Figure 7. Loss of proprioceptive synapses onto motor neurons is rescued by minor snRNA gene delivery in SMA mice.

(A) Immunostaining showing ChAT⁺ motor neurons (green) and VGluT1⁺ proprioceptive synapses (red) from the ventral horn of the lumbar spinal cord (L3–5) of unaffected control mice and SMA mice either untreated or injected with AAV9-U11/U12 and AAV9-U11/U12/U4atac. Age at tissue harvest was P12. Scale bar: 20 μm. (B) The scatter plot diagram shows the number of glutamatergic synapses impinging on motor neuron somata from the same experimental groups as in A. Each individual dot represents the number of VGluT1⁺ synapses per motor neuron somata. For each treatment group and control groups, n = 4–5 mice and ~15 motor neurons per animal. Both treatment groups show significant preservation of central proprioceptive synapses compared with the untreated SMA mice. One-way ANOVA was applied where significance is represented by ***P ≤ 0.001.