxis to a moving potential mate that emits a volatile sex pheromone poses a navigation challenge requiring rapid, precise responses to maximize reproductive success. Volatile chemicals form gradients that differ from soluble compounds, potentially making navigation based on comparisons between spatially separated sensors unreliable for small-bodied animals. Here we show that, rather than a simple spatial comparison, Caenorhabditis elegans males employ an antagonistic strategy, comparing inputs from sex-shared head (AWA) and male-specific tail (PHD) sensory neurons with distinct response properties. Despite sharing a receptor, SRD-1, these detectors play different roles: AWAs promote forward movement and acceleration, while PHDs induce reversals and deceleration. In rising pheromone gradients, AWA activity dominates; in falling gradients, AWA inactivates, allowing PHD to correct trajectories. AWAs are essential for mate-searching, while PHDs are crucial for complex tasks. A minimal computational model reproduces these behaviors and infers how head–tail signals are combined. Thus, a sexually dimorphic, antagonistic sensory system enables adaptive navigation in dynamic environments

Background: Nematodes communicate via diverse sex pheromones, including long-range volatile signals, short-range chemical cues, and contact-dependent molecules. While the ascaroside family of small molecules that mediate short-range attraction is well characterized, the identities and roles of volatile sex pheromones (VSPs) that act over longer ranges remain unknown. Results: Using GC–MS analysis of crude VSP extracts, we identified cyclohexyl acetate (CA) as a candidate mimic, sharing retention time and mass spectral features with natural VSPs. Behavioral assays demonstrated that CA acts as a concentration-dependent, male-specific attractant in Caenorhabditis. Pre-exposure to VSPs induced cross-adaptation to CA, suggesting shared sensory processing. Surprisingly, genetic and calcium imaging analyses revealed that CA perception is mediated primarily by AWC _on ( str-2 -expressing) neurons and involves VSP chemoreceptor srd-1 -independent pathways, which are distinct from the neural pathways involved in natural VSP perception. Conclusions: These data indicate that CA is unlikely to be a major VSP constituent; rather, it is a structural analog that elicits male-specific attraction via a parallel sensory circuit. The endogenous source of CA in C. remanei remains unresolved; our data do not establish whether females produce CA. Its structural and behavioral mimicry provides new insights into the complexity of chemosensory signaling and the potential for interspecies chemical eavesdropping in nematode ecology.

Motivation: Biocuration is the integration of biological information databases for the enhancement of research. Curation of these databases is challenged by the exponential growth of scientific data and literature. Integration of machine learning and artificial intelligence methods into biocuration workflows may help address this challenge. We report on the discussions, ideas, and recommendations gathered from a workshop “AI and biodata resources: implications for sustainability and best practices in biocuration” at the 18th Annual International Biocuration Conference 2025. Results: Participants agreed that while AI offers transformative potential for efficiency and expanded curatorial capacity, its integration faces substantial hurdles. Key challenges revolve around data and model quality. Reproducibility issues and a lack of open, domain-specific training datasets further compound these problems. Broader concerns include inconsistent data standards, underdeveloped ontologies, unstructured data, legacy systems, and underfunded teams. Despite these issues, several successful AI applications were identified, including tools for literature summarization and workflow assistance. Participants emphasized the need for a refined model of human-AI collaboration requiring clear data provenance and transparency, new skills, and avoiding over-reliance on AI-generated data. The workshop ultimately recommended concerted efforts in infrastructure development, standardization, training, and quality assurance to guide the community toward effective human-AI collaboration that maintains scientific rigor.

Gene family expansions are critical for functional diversification, yet the contributions of paralogs to metabolic pathways are often unclear. In Caenorhabditis , the expanded O-acyltransferase (OAC) family—enzymes that transfer acyl groups to hydroxylated substrates—remains poorly characterized despite having been implicated in lipid metabolism. Using CRISPR-Cas9 mutagenesis, behavioral assays, gas chromatographic-mass spectral (GC-MS) analyses, and metabolomics, we systematically analyzed 59 OAC-family protein-coding genes to define their roles in regulating signaling molecules. We found that four adjacent paralogs ( oac-13, oac-16, oac-25, and oac-28 ) on chromosome I are required for synthesizing volatile sex pheromones—airborne signals critical for male mate-searching. Specifically, oac -13 and oac-16 are necessary for producing both major pheromone components, while the identical tandem paralogs oac-25 and oac-28 regulate the production of the later-eluting component in gas chromatography. Disruption of these genes reduced production of key pheromone components and impaired male attraction. Metabolomics revealed that oac-16 and other OACs also modulate the synthesis and secretion of nonvolatile ascaroside pheromones, indicating dual roles in chemical signaling. This work uncovers functional specialization within an expanded gene family, illustrating how redundancy and divergence enable adaptive evolution of communication systems.

The life cycle of the model nematode Caenorhabditis elegans involves a choice between two alternative developmental trajectories. Hermaphroditic larvae can either become reproductive adults or, under conditions of crowding or low food availability, enter a long-term, stress-resistant diapause known as the dauer stage. Chemical signals from a secreted larval pheromone promote the dauer trajectory in a concentration-dependent manner, and their influence can be antagonized by increased availability of a microbial food source. The decision is known to be under neuronal control, involving both sensory and interneurons. However, little is known about the dynamics of the underlying circuit, and the circuit mechanisms by which short-term fluctuations in the ratio of food and pheromone experienced by individual larvae are remembered and averaged over several hours. To investigate this, we quantitatively characterized the neuronal responses to food and pheromone inputs by measuring calcium traces from ASI and AIA neurons, each of which has previously been implicated in regulation of dauer entry. We found that calcium in ASI increases linearly in response to food and similarly decreases in response to pheromone. Notably, the ASI response persists well beyond removal of the food stimulus, thus encoding a memory of recent food exposure. In contrast, AIA reports instantaneous food availability and is unaffected by pheromone. We discuss how these findings may inform our understanding of this long-term decision-making process.