Figure 2. Schwann cells are required for repositioning a peripheral nerve.

(A) The posterior lateral line nerve in cartoon superimposed on a 28 hours postfertilization zebrafish embryo. Schwann cells (yellow) co-migrate with axons (blue; Gilmour et al., 2002). Anterior (A) is to the left, posterior (P) to the right, dorsal (D) up, ventral down (v). (B) Zoom of dashed region in (A), showing the transition of the posterior lateral line nerve across the epidermal basement membrane (dark grey) from the epidermis (light grey) into the subepidermal space (unlabeled), with anterior-most portions of the nerve transitioning prior to posterior portions closer to the outgrowing axonal growth cones (Raphael et al., 2010). Dashed lines indicate cross sections shown in (C). (C) Cross sections through the posterior lateral line nerve showing the position of the nerve with respect to the basement membrane (Raphael et al., 2010). Anterior (far left) the nerve has transitioned across the basement membrane and is embedded in the subepidermal space. Middle, the nerve is transitioning, with basement membrane both superficial and medial to the nerve. Posterior (far right) the nerve is still within the epidermis, superficial to the basement membrane. In (C) superficial is up (S), deep (D) down, anterior left, posterior right. (A, B) adapted from Raphael et al., 2010.