Modulation of dopamine-dependent behaviors by the Caenorhabditis elegans Olig homolog HLH-17.

In vertebrates and invertebrates, dopamine signaling modulates a wide variety of physical and behavioral functions and exerts these effects through heterotrimeric G proteins. The soil nematode Caenorhabditis elegans has been used to model dopamine signaling and reacts reproducibly to alterations in dopamine levels through eight well-characterized dopaminergic neurons located in the head. In C. elegans, the basic helix-loop-helix transcription factor HLH-17 is strongly and constitutively expressed in the glia cells that ensheath four of the dopaminergic neurons, yet it is not required for specification or development of either the glia or the neurons. In this study, we sought to determine whether HLH-17 functions in dopamine signaling. We found that, unlike wild-type animals, hlh-17 animals are resistant to the effects of exogenous dopamine on egg laying and mobility. hlh-17 animals are also defective in the basal slowing and gustatory plasticity behaviors that require functional dopamine signaling. We also found that the expression of the dopamine receptor genes dop-1, dop-2, and dop-3 and the RGS protein gene egl-10 is significantly reduced in hlh-17 animals. Together these results point to a role for HLH-17 in dopamine signaling in C. elegans.