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DPY-10 is a collagen protein in the nematode's cuticle. Mutations in the dpy-10 gene induce various morphological changes that lead to animals with a dumpy or roller phenotype (Levy, Yang & Kramer, 1993). Here, we asked how such mutations affect body stiffness by comparing force-indentation curves in dpy-10(e128) and wild type worms. On average, dpy-10(e128) worms have a steeper force-indentation relationship, leading to a higher body stiffness (Fig 1.C). Average stiffness values were 2.5 0.9 N/m, SD, (n = 24) for dpy-10(e128) and 0.9 0.3 N/m, SD, (n = 25) for wild type (N2) hermaphrodites. Qualitatively, we observed that some of the dpy-10(e128) worms had a disrupted cuticle and their bodies spontaneously eviscerated after being immobilized to an agarose pad. Finally, we confirm the finding that dpy-10(e128) worms are shorter (Fig 1.D) and fatter (Fig 1.E) than wild type worms with an average body length of 712 68 µm (SD, n = 24) compared to wild type N2 worms 900 68 µm (SD, n = 25) and an average body width at the pharynx of 42 5.6 µm (SD, n = 24) compared to wild type N2 worms 36 4 µm (SD, n = 25) (Levy, Yang & Kramer, 1993). Panel F shows the Body relationship to scale. From these results, we conclude that the bodies of dpy-10(e128) are twice as stiff as wild type: to reach the same indentation, a much higher force was necessary to be applied to dpy-10(e128) than to wild type worms (Fig 1. A). Prior measurements of body stiffness with the same method revealed that dpy-5(e61) worms are softer than wild type worms (Park et al. 2007). Thus, body shape does not predict body stiffness. Why is one Dpy animal softer than wild-type and another one stiffer? We propose that dpy-10 is stiffer than wild-type because it has an increased internal glycerol concentration and increased pressure, that is absent from dpy-5(e61) (Wheeler and Thomas 2006).

One central goal of mechanobiology is to understand the reciprocal effect of mechanical stress on proteins and cells. Despite its importance, the influence of mechanical stress on cellular function is still poorly understood. In part, this knowledge gap exists because few tools enable simultaneous deformation of tissue and cells, imaging of cellular activity in live animals, and efficient restriction of motility in otherwise highly mobile model organisms, such as the nematode Caenorhabditis elegans. The small size of C. elegans makes them an excellent match to microfluidics-based research devices, and solutions for immobilization have been presented using microfluidic devices. Although these devices allow for high-resolution imaging, the animal is fully encased in polydimethylsiloxane (PDMS) and glass, limiting physical access for delivery of mechanical force or electrophysiological recordings. Recently, we created a device that integrates pneumatic actuators with a trapping design that is compatible with high-resolution fluorescence microscopy. The actuation channel is separated from the worm-trapping channel by a thin PDMS diaphragm. This diaphragm is deflected into the side of a worm by applying pressure from an external source. The device can target individual mechanosensitive neurons. The activation of these neurons is imaged at high-resolution with genetically-encoded calcium indicators. This article presents the general method using C. elegans strains expressing calcium-sensitive activity indicator (GCaMP6s) in their touch receptor neurons (TRNs). The method, however, is not limited to TRNs nor to calcium sensors as a probe, but can be expanded to other mechanically-sensitive cells or sensors.

Microtubules contribute to many cellular processes, including transport, signaling, and chromosome separation during cell division (Kapitein and Hoogenraad, 2015). They are comprised of αβ‐tubulin heterodimers arranged into linear protofilaments and assembled into tubes. Eukaryotes express multiple tubulin isoforms (Gogonea et al., 1999), and there has been a longstanding debate as to whether the isoforms are redundant or perform specialized roles as part of a tubulin code (Fulton and Simpson, 1976). Here, we use the well‐characterized touch receptor neurons (TRNs) of Caenorhabditis elegans to investigate this question, through genetic dissection of process outgrowth both in vivo and in vitro. With single‐cell RNA-seq, we compare transcription profiles for TRNs with those of two other sensory neurons, and present evidence that each sensory neuron expresses a distinct palette of tubulin genes. In the TRNs, we analyze process outgrowth and show that four tubulins (tba‐1, tba‐2, tbb‐1, and tbb‐2) function partially or fully redundantly, while two others (mec‐7 and mec‐12) perform specialized, context‐dependent roles. Our findings support a model in which sensory neurons express overlapping subsets of tubulin genes whose functional redundancy varies between cell types and in vivo and in vitro contexts.

Many biochemical networks are robust to variations in network or stimulus parameters. Although robustness is considered an important design principle of such networks, it is not known whether this principle also applies to higher-level biological processes such as animal behavior. In thermal gradients, Caenorhabditis elegans uses thermotaxis to bias its movement along the direction of the gradient. Here we develop a detailed, quantitative map of C. elegans thermotaxis and use these data to derive a computational model of thermotaxis in the soil, a natural environment of C. elegans. This computational analysis indicates that thermotaxis enables animals to avoid temperatures at which they cannot reproduce, to limit excursions from their adapted temperature, and to remain relatively close to the surface of the soil, where oxygen is abundant. Furthermore, our analysis reveals that this mechanism is robust to large variations in the parameters governing both worm locomotion and temperature fluctuations in the soil. We suggest that, similar to biochemical networks, animals evolve behavioral strategies that are robust, rather than strategies that rely on fine tuning of specific behavioral parameters.