SLC17A7 and proximal spinal muscular atrophy: In particular, the loss of VGluT1+ proprioceptive synapses on the soma and proximal dendrites of motor neurons has been shown to occur early in the disease course [18, 30, 37, 38] as well as independently from motor neuron loss in the SMNΔ7 mouse model of SMA [18, 27, 28].