Fig. 7

Developmental expression of P0. Sections of zebrafish larvae were labeled using the same method employed to generate Figure 3, illustrating developmental P0 expression in the hindbrain (A–E), the spinal cord (F–J), the visual pathways (K–N), the mesencephalon (O), and the telencephalon (P). The scale bar for images A–D,G,K–M is shown in A; the scale bar for images E,O is shown in panel E; the scale bar for images F,H,I,N is shown in panel F; the scale bar for images J,P is shown in panel J. Horizontal sections of the ventral hindbrain are shown at: A: 48 hours post-fertilization (hpf); B: 72 hpf; C: 96 hpf; D: 8 dpf. In A, the white arrow shows a P0-immunoreactive premyelinating oligodendrocyte; the black arrows indicate fine P0-immunoreactive processes arising from this and similar cells. In B–D, black arrows indicate longitudinally arranged myelinating fibers. White arrows in D show myelinating commissural fibers. E: Hindbrain, transverse section, 14 dpf; arrow demarcates P0 expression in cranial nerve roots emerging from the ventral surface of the developing brainstem. F: Spinal cord, transverse section, 10 dpf; arrows indicate locations of P0-expressing spinal tracts. G: Higher-magnification view of ventral spinal cord from panel F, arrow indicates P0 expression in a ventral spinal nerve root. H: Longitudinal and I,J: transverse sections of the spinal cord, 24 dpf; arrow in J indicates P0 expression in a ventral nerve root. K: Optic nerve, longitudinal section at 7 dpf. L: Optic chiasm, transverse section at 8 dpf. M: Optic tectum, longitudinal section, 10 dpf; arrow indicates P0-immunoreactive processes of oligodendrocyte shown in center of panel. N: Optic tectum, transverse section, 24 dpf; arrows show P0-immunmoreactive fibers of optic tract entering the tectum. O: mesencephalon and diencephalon, transverse section, 28 dpf. P: Telencephalon and eyes, transverse section, 28 dpf.