Figure 2.

Layer‐specific C9orf72 distribution changes in the developing and adult cortex. Immunostaining for C9orf72, neurofilament and layer specific markers in adjacent sections of the brain. At E16.5 (A) the cortex is divided into the Pax6⁺ ventricular zone (vz), Tbr2⁺ subventricular zone (svz), intermediate zone (iz), Nurr1⁺ subplate (SP), Tbr1⁺ layer VI/cortical plate (CP) and finally the marginal zone (mz) at the pial surface. C9orf72 expression appears throughout but is strongest in the marginal and intermediate zones. At E18.5 (B), further layers have formed in the cortical plate (layers II/II–VI, marked by SatB2 and Ctip2). Strong expression continues in the marginal zone and in a narrower region of the intermediate zone. By P35 all the layers of the cortex have formed (C) and the intermediate zone is absent. C9orf72 staining remains strongest in layer I at the pial surface and is also seen strongly in upper portions of layer II, throughout layer IV and the middle of layer VI. C9orf72 has also switched from a mainly cytoplasmic distribution at embryonic stages to a more uniform distribution, with staining seen throughout the cytoplasm and nucleus. Scale bars: 100 μm.