Exposure to metals induces morphological and functional alteration of AFD neurons in nematode Caenorhabditis elegans

Previous studies have revealed that metal exposure will cause severe deficits in perception behaviors. Here we investigated the effects of metal (Hg, Cu, Ag, and Cr) exposure on thermotaxis to cultivation temperature in Caenorhabditis elegans. Our data suggest that exposure to higher concentrations of examined metals induced severe deficits in thermotaxis, and a significant reduction in thermotaxis could be even observed in nematodes exposed to 2.5 μM of Hg. Moreover, exposure to higher concentrations of examined metals and 2.5 μM of Hg induced significant decreases in relative intensities and relative sizes of fluorescent puncta of cell bodies in AFD thermosensory neurons. In addition, exposure to higher concentrations of examined metals resulted in a significant reduction in relative intensities and relative lengths of sensory endings in AFD neurons. Furthermore, the relative transcript levels of ttx-1, which functions in specifying the fate of AFD neuron, were significantly decreased in nematodes exposed to 2.5 μM of Hg, and 50 and 100 μM of examined metals. Thus, metal exposure at high concentrations will induce the severe deficits in thermotaxis to cultivation temperature possibly by altering the morphology or development of AFD neuron and damaging the molecular basis for function of AFD neuron in nematodes.