Figure 8
Electron microscopy images of photoreceptor axon terminals in Pomt1 cKO mice. Rod spherules and cone pedicles are shown from control (Pomt1lox/lox) (a–e) and Pomt1 cKO (f–j) mice. At the rod spherule of control mice (a), processes from horizontal cells (asterisks) were located laterally apposed to the synaptic ribbon (blue arrow), and dendritic processes from rod bipolar cells were located below the ribbon. By contrast, horizontal cell processes in Pomt1 cKO mice (f) failed to reach their proper position relative to the rod synaptic ribbon, and dendritic processes from rod bipolar cells were barely visible at the synaptic cleft. At the cone pedicle (yellow dashed line in b and g; schematized in c and h, respectively), the number of invaginations (synaptic complexes) was higher in control (b) than in Pomt1 cKO (g) mice, and mitochondria (green arrows) were more abundant near the synaptic complexes of control (b,c) than of Pomt1 cKO (g,h) mice. Details of the synaptic complex at cone pedicles (red boxes in b and g) are schematized in panels c and h, and shown at a higher magnification in d and i for control and Pomt1 cKO mice, respectively. As noticeable, the lateral processes from horizontal cell (asterisks) and basal process from bipolar cells exhibited a normal appearance in control mice (c), but seemed disorganized relative to the synaptic ribbon (blue arrows) in Pomt1 cKO mice (i). Drawings in e and j schematize the differences observed between cone and rod synaptic triads of control and Pomt1 cKO mice, respectively.
