Fig. 3.

Secretagogin identifies bipolar cells with a makeup of immature neurons. (A) PSA-NCAM enwraps secretagogin⁺ bipolar cells (note that secretagogin is cytosolic). Open rectangles pinpoint the positions of A₁–A₃Insets and a terminal specialization, likely growth cone (A₄, open arrowheads). (B) CR⁺ and secretagogin⁺ processes run in parallel. (C) Secretagogin colocalizes with CR (arrowheads). (D₁ and D₂) β-III-tubulin coexists in secretagogin⁺ shell cells (arrowheads). Arrows in B–D and D₁ point toward the olfactory bulb. (E–E₂) Secretagogin⁺ neurons lack GFAP (arrowhead points to glial cell) immunoreactivity. [Scale bars: 20 μm (B and C), 10 μm (A and D₂), 7 μm (E₁), 5 μm (A₂), and 2 μm (A₄).]