Supplementary Figure 2: RE⁺ and CB⁺ excitatory neurons in LEC LII exhibit differential projection patterns.

(a) Confocal image showing the injection site of the retrograde tracer FG in the DG of a GAD67^EGFP mouse. The two panels below depict CB-immunostained and FG⁺ neurons in the LEC. The merged image reveals a clear segregation of the two populations, with FG⁺ neurons in LIIa and CB⁺ neurons in LIIb, and indicates that CB⁺ neurons do not project to the DG. (b) Confocal image showing the injection site of the retrograde tracer CTB in the OB of a GAD67^EGFP mouse. Only few CTB⁺ neurons in LIIa co-localize with RE⁺ neurons. (c) Confocal image of the PIR injected with the retrograde tracer CTB (RE staining was used here with the purpose to visualize the brain structure). CTB labeling can be detected in LEC LIIb and deeper layers, but not in RE⁺ neurons in LIIa. (d) Same as in c, except that the tracer CTB was injected in the contralateral LEC. CTB positivity can be detected in LEC LIIb, but not in RE⁺ neurons in LIIa. Scale bars, 200 μm (injection sites) and 50 μm. Abbreviations: cLEC, contralateral LEC; CTB, cholera toxin subunit B; DG, dentate gyrus; EGFP, enhanced green fluorescent protein; FG, fluorogold; L, layer; OB, olfactory bulb; PIR, piriform cortex.