Figure 7.

Embryonic human and mouse OECs do not express the Schwann cell precursor and immature Schwann cell marker Sox2. Coronal sections of the embryonic mouse (A–D¹) and human (E–L) olfactory systems. (A) At E16.5 in the mouse, immunostaining for Tubb3‐positive axons provides an overview of the olfactory system. (B,B¹) Higher‐power view of boxed region in (A), showing Sox2 expression in cells associated with Tubb3‐positive trigeminal axons, presumably developing Schwann cells. (C–D¹) In contrast, on the same section shown in (A–B¹), Sox2 is not expressed by OECs in the olfactory nerve layer of the olfactory bulb, or on the olfactory nerve. (E–F¹) At 7 weeks of human development, SOX2 is strongly expressed by cells on the TUBB3‐positive trigeminal nerve, presumably developing Schwann cells, but (G–H¹) SOX2 is not expressed by developing OECs on the olfactory nerve. (I–J¹) Similarly at 8 weeks of human development, SOX2 is detected in developing Schwann cells, but (K–L¹) is absent or expressed at very low levels in OECs on the same section. FB, forebrain; OB, olfactory bulb; OE, olfactory epithelium; ON, olfactory nerve; ONL, olfactory nerve layer; PN, peripheral nerve; TN, trigeminal nerve. Scale bar: 100 μm.