Figure 7. Paranodal junctions are disrupted when TDP-43 is deleted in adult Schwann cells.

(A) Immunostaining of adult sciatic nerves at 3 months after injection of tamoxifen (tam) or corn oil alone (oil) for E-cadherin (E-cad) (incisures) and neurofascin (NFasc). Scale bar, 5 μm. (B) RT-PCR for Nfasc spliceforms using sciatic nerves at 3 months after tamoxifen administration. +RT, reactions with reverse transcriptase; −RT, reactions without reverse transcriptase. (C) Immunostaining of adult sciatic nerves at 5 months after injection of tamoxifen (tam) or corn oil alone (oil) for contactin-associated protein (Caspr) (green), NFasc (blue), and Kv1.1 channel (red). Scale bar, 5 μm. (D) The sciatic nerve sections were immunostained for Krox20 and TDP-43 and quantified for the percentage of Krox20-positive nuclei that are TDP-43-negative. Immunostaining for Caspr and Kv1.1 was quantified for the percentage of Kv1.1-positive paranodes/juxtaparanodes that exhibit paranodal junction disruption defined as paranodal invasion of Kv1.1 and/or fragmented/shortened Caspr clusters. n represents the number of paranodes or nuclei analyzed for each mouse.

Figure 7—figure supplement 1. Neurofascin (NFasc) turns over faster at the incisures than at the paranodal junctions.

(A) Immunostaining of teased ventral roots from the TDP-43-icKO mice at 3 months after tamoxifen injection for NFasc (magenta), TDP-43 (yellow), myelin-associated glycoprotein (MAG) (green), and DAPI (blue). The cell contour of a TDP-43-KO Schwann cell is delineated with dashed lines, and NFasc is absent from its incisure. The incisures are indicated by arrows. (B) Immunostaining of teased ventral roots from the TDP-43-icKO mice at 3 months after tamoxifen injection for NFasc (red) and MAG (cyan). NFasc is absent from the incisure of the bottom Schwann cell but is still enriched at its paranode. The incisures are indicated by arrows, the paranode by a solid arrowhead, and the node by an open arrowhead. Scale bars, 5 μm.