Figure 1. Organization of the nodal region. Schwann cell microvilli contact the axonal membrane at nodes, and paranodal loops contact the axonal membrane at the paranodes. Some of the molecules that are localized to nodes, paranodes and juxtaparanodes are indicated along with their putative molecular interactions.

Figure 2. Schematic view of a myelinated axon. One myelinating Schwann cell has been unrolled to reveal the regions that form compact myelin, the incisures and the paranodes. Tight junctions are depicted as two continuous lines; these form a circumferential belt and are also found in the incisures. Gap junctions are depicted as ovals; these are found between the rows of adherens junctions.

Figure 3. The localization of myelin components in the mammalian peripheral nervous system myelin sheath. Protein zero (P₀), peripheral myelin protein of 22 kDa (PMP22), myelin basic protein (MBP), galactocerebroside (Gal-C) and sulfatide are found in compact myelin; connexin 32 (Cx32), E-cadherin and myelin-associated glycoprotein (MAG) are found in noncompact myelin.

Figure 4. erbB2 and erbB3 heterodimers are the neuregulin-1 receptors in Schwann cells. Neuregulin-1 binds to erbB3, causing erbB2 to phosphorylate both erbB3 and erbB2, and results in the activation of the Ras, phosphoinositol-3 kinase (PI3-K) and phospholipase C (PLC).

Figure 5. Summary of Schwann cell (SC) differentiation in developing rat sciatic nerve during embryonic (E) and postnatal (P) development. (a) Morphological aspects of differentiation; (b) Expression of transcription factors during differentiation. The thickness of the lines indicates the relative level of expression.

Figure 6. Temporal profile of Oct-6, Brn-5 and Egr2/Krox-20 expression in developing rodent peripheral nerve. The relative levels of Oct-6 and Egr2 messenger ribonucleic acid (mRNA) are depicted at different days of embryonic (E) and postnatal (P) development. The effect of axotomy (at arrowheads) on the levels of Oct-6 and Egr2 mRNA is depicted by the dashed lines.