[
Elife,
2022]
Animals must weigh competing needs and states to generate adaptive behavioral responses to the environment. Sensorimotor circuits are thus tasked with integrating diverse external and internal cues relevant to these needs to generate context-appropriate behaviors. However, the mechanisms that underlie this integration are largely unknown. Here, we show that a wide range of states and stimuli converge upon a single Caenorhabditis elegans olfactory neuron to modulate food-seeking behavior. Using an unbiased ribotagging approach, we find that the expression of olfactory receptor genes in the AWA olfactory neuron is influenced by a wide array of states and stimuli, including feeding state, physiological stress, and recent sensory cues. We identify odorants that activate these state-dependent olfactory receptors and show that altered expression of these receptors influences food-seeking and foraging. Further, we dissect the molecular and neural circuit pathways through which external sensory information and internal nutritional state are integrated by AWA. This reveals a modular organization in which sensory and state-related signals arising from different cell types in the body converge on AWA and independently control chemoreceptor expression. The synthesis of these signals by AWA allows animals to generate sensorimotor responses that reflect the animal's overall state. Our findings suggest a general model in which sensory- and state-dependent transcriptional changes at the sensory periphery modulate animals' sensorimotor responses to meet their ongoing needs and states.
[
PLoS Genet,
2018]
Neurons develop elaborate morphologies that provide a model for understanding cellular architecture. By studying C. elegans sensory dendrites, we previously identified genes that act to promote the extension of ciliated sensory dendrites during embryogenesis. Interestingly, the nonciliated dendrite of the oxygen-sensing neuron URX is not affected by these genes, suggesting it develops through a distinct mechanism. Here, we use a visual forward genetic screen to identify mutants that affect URX dendrite morphogenesis. We find that disruption of the MAP kinase MAPK-15 or the H-spectrin SMA-1 causes a phenotype opposite to what we had seen before: dendrites extend normally during embryogenesis but begin to overgrow as the animals reach adulthood, ultimately extending up to 150% of their normal length. SMA-1 is broadly expressed and acts non-cell-autonomously, while MAPK-15 is expressed in many sensory neurons including URX and acts cell-autonomously. MAPK-15 acts at the time of overgrowth, localizes at the dendrite ending, and requires its kinase activity, suggesting it acts locally in time and space to constrain dendrite growth. Finally, we find that the oxygen-sensing guanylate cyclase GCY-35, which normally localizes at the dendrite ending, is localized throughout the overgrown region, and that overgrowth can be suppressed by overexpressing GCY-35 or by genetically mimicking elevated cGMP signaling. These results suggest that overgrowth may correspond to expansion of a sensory compartment at the dendrite ending, reminiscent of the remodeling of sensory cilia or dendritic spines. Thus, in contrast to established pathways that promote dendrite growth during early development, our results reveal a distinct mechanism that constrains dendrite growth throughout the life of the animal, possibly by controlling the size of a sensory compartment at the dendrite ending.
[
Bio Protoc,
2019]
Cell type-specific molecular profiling is widely used to gain new insights into the diverse cell types that make up complex biological tissues. Translating ribosome affinity purification (TRAP) is a method in which the cell type-specific expression of epitope-tagged ribosomal subunits allows one to purify actively translating mRNAs without the need for cell sorting or fixation. We adapted this method for use in <i>C. elegans</i> to identify novel transcripts in single cell types or to identify the effects of environmental changes on the transcriptomes of larger cohorts of cells. In this protocol, we describe methods to generate transgenic animals bearing tagged ribosomes in cells of interest, prepare these animals for immunoprecipitation, purify ribosome-mRNA complexes, and obtain purified mRNA for next-generation sequencing.
de Bono, Mario, Amin-Wetzel, Niko, Sengupta, Piali, Philbrook, Alison, Kazatskaya, Anna, Yuan, Lisa
[
MicroPubl Biol,
2020]
A subset of sensory neurons in C. elegans contains compartmentalized sensory structures termed cilia at their distal dendritic ends (Ward et al. 1975; Perkins et al. 1986; Doroquez et al. 2014). Cilia present on different sensory neuron types are specialized both in morphology and function, and are generated and maintained via shared and cell-specific molecules and mechanisms (Perkins et al. 1986; Evans et al. 2006; Mukhopadhyay et al. 2007; Mukhopadhyay et al. 2008; Morsci and Barr 2011; Doroquez et al. 2014; Silva et al. 2017). The bilaterally symmetric pair of URX oxygen-sensing neurons in the C. elegans head (Figure 1A) is thought to be non-ciliated (Ward et al. 1975; Doroquez et al. 2014) but nevertheless exhibits intriguing morphological similarities with ciliated sensory neurons. URX dendrites extend to the nose where they terminate in large bulb-like complex structures (Ward et al. 1975; Doroquez et al. 2014; Cebul et al. 2020) (Figure 1A). These structures concentrate oxygen-sensing signaling molecules (Gross et al. 2014; Mclachlan et al. 2018) suggesting that similar to cilia, these structures are specialized for sensory functions. Microtubule growth events similar to those observed in ciliated sensory neurons were also reported at the distal dendritic regions of URX, implying the presence of a microtubule organizer such as a remodeled basal body (Harterink et al. 2018). Moreover, a subset of ciliary genes is expressed in URX (Kunitomo et al. 2005; Harterink et al. 2018; Mclachlan et al. 2018). We tested the hypothesis that URX dendrites contain cilia at their distal ends.