Fluid dynamics alter Caenorhabditis elegans body length via neuromuscular signaling with TGF-β/DBL-1

Abstract

Skeletal muscle wasting is a major obstacle for long-term space exploration. Similar to astronauts, the nematode Caenorhabditis elegans displays negative muscular and physical effects grown in space microgravity. However, it is still unclear what signal molecules and behavior affect the negative alterations. We here studied key signaling molecules involved in alterations of C. elegans physique in response to fluid-dynamics on the ground-based experiments. Like as spaceflight experiment with 1G accelerator onboard, a myosin heavy chain myo-3 and a TGF- dbl-1 gene expression altered increasing the fluid dynamic parameters viscosity/drag resistance or depth of liquid culture. These gene expression also drastically increased grown liquid medium as compared with moist agar surface. In addition, body length enhanced in WT and body-wall cuticle collagen mutants, rol-6 roller and dpy-5 dumpy, grown in liquid culture. On the other hand, in a TGF- gene dbl-1 and its signaling pathway sma-4/Smad mutants, their body lengths did not alter in liquid. Similarly, a D1-like dopamine receptor DOP-4 and a mechanosensory channel UNC-8 were required for altered physique in which DBL-1 signaling did not upregulated in liquid. Since C. elegans contraction rates are much higher in swimming mode in liquid than clawing mode on agar surface, we studied the relationship between body-length enhancement and contraction rate. Mutants significantly reduced contraction rate commonly show smaller size, although the rate in dop-4, dbl-1 and sma-4 mutants still increased in liquid. These results suggest that neuromuscular signaling via TGF-/DBL-1 to alter body physique in response to environmental conditions including fluid dynamics.