FIGURE 2.

Myelin clusters endogenous Kv1.2 channels along axons of hippocampal neurons. A, myelin segments from myelinating oligodendrocytes clustered endogenous Kv1.2 channels along the axon of a mature hippocampal neuron in culture. Coculture of hippocampal neurons and oligodendrocytes was costained for endogenous Kv1.2 (green) and MBP (red) at 28 DIV. B, endogenous Kv1.2 was distributed smoothly along unmyelinated axons of a hippocampal neuron at 28 DIV. C, distribution patterns of Kv1.2 (green) and Nav (red) channels along unmyelinated axons of a hippocampal neuron at 28 DIV. In A–C, blue arrows, axons; blue arrowheads, dendrites; black arrows, myelin segments; black arrowhead, a myelin segment of an axon that did not express Kv1.2. D, immunofluorescence intensity profiles of Kv1.2 channels along the myelinated axon in A (red) and the unmyelinated axon in B (blue). E, immunofluorescence intensity profiles of Kv1.2 (blue) and Nav (red) channels along the unmyelinated axon in C. F, axonal Kv1.2 channels (green) were clustered in putative JXP regions in an MBP-positive myelin internode (red). White arrowheads, Kv1.2 clusters in putative JXP regions. G, Nav channels (green) localized in a heminode, indicated by a white arrowhead. H, segregation of Kv1 and Nav channels into the putative JXP and nodal regions, respectively. White arrowheads, putative nodes of Ranvier. I, summary of myelin internode length and percentage of the putative Kv1.2 JXP targeting at three developmental stages (n = 4 cocultures). Scale bars, 100 μm in A–C and 20 μm in F–H. **, p < 0.001 (t test). Error bars, S.E.