Hypergravity hinders proper dendritic patterning of a sensory neuron in the nematode Caenorhabditis elegans.

Altering gravity force can modify the three-dimensional spatial environment inside living animals that are adapted to earth's gravity. This may have deleterious effects on biological processes such as developmental patterning that requires proper molecular interactions in a 3D spatial environment. Here, we exposed the nematode Caenorhabditis elegans to a gravity force of 100G and observed effects to the development of the PVD touch sensory neurons that exhibit an intricate and stereotyped dendritic branch patterning. We found that hypergravity force increases the incidence of specific quaternary branching defects that occur in the narrow basement membrane space between muscle and epidermal layers during the L4 larval developmental stage. Normally the growing PVD neuron extends dendritic branches across the body of the worm by following a SAX-7/L1CAM epidermal cue, but in 100G gravity some branches suddenly turn and instead follow longitudinal neurons forming "L" and "T" shaped branch defects. Interestingly, hypergravity-induced dendrite defects were suppressed in mutants with impaired hemidesmosomal structures in the basement membrane of the epidermis. We speculate that hypergravity compresses rigid muscle and epidermal layers together such that cells and structures that are normally far apart are brought close together. These modified spatial dynamics may cause inappropriate molecular interactions resulting in improper developmental patterns in environments of altered gravity such as spaceflight.