Signaling pathways that modulate cell adhesion and cytoskeleton have been shown to localize potassium channels to the plasma membrane of neurons, which may in turn impact activity-dependent regulation of development of neuronal connectivity. However, the molecular and cellular mechanisms of potassium channel localization in relation to neuronal morphogenesis and activity are not well-understood. We are testing whether Wnt and Cadherin factor, β-catenin, increases membrane localization of hERG channels to modulate electrical activity and axon pathfinding, in vivo, in vitro and in silico. Expression of a β-catenin mutant that disrupts its interaction with a-catenin in individual GFP expressing retinal ganglion cells (RGCs) in Xenopus embryos resulted in fewer filopodia in, and more round and less complex (lower fractal dimension) growth cones, as well as more meandering axons in whole brains. Still and time-lapse imaging of primary cultures of RGCs from Xenopus embryos show both correlation between and variability in growth cone filopodial and axonal dynamics, whereas voltage clamp electrical recordings of these cultured RGCs reveal channel activity. Computational modeling of the effects on increasing numbers of potassium channels on action potentials suggests differences in adaptation. The next stages of this project include measuring protein localization and quantifying the effects of gain of function of hERG (individually and together with loss-of-function of β-catenin) on multiple morphological and electrical parameters in individual developing RGCs from Xenopus laevis tadpoles in whole brains and in vitro.
Kaur et al. (Sun,) studied this question.