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. Author manuscript; available in PMC: 2019 Jul 3.
Published in final edited form as: Cell Rep. 2018 May 1;23(5):1286–1300.e7. doi: 10.1016/j.celrep.2018.03.137

Figure 2. Sensory and Motor Subpopulations of CSNs Project Axons and Form Circuits in Segregated Dorsoventral Positions of the Spinal Cord.

Figure 2

(A) Schema of anterograde tracer (BDA) injection into the sensorimotor cortex. (B) BDA was injected into the medial (motor, red spots) or lateral (sensory, blue spots) area of the cortex, where retrobeads+/PRV− (blue dotted area) and retrobeads+/PRV+ CSNs (red dotted area) are located. (C–E) Projections of CS axons into the cervical cord gray matter labeled by Emx1-Cre; lsl-tdTomato mice (C). CS axons from medial (D, motor CST) or lateral cortical areas (E, sensory CST) traced with BDA project to the ventral and dorsal spinal cord regions, respectively. Rightmost panels show axon distribution heatmaps at levels C4–5 and C6–7, with red representing the highest numbers of axon pixels and blue representing the lowest. (F–H) Presynaptic terminals of CS axons in the cervical cord, labeled with synaptophysin (Syp)-tdTomato. The entire population of CS axon terminals are labeled through the use of Emx1-Cre; lsl-Syp-tdTomato mice (F). CS axons from medial (G, motor CST) or lateral cortical areas (H, sensory CST) were labeled by focal cortical injections of AAV1-Syn-EGFP-Cre into lsl-Syp-tdTomato mice. Right-hand panels show presynaptic terminal distribution heatmaps at levels C4–5 and C6–7. Scale bars, 200 μm. (I and J) Distribution of CS axons (I) and presynaptic terminals (J) in lamina I–X of the cervical cord. Whole CST, green; motor CST, red; sensory CST, blue. Data are represented as mean ± SEM (n = 4). See also Figure S1.