Vidal-Gadea, Andres et al. (2015) International Worm Meeting "Geographical tuning in magnetotactic response across C. elegans wild-type isolates."

Ward, Kristi, Beron, Celia, Vidal-Gadea, Andres, Pierce-Shimomura, Jonathan

[International Worm Meeting, 2015]

Rotation of the earth's liquid core generates a magnetic field used by many organisms to navigate their environment. While some animals such as turtles and birds use the magnetic field to engage in horizontal migrations, other organisms like magnetotactic bacteria use it to guide their migrations vertically. We find that C. elegans readily orients to artificial magnetic fields of earth strength. When assaying responses to the natural magnetic field of the earth, we found that worms appear to use the geomagnetic field to guide vertical migrations via an identified a pair of sensory neurons. Because the orientation of the geomagnetic field differs across the globe, we tested the magnetotactic ability and migratory preference of the standard lab strain (N2), and of wild-type strains isolated from different locations across the planet. We found that different populations displayed an innate preference to migrate at an angle to magnetic fields of earth-strength that would optimize their UP or DOWN direction when burrowing in their native global location. For instance, in England the geomagnetic field pierces the earth at +66 degrees (north points down). We found that well-fed British N2 worms prefer to migrate 120 degrees to an earth-strength artificial magnetic field. This seemingly arbitrary angle corresponds to the optimal angle to orient them upward when burrowing in England. By contrast, starved N2 worms migrated in the opposite direction (i.e. 300 degrees to the field), which would orient them downward in England. Consistent with natural populations adapting to local magnetic fields, we next found that worms isolated from Australia, where the geomagnetic field emanates out of the earth at -66 degrees (north points up), displayed an opposite innate pattern of migratory preference. Similar results were found for wild-type worms from Hawaii. This pattern of optimal natural variation in magnetic orientation in C. elegans serves as an excellent example to relate spatiotemporal genetic variation with a behavioral trait. The breath in number and distribution of wild-type C. elegans populations makes this a promising model for studying the effects of natural and artificial magnetic field variation on the behavior of a genetically tractable animal.

Vidal-Gadea, Andres et al. (2015) International Worm Meeting "Burrowing behavior of C. elegans used to study neuromuscular disorder models."

Vidal-Gadea, Andres, Parikh, Adhishri, Pierce-Shimomura, Jonathan, Cohn, Jesse, Hwang, Grace, Beron, Celia

[International Worm Meeting, 2015]

The nematode Caenorhabditis elegans is a powerful model system for the study of human neuromuscular function and disorders. However, many worm models of human disease only show mild crawling phenotypes. In their natural habitat, C. elegans likely spends much of the time burrowing through the soil matrix. We developed a burrowing assay to challenge motor output by placing worms in agar-filled pipettes of increasing densities. We find that burrowing involves distinct kinematics and turning strategies from crawling that vary with the properties of the substrate. We show that Duchenne muscular dystrophy model (dys-1) mutants crawl normally but are severely impaired in burrowing. In stark contrast with wild-type, muscular degeneration in the dys-1 mutant is hastened and exacerbated by burrowing. We performed a genetic screen and isolated several suppressor mutants with proficient burrowing in a dys-1 mutant background. Further study of burrowing in C. elegans will enhance the study of diseases affecting neuromuscular integrity, and provide insights into the natural behavior of this and other nematodes.

Bainbridge, Chance et al. (2015) International Worm Meeting "Investigating the neuromolecular mechanism for magneto-transduction in C. elegans."

Beron, Celia, Khalil, Moe, Bainbridge, Chance, Boutz, Daniel, Rickert, Trevor, Gokce, Sertan, Ghoashian, Navid, Ward, Kristi, Marcotte, Edward, Pierce-Shimomura, Jonathan, Papoulas, Ophelia, Ben-Yakar, Adela, Vidal-Gadea, Andres

[International Worm Meeting, 2015]

A wide range of organisms use the earth's magnetic field to orient. Much of our understanding about the molecular basis for this behavior comes from work on magnetotactic bacteria. These organisms build nanometer-sized "compasses" from magnetic iron extracted from their environment. Evidence of similar biological magnetite has been reported in many magnetotactic animals (including C. elegans). It remains unclear if and how animals may use these "biological compasses" in this exciting form of sensory transduction. We have recently found that C. elegans readily orients to the magnetic field of the earth in a way that is consistent with a magnetite-based mechanism. Worms appear to use the magnetic field during vertical migrations using an identified a pair of sensory neurons. These neurons are required for magnetotaxis and respond cell-autonomously to earth-strength magnetic fields in calcium imaging experiments. We are attempting to identify the molecular machinery responsible for magnetotransduction using complementary biochemical, genetic and physiological approaches. To determine proteins associated with a hypothetical "worm compass", we performed mass spectrometry on iron particles isolated from C. elegans. Next, to determine whether these proteins are required for magnetotaxis, we assayed the magnetotactic ability of the corresponding mutants. For the subset of mutants that display defective magnetotaxis, we are analyzing the subcellular localization of their respective proteins near candidate compass structures. In parallel, we are testing the requirement of these genes in physiological responses to magnetic fields via calcium imaging. The genetic and behavioral tractability of C. elegans makes this a promising model for elucidating potentially conserved mechanisms by which many animals detect and orient to magnetic fields. .

Bainbridge C et al. (2016) J Neurosci Methods "Method for the assessment of neuromuscular integrity and burrowing choice in vermiform animals."

Schuler A, Vidal-Gadea AG, Bainbridge C

[J Neurosci Methods, 2016]

BACKGROUND: The study of locomotion in vermiform animals has largely been restricted to animals crawling on agar surfaces. While this has been fruitful in the study of neuronal basis of disease and behavior, the reduced physical challenge posed by these environments has prevented these organisms from being equally successful in the study of neuromuscular diseases. Our burrowing assay allowed us to study the effects of muscular exertion on locomotion and muscle degeneration during disease (Beron et al., 2015), as well as the natural burrowing preference of diverse C. elegans strains (Vidal-Gadea et al., 2015). NEW METHOD: We describe a simple, rapid, and affordable set of assays to study the burrowing behavior of nematodes and other vermiform organisms which permits the titration of muscular exertion in test animals. RESULTS: We show that our burrowing assay design is versatile and can be adapted for use in widely different experimental paradigms. COMPARISON WITH EXISTING METHOD(S): Previous assays for the study of neuromuscular integrity in nematodes relied on movement through facile and homogeneous environments. The ability of modulating substrate density allows our burrowing assay to be used to separate animal populations where muscular fitness or health are not visible differentiable by standard techniques. CONCLUSION: The simplicity, versatility, and potential for greatly facilitating the study of previously challenging neuromuscular disorders makes this assay a valuable addition that overcomes many of the limitations inherent to traditional behavioral tests of vermiform locomotion.