Functional genetics of migraine: analysis of sodium pump and P/Q channel homologs from C elegans

Abstract

Familial Hemiplegic Migraine (FHM) provides a unique window into migraine pathophysiology. FHM is caused by missense mutations in 3 genes encoding subunits of a Ca and Na channel and the Na, K‐ATPase. We’ve published that FHM2 mutations produce hypomorphic kinetic alterations in Na/K pump function, but the effects of FHM1 P/Q channel mutations and the mechanism perturbed in common by the 3 loci remain controversial. In C. elegans neurons we were able to define functional interaction between the FHM1 (unc‐2) and FHM2 (eat‐6) homologs, allowing us to define their neuronal signaling pathway. We measured stress‐induced serotonin (5HT) synthesis in the ADF neuron using a tph‐1::GFP promoter reporter construct. Worms were heat‐stressed at 15–25°C and GFP fluorescence quantitated. At all temperatures the unc‐2 mutants have decreased, and the eat‐6 or double mutants have enhanced, tph‐1 synthesis compared to WT (all P<0.001). We also measured aldicarb‐sensitivity and showed unc‐2 hypomorphs have aldicarb‐resistance, whereas eat‐6 hypomorphs are aldicarb‐hypersensitive, with the double mutant, again, the same as eat‐6 alone (all P<0.001). Thus in two different neuronal phenotypes, hypomorphs of the FHM homologs had opposite effects, and in both eat‐6 is epistatic to unc‐2‐‐ meaning upstream in the pathway. Genetic and pharmacological block of calcium signaling proteins reveal novel intermediates in the pathway. Supported by NIH grant to JJG.